Edexcel GCSE Biology Extension Unit B3

Revision notes

HideShow resource information

Functional foods

·         Prebiotics- contain sugar called oligosaccharides- carbohydrate molecule3-10 simple sugar units (feed the good bacteria in our guts)

·         Probiotics- contain good bacteria  (produced when bacteria ferment milk)

·         Margarine- stanol ester (carbon compound = organic acid + alcohol comes from plant sterols fatty substances found in wheat and maize)     

·         Plant sterol- cholesterol drop by 10%

1 of 44

Production of Yoghurt

  • 1.      Milk heated to sterilise and get rid of unnecessary bacteria
  • 2.      Milk is stirred to mix ingredients
  • 3.      Milk Protein is added
  • 4.      Lactobacillus bacteria + milk (whilst warm)> ferment sugar lactose in milk> lactic acid         
  • 5.      Lactose> (Lactobacillus)> Lactic Acid
  • 6.      Lactic Acid- lowers pH milk- milk proteins coagulate
2 of 44

Production of Soy Sauce

  • Soya beans are cooked to kill all of the bacteria on their surface
  • Mixed with ground roasted wheat
  • Aspergillus mould is added to the mixture
  • Mixture spread out on warm shallow trays and supplied with air
  • Enzymes produced- Aspergillus mould catalyse breakdown of proteins + carbohydrates in mixture
  • Amino acid and sugar content of mixture increases
  • Brine (sodium chloride solution) added to mixture to give soy sauce salty taste and preservation
  • Yeasts and lactobacillus bacteria (able to tolerate high levels of sodium chloride and low levels of oxygen) added to brine mixture to stop activities of Aspergillus mould
  • Sugars in mixture fermented by yeasts and lactobacillus bacteria
  • Raw soy sauce drained from mixture, mixture is filtered and pasteurised to kill bacteria at 72 degrees 
3 of 44

More on microorganisms and food

  • Rennet- mixture two protein-digesting enzymes- cause milk form solid curds called raw cheese
  • Rennet= enzyme chymosin
  • Production of chymosin= genetically modified bacteria. Enzyme works like rennet but its activity is more predictable and it contains fewer impurities and is vegetarian friendly
  •  Cheese made is GM free because only the enzyme is made by GM Organisms
  •  Gelling agents- substances added to food to thicken it- Gelatine (made from animal bones
  • Gelatine- non-vegetarian, carrageen extract (reddish-purple seaweed carrageen)- alternative
  • Production of citric acid= Aspergillus Niger mould; citric acid- prevents breakdown vitamin C



4 of 44

More on microorganisms and food

  • Corynebacterium glutamicum bacterium produce amino acid glutamic acid
  • Neutralisation of acid makes sodium salt monosodium glutamate
  •  MSG enhances the food flavour
  • Bacterium Acetobacer produces vitamin Cfermentation
  • Yeast fungus Saccharomyces cerevisiae produce invertase (sucrase)
  • Invertase promotes breakdown of sugar sucrose into glucose and fructose
  •  Sucrose>(Invertase)>Glucose  + Fructose
  •  Invertase is used to convert solid insides of chocolate into liquid centre
  • Glucose isomerase enzyme converts glucose into fructose which is sweeter 
5 of 44

Eating well


·         Describe the importance of having a well-balanced diet.

·         The importance of having a balanced diet (a balanced diet is one that contains proportional amounts of the food groups to give the eater the daily amounts of nutrition they need) is because it makes you more likely to be healthy and be in better physical fitness.

·         Explain that obesity may lead to a number of health problems.

·         Obesity may lead to health problems as the constant abuse to your body could clog up major blood vessels such as your coronary artery which can lead to a heart attack, also it can lower the amount of oxygen in your blood which could go as far as giving you a stroke.

·         Body Mass Index (BMI)= Body Mass (kg)/(body height)^2 (m^2)

6 of 44

Feeding the world

·         Plant breeding- hybridisation crossing two different varieties with desirable resistant characteristics and crossing concentrates the desirable characteristics into new hybrid variety which is reproduced asexually

·         Genetic Engineering: identify, isolate, insert genes from genetic material of one cell to other

·         Microorganism growth for food in fermenter containers

·         Single-cell protein (SCP) produced by microorganisms and fast growing high protein vitamin mineral content. Microorganisms double their mass whereas plants and animals we eat may take weeks and months to grow to full size- major benefit.

