Biology B3 - Edexcel

GCSE Extension Science Edexcel - Biology B3

From the CGP revision guide and school notes.

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  • Created by: Mia
  • Created on: 11-05-12 20:57

Production of Yoghurt

1) Milk heated to 72C to kill off other microbes. Allow to cool.

2) Add bacteria Lactobacillus Bulgaricus in a fermenter at roughly 40C producing Lactose.

3) Lactase (enzyme produced by bacteria) anaerobically feeds on the lactose to produce Lactic Acid (fermentation).

4) The lactic acid denatures the Casein (milk protein) causing it to coagulate the milk.

5) Fruits and flavours added.

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Production of Soy Sauce

1) Soya Beans are soaked, boiled and mashed into a paste then mixed with roasted wheat.

2) A culture containing Aspergillus Oryzae is added.

3) Mixture is kept warm and aerated (for a few days).

4) Poured into a large tank and mixed with Salt Water. The liquid is left to ferment for 6 months.

5) Filtered, pasteurised and put into sterile bottles.

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Functional Foods

Functional foods = health benefits.

Plant Stanol Esters = chemicals that can lower blood cholesterol = reduce risk of heart disease.

Added to spreads and butter. Stanols occur naturally in plants, produced comercially by bacteria.

Prebiotics = Carbs called oligosaccharides - promote (food for) 'good bacteria' in the gut. 

Probiotics = bacteria for gut which help digestion.

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Microbial Products

Invertase turns sucrose (sugar) into glucose and fructose (sugar which is sweeter so less sugar needed = lower calories and cheaper). Produced by Saccharomyces Cerevisiae.

Chymosin. Cheese is made using rennet - from the lining of a calf's stomach containing chymosin which clots the milk.

To make veggie = genes for making chymosin were isolated and put into plasmaid which is inserted into yeast cells and grown on an industrial scale.

Vitamin C = dietary supplement and added to foods (bread) as a preservative. Acetobacter (bacterium) produces a chemical easily converted to Vitamin C (used commerically because cheaper and easier than extraction from fruit)

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Microbial Products

Citric Acid = flavouring + preservative to fizzy drinks. Found naturally in citrus fruits (fizzy drinks = no fresh fruit so added in afterwards). Commercially produced by Aspergillus Niger (fungus).

Monosodium Glutamate (MSG) = flavour enhancer for foods. Made from Glutamic Acid which is produced by Corynebacterium Glutamicum (bacteria).

CG secretes glutamic acid (amino acid) into the meduim in which they are grown.  The Glutamic Acid is then used to make monosodium glutamate (a sodium salt).

Carrageenan (produced from seaweed carrageen) = a gelling agent and emulsifier in ice cream, jellies etc...

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Unbalanced (too much or not enough of some nutrients) = health problems.

Protein Deficiency - Cause condition Kwashiorkor. Most common in developing countries.

Vitamin Deficiencies - Cause all sorts, e.g. scurvy = lack of vitamin C.

Mineral Deficiencies - Cause all sorts, e.g. anaemia = lack of iron - red blood cells can't carry enough oxygen around the body.

Obesity - too much for activity level or underactive thyroid gland. Increased risk of, diabetes, arthritis, high blood pressure, coronary heart disease and forms of cancer (breast cancer).

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Genetically Modifying Plants

  • To make herbicide-resistant plants - to remove weeds so no competition
  • To make disease/pest resistant plants
  • To increase nutritional value /shelf life / flavour/ texture of plants.
  • To modify crops so they can grow in a hostile environment
  • To modify so they contain medical benefits/vaccines


1) Cell with desired DNA (e.g. herbicide resistance). Desired DNA is cut out using Restriction Enzymes.

2) Plasmaid is cut open also using restriction enzymes = Sticky Ends.

3) The DNA is inserted into the Plasmaid. The sticky ends are bonded with DNA Ligase.

