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Biology Unit 2Biology Unit 2AQA Additional ScienceAQA Additional Science

W RichardsThe Weald School

02/03/15B2.1 Cells and Cell TransportB2.1 Cells and Cell Transport

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4)1)

5)

3)

A Typical Animal CellA Typical Animal Cell

Ribosomes – protein synthesis happens here

Mitochondria - energy is released here during respiration Cell Membrane –

controls what comes in and out

Cytoplasm - this is where the reactions happen and these are controlled by enzymes

2) Nucleus – controls the cell’s activities

02/03/15A Typical Plant Cell:A Typical Plant Cell:Cell wall – made of cellulose which strengthens the cell

Cell membrane – controls what comes in and out

Nucleus – controls what the cell does and stores information

Large vacuole – contains sap and helps support the cell Cytoplasm –

Chemical reactions happen here

Chloroplasts (containing chlorophyll) – this is needed for photosynthesis

02/03/15Bacteria and YeastBacteria and YeastBacteria and yeast are two examples of single-celled organisms:

Bacteria – containing cytoplasm and a membrane surrounded by a cell wall. The genes are NOT in a distinct nucleus.

Yeast – contain the usual cytoplasm, nucleus and membrane surrounded by a cell wall.

02/03/15More specialised animal cellsMore specialised animal cellsRed Blood Cell

Carries oxygen around the body

No nucleus and large surface area

I.D:Function:

Features:

White blood cell

Egg cell (ovum)

Ciliated epithelial cell

Nerve cell (neurone)

02/03/15DiffusionDiffusionDiffusion is when something travels from an area of high concentration to an area of low concentration. For example, consider the scent from a hamburger…

The “scent particles” from this hamburger are in high

concentration here:

Eventually they will “diffuse” out into this area

of low concentration:

Oxygen passes into cells by diffusion

02/03/15Diffusion SummaryDiffusion SummaryDiffusion is when particles spread from an area of high concentration to an area of ___ concentration. The particles move along a “concentration _____” and this process takes no _____ (it’s a “passive” process”). Diffusion can be accelerated by increasing the _______ of the particles, which makes them move _______.

Words – faster, low, gradient, temperature, energy

02/03/15B2.2 Tissues, Organs and OrgansB2.2 Tissues, Organs and Organs

02/03/15Cell specialisationCell specialisation

White blood cell

Egg cell (ovum)

Ciliated epithelial cell

Nerve cell (neurone)

During the development of a multi-celled organism cells differentiate to form specialised cells:

02/03/15Cells, tissues, organs and systemsCells, tissues, organs and systemsBasically, all living things are made up of cells…

A group of CELLS makes up a TISSUE

A group of TISSUES makes up an ORGAN

A group of ORGANS makes up a SYSTEM

A group of SYSTEMS make up an ORGANISM

02/03/15Another exampleAnother exampleHere’s another example in humans:

Muscle cells

Muscle tissue

Organ

System

Organism

02/03/15An example organ: The StomachAn example organ: The StomachConsider one of the body’s most important organs – the stomach:

The stomach contains many different types of tissue, including:

1) Muscular tissue, to “churn up” the contents

2) Glandular tissue, to produce digestive juices

3) Epithelial tissue, to cover the outside of the stomach

02/03/15An example system: The Digestive SystemAn example system: The Digestive SystemThe whole point of digestion is to break down our food so that we can get the bits we need from it. Basically, here’s how it works:

1) Glands such as the salivary gland and the pancreas produce digestive juices

2) Digestion occurs in the stomach and small intestine

3) Bile is produced by the liver and helps break down fats

4) Food is absorbed in the small intestine

5) Water is absorbed in the large intestine, leaving behind the faeces

02/03/15Examples of Plant TissueExamples of Plant Tissue1) Epidermal tissue, which covers the plant

2) Mesophyll, where photosynthesis occurs

3) Xylem and phloem, which are used to transport substances around the plant

02/03/15B2.3 PhotosynthesisB2.3 Photosynthesis

02/03/15PhotosynthesisPhotosynthesisBasically, photosynthesis is the process through which a plant makes its own food using carbon dioxide and water:

