Biology Igcse Notes

7/30/2019 Biology Igcse Notes

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IGCSE Biology Notes

Contents

The Variety of Life

. Taxonomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. The Binomial Naming System . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Kingdoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Animal Kingdom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Protoista . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Charaeristics of Ling Things . . . . . . . . . . . . . . . . . . . . . . . . . .

. Branching Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Couplets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Key . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cells, Diffusion & Osmosis

. Specialised Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Cell Aities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Enzymes

. Properties of Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. How Enzymes Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Uses for Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Immobilisng Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Nutrition & Balanced Diets

. Food Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Sugar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Fat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


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Protein (Biuret test) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Drugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Alcohol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Digestion & Absorption

. Teeth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Tooth Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Duodenum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Small Intestine (Ileum) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Ler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Large Intestine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Nutrition in Plants . Photosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. The Leaf . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chloroplasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Stomata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Transport in Animals

. The Circulator y System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Arteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Veins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Composition of the Blood . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Blood Cloing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Tissue Fluid Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. The Lymphatic System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The Immune System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Transplants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Transport in Plants

. Osmosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Transpiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Faors Affeing Transpiration . . . . . . . . . . . . . . . . . . . . . . . . . .

. Xerophytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Movement of Photosynthetic Produs . . . . . . . . . . . . . . . . . . . . . . .

. Systemic Pesticides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


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Respiration & Gaseous Exchange

. Aerobic Respiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Anaerobic Respiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Yeast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Calorimeters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. The Lungs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Increase in Breathing Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cigaree Smoke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Excretion & Homeostasis

. Excretion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Homeostasis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. The Pancreas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Reproduction

. Asexual Reproduion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Baeria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Funghi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

List of Figures

A baerium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A pical plant cell. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A pical animal cell. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The process of osmosis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A plant cell reaing to different pes of turgor pressure. . . . . . . . . . . . . .

The aion of an enzyme. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The alimentary canal (digeste system). . . . . . . . . . . . . . . . . . . . . . .

A cross-seion of a human tooth. . . . . . . . . . . . . . . . . . . . . . . . . .

A single human llus om the small intestine. . . . . . . . . . . . . . . . . . .

A pical leaf. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A chloroplast. On each membrane are many molecules of chlorophyll. . . . . . .

A single stoma. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Diagram of a human heart. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Human blood vessels. The lumen in the artery is much smaller than the lumen inthe vein, as the blood is at a much higher pressure. . . . . . . . . . . . . . . . .

Red blood cells. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


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Antigens on a cell. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A lymphocyte. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A lymphocyte indentiing a baerium. . . . . . . . . . . . . . . . . . . . . . .

A root hair cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Water vapour build-up around a stoma. . . . . . . . . . . . . . . . . . . . . . .

A simple calorimeter used to measure the energy value of a respiratory substrate.

The lungs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Some alveoli. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The aion of breathing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Part of the lining of the respiratory passages. . . . . . . . . . . . . . . . . . . .

The excretor y system. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Urea produion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The Suure of an amino acid. R can stand for anything. The NH part ofthe molecule (ammonia) is toc, and is converted into urea. Deamination is theremoval of the niogen-containing part of the amino acid. . . . . . . . . . . . .

How urine is produced there are two processes: ula-filation, and seleereabsorption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

An indidual glomerulus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Kidney failure if one or both kidneys fail then dialysis is used or a ansplantperformed to keep urea and solute concenation in the blood constant. . . . . . .

Kidney ansplant may be necessary as Rhenal dialysis is inconvenient for the patient

and costly. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A summary of how body and blood temperature are maintained. . . . . . . . . .


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The Variety of Life

. Taxonomy

This is the scientific name for puing things into groups classification and naming.

This largest group is called a kingdom.

The system was desed in the th Century by Carl Linnaeus. Kingdom

Phylum .increasingsimilari Class Order

Family Genus

Species

. The Binomial Naming System

All organisms have two Latin (a unersal language) names Genus and Species. The Genus iswrien with a capital leer. When handwriting, both words are underlined. When ping, they areput in italics. For example:

Homo Sapiens(Handwrien)

Felix cattus

(Typed)

. Kingdoms

Animalia

Plantae

Baeria (monera, prokaryote)

Fungi

Protoista

Animal Kingdom

There are Phyla. Among them are:

Chordates (vertebrates) (in order of evolution:)

Fish


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Amphibians

Reptiles

Birds Mammals

Arthropods

Inses

* Grasshoppers, buerflies, beetles, ants etc.

* , described world species

* Three body regions: head, thorax, abdomen

* S legs aached to the thorax (which has segments)

* Adults with one or two pairs of wings aached to the thorax (some have none)

* Tow antennae

* Lateral compound eyes

Arachnids

* Spiders, scorpions, ticks, moites, etc.

* , described world species

* Two body regions: cephalothorax, abdomen

* Eight legs

* No antennae

* Mouth parts are chelicerae (modified appendages) which in spiders are fangs

Crustaceans

* Technically a subphylum

* Classes include crabs, shrimps, lobsters, barnacles, isopods etc.

* , described world speies

* Two body regions

* Two pairs of antennae

* or more pairs of legs

* Primarily aquatic, few terrestrial

Myriapods

* Chilopods Centipedes

, described world species

well-defined head

first pair of legs modified for envenomation

flaened top to boom

one pair of legs persegment


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one pair of antennae

* Diplopods

Millipedes

, described world species

Two pairs of legs per segments, first four segments have pair of legs

one pair of antennae

well-defined head

usually cylindrical

Nematodes

Roundworms

Can be microscopic, or up to m in length

Can be ee ling or parasitic No circulatory or respiratory system

Suure is a tube within a tube

No chaetae

Use sexual reporoduion

Molluscs

So bodied

No segmentation

Single muscular foot

Hard external shell (calcium carbonate) or internal shell

Most have rasping tongue (radula)

Filter feeders mussels

Carnorous oopi

Marine organisms with shells (except barnacles and crustaceans)

Terrestrial snails & slugs

Annelids

Segmented worms (e.g. earthworm)

Leeches

Sexual and asexual reporoduion (depending on species)

Vascular and nervous system

No legs but may have chaetae (stiff hairs) to aid movement

may have obous head


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Protoctista

Single-celled Eukaryotes Protista

Protozoa & Protophyta

Multicelled

Seaweed

* Kelp

* Algae

Slime molds

Amoeba

Ciliates

Diatoms

Paramecia

Forams

etc.

. Characteristics of Living Things

M ovement

R espiration

S ensiti

G rowth

R eproduion

E xcretion

N uition

. Branching Keys

A key is a means of identiing an unfamiliar organism om a seleion. Indidual organisms arefound by following a series of paired, numbered options, or a chart which offers no more than twochoices at each stage. A key either wrien in couplets, or as a chart:

They have a proper nucleus as opposed to Baeria. Eukaryots are aquatic/plant-like organisms that dont fit in theAnimal/Plant/Baeria kingdoms.


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Pili

Plasmid

Ribosomes

Cytoplasm

Plasma membrane

Cell wall

Capsule

Nucleoid (circular DNA)

Bacterial Flagellum

Source: http://en.wikipedia.org/wiki/File:Average_prokaryote_cell-_en.svg

Figure : A baerium.

