YEAR 10

IGCSE BIOLOGY

REVISION GUIDE

DBGS

Prepared by William Green 2011

DIGESTION AND NUTRITION

Digestion is presented as a means of transforming complex food substances into smaller molecules prior to absorption into the body. The functions of the human digestive systems are examined, as well as the role of enzymes as catalysts. Digestion is the breaking down of large molecules of food into smaller ones, eventually going into the blood.

1. Mechanical Digestion 2. Chemical Digestion

Enzymes Salivary glands make amylase Glands in stomach (Gastric Glands) make Pepsin (Protease) Pancreas make amylase, lipase, trypsin (Protease)

Enzyme Functions Amylase breaks down starch into maltose Protease (pepsin, trypsin) breaks down protein into polypeptides Lipase breaks down fat into glycerol and free fatty acids

Test for starch: Iodine turns from brown to blackTest for glucose: heat substance in water bath with Benedict’s solution, will turn orange if glucose is present

How absorption is increased in small intestine Villi: folds, increase surface area Each villus: has many blood capillaries

Factors which affect enzyme activity pH, there is an optimum pH, above or below this results in denaturation Temperature, there is an optimum temperature.

o In body 37o C is optimum o Low temperature slows down enzymes o High temperature permanently denatures enzymes

What is an enzyme A protein which acts as a catalyst, which speeds up the rate of reaction.

When enzymes are used Washing up powder. Protease breaks down protein stains.

Function of large intestine absorb - water, vitamins, and minerals colon produces vitamin K

This section provides the opportunity for investigating how the human breathing system allows the exchange of fasces between alveoli and the blood capillaries. The effects of cigarette smoke on health are considered.

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GAS EXCHANGE

Structure of the Breathing System

Alveoli and Gaseous Exchange

There are millions of alveoli, therefore large surface area

surface lining is moist, so gasses can dissolve before diffusing

Thin membrane pulmonary artery brings deoxygenated blood pulmonary vein brings oxygenated blood diffusion of oxygen and carbon dioxide into and out of

the blood

How we clean the air we breath

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Lining the nose and lungs are goblet cells, which produce mucus dirt and germs get caught in the mucus and is flicked up back to the mouth by cilia.

Smoking and Lung Disease CO - reduces the oxygen carrying capacity of the blood Nicotine - is addictive, relaxes muscles, raises blood pressure, and increases fatty substances in the blood Smoking causes smokers cough - mucus gets caught in bronchioles cilia, and are too clogged up to flick mucus back up Bronchitis - bursts alveoli walls (emphysema) therefore a reduced area for oxygen and carbon dioxide to

diffuse. Cancer - carcinogens in tobacco cause cells to divide more than they should. This causes a tumour. Heart Disease - tendencies for blood to clot will increase, due to increased fat. Tar - clogs up cilia

Composition of air breathed in and outInhaled Exhaled

Oxygen  21% 16%

CO2 0.04% 4%

Nitrogen 79% 79%

Water Vapour Little Lots

Breathing In Intercostal muscles contract diaphragm moves down (contracts) Ribs move up and out Thorax volume increases, pressure decreases air drawn into lungs

Breathing Out Intercostal muscles relax diaphragm relaxes Ribs move down and in Thorax volume decreases, pressure increases air forced out of lungs

TRANSPORT SYSTEM

This section allows transport systems to be examined. The need for transport systems in large organisms is considered, together with the ways in which the major transport systems of plants and mammals function.

Red Blood Cells - Erythrocytes Carry oxygen around the body (haemoglobin) No nucleus (More oxygen carrying possible) Biconcave - maximum surface area Haemoglobin combines with oxygen - oxyhaemoglobin lack of haemoglobin - anaemic 5 million Red Blood Cells per mm3

White Blood Cells - Leukocytes Irregular shape 7000 per mm3 Phagocytes (engulf the bacteria)

o bacteria into vacuole o enzymes destroy it

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Lymphocytes o Produces antibodies which recognise antigen on bacteria membrane o disable bacteria o finally ingested by phagocytes o immunity

Platelets fragments of cells 250000 per mm3 they clump together to clot blood make chemical that converts fibrinogen into fibrin - strands across wound.

Plasma contains fibrinogen contains serum, water, salts, gasses, hormones, glucose and wastes It is made up of 90% water.