·         Microorganisms multiply- using nutrients fermenter source energy materials source growth

·         Nutrient is replaced as it is used up. Fermenter run for months microbial mass is removed at regular intervals and processed into food

7 of 44

Genetically modified plants

·         Herbicides- a chemical used to kill weeds

·         Transfer herbicide resistant gene into crop plants using agrobacterium tumefaciens bacterium

·         Plant infected with agrobacterium produces cancerous growth tumour called crown gall

·         Herbicide resistance gene inserted into the Ti plasmid (tumour inducing small loop of DNA in the agrobacterium cell)

·         The Ti plasmid causes plant infected with agrobacterium to produce a crown gall.

·         The cells of the crown gall each contain a Ti plasmid with the herbicide resistance gene

·         Pieces of tissue cut from the crown gall are cultured and grow into plants

8 of 44

Producing herbicide-resistant plants using Agrobac

·         Restriction enzyme restriction endonuclease cuts out herbicide resistance gene

·         Ligase enzyme sticks gene into Ti plasmid of agrobacterium tumefaciens

·         Plasmid with resistance gene put back in agrobacterium tumefaciens

·         Bacterium infects plant

·         Plant produces a crown gall- its cells contain plasmid with resistance gene

·         Cells from gall grow in culture

·         Gall cells grow into herbicide resistant plant

9 of 44

Genetically modified plants

·         Bacterium Bacillus Thuringiensis kills leaf-eating caterpillars and larvae of mosquitoes/flies

·         Bacillus Thuringiensis produces toxin insecticidal crystal protein which attacks caterpillar’s gut

·         Crop plants have been genetically modified using the gene for ICP from Bacillus Thuringiensis with Agrobacterium as a vector

·         Gene controlling production ICP inserted into Ti Plasmid of agrobacterium, crop plants infected with genetically modified bacterium and pieces of tissue are cut from crown galls which develop and are cultured into plants

10 of 44

GM Crop Cons

·         Not natural and may affect health

·         Harm wildlife

·         Pollen from crops genetically modified to resist herbicides may transfer to wild plants, if they are weeds there is a danger of resistant weed development

11 of 44

GM Crops Pros

·         Easier for formers to control the weeds and insects that reduce the amount of food produced

·         Volume of herbicides and insecticides reduced

·         Reducing use of herbicides and insecticides reduces risks to wildlife and damage to environment 

12 of 44

Genetically engineered insulin

·         Human insulin gene in the section of human DNA is stuck to section of bacterial plasmid with ligase enzyme. The gene is cut out with and the plasmid cut open by restriction enzyme

·         Plasmid is put into bacterium

·         Bacteria with insulin gene grown in fermenter

·         Insulin is separated off and purified

·         Fermenter filled with solution all substances bacterial cells require to grow

·         Role of insulin: control level of sugar in the blood

13 of 44


·         DNA building blocks called nucleotides: adenine (A) thymine (T) guanine (G) and cytosine (C)

·         Group of 3bases controls the position of amino acids in the protein molecule

·         Genome is all of the DNA in each cell of an organism

·         Samples of cells taken from anonymous volunteers

·         Chromosomes of cells were broken up into pieces to get at their DNA

·         Pieces of DNA were made to provide enough material to work on

·         DNA was then placed inside machines called sequencers and probable order bases displayed on computer screen

14 of 44


·         Bioinformatics: find which genes codes for which proteins

·         Show in which cell a gene is active

·         Show when gene is active

·         Helps to make a molecular atlas of the cell

15 of 44

Genomics in medicine

·         Combining genomics with pharmacology- potential to make drug treatments for genetics

·         Salbutamol- treat people asthma act on muscles control opening closing of tubes take air into and out of lungs. One version is unresponsive to salbutamol; another form of asthma treatment is needed. This is the analyzing of genes responsible for different versions of muscles that people unresponsive to salbutamol can be identified.

·         Enzymes liver breakdown drugs. Variation in genes that code for enzymes means action in some people may be more than others.

·         Genomics could be used to find out how effective a patient’s liver enzymes actually are.