Plant cells Animal Cells

Always have cell wall made of cellulose and hence a definite shape No cell wall, hence no difinite shape

Usually have large, permanent vacuole Any vacuoles are small and temporary

Some have chloroplasts Never have chloroplasts

Up to mm long Usually less than .mm long.Examples:

palisade cells cheek lining cells

phloem sieve tube elements muscle fibres

root hair cell red blood cells

Table : Differences between plant and animal cells.


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Golgi body(Golgi apparatus)

Golgi vesicles

Cytoplasm

Peroxisome

Mitochondrion(mitochondria)

VacuoleTonoplast

thylakoid membrane

Starch grain

Cell wall

Plasma membrane

Plasmodesmata

Filamentouscytoskeleton

Small membranousvesicles

Smoothendoplasmicreticulum

Ribosomes

Nuclear pore

Vacuole

Chloroplast

Nucleus

Nuclear envelope

NucleolusRough

endoplasmicreticulum

Source: http://en.wikipedia.org/wiki/File:Plant_cell_structure_svg.svg (Public Domain)

Organelle Function

Nucleus Conols the cells aities, contains DNA

Cytoplasm Where metabolic reaions take placeCell membrane Partially permeable, conols the eny/et of substances

Mitochondria Where aerobic respiration takes place

Cell wall (plants only) Fully permeable, prevents cell om bursting

Permanent vacuole Storage area, contains cell sap

Chloroplast (plants only) Where photosynthesis takes place

Figure : A pical plant cell.

Sperm cell designed to fertilise eggsA sperm cell is very small and has a lile tail which prodes movement so it can swim and findan egg to fertilise.Its head contains enzymes (in the vacuole) which allow it do digest its way through an eggmembrane so the two nuclei can join.It contain half the number of chromosomes in the nucleus these caryy genetic informationom the father, which will be passed on to the offspring.


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Smooth endoplasmic reticulum

Rough endoplasmic reticulum

Plasma membrane

Mitochondrion

PeroxisomeCytoskeleton

Free Ribosomes

Ribosomes

Nucleus

Nucleal poreNucleal envelope

ChromatinNucleolus

Golgi vesicles

(golgi apparatus) Lysosome

Centrioles

Cytoplasm

Secretory vesicle

Source: http://en.wikipedia.org/wiki/File:Animal_cell_structure_en.svg (Public Domain)

Organelle FunctionNucleus Conols cell aities, contains DNA

Cytoplasm Where metabolic reaions take place

Cell membrane Partially permeable, conols eny/et of substances

Mitochondia Site of aerobic respiration

Figure : A pical animal cell.

Ovum (egg) cell designed to be fertilisedAn ovum is large and bulky because no ae ovement is needed it just sits and waits for thesperm to find it.It contains yolk (in the cytoplasm) which prodes a large food store needed for the developing

young organism once its fertilised.It contains half the number of chromosomes, which carry genetic information om the mother this will be passed on to the offspring.

Palisade cell for photosynthesis


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A palisade cell is tall with a large surface area. Its found on the top side of a leaf ideal for goodabsorpion of carbon diode and light both are needed for photosyntheses.Theyre packed with chloroplasts, which contain the green pigment chlorophyll, which is needed

for photosynthesis.

Ciliated cell to stop lung damageCiliated cells line all the air passages in the lungs. Mucus is sticky and so aps dust and baeria.The cilia wa and sweep up the mucus to the back of the throat where it is swallowed. Thebaeria are then killed by the acid in the stomach.

Root hair cell for absorbtionThe long hair cell increases the surface area of the root, which helps absorption of water andminerals.It has a very thin cell wall, which makes it easier for minerals to pass across into the root itself.

Red blood cells (erythrocytes) for ansportThey do not contain a nucleus, so there is more room for the protein molecule to carry oxygen.Their biconcave shape ges them a large surface area for gas exchange.

Muscle cells for movementMuscle cells have protein strands that can slide across each other for conaion. Each cell hasseveral nuclei. There are pes smooth, skeletal and cardiac.

Tissues A tissue is a group of similar cells, working to perform the same funion, e.g. muscletissue is made om muscle cells.

Organs Different tissues are arranged to form an organ. They work together to perform a particularfunion, e.g. the heart.

Organ Systems A group of organs working together form an organ system, e.g. the circulatorysystem.

. Cell Activities

All cells exchange gases, nuients and other materials between themselves and their surroundings.

Diffusion is the ee movement of particles of a substance (atoms, ions or molecules) om regionsof high concenation to regions of lower concenaion. The process continues until the particlesare evenly distributed. This is movement down a concenation gradient.

Diffusion is the usual way in which molecules move into or out of cells.

Concentration gradient refers to the difference in concenation between one region and another.The greater the difference in concenaion, the steeper the concenation gradient, and the fasterthe rate of diffusion. Surfaces qhere gas exchange occurs oen maintain a steep diffusion gradientso that idffusion occuras rapidly. For example:


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across the linging of the air sacs (alveoli) in the lungs of humans

across the surface of cells bordering air spaces in the leaves of plants

Osmosis is a specific pe of diffusion. It is the diffusion of water om a dilute solution to amore concenated soution throuh a partially permeable membrane. Cell membranes are partiallypermeable membranes, and it is by osmosis that water moves into and out of cells.

In osmosis, water diffuses om a high water concenation to a low water concenation (seeFigure ).

Cells placed in distilled water will gain water by osmosis. This is because there is a lowerconcenation of water inside than outside. The cells are said to be turgid.

Cells placed in a concenated solution will lose water by osmosis. This is because there isa greater concenation of water inside the cell. The cells are said to be flaccid. In severecases the cell membrane is pulled away om the cell wall. The cells are then said to be

plasmolysed. Eventually the process may stop because the concenations on both sides ofthe cell membrane have equalised (see Figure ).

Active transport is a chemical process that results in a movement of particles in an opposite dir-eion to that expeed by diffusion. Substances are taken scross a membrane om a region oflow concenation to a region of higher concenation, i.e. against a concenation gradient. Asits name implies, it is an ae process and requires energy supplied by respiration.

S olute,e.g. sugar

Water

Par t ially permeable membrane

Direct ion of wate rmovement

Dilute s olut ion(High water concentration)

Concentrated solut ion(Low water concentr ation)

Figure : The process of osmosis.

Enzymes

Enzymes are biological catalysts. They speed up the chemical reaions which go on inside lingthings, and are exemely efficient.


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Plasmolysed Flaccid Turgid

Vacuole

Source: http://commons.wikimedia.org/wiki/File:Turgor_pressure_on_plant_cells_diagram.svg (Public Domain)

Figure : A plant cell reaing to different pes of turgor pressure.

Enzymes are made inside cells. Once formed, the enzymes may leave the cell and do its job outside.Such enzymes are called extracellular enzymes. They include the digeste enzymes which breakdown food substances in the gut.

Other enzymes work inside the cell. They are called intracellular enzymes. Their job is to speedup he chemical reaions occurring in cells, and also conol them.