That’s a nice plant. I’m going to put it in the sun and give it lots of water

and air…

CO2

H2O

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Travels up from the roots

WATER

CARBON DIOXIDEEnters the leaf through small holes on the underneath

SUNLIGHTGives the plant energy

CHLOROPHYLLThe green stuff where the chemical reactions happen

Photosynthesis – the 4 things you needPhotosynthesis – the 4 things you need

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Carbon dioxide + _____ glucose + _____

6CO2 + 6H20 C6H12O6 + 6O2

Sunlight

Chlorophyll

Sunlight

Chlorophyll

The GLUCOSE produced by photosynthesis is used by the plant for _______ (through ____________). It is stored in the plant as ___________.

Words – respiration, starch, water, oxygen, energy

Photosynthesis equationsPhotosynthesis equations

02/03/15Limiting PhotosynthesisLimiting Photosynthesis

1. Temperature – the best temperature is about 300C – anything above 400C will slow photosynthesis right down

2. CO2 – if there is more carbon dioxide photosynthesis will happen quicker

3. Light – if there is more light photosynthesis happens faster

What factors could limit the rate of photosynthesis?

02/03/15Drawing graphs of these factorsDrawing graphs of these factors1. Temperature

Photosynthesis is controlled by enzymes – these are destroyed at temperatures above 400C

2. Carbon dioxide

3. LightPhotosynthesis increases at first but is then limited by a lack of increase in temp or CO2

Photosynthesis increases at first but is then limited by a lack of increase in temp or light

02/03/15Encouraging PhotosynthesisEncouraging PhotosynthesisUsing knowledge of limiting factors, explain how plant growth is encouraged in a greenhouse:

02/03/15What is the glucose used for?What is the glucose used for?1) Glucose (sugar) can be used to make long chains of insoluble starch…

Glucose molecules

Starch molecule

2) Glucose can be used to make cellulose for cell walls…

3) Glucose can be combined with nitrates to make proteins (for growth)…

4) Glucose can be converted into lipids (fats or oils) to store in seeds…

Glucose molecules

Glucose molecules

Glucose molecules

Cellulose

Proteins

Lipid structure

02/03/152 common nutrients…2 common nutrients…

Nitrates: Used to make proteins Lack of it leads to stunted growth

Magnesium: Used to make chlorophyll Lack of it leads to yellow leaves

02/03/15B2.4 Organisms and their EnvironmentB2.4 Organisms and their Environment

02/03/15Factors affecting organismsFactors affecting organismsVarious factors can affect the development of organisms:

Availability of carbon dioxide

and oxygen

Amount of water

Temperature

Availability of nutrients

Amount of light

Factors affecting

organisms

02/03/15Taking samples of an ecosystemTaking samples of an ecosystemUsing different “sampling techniques” we can measure changes

in an ecosystem. The two main measurements are:

1) The physical conditions of a habitat (temperature etc)

2) The populations of different species in that habitat

Some common ways of measuring…

Measuring temp, pH etc

Taking animal samples

Help!

Taking samples using quadrats

02/03/15B2.5 ProteinsB2.5 Proteins

02/03/15Introduction to EnzymesIntroduction to EnzymesEnzymes are biological catalysts. They help the reactions

that occur in our bodies by controlling the rate of reaction.

An enzyme is basically a protein molecule made up of long chains of amino acids. These molecules are then “folded” to create a certain shape. Proteins are used in hormones, antibodies and muscle tissue.

The enzyme’s shape helps another molecule “fit” into it:

This shape can be destroyed by high temperatures or the wrong pH:

Enzyme Substrate

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Enzymes are denatured

beyond 40OC

EnzymesEnzymesEnzymes work best in certain conditions:

Enzyme activity

Temp pH pH400C

Could be protease (found in the stomach)

Could be amylase (found in the intestine)

Enzymes are used in industry to bring about reactions at normal temperatures and pressures that would otherwise be expensive. However, most enzymes are denatured at high temperatures and can be costly to produce.