16 of 44

Personalised drug treatments will have the outcome

·         Better Medicines- target particular diseases, damage to healthy tissues is reduced

·         Safer Drugs-  less likelihood of adverse drug reactions

·         More accurate drug dosages- individual genomic profile how well body processes medicines

·         Better vaccines- new vaccines made from genetic material benefits without side effects

·         Traditional medicine refers to the treatment of ill health using plant-based medicines. 

17 of 44

Medicinal plants

·         Strychnos plants Amazon rainforest source curare substance relaxes muscles. Hunters rainforest tip blowpipe darts with curare before shooting birds- muscles which control breathing stop working animals suffocate and fall. Operations- doctors low dose curare relax muscles patient making easier to control breathing.

·         Plant substances produced fall into two groups:

·         Substances which affect nervous system (morphine, curare and cocaine)

·         Substances which control a variety of heart problems (e.g. digitoxin)

·         50% of all drugs fight disease cannot synthesized directly sourced from plants

·         Anti-cancer drugs (vinblastine vincristine) sourced from rosy periwinkle tropical rainforests

18 of 44


·         Aspirin: bark leaves willow tree ingredient salicin relieves pain reduce fever. Salicylic acid made from salicin (irritates stomach lining)

·         Aspirin: swelling joints and other tissues reduces, forms blood clots and reduces fever

19 of 44

Malaria and quinine

·         Malaria: single celled parasite Plasmodium- attack red blood cells, flu-like symptoms high fevers heavy sweating

·         Plasmodium carried by female Anopheles mosquitoes

·         Chewing bark of Cinchona tree useful treatment for malaria. Active ingredient= quinine- lowers body temperature and kills parasites in red blood cells.

·         World War II cut off quinine so chloroquine developed more effective easier to make, some strains of parasite resistant to the drug however. 

20 of 44


·         Artemisinin: Artemisia annua shrub: derivatives (artemether and artelinate): kill Plasmodium (parasite that causes Malaria) and prevents it from reproducing inside the mosquito vector.

·         Artemisinin: only active few hours in body- combination other anti-malarial drugs increase effectiveness and is used in place of malaria parasite developing resistance to chloroquine.

·         Genetically-engineered yeast cells produce substance like Artemisinin which easier converted into Artemisinin itself.

·         Artemisinin: use treatment cancer- damages cancerous cells and slows development of the vessels supplying blood to cancerous tissues.

21 of 44


·         Taxol: anti cancer drug from bark of yew tree- stops cells from dividing- paralyses spindle fibres. Semi-synthetic version of Taxol from twigs of yew tree called paclitaxel

22 of 44

Stem cell research

·         Stem cell research: egg cell divides into two mitosis, embryo develops- embryonic ball cells all the same and unspecialized- embryonic stem cells.

·         As cell division continues fetus develops and cells become different tissues organs of body- differentiation

·         Adult stem cells- bone marrow rise to blood cells replacing old cells with new ones.

·         Small numbers stem cells remain other body tissues as well. Injury disease damages a tissue then its stem cells divide and differentiate into new cells- stem cell therapy.

·         Stem cells source of new cells replace diseased damages tissues.

23 of 44

Parkinson's disease

·         Small cluster cells brain produce chemical neurotransmitter dopamine people with Parkinson’s disease not produce enough dopamine no muscle control.

·         US Scientists- 10-15 healthy stem cells brain tissue of person suffering with Parkinson’s.

·         Unspecialized cells grown in solution of life encouraged to differentiate into cell producing dopamine, divided by mitosis into millions of cells put back into the brain tissue of the patient. 

24 of 44

Girl or boy?

·         Girl or boy? Baby’s sex depends whether woman’s egg fertilized by a sperm carrying an X chromosome or Y chromosome.

·         IVF two or three fertilized eggs chosen transfer back into woman’s womb without harming embryo and test to see if it has genes cause disease

·         Duchenne muscular dystrophy fragile X and hemophilia occur boys. Male linked genetic disorders history then testing to find out sex of embryo can be useful 

25 of 44

Ethical issues

·         Ethical issues:

·         Healthy cells sick person cloned used repair person’s damaged tissues.

·         Person transplant make use brain dead clone for him source of tissues and organs for transplantation.