An example of a reaion conolled by an enzyme:

maltose(substrate)maltase(enzyme) glucose(product)

The substance which the enzyme as on it called the substrate in this case maltose. The new

substance or substances formed as a result of the reaion are the products. In this case there is justone produ, glucose. The enzyme catalysing this particular reaion is maltase. This reaion cango in either direion it is reversible. If there is a lot of maltose present compared with glucose,the reaion will go om le to right. If there is a lot of glucose compared to maltose, it will goom right to le. Most metabolic reaions are reversible.

. Properties of Enzymes

. They are always proteinsWe need to take proteins in, a our food to produce enzymes.

. They are specific in their actionEach enzyme conols one particular reaion, or pe of reaion maltase will only a onmaltose, and sucrase on sucrose.

. They can be used multiple timesThey are not altered by the reaion that they catalyse. However, they run down eventually andhave to be replaced.


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. They are destroyed by heatingIn common with all proteins, they are denatured by proteins. Normally this happens at C.

. They are sensitive to pHTheir effeeness depends on the degree of acidi or alkalini of the solution which they arein. Most inacellular enzymes work best in neual conditions.

. How Enzymes Work

Substrate entering

active site of enzymeEnzyme/substrate

complex

Enzyme/products

complex

Products leaving

active site of enzyme

ProductsSubstrate

Active s ite

Enzyme changes shape

slightly as substrate binds

Source: http://en.wikipedia.org/wiki/File:Induced_fit_diagram.svg (Public Domain)

Figure : The aion of an enzyme.

Figure shows in a simplified way how enzymes are believed to work. When a substrate moleculehappenes to impa on the ae site of an enzyme, the reaion takes place and the produs leave,

eeing up the enzyme for another reaion.Each enzymes ae site has a specific shape, into which only one pe of substrate will fit. This iswhy the enzyme is specific in its aion.

When an enzyme is denatured by heat, the shape of its ae site changes, so substrates no longerfit in it, and it is not effee.

Anything which helps substrates to come into conta with the enzyme at a faster rate will increasethe rate at which the enzyme can catalyse reaions. Higher temperatures mean that moleculesmove around mroe quickly a rise in temperature of Ccan double the rate of reaion.

Some minerals and tamins also increase the rate of reaion.

Some poisons, such as cyanide and arsenic, inhibit enzymes by blocking the ae site. Some

poisons block ae sites permanently, others temporarily. This is also how some pesticides work.

. Uses for Enzymes

Enzymes can be exaed om organisms in a purified form, and then used in many scientific,domestic and industrial processes. A common useage is in biological washign powders. Variousprotein-digesting (proteases) are added to the washing powder, and they dissolve protein stains.


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Biological washing powders are advantageous because they work at relately low temperatures. Thismeans they are usefulfor washing delicate fabrics, and can save elerici. However, some peopleare allergic to them.

Enzymes are normally exaed om microbes, which are grown on a large scale in fermenters.Some examples of enzyme use:

Proteases are used for tenderising meat, skinning fish, remong hair om hides, and breakingdown proteins in baby foods.

Amylases convert starch to sugar in making syrups, uit juices, chocolates and other food produs.

Cellulase breaks down cellulose and is used for soening vegetables, remong the seed coat omcereal grain, and exaing agar jelly om seaweed.

Isomerase converts glucose into uose. Fruose is muchsweeter than glucose; this makes it

useful in sweets, syrups and slimming foods, as only small amounts are needed to sweeten theprodu.

Catalase releases oxygen om hydrogen perode, and is used in making foam rubber om latex.

. Immobilisng Enzymes

Biotechnologists have developed a beer method of using enzymes than simply ming the enzymewith the substrate. The enzymes are aachedf to an inert surface, usually glass or plastic beads. Thebeads are then brought into conta with the substrate so that the reaions can take place.

One way of bringing the beads into conta with the substrate is to immerse them in a solution

of the substrate, and then wait for the reaion to be completed before colleing the produ andstarting again. This is called batch processing.

The other way is to slowly pour a solution of the subate through a column of the beads, andthe colle the produ om the boom. The substrate is aed upon progressely as the solutionickles down the column. This is calledcontinous flow processing, because the produ is colleedall the time. it is more efficient than batch processing.

Nutrition & Balanced Diets

Nuition is the study of food and feeding processes. Food is the material om which organismsobtain the energy and the raw materials to constru, maintain and repair the body.

Plants are autotrophic they produce their own food, and come at the boom of the food chain.Humans and other animals are heterotrophic (also known as holozoic) they eat other plants andanimals, and cannot produce their own food.

Humans require abalanced diet. This is one which supplies the different pes of food in adequateamounts and the corre proportions, and prodes the body with sufficient energy for its needs. Abalanced diet maintains a healthy and ae life and, where necessary, growth.

Humans use food for:


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Energy for body processes (usually obtained om carbohydrates and fats sometimes om proteinwhen in a state of starvation).

Building materials, to build the cells of the body (proteins, fats, tamins, minerals). Chemical reaions in the body (proteins, tamins, minerals, water).

There are seven chemical components of a balanced diet:

Carbohydrates To prode energy.

Sugar Different kinds of food contain different pes of sugar: glucose or uose in uit, laosein milk, or sucrose in ordinary table sugar. The formula for glucose, the simplest possiblesugar, is CHO. It is a monosaccharide it is made into chains of polysaccharides. Twoglucose molecules bonded together form one maltose molecule.

Starch is found in bread, potatoes and cereals. Starch is a polysaccharide made of a spiral chainof glucose molecules, and is used as the food reserves of plants.

Cellulose is a polysaccharide made of a straight chain of glucose molecules, and is used to buildplant cell walls.

Glycogen is a polysaccharide, and is used as the food reserves of animals, stored in the ler andmuscles.

Fats To prode energy, insulation, and to constru parts of cells.

Animal fats are obtained om lestock, such as cale or pigs. They are eaten in the form ofbuer, dripping or lard. They contain saturated fa acids, which are unhealthy in largeamounts. Fat contains twice as much energy per gram as carbohydrates and proteins do,and they are solid at room temperature.

Plant fats, or oils, for example ole oil or corn oil, are liquid at room temperature. They containpolyunsaturated fa acids, which are more healthy than satureated fa acids.

Proteins To build muscle, make enzymes and hormones, and constru parts of cells. It is nor-mally obtained om the muscles of animals. The disease caused by protein deficiency is calledkwashiorkor. Some plants, such as soya beans and maize, contain relately large amounts ofprotein compared to other plants, so it is possible to obtain most of the necessary amino acidsom plant-based foods. Proteins are made om amino acids. of which there are differentpes. An organisms DNA prodes the template for linking amino acids in different orders toproduce proteins (there are a large number of possible combinations). Protein contains Niogenand Sulphur.

Minerals are ions of certain elements (i.e. inorganic), which are needed for particular purposeswithin the body. For example:

Calcium is needed for bone formation. Without calcium, bones are so. Calcium deficiency iscalled rickets.


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Iron is required for haemoglobin, in blood. Oxygen is ansported around the body by bindingto haemoglobin. Iron is plentiful in ler and kidneys. Iron deficiency results in anaemia.

Vitamins Various biological compounds required by the body. Some examples:Vitamin A is neede by the eyes. Vitamin A deficiency is called xerophthalmia and leads to

blindness.