Substances Transported by the BloodSubstance From To

Oxygen Lungs Body Cells

Carbon Dioxide Body Cells Lungs

Urea Liver Kidney

Food (Glucose) Intestine Body Cells

Hormones Glands Target Organs

Heat Muscles/Liver Whole Body

Transport Systems - Veins, Arteries, Capillaries Arteries carry oxygenated blood away from the heart around the body Veins carry deoxygenated blood from the body to the heart and then to the lungs Capillaries link arteries to veins. They are the site of diffusion with tissue Veins have valves to prevent backflow of blood Veins have a thin wall Arteries have thick walls, this allows from stretching (pulse) Arteries have a narrow lumen, allowing for high pressure Coronary arteries are around the heart The heart has double circulation, meaning blood goes through the heart twice, once oxygenated, and once

deoxygenated. Cholesterol can cause blocking of the coronary arteries It can also cause blood pressure to increase.

Prepared by William Green 2011

RESPIRATION

Respiration – takes place in plants and animals

Aerobic Respiration with oxygen Glucose + oxygen -> Carbon dioxide + Water + Energy C6H12O6 + H2O -> CO2 + H20 + Energy

Anaerobic Respiration without oxygen Glucose -> Energy + Lactic Acid (Instead of CO2) Lactic Acid builds up in the muscles and makes them ache. Muscle cramps To get rid of lactic acid, aerobic respiration occurs Lactic acid + O2 -> CO2 + H20 + Energy Amount of oxygen required in the above is called oxygen debt

Differences Between Aerobic and Anaerobic RespirationAerobic Anaerobic

Required Oxygen No oxygen

No lactic acid Lactic Acid produced

Large amount of energy Less energy released

Water and Carbon Dioxide produced Lactic Acid and energy produced. (No CO2 and H20)

Uses of Energy produced making muscles work growth and repair of cells maintaining body temperature transport of substances in the blood never impulse plants use energy for photosynthesis

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CELLS AND LIVING ORGANISMS

This section looks at the cell as the basic unit from which most living organisms are constructed. The pats of a cell are identified and their functions considered. Differences between plant and animal cells performing different functions within a plant or animal are discussed. The particular role of the cell membrane in the uptake or loss of water is examined.

All living organisms are made up of cellsKnow the diagram of plant and animal cell, as well as labelling

Differences between plant and animal cells:PlantCell Wall

Animalno cell wall

Permanent vacuole temp. vacuole

chloroplast no chloroplast

starch grains glycogen granules

regular shape irregular shape

DefinitionsNucleus

controls chemical reactions contains information to make living organism tells cell what to do

Cytoplasm where chemical reactions take place

Cell Membrane controls what comes in and goes out of cell

Cell Wall made of cellulose gives cell strength and support

Vacuole contains salt and sugar solution, called cell sap supports cell

Chloroplast contains chlorophyll for photosynthesis

Mitochondria release energy by cellular respiration

A group of specialised cells working together are called tissue

Osmosis and DiffusionPrepared by William Green 2011

Diffusion is the movement of molecules from an area of high concentration to an area of low concentration., until equilibrium is reached.

Larger Molecules - slower rate of diffusion

Osmosis is the movement of water molecules from an area of high concentration (weak solution) to an area of low concentration (strong solution), though a partially permeable membrane, until equilibrium is reached.

when plant cell vacuoles swell up, cells become turgid when lacking water, the plant wilts, and the cells become flacid when lots of water leaves, cytoplasm comes away from cell wall, this is called plasmolysis

HOMEOSTASIS

Homeostasis is defined as the maintenance of constant internal conditions within organisms. The principle can be developed in a wide range of contexts, including the maintenance of balanced water levels in the blood, the regulation of body temperature in mammals, the regulation of blood glucose levels and the removal of excretory products, such as urea.

Osmoregulation: the regulation of water levels by the kidney Low water level in blood

o water is reabsorbed from the kidney nephron into the blood concentrated urine produced

high water levels in the blood o less water is reabsorbed from filtrate in the kidney nephron

dilute urine produced

Excretion: is the removal of waste products of metabolic reactions made inside the body cells

The kidney

Purpose1. removal of nitrogenous waste (urea) 2. production of urine 3. osmoregulation

Removal of Urea urea is made in liver amino acids -> ammonia -> urea -> blood transports it to the kidney

Production of UrineKidney has filtration units called nephrons (they clean the blood)

Types1. Ultrafiltration: small molecules are filtered through the nephrons, large

molecules, such as red blood cells and proteins are not filtered. 2. Selective Reabsorption: useful molecules are returned to the blood. The rest is

sent to the bladder as urine.

Humans are endothermic, warm blooded. Have body temperature of 36.7oC.