4) Add the plasmaid into the bacteria Agrobacterium Tumefaciens (it is able to transfer genetic data). The bacteria can infect the plant.

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Genetically Modifying Plants

Biotechnology/GM Plants could help malnutrition in developing countries by:

  • GM to be resistant to pests
  • GM to grow in hostile environments
  • GM to combat a certain deficiency. e.g. 'Golden Rice' to combat Vitamin A deficiency.

Disadvantages of GM crops:

  • Transplanted genes may be released into the environment ('superweeds').
  • May Reduce biodiversity (affects numbers of weeds, flowers and wildlife).
  • Safe? Worries of allergies (although none have been found).
  • In developing countries the problem is money not availabilty of food.
  • Still cannot be grown if there is poor soil.
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Asprin = a pain killer from the bark of a willow tree. The active ingredient is Salicin.

Taxol = an Anti-cancer drug from the bark of a Pacific Yew tree. The active ingredient is Paclitaxel.

Although, the tree is protected as it is slow growing and harvesting taxol kills the tree so have to find other ways to produce the drug.

Quinine = a Malaria Treatment drug from the bark of a Cinchona Tree. The active ingredient is Quinine.

Artemisinin = a Anti-malaria drug from the plant Artemesia Annua/Chinese Wormwood. The active ingredient is Artemisinin.

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Drug Development

Drug development is very expensive and can cost a lot of money due to the patent on it = very controversial.


  • Drug companies could charge less and still make a profit.
  • Making a profit from illness is unethical.
  • Drugs should be allowed to be copied and produced more cheaply.


  • The drug companies need to cover the costs of the expensive research that went into making the drug.
  • No reason to develop new treatments if cannot get a profit.
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The study of Genomes and their uses, some of which are:

  • Research could lead to discovery of specific genes which link to a disease and therefore could get an earlier diagnosis or prevention of a disease.
  • Can help understanding of how a specific gene causes a disease. This could result in a new treatment for the disease.
  • Could help to predict how specific genes can link to the person's response to a drug - tailor made drugs = less side effects.
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Reproductive Technology

In vitro fertilisation (IVF) is used to help infertile couples have children.

Need healthy sperm, eggs and uterus - any of them can be donated.

Against IVF:

  • Not natural.
  • Not all eggs from the woman are implanted and throwing them away is unethical (denying life etc...)
  • Increases chances of multiple pregnancies, e.g. twins, could be danger to mother's health or a financial burden.
  • What happens if surrogate mother does not want to give up the child.
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Screening Embryos

  • Screening is allowed for genetic disorders.
  • Screening is allowed for a 'tissue match'. A baby which would have the same genetics so could be used to help give tissue to a sick sibling. Spare part child?
  • Illegal to choose sex of baby unless there is a medical reason (e.g. a genetic disorder affecting one gender in the family).
  • Specific cells can be removed from an embryo before being implanted. Could, in theory, let parents choose characteristics of their baby. Slippery slope to designer babies.
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Stem Cells

Embryonic Stem Cells can differentiate into any sort of cell. Stem Cells are also found in adult's bone marrow but are not as versatile.

Stem Cells could cure many health problems:

  • Blood diseases (e.g. Sickle Cell Anaemia) can be treated by bone marrow transplants. New blood cells to replace the old ones.
  • Embryonic stem cells could be used to regrow faulty cells in sick people (e.g. muscle cells or nerve cells)

Parkinson's Disease - loss of a particular type of neurone in the brain that affects movement. New nerve cells could be grown with stem cells.

Controling the differentiation of the stem cells is done by changing the environment they are grown in but is very difficult and unreliable.

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Stem Cell Ethics

Against Embryonic Stem Cells:

  • Each one has potential human life and should not be destroyed as this would be killing it.
  • Research should not be done on them because once fertilised they can be considered alive.
  • Use other sources of stem cells, e.g. bone marrow.


  • Caring for the suffering is more important than 'potential life' which cannot survive on their own yet.
  • Embryos are usually unwanted from fertility clinics and would otherwise have been destroyed. 