Vitamin C keeps the lining of the mouth and gums healthy. It is found in green vegetables, butis destroyed by heating. Lack of it causes scurvy.

Vitamin D is needed to enable calcium to harden bones. Lack of it causes rickets.

Water Makes of -% of the body. The bodys chemical reaions take place in it. Humansneed about lie of water every day.

Fibre Stimulates the smooth passage of food through the gut. Mainly made of cellulose, it aids

faeces formation.

Too much energy-rich food will cause the indidual to become overweight, while too lile willcause them to become underweight.

Malnuition is the result of not hang a properly balanced diet. If the body does not recee thecorre chemical components in the right proportions, it cannot funion efficiently.

In humans, as in other animals, complex organic food can enter body cells only if it is first brokendown into smalll soluble molecules. In humans, the stages int his process are:

Ingestion Food is taken into the mouth.

Digestion The breakdown of complex organic foods into small, soluble molecules.

Absorption The uptake of soluble food substances into the body across cell membranes.

Assimilation The use of soluble food substances by cells in the body.

Egestion The removal of undigested food om the body (not to be confused with excretion orsecretion).

In humans, the alimentary canal (gut) is responsible for the ingestion, digestion, absorption andegestion of food.

. Food Tests

Sugar

. Mash the food and add water.

. Add cm3 of the food to a test tube.


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. Add cm3 of Benedis solution to the test tube.

. Shake the test tube.

. Place the test tube in a waterbath for appromately minutes. If a precipitate develops, sugar ispresent. The colour of the mture ges a rough indication of how much sugar is present: greenis the lowest concenation, yellow higher, brown still higher, and red the highest concenation.

Starch

. Add drops of dilute iodine solution to the food sample.

. If the colout changes to blue-black, starch is present.

Fat

. Pour appromately cm3 of absolute ethanol into a test tube.

. Add a small amount of the food sample to the ethanol.


. Add appromately cm3 of water to the test tube.

. If the mture turns cloudy white, fat is present.

Protein (Biuret test)

. Mash the food and add water.

. Add cm3 of the food to a test tube.

. Add a small amount of dilute sodium hydrode solution until the mure clears.

. Add a few drops of dilute copper sulphate solution.


. If the solution turns purple, protein is present.

. Drugs

A drug is something which changes the way the body works. Useful drugs include painkillers andantibiotics. Harmful drugs can be addie, and harm the body in some way.

Addiion can be chemical when the body becomes adjusted in such a way that it needs the drug,or psychological when the addied person feels a constant need for the drug.

Withdrawal symptoms om a drug include fever, and nausea.


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Alcohol

Reduces ai of nervous system.

Removes inhibitions, causes relaxation.

Impairs judgement

Is poisonous to the ler. Alcohol poisoning causes a coma and death.

Digestion & Absorption

Food must get into the blood in order to be carried to the bodiys cells. Only soluble food cando this. Most food is insoluble, and is broken down into soluble particles through the process ofdigestion, which occurs in the digeste system (see Figure ).

Digeste juices break down the food, starting in the mouth with sala (om the salary glands).The food is then swallowed, and other juices om the ler and pancreas are added. Bile is producewdin the ler, and then stored in the gall bladder, before being added to food in the stomach.

Muscles keep the walls of the stomach and small intestine mong, ming up the food and digestejuices, and keeping blood mng through the digeste system.

When the food has been completely broken down, it is absorbed into the blood in the small intestine,which has a good blood supply and thin walls, which allows food to pass easily into the blood throughthe process of diffusion.

Some food cannot be digested, and is egested through the anus.

. Food in chewed and med with sala in the . ( minute)

Starchsalivary

amylaseSugars

. The carries the chewed-up food to the stomach, using muscular walls which pushfood with a wave of conaion (peristalsis). ( seconds)

. Acid digeste juices, ideal for pepsin (an enzyme that breaks down proteins), are added in the. The food and the digeste juices are med. ( hours)

Proteinspepsin Amino acids

. More alkaline juices om the pancreas (to neualise the stomach acid) are added in the . There is more ming, then the fully digested food is absorbed into the blood. (hours)

Starchpancreatic

amylaseSugars

Fatsbile Fat droplets

Fat dropletslipase Fatty acids and Glycerol


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Descending colon

Ascending colon

Transverse colon

Colon

Commonbile duct

Duodenum

Gallbladder

Liver

Oral cavity

Sublingual

SubmandibularParotid

Salivary Glands

Pharynx

Tongue

R sophagus

Pancreas

Stomach

Pancreatic duct

Ileum(small intestine)

Anus

Rectum

Appendix

Cecum

Source: http://commons.wikimedia.org/wiki/File:Digestive_system_diagram_en.svg (Public Domain)

Figure : The alimentary canal (digeste system).

. Only undigested waste material reaches the . The water is taken back into thebody, leang solid waste. ( hours)

. Undigested food is stored in the reum, and then the solid waste is egested through the anus asfaeces.


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. Teeth

Enamel

Dentine

PulpGum

Cementum

Bone

Blood vesse

Nerve

C

r

o

w

n

R

oo

t

Source: http://commons.wikimedia.org/wiki/File:Tooth_Section.svg (Public Domain)

Figure : A cross-seion of a human tooth.

An adult teeth has, at most, teeth. Thre are four main pes: , , -and . Incisors are for cuing pieces off food, while canines are for griping it. Pre-molars andmolars are for grinding the food down until it can be swallowed easily.

The outside of a tooth is formed by hard enamel. Beneath this is a layer of hard dentine. In thecene is a so area called the pulp ca, which contains small blood vessels and a nerve (see Figure). Tiny channels containing extensions of ling cells tun outom the pulp ca into the dentine.These make the dentine sensite. The enamel and dentine are made hard by the presence of calciumphosphate, the same substance that makes bones hard.

The outside of the root is covered by a material called cement. Aached to the cement are toughfibres which run into the jaw bone. These fibres hold the tooth in its socket; they allow the tooth

to move slightly, and cushion it om being jarred when it hits something hard.

Tooth Decay

Tooth decay is caused by baeria in the mouth. These baeria form an insible layer called plaqueon the surface of the teeth.

Aer a meal, the baeria feed on any sugar present and turn it into acid. The acid eats into the


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teeth. Within appromately one hour the acid is neualised by the sala. However, the decay hasoen already started by this time.

Decay usually starts between the teeth and in the creces on the crowns. The acid eats through the

enamel into the dentine, allowing baeria to get into the pulp ca. In severe cases the baeriamay spread to the base of the tooth, causing an abscess.

Baeria may also get between the tooth and the gum, causing the gum to bleed. Sometimes thefibres aaching the tooth to the jaw are aacked, in which case the tooth gets loose and eventuallyfalls out.

There is strong edence that fluoride helps to prevent tooth decay. It strengthens teeth when theyare forming, and makes the enamel more resistant to acid.

Where there is not enough fluoride naturally occuring in public drinking water supplies, it is addedartificially. This has led to a large improvement in the general dental health of the population.