·         For some people thought using brain dead clone is morally wrong. Respect for human life should outweigh possible benefits.

·         Genetically modify cows produce hormones such as insulin in their milk 

26 of 44

Instinctive behaviour

·         Behaviour: responses of animals to what is going on around them

·         Instinctive: split-second behaviour which is automatic and not thought about

·         Instinctive responses are inherited from parents and reinforced by natural selection

·         Example: woodlice: intensity of light- lighter more active woodlice

·         Example: herring gull chick after hatch pecks at parent’s beak for food brings half digested food into mouth which the chick eats- instinctive behaviour. Red spot on beak is a signal to the chick.

27 of 44

Learned behaviour conditioning

·         Behaviour which changes in the light of experience is learned.

·         Ivan Pavlov- production of saliva dog’s mouth. Food (primary stimulus) placed dog’s mouth flow of saliva increased and also when his hand (a secondary stimulus) smelt - Pavlov conditioned dogs produce saliva in response to ringing of a bell- classical conditioning.

·         Trial and error learning another type of conditioning. B.F. Skinner. Lever in a Skinner box key to animal’s learning- pressing level = food and animal quickly associate the pressing with reward

28 of 44


·         Imprint- form of learning in which the child becomes attached to the parent.

·         Attachment occurs during a sensitive period early on in an animal’s life.

·         Getting used to a stimulus which you avoid to begin with is called habituation.

·         Communication: behaviour that influences actions of other individuals

·         Making sounds giving signals releasing chemicals called pheromones ways to communicate

·         Example: Honeybees: queen dominates the colony, sterile workers rest of community and males are the drones.

29 of 44


·         Example: Bees: produce honey from nectar collected from flowers and pollinate flowers to produce beeswax- usually visit same type of flower at the same time of day, sense of direction, check bees returning to hive by touching them with their antennae feelers: communication example.

·         Example: Bees: search for flowers using position of sun in sky. When they return to the hive, the bees tell the others where the flowers are by dancing either at the hive entrance or on the honeycombs inside- type of direction and angle of movements tell other bees the distance direction they need to fly. 

30 of 44

Bee dance

·         Example: Honeybees: pheromones to communicate- queen produce pheromone queen substance passes to workers when they touch her with their mouth parts. Queen substance:

·         Tells all other bees that hive queen is present good health

·         Workers remain sterile

·         Prevent rival queens developing from eggs the queen lays

·         Attracts males during mating flight

31 of 44

Courting behaviour

·         Example: Peacocks: attract peahens breading season then vibrate their tail features when female arrives

·         Example: male woodland birds: attract females using sound and songs advertise their presence.

·         Some animals produce chemicals which smell pheromones

·         Female silk mothers produce pheromones which carry downwind and attract males.

·         Antennae so sensitive that males can detect the pheromone several kilometres from the female producing it.

·         Males pick up scent and head towards her, but if the pheromone is of a different species…

32 of 44

Mating systems and parental care

·         Pair bonding reinforced during breeding season: male and female of the same species

·         Example: Red Deer: the males compete each other best places inside mating area males best at defending these prime spots mate with most females.

·         Animal species where males and females pair for the breading season are monogamous

·         Animal species where an individual mates with a number of mates are polygamous species.

·         Parental care includes feeding protecting helping offspring to interact with others. If care increases chances of offspring surviving then parents indirectly benefit because their genes are passed to a new generation.

33 of 44

Parental care

·         Parental care most common with vertebrates mammals and reptiles

·         Example: crocodile: parents respond to calls of young hatched from eggs and both parents dig out hatchlings and carry them in their mouth to the river to wash them.

·         Example: cuckoos: female lays an egg in nest of another species cuckoo chick hatches it pushes the eggs and chicks of the resident species out of the nest and the resident parents think that the cuckoo chick is their own and feed it. 

34 of 44

Feeding behaviour

·         Example: Hyenas: sense where lions have brought down antelope, hyenas scavenge remains.

·         Herbivores cows and sheep concentration of protein in glass is low so they eat more food.