02/03/15Enzymes in digestionEnzymes in digestionEnzymes can be produced by the body to help _______. When they come into contact and react with food they break it down into ______ pieces which can then pass into the ______:

Amylase (produced in the mouth, pancreas and small intestine) breaks _______ (a carbohydrate) down into glucose:

Protease (produced in the stomach, pancreas and small intestine) breaks _______ down into amino acids:

Lipase (produced in the pancreas and small intestine) breaks fats (_____) down into fatty acids and glycerol:

Words – blood, lipids, proteins, digestion, starch, smaller

Bloo

dstr

eam

02/03/15The digestive systemThe digestive systemThe whole point of digestion is to break down our food so that we can get the bits we need from it…

The main foods affected are CARBOHYDRATES – these are broken down into GLUCOSE.

Hydrochloric acid is produced in the stomach to kill bacteria. Digestion also depends on “enzymes”...

02/03/15Bile and The LiverBile and The LiverBile is a chemical produced in the

liver and stored in the gall bladder. It has 2 functions:

1) It neutralises stomach acid and produces alkaline conditions for enzymes to work in

2) It emulsifies (“breaks down” fats:

Fat globules

Fat droplets

02/03/15Industrial uses of enzymesIndustrial uses of enzymes1) Enzymes are used in washing powders to help digest fats and proteins in food stains. Biological washing powders will only work on 400C or lower.

2) Enzymes are used in baby foods to “pre-digest” the proteins.

3) Enzymes are used to convert starch into sugar which can then be used in food.

4) Conversion of glucose into fructose using isomerase – glucose and fructose are “isomers” (they have the same chemical formula), but fructose is sweeter.

02/03/15B2.6 Aerobic and Anaerobic RespirationB2.6 Aerobic and Anaerobic Respiration

02/03/15Respiration IntroductionRespiration IntroductionI enjoy taking samples using quadrats. In order to do this, I need energy. Where

does this energy come from?

Our energy comes from a process called respiration, which basically involves turning food and oxygen into energy and this reaction is controlled by enzymes.

02/03/15(Aerobic) Respiration(Aerobic) Respiration

Words – breathing, energy, grow, respiration, food, mitochondria

All living organisms have to move, _____, reproduce etc. Each of these life processes needs ENERGY. ___________ is the process our bodies use to produce this energy:

Glucose + oxygen water + carbon dioxide + ENERGY

The glucose we need comes from ______ and the oxygen from _________. Water and carbon dioxide are breathed out. The MAIN product of this equation is _________. Respiration happens in _________ in cells.

02/03/15Uses for this energyUses for this energyAnimals and plants have many uses for the energy they generate from respiration:

1) To build up sugars in ______

2) To build up body _______

3) To maintain a constant body ___________ (warm-blooded mammals only)

4) To build up sugars, ________ and other nutrients in plants

5) To build up amino acids and ________

Words – nitrates, tissue, proteins, respiration, plants

02/03/15The Effect of Exercise The Effect of Exercise Heart rate/min

Breathing rate/min

100

75

50

25

225

175

125

75

5 mins 10 mins 15 mins 20 mins

Rest Exercise Recovery

During exercise the following things happen: heart rate increases, breathing increases and arteries supplying muscles dilate. These three things all help muscles to get the oxygen and glucose they need.

02/03/15Muscles and exerciseMuscles and exerciseWhen we exercise our muscles are supplied with more oxygen and glucose, increasing the rate of respiration.

Muscles store glucose as glycogen which can then be converted back into glucose during exercise.

02/03/15Anaerobic respirationAnaerobic respirationUnlike aerobic respiration, anaerobic respiration is when energy is provided WITHOUT needing _________:

This happens when the body can’t provide oxygen quick enough for __________ respiration to take place.

Anaerobic respiration produces energy much _______ than aerobic respiration but only produces 1/20th as much.

Lactic acid is also produced, and this can build up in muscles causing ______ and an oxygen ______.

This “debt” then needs to be “repaid” by deep breathing to ________ the lactic acid.