. Duodenum

Food leang the stomach enters the . Secretions om the ler and pancreas are added(pancreatic juice contains all three pes of digeste enzymes). Bile is stored in the gall bladder,and emulsifies fats. Sodium hydrogen carbonate neualises the stomach acid.

. Small Intestine (Ileum)

Digestion is completed in the (or ), which secretes digestove enzymes, andabsorbs food.

The small intestine is covered in millions of tiny protusions called (see Figure ). They increasethe surface area, and so increasing the rate at which the small intestine can absorb food. Each llushas a thin surface layer, so there is only a short distance for absorption. Inside is a network ofcapillaries to caryy away the absorbed sugars and amino acids. There is also a laeal, to carry awaythe absorbed fa acids to the lymhpatic system. Conneed to the capillaries is a blood vessel,which carries the absorbed foods to the hepatic portal vein, and then on to the ler.

. Liver

Many cells perform a wide range of funions in the ler, in processing the absorbed foods.

..glucagon

====

insulin Glycogen stores

Glucose Energy a Respiration.to other tissue a the circulation


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Thin surface layer

Capillaries

Lacteal

Blood vesse

Figure : A single human llus om the small intestine.

..

Synthesis of plasma proteins e.g. fibrinogen

Amino acids Excess are deaminated Urea for excretion.to other tissue a the circulation

.. Fat storesFa acids Fats for cell membranes.

Energy a respiration

. Large Intestine

Water and salt are absorbed in the C. Undigested food is stored in the , along withbaeria and some dead cells. This forms faeces and is passed through sphiners out of the anus.


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Nutrition in Plants

. Photosynthesis

P is the process by which green plants make glucose and other organic molecles ominorganice molecules, using light energy. The light energy is apped by chlorophyll. The overallprocess for photosynthesis can be summarised as:

Carbon Dioxode + Waterchlorophyll

light energyGlucose + Oxygen

Glucose is not the only organic substance made by photosynthesis. Other carbohydrates are alsoformed, which can then be converted to fats, or, by combining with minerals, form amino acids andtamins. Photosynthesis is the source of all organic substances in the plant.

.Carbon dioxide + Waterchlorophyll

light energy Glucose and other sugars + Oxygen

.

respired or used tomake:

starch

sucrose

cellulose

proteins

fats

tamins

chlorophyll

.excretedorrespired

Products of Photosynthesis Glucose and other sugars:

Much of the glucose is converted to for temporary storage in the leaf. At night, the starchmay be broken down to the sugar and ansported through th phloem to other parts ofthe plant.

In the leaf, and throughout the plant, glucose is broken down in to release energy.

In growing regions, glucose is converted to to make cell walls.


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In the leaf, some glucose is combined with niate to form . These are later incorpor-ated in to to make enzymes and to make struural parts of cells, such as membranes.If there is a shortage of niate, the plant is unable to grown properly, and is weak and unhealthy.

In the leaf and elsewhere, glucose and other sugars are used to make for struures such ascell membranes and to make which have essential uses for the plant.

Some glucose is combined with minerals, especially magnesium, to form , the greenpigment used to ap light in photosynthesis.

Oxygen:

Used in throughout the plant.

Excreted through stomata as a .

. The Leaf

Cuticle

Upperepidermis

Palisademesophyll

Spongy

mesophyll

Lowerepidermis

Stoma Guard cells

Xylem

Phloem

Vascularbundle

Source: http://en.wikipedia.org/wiki/File:Leaf_anatomy.svg (CC-BY-SA-2.5)

Figure : A pical leaf.

Each leaf is aached to the stem or branch by a , This leads to the in the leaf. Leavesare covered by a layer of waxy meial called the , which is normally thick and waterproof.It prevents the leaf om losing too much water in hot weather.

Immediately under the cuticle is a layer of cells called the . which forms the skin ofthe leaf. The epidermis may be pierced by lots of tiny holes called (singular ). Thestomata are mainly on the lower side of the leaf. They allow gases to diffuse in and out of the leaf,and water vapour to escape. Each stoma is flanekd bvy a pair of which can open andclose. They close in hot, dry weather to prevent too much water evaporating om the leaves.


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Leaves are generally flat, sometimes large, and oen numerous. The result is that they have a largesurface area for aborbing Carbon diode and ligt. The veins help to support the leaf, and hold itout flat, so that it can catch the mamum amount of light. In many plants the leaves are positioned

in such a way that they dont shade each other.Between the upper and lower epidermis are ltos of cells which together makes up the .These cells contain , and this is where photosynthesis takes place. The mesophylltowads the upper side of the leaf consists of cells shaped like bricks, and arranged neatly side byside. They are called . The other mesophyll cells are rounded and more irregular intheir arrangement. They are called .

Between the mesophyll cells are into which he stomata open. When photosynthesis istaking place, carbon diode diffuses through the open stomata into the air spaces. It then diffusesinto the cells.

Phototsynthessis takes place mainly in the palisade cells. They contain most of the chloroplasts,

and they are near the surface of he leaf that gets most light. the chloroplasts are oen clusteredtowards the tops of the cells, in the best position for catching light.

The vein is made up of two parts: the towards the top, and the below. The xylembrings water and mineral salts to the elaf. The phloem takes soluble sugar and other produs ofphotosynthesis away om the leaf. Together thexylem and phloem are calld .

Chloroplasts

Chloroplasts are filled with rows of thin interconneed . Millions of molecules are laid out on these membranes.

Chlorophyll is a complex organic green which contains , and it plays a tal role

in photosynthesis, by absorbing blue and red light, but refleing green light.

Stomata

Stomata allow carbon diode and oxygen to diffuse in and out of leaves. They are also the mainroute by which water vapour excapes om the plant. In hot, dry weather there is a risk that theplant may run short of water. For this reason it is important that the stomata should be able toopen or close according to the weather conditions.

When th estoma opens, the guard cells take up water om the neighbouring epidermal cells; as aresult the guard cells swell up and become more turgid. As they swell up they bend, so the gap

between them widens (see Figure ). They swell up because the inner wall of the guard cells isthicker, and less elastic, than the outer wall.

The stoma closes by the reverse rocess. Water passes out of the guard cells, so they become lessturgid. As a result the guard cells straighten, and the gap between them narrows.

Around the stoma are sausage-shaped .


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outer membrane

intermembrane space

inner membrane

stroma(aqueous fluid)

thylakoid lumen(inside of thylakoid)

thylakoid membrane

granum(stack of thylakoids)

thylakoid(lamella)

starch

ribosome

plastidial DNA

plastoglobule(drop of lipids)

Source: http://commons.wikimedia.org/wiki/File:Chloroplast.svg (CC-BY-SA-(any version) or GNU FDL)

Figure : A chloroplast. On each membrane are many molecules of chlorophyll.

Transport in Animals

All organisms which are large require a ansport system, to move substances around the body.Single-celled organisms with low levels of ai do not require ansport systems.

Humans have two main ansport systems:

Circulatory system

Lymphatic system

. The Circulatory System

Single Circulatory Systems e.g. fish: .Heart

.GillsTissuesBlood passes once through the heart on its way around the body.

Double Circulatory Systems e.g. humans:


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guard cell

vacuole

chloroplast

epidermal cell

stoma almost closed

stoma wide open

The guard ce lls have taken

in water by osmosis, asindicated by the arrows.