Legal in the UK as long as strict guidelines are followed.

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Instinctive and Learned Behaviour

Instinctive Behaviour is inherited and the same within species . It is the right way to respond to a stimulus straight away without being shown. Often links to the survival of the animal.

E.g. Earthworms move away from light.

Learned Behaviour - Learnt from the animal's experiences and lets it respond to changing conditions.

E.g. Birds kept in isolation when young do not learn proper bird song.

Habituation = when there is a repeated stimulus, which is neither harmless nor beneficial, the animal quickly learns not to respond to it.

E.g. Crows learn that scarecrows are not harmful and ignore them.

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Classical Conditioning - animal learns passively to associate a 'neutral stimulus' with an important one. Response is automatic and reinforced by repition.

E.g. Pavlov's dogs. Associated the bell ringing with the food and eventually salivated at the sound of the bell instead of the food itself.

Operant Conditioning - animal learns acitvely using trial and error to associate an action with reward and punishment.

E.g. Skinner box. An option of buttons to press one of which to get food. After a while pigeons and rats learnt to only press the one which would bring them food.

We use conditioning to train animals e.g. dogs to sit with reward of food.

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Sound - language. e.g. bird's calls to declare territory, attract a mate or warn others about predators.

Chemical - Pheremones: externally released chemicals which other animals of the same species can pick up and respond to. e.g. to mark territory or alert others if they are under attack.

Physical - facial features or body language. Although, these are species specific e.g. when a money shows it's teeth.

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Feeding Behaviours

Herbivores spend a lot of time eating because plants are low in nutrients such as amino acids whereas carnivores spend a lot less time eating but must make sure their diet contains a lot of protein.

Live/hunt in packs because:

  • More chance of getting larger/more prey.
  • More intimidating.
  • Group defence against predators and defend catch.
  • Dilution - less chance of individual being eaten.
  • Confusion of predators by rapid direction changes.
  • Vigilance - many eyes and ears to see predators and prey.


  • Sharing food - hierarchy
  • Less stealth
  • Chance of being cast out - reproductive reasons.
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Reproductive Behaviours

  • Songs or calls
  • Pheremones
  • Fighting - display strength
  • Courtship displays (songs, dances, brightly coloured etc...)

Female chooses a mate which demonstrates the best survival skills (be fit/healthy) so that her young will inherit the skills and increase their chances of survival.

Some animals look after their young:

  • Protection - one parent stays with them or nests for protection.
  • Feeding
  • Teaching skills - e.g. how hunt. Imitating behaviour.

Looking after young increases their survival but can put the parent in danger. Do it because: less time pregnant which is more risky + they want to ensure the species survives.

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Human Evolution and Development

Humans are Great Apes along with:

  • Chimpanzees
  • Gorillas
  • Orang-utans (Pango)
  • Bonobos (Pan)

Humans evolved from hunter gathers roughly 11,000 years ago.

Closest living relative = Bonobos - 98% of DNA the same.

Great Apes and humans:

  • Live in complex socities
  • Alter their environment for their needs
  • Use tools
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Exploitation of Animals

  • Food - Meat
  • Labour - Originally used for farms
  • Clothing and domestic materials (e.g. leather/wool/fur)
  • Medicine - transplanting organs/antibodies for vaccines/drugs/testing stuff.
  • Entertainment - Racing, Zoos etc....
  • Companionship - Pets

Animal Rights:

  • Animal testing - put in pain or discomfort OR beneficial to humans?
  • Hunting - Put under great stress OR keeping amount under control?
  • Entertainment - Cruel as locked up OR treated nicely and help endangered species?
  • Farming - Mistreated in factories OR a necessity for humans?
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Iamgoingtofail Myexams


cheers babe xoxox

joe l 567


Really useful



great work!!

Ioana Cozma


Hey, have you made any physics notes? If yes could you please post them?

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