Words – debt, oxygen, fatigue, oxidise, aerobic, quicker

Glucose lactic acid + a bit of energy

02/03/15B2.7 Cell Division and InheritanceB2.7 Cell Division and Inheritance

02/03/15Modern GeneticsModern Genetics

Guten tag! My name is Gregor Mendel. I am the father of modern genetics

because of the work I did on pea plants in 1865…

Take two plants; one which is pure-bred for tallness and one pure-bred for shortness, and cross them:

X

Mendel’s experiment:

02/03/15Modern GeneticsModern Genetics

All the plants produced were tall.

Now cross two of these plants…

3 out of every 4 plants were tall, leading Mendel to hypothesise that “for every characteristic there must be two determiners”

02/03/15Modern GeneticsModern Genetics

Achtung! Unfortunately, nobody knew about chromosomes or genes when I

published my findings so no one believed me until after my death, when more

powerful microscopes were available.

02/03/15Cells, Genes and ChromosomesCells, Genes and Chromosomes

Chromosomes contain the genetic information (genes) and are normally found in pairs in the nucleus (humans have 23 pairs). They are replicated every time a cell divides by mitosis.

02/03/15Mitosis vs. MeiosisMitosis vs. MeiosisMitosis:

1. Used for growth and repair of cells

2. Produces a “clone”

3. Cells with identical number of chromosomes and genetic information are produced

Meiosis:

1. Used to produce gametes for sexual reproduction – occurs in the testes and ovaries

2. Each daughter cell has half the number of chromosomes of the parent

During meiosis copies of the genetic information are made and then the cell divides twice to form four daughter cells.

02/03/15Sexual ReproductionSexual Reproduction

The human egg and sperm cell (“GAMETES”) contain 23 chromosomes each and are created by meiosis.

When fertilisation happens the gametes fuse together to make a single cell called a ZYGOTE. The zygote has 46 chromosomes (23 pairs) and continues to grow through mitosis, producing cells with the same genes.

02/03/15Stem CellsStem CellsA while ago we considered examples of specialised cells:

White blood cell

Egg cell (ovum)

Ciliated epithelial cell

Nerve cell (neurone)

A “stem cell” is a cell that hasn’t yet become specialised and can be found in embryos or bone marrow. These cells can be used to treat certain conditions but the use of these cells is very controversial.

02/03/15Stem cell researchStem cell researchStem cells are cells that have not yet specialised:

Egg and sperm

Embryo

Cloned embryos

These stem cells have the potential to develop into any kind of cell. In grown adults they can be taken from bone marrow or they can come from embryos from unused IVF treatments. They can be used to treat conditions such as paralysis.

The ethical issue:

Should these embryos be treated as humans?

02/03/15Making decisionsMaking decisionsSome questions cannot be answered by science and need to be considered on ethical grounds.

Factors that might influence a decision:

• Beliefs/religion

• What does “the right thing” mean?

• “Playing God”

• Risks – acceptable or unacceptable?

• Social and economic contexts

02/03/15Boy or Girl?Boy or Girl?

X Y X

XX XYGirl Boy

“Allele”

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Father

Mother

Son

Daughter

Boy or Girl?Boy or Girl?

02/03/15Key wordsKey wordsGamete

Zygote

Allele

Dominant

Recessive

Homozygous

Heterozygous

•This allele determines the development of a characteristic

•This is formed when an egg is fertilised by a sperm

•This allele will determine a characteristic only if there are no dominant ones

•This word refers to a pair of chromosomes being made of two different alleles of a gene

•An egg or a sperm are called this

•This word refers to a pair of chromosomes being made of two of the same alleles of a gene

•An alternative form of a gene

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Some facts:

- DNA has a “double ______” structure

- This contains instructions on what a cell does, how the organism should work etc

- The instructions are in the form of a ______

- The code is made up from the four ____ that hold the strands together

- The bases represent the order in which _____ acids are assembled to make specific ________

- Everyone (apart from identical ______) has different DNA and people can be identified by “DNA finger printing”

How genes work - How genes work - DNADNA

Words – twins, helix, amino, code, bases, proteins

02/03/15Eye colourEye colourIn eye colour the brown eye allele is dominant, so we call it B, and the blue eye is recessive, so we call it b:

bbBB Bb

Homozygous brown-eyed

parent

Heterozygous brown-eyed

parent

Blue-eyed parent

What would the offspring have?