Figure : A single stoma.

.HeartTissues .Lungs. .deoxygenated blood

. .oxygenated blood

.oxygenated blood

..deoxygenated blood

Arteries

Aorta takes oxygenated blood om the heart to the body


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Pulmonary artery takes deoxygenated blood om the heart to the lungs. The only artery whichcarries deoxygenated blood.

Veins

Superior Vena Cava brings deoxygenated blood om the head and arms back to the heart

Inferior Vena Cava brings deoxygenated blood om the body back to the heart

Pulmonary Vein brings oxygenated blood om the lungs back to the heart. The only vein whichcarries oxygenated blood.

Diastole(lling)

Systole(pumping)

Right and left

ventricles

Antrioventricularvalve

Pulmonary veins

Right and left

Atrium

Pulmonary artery

AortaSemilunar

valve

Anteriorvena cava

Posterior

vena cava

Source: http://commons.wikimedia.org/wiki/File:Human_healthy_pumping_heart_en.svg (Public Domain)

Figure : Diagram of a human heart.

When the heart is relaxed (), both sides fill up with blood om the veins.

The aia then cona ( ). So blood is forced into the venicles through thevalves.

A aion of a second later, the venicles cona ( ). The valves betweenthe aia and venicles close, so blood is squeezed in to the arteries.


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The heart relaxes again and fills up with blood.

Cardiac arrest/Myocardial infarction Heart aack

Atheroschlerosis/atheroma/angina Lack of oxygen to ehart due to fat build-up in coronary arter-ies, leading to chest pain.

Sinoatrial node Group of cells taht regulate heart beat (pacemaker).

Hypertensive High blood pressure

Stroke Atheroschlerosis depres an arteryin the brain of oxygen.

Lumen

Collagen bres

Thin layer of musc le

and elast ic bre

S mooth endothelium

Artery Vein

Capillary

Nucleus of

endothelial cell

S ingle layer of

endothelial cells

Figure : Human blood vessels. The lumen in the artery is much smaller than the lumen in thevein, as the blood is at a much higher pressure.

Composition of the Blood

Plasma is % water. Plasma ansports carbon diode om the organs to the lungs, solubleprodus om the small intestine to the organs, and urea om the ler to the kidneys. Thefollowing cells are suspended in it:


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Red Blood Cells Erythrocytes Red blood celsl are disc-shaped and biconcave. These cells haveno nucleus, so they can carry more oxygen. Red blood cells contain a chemical called .This combines with oxygen to form oxyhaemoglobin.

A red blood cells lifespan is about four months. Aer this time it goes to the spleen, which removesworn out red blood cells om circulation.

Source: http://commons.wikimedia.org/wiki/File:Erythrozyten_und_Osmotischer_Druck.svg (Public Domain)

Figure : Red blood cells.

White Blood Cells Phagocytes & Lymphocytes There are several different pes of white bloodcells. They are all larger than red blood cells, and have a nucleus. Lymphocytes have a nucleus which

occupies most of the cell.

White blood cells prote the body om baeria.

Phagocytes can squeeze through capillary walls, move towards baeria, and ingest them.

Lymphocytes produce chemicals which destroy baeria, by makign them stick together.

Platelets These are agments of blood cells budded off in the red blood marrow. These cells havea sticky surface, and help to clot the blood at wounds, to stop bleeding.

Blood Clotting

. Blood vessel wall is damaged or broken.

. The protein within the blood vessel wall is exposed. This causes platelets to release an enzyme(thrombin).

. Blood plasma carries a soluble protein called .

. Enzymes secreted by platelets cause soluble fibrinogen to turn into insoluble .


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. Fibrin forms long threads which precipitate out of the blood.

. The fibrin threads tangle together and ap red and white blood vessels in the clot.

. The clot dries and hardens, forming a scab.

Tissue Fluid Formation

. Arteriole brings blood into the capillary bed

. The arteriole dides into a network of small capillaries

. Fluid leaks out of the capillaries, especially at the beginning of the capillary bed, and bathes thebody cells.

. The fluid is called . It carries glucose and oxygen om the blood to the cells.

. Tissue fluid containing CO and urea leaks back into the cappillaries at the venous end of thecapillary bed.

. Venule carries blood back to a vein.

. The Lymphatic System

Lymph nodes contain white blood cells, and a as aps for baeria and foreign particles. Tissuefluid containing foreign and waste materials drain into the lymphatic system, pass through a lymphnode, and re-enter the blood circulation.

The Immune System

All cells have protein molecules on their surface membranes called (See Figure ).

Figure : Antigens on a cell.

Lymphocytes (see Figure ) produce . Theseare chemicals which rea to foreign antigens and destroythe foreign cells. Lymphocytes recognise antigens on thesurface of body cells and do not produce antibodies againstthem.

Figure : A lymphocyte.

If foreign cells, e.g. baeria, enter the body, lymphocytes recog-nise these as foreign due to their different antigens. The lymph-ocytes will then release antibodies to destroy the baeria.

There are thousands of lymphocytes which each produce a dif-ferent antibody. Thus, thousands of different pathogens can bedestroyed. Lymphocytes also produce memory cells, which re-main in the lymph nodes. These memory cells can produce antobodie very quickly if the sameforeign antigen enters the body again. These antibodies destroy the baeria before they cause alarge infeion the body is immune to that species of baerium.


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Transplants

If a patient needs to have an organ ansplanted into their body, dors must ensure that the antigens

on the donor organ are very similar to the patients antigens. Otherwise, there is a chance that thepatients lymph nodes will produce antibodies against the organ, rejeing it.

Brothers and sisters have similar DNA and are oen used as donors. Patients are kept in sterileconditions aer the operation, and are on drugs to suppress their immune system for the rest oftheir life immunosuppresse drugs).

Transport in Plants

Plants need ansport systems to:

Move water om the soil to the leaves for use in photosynthesis.

Move photosynthetic produs om the leaves to other parts of the plant e.g. uit amd growingparts of the plant.

Xylem vessels ansport water om the roots to the leaves. Xylem vessels are long, continuous tubes it is dead tissue containing . Lignin makes the xylem vessels strong, and is depositedunevenly, which leads to pits in the walls through which water can enter and leave the tubes.

Phloem tubes (sieve tubes) are ling tissue. At the end of each cell making up the tube, the cellwall is perforated to allow easy movement of sucrose. The movement of sucrose om the leavesto where it is needed is called anslocation. Phloem cells contain few organelles. The majori

of aities are performed by a companion cell which prodes energy to the phloem cell.

Root hair cells are found on young roots. They increase the surface area of the root for absorptionof water an mineral ions. They last for appromately one day.

. Osmosis

Water moves by osmosis across the root.

Osmosis is the net diffusion of water molecules om a region of high water potential to a region oflow water potential through a partially permeable membrane (down a water potential gradient).

Water potential of a substance is a measure of how much water there is int it, and how easily the watermolecules can move around. Substances with a lot of water have a high water potential. Substanceswith a lile water have a low water potential. Water moves om areas of high water potential toareas of low water potential.