·         Example: Wildebeest: where rain is, grass grows and wildebeest eat and move respectively

·         Example: Chimpanzee: uses stick to dig out insects from holes in a log of wood

35 of 44

Foiling predators

·         Tigers and zebras have stripes- tiger’s stripes camouflage

·         Living in herds protects the majority of herd members from predation- successful evolutionary strategy as one can be on look out whilst the other is feeding. Most of individuals in the herd survive to produce offspring that inherit the herding instinct.

·         Eyes positioned side of head allows antelopes rabbits watch for predators approaching from behind and front.

·         Long lever like legs help prey like antelopes to dodge a predator’s first rush and run to safety.

·         Threatening predators: musk ox form a defensive circle to resist attack by wolves- vulnerable animals protected by barrier of horned heads pointing out towards the circling wolves

36 of 44

Catching prey

·         Carnivores eat meat: fox’s eyes close together face front narrow field of view accurately judge distance; bear’s large pointed canine teeth grip tear struggling prey; cheetah’s thin long body flexible spine let its front and hind legs overlap allowing long strides- 110km/h; tiger’s stripes camouflage; moving where prey plentiful increases chances of predators catching prey

·         Scavengers- animals feed on remains of prey killed by predators

37 of 44

Non-verbal communication

·         Facial expressions, chimpanzee smiling means fear not happiness- broad smile face shape

·         Gesture and posture also reflect emotion: scent glands on side of face and tail cat territory

38 of 44

Being Human

·         Language: spoken written voice box amplify sound produced air passing vocal cords

·         Brain interpret the sounds and speech generally recognized biggest difference- self awareness

·         Patterns marks sides of fossil skulls **** erectus indicates area brain enables human speak

·         Writing systems based on pictures or alphabet of letters.

39 of 44

Self awareness

·         Socrates: we know our existence as an individual own thoughts conscious outcomes actions

·         Dolphins have a big brain: ability to understand language and remember information. Love to bow-ride swimming just to one side of the bows of a ship so they can surf the ship’s wave.

·         We may also recognize another person’s mental state and use our understanding to influence their behaviour to our advantage. A young chimpanzee sees some food not noticed by older and more dominant individuals. Young gives alarm call and other chimpanzees are distracted because they think a predator is nearby. This allows the youngster to make way with the food.

·         Self- conscious= too aware.

40 of 44

Family society

·         Modern day: farm’s established and animals and plants with characteristics which were useful to us are selected and bred. Food is now provided by relatively few people working in farming industry and technology and mass transport equals more transportation.

41 of 44

Humans and other apes

·         Great apes: human, gorilla, chimpanzee and orangutan: 99% genetic material is the same. They cooperate with other, make tools, solve problems, quarrel between themselves and comfort one another.

·         Threaten survival of great apes of the wild: hunting for bush meat, civil war and clearing forests.

·         Bush meat: meat of wild animals that live in tropical woodlands 

42 of 44

Using animals

·         Human control of their breeding living conditions lead to domestication of animals-tame.

·         Dogs bred from wolves helped us to guard our homes

·         Cats kept the rats and mice that raided our food stores out

·         Horses were attached to carts and ridden into war

·         Herd animals were used as a source of food

·         Domesticating animals enable humans shift from hunter lifestyle to permanent community

·         Experiments on animals are often used as part of scientific research into the production of modern medicines. Most of the experiments are carried out on rats and mice.

43 of 44

Issues about animals

·         Anthropomorphism describes way humans pin their thoughts and behaviour onto animals and objects.

·         Animal rights: Battery hens: reared intensively peck themselves in frustration. Behaviour prevented removing the tips of the birds’ beaks- cruel

·         Morals and ethics- alternative to animal testing- discovering how effective or safe a new medicine might be. 

44 of 44



This is beautiful, cheers!


Amazing! Thanks!!

richard Webb

These are great, sitting the exam in the summer and have found pretty much nothing for revising with so thanks!  If you have anything else please put them on!?


this is great, thanks. Perfect condensed notes


arent you gnna make physics P3 revision cards? if u are please do asap


These are so good!! i'm sure you will pass this with flying colours, and i hope i do too :)


these have probably saved me from failing my biology gcse with two lessons left to learn most of the second topic, thankyou so much!

Muddassir Ahmad

this is great !!!!!!!!!!!!!!!!!!!!!

Similar Biology resources:

See all Biology resources »See all resources »