Homeostasis: the maintenance if internal conditions within an organism1. balance of water levels (osmoregulation)

Prepared by William Green 2011

2. regulation of body temperature 3. regulation of blood glucose level 4. removal of excretory products

Regulation of body temperature Sweating - sweat glands - lets out a solution of urea, salt and water Vasodilation & Vasoconstriction

o Hot Weather - Vasodilation capillaries close the skin dilate increased blood flow through skin heat loss by radiation skin fells warmer and looks redder

o Cold Weather - Vasoconstriction capillaries close to skin constrict reduced blood supply to the skin less heat lost through skin skin feels cold and looks pale

Regulation of Glucose levels Carbohydrate (stimulus): Pancreas (receptor) -> stimulated and secretes hormone insulin -> insulin decreases

glucose levels to normal Insulin causes body cells to absorb more glucose and change it into glycogen

o Diabetes: when pancreas doesn’t create insulin. Diabetics take insulin shots. It is not taken orally because it is a protein and would be digested by protease

All organisms respond to changes in their environment and this section explores some of the ways in which they do this. The human eye is studied as an example of a receptor organ.

COORDINATION

Stimuli: Changes in external or internal environment which cause a response Receptor: Cells in the body which detect stimuliEffector: Part of the body which responds to stimuli

Central Nervous System1. Brain 2. Spinal Chord

Nerves: a bundle of nerve cells. A nerve cell is called a neurone.1. Sensory Neurone: Carries impulses from the receptor to the central nervous system 2. Motor Neurone: Carries impulses from teh central nervous system to the effectors 3. Relay neurone: connects the sensory neurone to the motor neurone.

Prepared by William Green 2011

Motor Neurone

Myelin Sheath: Is fatty and insulates electricity inside the axon. Dendrites: Receive nerve impulses from sensory cells.

Reflex Action, Involuntary/Voluntary Reflex arc is the path taken by an impulse in a reflect arc Stimulus->Receptor->Sensory neurone->Relay neurone->Motor Neurone-> Effector->Response

Spinal Chord (Reflex arc only concerned with stimulus from the skin) Stimulus (sharp object) -> Sensory neurone (through dorsal route in white matter) -> (synapse in grey matter)

-> relay neurone -> (synapse) -> motor neurone (in white matter) -> muscle effector (move hand)

The EyeKnow the structure of the eye.

How we see Light rays from objects are refracted by the cornea and focussed by the lens. This forms an upside down

image on the retina. This upside down image is corrected by our brain so we see the correct way up.

Focussing on Distant objects1. ciliary muscles relax 2. suspensory ligaments become tight 3. lens get pulled thin and flat. (less convex) 4. It is the first of the above images

Focussing on near Objects1. ciliary muscles contract 2. suspensory ligaments relax 3. lens becomes fatter and rounder (more convex) 4. second of above images

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Rods and Cones: Contain light sensitive pigments which are bleached in light and generate an impulse

Rods Cones

120 million present 6 million present - mainly on fovea

sensitive to low light concentrations sensitive to bright light concentrations

black and white image colour image

fuzzy image sharp and clear image

PHOTOSYNTHESIS

This section examines the physiology of photosynthesis and how it related to agriculture and food production. The value of photosynthesis as an oxygen producing process is examined and is related to the maintenance of the composition of the atmosphere.Photosynthesis is a chemical reaction in plants to make food. It only occurs in the presence of light.

Word Equation

Carbon Dioxide + Water  glucose + oxygen

Symbol Equation CO2 + H20 --> C6H12O6 + O2

Requirements for Photosynthesis Light Energy CO2 H20

Rate of Photosynthesis - can be measured by how much O2 is given off.

Limiting Factors - you need all three for photosynthesis to occur Light - Light increases, rate of photosynthesis increases up to a certain point CO2 - CO2 increases, rate of photosynthesis increases up to a certain point Temperature - must not get too hot or too cold

Overcoming Limiting Factors Light - artificial light, during night, especially red or blue, grow in unshaded areas CO2 - Have a canister of CO2 in greenhouse Temperature - find a warmer place. Use a greenhouse

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The Leaf

1. CO2 enters through the stomata 2. Spongy cells have a space for exchange of gasses 3. Chloroplasts in palisade cells, on the upper surface of leaf, most light on that part 4. Xylem - Carries water from roots to leaf. Phloem carries glucose from leaves to rest of the plant.

Is starch produced by photosynthesis? Put leaf in boiling water for 15 seconds. This kills it, makes it soft, makes cell walls permeable Put leaf in alcohol in test tube. Put the test tube in hot water bath. This decolourises it. Remove and wash the leaf Put iodine of the leaf If starch is present, the leaf turns blue black.

Nitrogen - Nitrogen as nitrates is absorbed from the soil to make protein.

You will also need to know tests for whether a plant needs light, does it need CO2 , and is O2  produced.The first two can be done with putting them without the variable, and then testing for starch.