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. Transpiration

Water does not move by osmosis in the xylem. The xylem is dead tissue, and there are no cell

membranes. Water moves up the xylem because of anspiration.Transpiration is the loss of water vapour om a leaf through the stomata.

% of water that is absorbed is lost in anspiration.

The remaining % is used in photosynthesis.

As water leaves the xylem vessels it reduces the water pressure at the top of the x ylemm, so watermoves upwards towards a lower pressure. Transpiration produces a tension (pull).

Water molecules are sticky; they stick to each other (), and this helps water to be pulledup the xylem. Transpiration is aided by this cohesion.

Factors Affecting Transpiration

Wind speed Wind removes water vapour om around the stoma, so it increases the water potentialgradient (the water potential of the atmosphere around the toma becomes more negate) (seeFigure ).higher wind speed, higher transpiration

Humidity The higher the humidi, the lower the water potential gradient, so less water evaporatesom the leaves.higher humidity, lower transpiration

Light intensity During sunlight, stomata open to allow CO in for use in photosynthesis.

higher light intensity, higher transpiration

Temperature One a hot day, water evaporates more quickly om the leafhigher temperature, higher transpiration

If the plant loses too much water, it loses turgor pressure in the cells and may wilt the stomatawill close at this point.

Water supply If there is not enough water, the plant will clsoe its stomata to conserve water.lower water supply, lower transiration

Leaf surface area A greater leaf surface area means more stomata for water to siffuse out of.higher surface area, higher transpiration

Stomata Water is mainly lost through stomata the more stomata there are, the more anspirationthere is. Most stomata are located on the underside of the leaf.more stomata, higher transpiration

Air spaces More air spaces in the spongy mesophyll of a leaf mean there is mroe space for water tocolle.mroe air spaces, higher transpiration


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. Xerophytes

Xerophytes are plants taht are specially adapted to le in exeme conditions. Some examples of

adaptations:

Thick cuticle stops unconolled evaporation through leaf cells.

Small leaf surface area less surface area for evaporation, e.g. conifer needles, caus spines

Low stomata density smaller surface area for diffusion

Sunken stomata maintains humid air around stomata, e.g. marram grass, cai

Stomatal hairs (trichores) maintains humid air around stomata, e.g. marram grass, couch grass

Rolled leaves maintains humid air around stomata, e.g. marram grass

Extensive roots mamise water uptake, e.g. cai

. Movement of Photosynthetic Products

Photosynthesis occurs in the leaves. It produces glucose leaves are a . Glucose is convertedinto sucrose for ansport around the plant. Sucrose is a disaccharide. it is less reae than glucose,and does not get used up as easily as glucose.

Sucrose enters the phloem tubes, and is taken to wherever it is needed, e.g. growign shoots, devel-oping uits, roots (anywhere where respiration is happening).

The places where sucrose is taken to are called . movement of organic substances is called (also applies to amino acids, lipids etc.).

Once at the sink sucrose may be converted to starch for storage (e.g. potatoes), or it may be convertedto other sugars (e.g. uose in uits). In this way very high concenterations of sugars can be builtup without affeing the water potential of cells. Sucrose can also be converted back to glucose forrespiration.

. Systemic Pesticides

Systemic pesticides are absorbed into the plant and ansported throughout the plant in the phloem.The targeted organism (e.g. an inse) feeds on the plant and eats the pesticide and dies.

Systemic pesticides are much more effee than conta pesticides, but long term effes on humansare unknown, and consumers may not want to eat produs eated with them.

Respiration & Gaseous Exchange

Every cell in every ling organism needs energy. Energy is obtained om food by the process ofrespiration. There are two pes of respiration:


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. Aerobic Respiration

The break-down of glucose using oxygen to release energy used by cells ( mol Adenosine Tri-

phosphate (ATP)).Energy (in the form of ATP) is used in muscle conaion, ae ansport, reaions(building up substances), reaions (destroying substances). Anabolic and catabolic re-aions are together known as reaions. Some energy is released as heat.

Glucose + Oxygen Carbon dioxide + Water + energy

C6H12O6 + 6 O2 6 CO2 + 6 H2O + 38 mol ATP

CO and HO are byprodus of respiration.

. Anaerobic Respiration

The break-down of glucose without oxygen to release energy used by cells. Less energy is produced( mol ATP).

Yeast

Yeast is a single-celled fungus which can respire anaerobically.

Glucose Ethanol + Carbon dioxode + energy

C6H12O6 2 C2H5OH + 2 CO2 + 2 mol ATP

. Calorimeters

Different foods contain different amoutns of energy. Fats contain about twice as much energy ascarbohydrates and proteins. The amount of energy in food can be measured using a calorimeter.

. The Lungs

The alveoli are adapted for efficient gas exchange:

Large surface area Increased by the alveoli. ,, alveoli m2.

Thin epithelium A Two cell layer separates the air in the alveoli om the blood in the capillaries only a short distance forgases to diffuse.

Moist Gases dissolve in solution before diffusion more efficent effusion. Prevents dehydration ofcells.


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Blood supply A good blood supply to and om the lungs by a capillary network keeps concenationgradients different by remong oxygenated blood om the lungs and bringing deoxygenatedblood to the lungs.

Increase in Breathing Rate

ncreased respiration causes an increase in the produion of CO. CO dissolves in water to formcarbonic acid.

CO2 + H2O H2CO3 H+ + HCO3

H+ ions lower the pH of the blood, and are taken up by oxyhaemoglobin, which then releasesoxygen.

Increased CO is deteed by chemoreceptors located in the carotid arteries, aorta, and medulla in

the brain.Chemoreceptors send impulses to the medulla. The medulla then sends impulses to the intercostalmuscles and the diaphragm, causing them to cona more equently (increased ventilation).

Cigarette Smoke

There are three major chemicals in cigaree smoke:

Nicotine An addie drug

Higher heart rate

Higher blood rateTar Paralyses the cilia on ciliated cells

Makes goblet cells over-produce mucus

Too much mucus

Smokers cough to remove the mucus

This can damage the alveoli walls, which can lead to emphysema (surface area of alveolireduced, so less oxygen can be absorbed)

Is a carcinogen (benzene)

Carbon monoxide binds irreversably with haemoglobin, therefore the oxygen carrying capaci of

the blood is greatly reduced. Smokers have 10% of their haemoglobin bound to CO thisforms Carbaminohaemoglobin.

Other smoking-related diseases:

Chronic bronchitis Smoke irritates the bronchi and bronchioles, damages the mucus membranes,and narrows the tubes. It reduces the cilia aion, so mucus cannot be removed, which leads tobaerial infeions. It is more difficult for O to diffuse into the blood.


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Excretion & Homeostasis

. Excretion

Excretion is the removal om the body of waste produs of metabolism (which may be toc) andsubstances which are in excess of requirements, e.g. CO and urea. CO is removed a the lungs.Urea is removed a the kidneys.

Rhenal artery Brings oxygenated blood full of urea to the kidneys.

Rhenal vein Takes deoxygenated blood which is ee om urea back towards the heart a the VenaCava.

Kidney Removes unwanted (and excess) substances om the blood, turns them into urine, andpasses the urine on to the bladder. It does this by filtering the blood. cm3 of blood is

filtered by the kidneys every minute.