02/03/15Eye colourEye colourExample 1: A homozygous brown-eyed parent and a

blue-eyed parent:

Example 2: 2 heterozygous brown-eyed parents

BB bbX Bb BbXParents:

Gametes:

Offspring: Bb Bb BbBb BB Bb bbbB

B B bb B bB b

(FOIL)

All offspring have brown eyes 25% chance of blue eyes

02/03/15Eye colourEye colourExample 3: A heterozygous brown-eyed father and a blue-eyed mother:

Bb

Bb Bb bbbb

bb

b bB b

Equal (50%) chance of being either brown eyed or blue eyed.

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B bbb

Another methodAnother methodExample 3: A heterozygous brown-eyed father and a blue-eyed mother:

B bb Bb bbb Bb bb

Father

Mother

02/03/15Example questionsExample questions1) In mice, white fur is dominant. What type of offspring would you expect from a cross between a heterozygous individual and one with grey fur? Explain your answer with a genetic diagram.

2) A homozygous long-tailed cat is crossed with a homozygous short-tailed cat and produces a litter of 9 long-tailed kittens. Show the probable offspring which would be produced if two of these kittens were mated and describe the characteristics of the offspring (hint: work out the kitten’s genotype first).

02/03/15Inherited diseasesInherited diseases1) Cystic fibrosis – a disorder or cell membranes. It’s caused by recessive alleles so both parents need to be “carriers”:

2) Polydactyly – a condition where a person has extra fingers or toes. It’s caused by a dominant allele so can be passed on by a parent who already has it:

Embryos can be screened for alleles that cause these diseases before birth.

Ff FfX

Pp ppX

02/03/15Family Pedigree ChartsFamily Pedigree Charts02/03/15

Consider the following chart of the offspring and grandchildren between two polydactyly carriers:

Key:= male

= female

= P allele

= p allele

Q. Describe the genotype and the phenotype of each of the grandchildren. Also, which member of this

family has got polydactyly?

02/03/15B2.8 SpeciationB2.8 Speciation

02/03/15FossilsFossilsFossils provide evidence of early life and could have been formed in many ways. Four examples:

This fossil of a bat was formed due to hard parts of the

animal not decaying

This bee and orchid pollen were preserved in amber – the amber lacked some of the

conditions needed for decay to happen

This fossil was formed by parts of its body being replaced by minerals

Fossilised footprints

02/03/15Fossil recordsFossil recordsFossil records can provide a useful way of observing a species’ development:

The problem is, many early forms of life only had soft bodies and the few remaining traces of them have been destroyed by geological activity. This makes it difficult for scientists to know what happened in the distant past.

The “Stenheim skull”, found in

Germany in 1933

Oh no…

02/03/15Extinct SpeciesExtinct Species

Dodo

Sabre-toothed tigers and mammoths

02/03/15ExtinctionExtinction

Words to use: deforestation, competition, dinosaurs, human, environment

Extinction can happen due to an organism’s inability to adapt and die because of:

• Increased _______• New predators• Changes in the _________• New diseases

Alternatively, a “mass extinction event” can happen, for example the extinction of the __________.

In modern days animals are in danger due to _____ activity, e.g. pollution, hunting, __________ etc…

Oh no…

02/03/15Geographic isolationGeographic isolationDifferent species can be formed by “geographic isolation”, for example, consider an African elephant:

1) Elephants are separated by a geographic feature e.g. a _________

2) Elephants on each side of the mountain have different ______ in their _____ pool

3) Some offspring have characteristics that help them survive

4) Their weaker _______ die out and the offspring are so genetically removed that they’re incapable of ________ with each other – they’re now different ________

Words – species, mutations, mountain, gene, ancestors, reproducing