TRANSPORT IN PLANTS

Water and minerals are absorbed by the root hairs and then into the xylem

Xylem and PhloemXylem transports water from root hairs to leavesPhloem transports glucose from leaves to the rest of the plant

Transpiration- it is the movement of water from root hairs to leaves where it evaporated and is released through the stomata

The evaporation causes suction due to the difference in pressure, and pulls water up through the leaves. This continuous cycle is known as a transpiration stream.

Functions of transpiration Cools plant Brings water and minerals to the plant

Prepared by William Green 2011

 Differences between the Xylem and PhloemXylem Phloem

Dead tissue make it up living tissue

vessels lined with lignin vessels lined with cellulose

Transports Water Transports glucose Environmental Factors Affecting Transpiration

Light o opens the stomata, therefore more evaporation

temperature o on a hot day evaporation occurs more rapidly

Air Movement o Wind removed water vapour around the leaf

Humidity o Low humidity, therefore higher concentration of water vapour in leaf the air. (diffusion high)

Potometer - measures water uptake by rootsThis section introduces respiration as a process for transferring energy from food (e.g. glucose) to the cells of an organism. Oxygen is normally required for respiration and carbon dioxide is produced as a waste product.

REPRODUCTION IN PLANTS

No individual organism is immortal; reproduction avoids extinction. Most organisms reproduce sexually, many asexually as well

Asexual methods of reproduction- Binary fission, bacteria- Spores, fungi- Budding, yeast- Identical twinning, a single zygote may develop into two babies- Vegetative propagation, outgrowths of new plantlets

Types of vegetative propagation- Runners, strawberry- Rhizomes, raspberry- Stem tubers, potato- Bulbs, daffodil

Plants can also be asexually reproduced artificially. This allows for maintaining good varieties of house-plants, and some crops, rapidly multiply new varieties, selective breeding, maintain seedless crops such as oranges and grapes.

1. Cuttings are lengths of stems or leaves2. Grafting is the insertion of a shoot or bud from one plant to a related plant3. Tissue culture is a fast way of producing plants genetically identical. Small amounts of partent plant tissue

are grown on agar into plantlets

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A flower is the organ of sexual reproduction in flowering plants

Peduncle: The stalk of a flower. Receptacle: The part of a flower stalk where the parts of the flower are attached. Sepal: The outer parts of the flower (often green and leaf-like) that enclose a developing bud. Petal: The parts of a flower that are often conspicuously coloured. Stamen: The pollen producing part of a flower, usually with a slender filament supporting the anther. Anther: The part of the stamen where pollen is produced. Pistil: The ovule producing part of a flower. The ovary often supports a long style, topped by a stigma. The mature ovary is a fruit, and the mature ovule is a seed. Stigma: The part of the pistil where pollen germinates. Ovary: The enlarged basal portion of the pistil where ovules are produced

There are two main stages in sexual reproduction

1. Pollination: transfer of pollen from stamens to stigmas2. Fertilization: fusion of male gamete with female gamete inside the ovule. This results from the growth

of pollen tubes from the pollen on the stigmas to the ovules

Pollination of a flower can be either self pollination or cross pollination:

Self pollination is the transfer of pollen from the stamen to any stigma on the same plant.Cross pollination is the transfer of pollen from the stamen of one plant to the stigma of a different plant

Comparisons of flowers adapted for wind or insect pollination

Position of stamen Insect pollinated Wind pollinated Position of stigma Enclosed with flower Exposed Type of stigma Sticky Feathery Size of petals Large Small Colour of petals Brightly coloured Not brightly coloured, usually green Nectaries Present as a reward Absent Pollen grains Larger, sticky grains Smaller, smooth inflated grains

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Plant Fertilisation

Fruit and Seed dispersal

Fruits serve two main functions.1. Protection of the seed2. Dispersal of the seed

Seeds are designed are dispersed either by wind, water, animal or eaten

PLANTS RESPONSE TO THE ENVIRONMENT

Phototrophic response: growth in response to directional stimulus, lightTop of the plant shoot is the receptor of light for growthAuxin is a chemical growth regulating substance, which is produced at the tip of shoots when exposed to light.

Auxin diffuses down the shoot, on the side which is shaded o it causes cells in zone of cell elongation to grow faster o therefore one side is long/bigger than the other, so the plant bends towards the light.

Tropisms are the growth movement of a plant toward or away from a stimulus. Usually controlled by hormones

Light PhototropicGravity Geotropic

Phototropisms uses the hormone auxin at the shoot tips.

Geotropism uses auxin in the root at the root tips

Also go to BBC KS4 Bitesize, www.biology-resources.com/biology-questions.html or www.biotopics.co.uk/newgcse/intro.html

Prepared by William Green 2011