Ureter Tubes which conne the kidneys to the bladder.

Bladder A muscular bag which can store urine. Can store up to about cm3 before the need tourinate (miuration) becomes compelling.

Sphincter Muscle which, when it conas, urine is prevented om leang the body, and when itrelaxes, urine can leave the body.

Urethra Tube which carries urien om body.

. Homeostasis

Homeostasis is the maintenance of a constant internal enronment. Examples:

Body temperature

Blood pH

Blood pressure

Blood glucose concenation

Blood water concenation

The mechanism by which homeostasis is maintained is by using negate feedback systems, whichmaintain stabili in the body.


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..NORM

.Body detes change and a correemechanism is put in place.

.NORM

.Body detes change and a correemechanism is put in place.

.Rise aboveNorm

. DecreasebelowNorm

.Return toNorm

.Return toNorm

. (i.e. a change)

.deteed by a

.co-ordinated by a -

.a change occurs in an

.which causes a

Sweating water evaporates, takes heat om the surface of the skin

Vasodilation causes more blood to avel to capillaries near skin surface

heat is radiated away om the body

skin appears flushed, because there is more blood flowing through the surface capillaries

Raised hairs aps air (which insulates) next to skin surface

Vasoconstriction reduces blood flow to surface capillaries

skin is pale, because there is hardly any blood flowing through surface capillaries


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. The Pancreas

The pancreas is both an gland and an gland.

Exocrine gland a gland that secretes externally through a du the pancreas secretes pancreaticjuice, produced in Acinar cells, into the pancreatic du.

Endocrine gland a gland that secretes hormones direly into the bloodstream the pancreassecretes the hormones insulin and glucagon, om the Islets of Langerhans, into the bloodstream.

Reproduction

. Asexual Reproduction

One parent

Offspring is genetically indentical

Does not involve gametes

New diploid cells are produced direly by mitosis (by other diploid cells)

Bacteria

Baeria reproduce by binary fission.

.Funghi


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antibodies

DNA

bacterium

body cell

nucleus

lymphocyteantibodies can

bind to t he

bacterial

antigens, and

des tr oy the

bacterium

antibodies do

not bind to body

cell ant igens,

and body cell is

not dest royed

Figure : A lymphocyte indentiing a baerium.

.

..nucleus

.cell membrane

.cytoplasm

.cell wallFigure : A root hair cell

..stoma

.leaf underside .boundary layer(water vapour)Figure : Water vapour build-up around a stoma.


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crucible

substrate

thermometer

water

oxygen

Figure : A simple calorimeter used to measure the energy value of a respiratory substrate.

Trachea

Cardiac notch

Bronchioles

Tertiary bronchi

Secondary bronchi

Primary bronchi

Larynx

Source: http://en.wikipedia.org/wiki/File:Diagrama_de_los_pulmones.svg (GNU FDL)

Figure : The lungs.


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Connective tissue

Alveolar sacs

Alveolar duct

Mucous gland

Mucosal lining

Pulmonary vein

Pulmonary arteryAtrium

Alveoli

Capillary beds

Source: http://commons.wikimedia.org/wiki/File:Alveolus_diagram.svg (Public Domain)

Figure : Some alveoli.

Inhalation Exhalation

Source: http://commons.wikimedia.org/wiki/File:Expiration_diagram.svg (Public Domain)

Figure : The aion of breathing.


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ci l iated cel l

columnar

epithelial

cells

goblet

cell

basement

membrane

cil ia beatingmucus released from

goblet cell

Figure : Part of the lining of the respiratory passages.


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bladder

ur eter

kidney

rhenal

arteryrhenal

vein

sphincte

urethr

adrenal glands(s ecr et e adrenalin)

Figure : The excretory system.


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1. Protein is taken

to alimentary canal.

2. Protein is digest ed

to amino acids.

3. Amino acids ar e

absorbed into blood,

and taken to liver in

hepatic port al vein.

4. Amino acids t hat ar e

needed are r eleased into

circulation.

5 . Amino acids which

are not needed are

deaminated to ammonia

or a c arbohydrate .

6. Ammonia is

convert ed to urea.

7. Urea is car ried to

kidney, where it is

filte re d from the blood.

Figure : Urea produion.

C COH

OR

H

NH

H

Figure : The Suure of an amino acid. R can stand for anything. The NH part of themolecule (ammonia) is toc, and is converted into urea. Deamination is the removal of the niogen-containing part of the amino acid.


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.

..Bloodvesselbringingbloodtothe

glomerulusiswiderthantheonetakingit

away.

Thiscausesapressureto

buildupin

theglomerulus.Morewatercanbe

absorbedundertheinfluenceofADHa.

..Fluidcontainingsmallmolecule

se.g.

urea,salts,glucoseisfilteredoutofthe

bloodintoBowmanscapsule

(ula-filation).

..FilatemovesalongtheRhenalTubule.

Usefulsubstancesarereabsorbedbackinto

theblood,e.g.glucose,somesalts,and

somewater(seleereabsorption)forthis

purpose.

Thisrequiresaeansport,

whichinturnrequiresATP.Thecells

liningtheRhenaltubecontainmany

mitochondriaforthispurpose.

..SaltissuessurroundingtheLoopof

Henlemeansthatwaterdiffusesoutofthe

Lo

opofHenleintothetissue.

..Fluidcontainingwater,saltsand

ureacontinuesalongtheRhenaltube.

..Cleanbloodpassesoutofthekidne

yathe

Rhenalvein.

..Urineetsthekidneyatheureter.

.Loopof

Henle

.Rhenal

tubule

Figure:Howurineisproducedtherearetwoprocesses:ula-filation

,andseleereabsorption.

aADH

isahormone.


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Source: Grays Anatomy (Public Domain)

Figure : An indidual glomerulus.


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.

. Air ap and airdeteor

.Clean blood

.Venous pressure monitor

. Removed bloodfor cleaning

.Arterial pressuremonitor

.Blood pump

. Heparin pump (toprevent cloing)

. Dialyser inflowpressure monitor

.Used dialysate

.Fresh dialysate.Dialyser .Patient

Source: http://commons.wikimedia.org/wiki/File:Hemodialysis-en.svg (GNU FDL and CC-BY-SA-ALL)

Figure : Kidney failure if one or both kidneys fail then dialysis is used or a ansplant performedto keep urea and solute concenation in the blood constant.


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Diseased

kidneys

ArteryVein

Transplanted

kidney

Transplanted

ureter

Bladder

Figure : Kidney ansplant may be necessary as Rhenal dialysis is inconvenient for the patient andcostly.


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.

.enronmental

temperature

. skintemperature

.skinwarmreceptors

.skincoldreceptors

.cerebalcortex

.

anteriorhypothalamus

.sweating

.skinarteriolesdilate

metabolicrate

decreases

.hairsonbodylie

flat

.posteriorhypothalamus

.shering

.skinarterioles

constri

.hairraised

.adrenaline

.meta

bolicrate

increases

thyrone

. bloodtemperature

.

.

.negativefeedback

.negativefeedback

.inhibition

.inhibition

Figure:Asummaryofhowbodyandbloodtemperaturearemaintained.

Biology Igcse Notes

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