Edexcel B2 Revision Cards

Front 1

1. Name all of the parts of an animal cell.

2. Name the parts that a plant cell has that an animal cell does not.

Back 1

1. Cell membrane, cytoplasm, nucleus, mitochondria.

2. Cell wall, vacuole and chloroplasts.

Front 2

1. Describe the functions of each of these organelles: cell membrane; cytoplasm; nucleus; mitochondria; cell wall; vacuole; and chloroplasts.

Back 2

1. Cell membrane: controls what goes into and out of the cell. Cytoplasm: where most of the chemical reactions within the cell take place. Nucleus: contains DNA and controls the cell. Mitochondria: where respiration takes place. Cell wall: supports the plant cell. Vacuole: filled with cell sap and keeps the cell rigid. Chloroplast: contains chlorophyll and is the site of photosynthesis.

Front 3

1. Why are light microscopes useful?

2. Why are electron microscopes useful?

Back 3

1. They allow us to see things such as cells that are too small to see with the eye.

2. They allow us to see even smaller things such as bacteria in more detail than a light microscope can as they have a much higher magnification.

Front 4

1. Describe the structure of a bacterial cell.

2. Describe the functions of the bacterial cell wall, flagella, chromosomal DNA and plasmid DNA.

Back 4

1. It is surrounded by a cell wall wth a cell membrane inside it; they have no nucleus, just a circular chromosome containing their main DNA and smaller circular plasmid DNA; some have a tail-like structure called a flagellum.
2. Cell wall: supports the cell; flagella: allows the cell to move; chromosomal DNA: contains the genetic material of the cell; plasmid DNA: contains extra genetic material, e.g. genes for antibiotic resistance.

Front 5

1. What is a gene?

2. What is a chromosome?

3. Describe the structure of DNA.

Back 5

1. A section of DNA that codes for a specific protein.
2. A long strand of DNA found in the nucleus that contain genetic information.
3. DNA is a double helix made up of 2 strands. The 2 strands are linked by hydrogen bonds between the bases. There are 4 types of base: A, T, C and G. They pair up by complementary base pairing. A with T and C with G.

Front 6

1. What was Franklin and Wilkins role in the discovery of the structure of DNA?

2. What was Watson and Cricks role in the discovery of the structure of DNA?

Back 6

1. They used x-rays to take photographs of DNA and worked out how the atoms were arranged from the patterns they saw.
2. They built a 3D model of DNA using data from other scientists including Franklin and Wilkins.

Front 7

HIGHER ONLY
1. What was the Human Genome Project?

2. What are the implications of it?

Back 7

1. An international effort to sequence the entire human genome that involved scientists from many countries working together.
2. Improved testing for genetic disorders; new treatments for genetic disorders; new ways to see how humans have evolved; and personalised medicines.

Front 8

1. What is genetic engineering?

2. Give an advantage and disadvantage for each of these examples: golden rice; the production of human insulin by bacteria; and hebicide-resistant plants.

Back 8

1. The removal of a gene from one organism followed by its insertion into a different organism.
2. Golden rice: advantage: provides a source of beta-carotene to humans who may not have enough in their diet and are at risk of blindness from vitamin A deficiency. Disadvantage: GM rice could cross-breed with wild rice.
Human insulin: advantage: cheap to make huge quantities. Disadvantage: slightly different to human insulin so doesn't suit everybody.
Herbicide-resistant crops: advantage: reduces amount of crop spraying necessary. Disadvantage: could result in herbicide resistant weeds if cross-pollination takes place.

Front 9

1. What is mitosis?

2. What is it for?

3. Are the cells diploid or haploid? What does this mean?
4. What is the diploid number of chromosomes in a human cell?

Back 9

1. Type of cell division that produces two daughter cells that are genetically identical to the parent cell.
2. It is for growth, repair and asexual reproduction.
3. The cells are diploid which means that they have two sets of chromosomes.
4. 46 or 23 pairs.

Front 10

1. What is meiosis?
2. What is it for?
3. Are the cells diploid or haploid? What does this mean?
4. What is the haploid number of chromosomes in a human cell?
5. What happens at fertilisation?

Back 10

1. A type of cell division that produces 4 daughter cells that are genetically different to each other and the parent cell.
2. It is for the production of gametes (sex cells).
3. The cells are haploid which means that they have half the number of chromosomes.
4. 23
5. Haploid gametes combine to form a diploid zygote.

Front 11

1. What are clones?
2. Name 2 naturally formed clones.
3. What is an advantage and a disadvantage of cloning?

Back 11

1. Individuals that are genetically identical.
2. Identical twins and plants grown from cuttings
3. Advantage: guarantees that all offspring will have the desired characteristic.
Disadvantage: very rarely successful.

Front 12

HIGHER ONLY
1. Describe the 5 stages of cloning a mammal.

Back 12

1.
1. Diploid nucleus removed from cell of animal being cloned.
2. Haploid nucleus removed from donor egg cell.
3. Diploid nucleus inserted into egg cell.
4. Egg cell stimulated to divide by mitosis and become an embryo.
5. Embryo inserted into surrogate mother.

Front 13

1. What are embryonic stem cells?
2. What are the advantages and disadvantages of embryonic stem cell research?
3. What are adult stem cells?
4. What are the advantages and disadvantages of adult stem cell research?

Back 13

1. Cells found in embryos that can become any type of cell.
2. Advantage: could be used to treat many different problems. Disadvantage: the embryo is killed during the collection of the cells.
3. Cells found in differentiated body tissue that can become a limited number of different cells.
4. Advantage: no need to kill any embryos. Disadvantage: stem cells are taken from a different person so the body may reject them - e.g bone marrow transplants.

Front 14

1. What are proteins made from?

2. What is the genetic code?

3. How does a gene code for a protein?

Back 14

1. Amino acids.
2. The order of bases on a DNA strand.
3. The sequence of bases determines the order of amino acids that make up the protein.

Front 15

HIGHER ONLY
1. What is transcription?

2. What is translation?

Back 15

1. The process that takes place inside the nucleus where one strand of DNA is copied into messenger RNA (mRNA).
2. The process that takes place on a ribosome in the cytoplasm where the mRNA is read 3 bases at a time (called base triplets or codons) and amino acids are added to a growing chain by transfer RNA (tRNA) molecules.

Front 16

1. What is a mutation?

2. What effects can mutations have?

3. Why do mutations have these effects?

Back 16

1. A change in the sequence of bases that make up a gene.
2. They can have no effect; lead to proteins that don't work as well or at all; or proteins that work better.
3. Because the sequence of bases controls the sequence of amino acids that make up the protein so if that is changed then the shape of the protein may change too.

Front 17

1. What are enzymes?

2. State 3 functions of enzymes.

3. What does the term substrate mean?

Back 17

1. They are proteins that function as biological catalyst - they speed up reactions.
2. Replication of DNA; digestion; and making new proteins.
3. It is the molecules that the enzyme works on.

Front 18

1. What 3 factors affect the rate of enzyme catalysed reactions and how do they affect them?

Back 18

1. Temperature: as it increases so does the rate of reaction until the optimum temperature is reached. Too far above that temperature the enzyme is denatured and doesn't work at all.
pH: enzymes have an optimum pH at which they work best and are denatured if they are in too high or low pH.
Substrate concentration: as you increase the substrate concentration the rate of reaction increases until all of the enzyme molecules are busy and it can't increase anymore.

Front 19

1. What is the lock-and-key hypothesis?

2. How does it explain enzyme specificity?

3. How does it explain enzymes being denatured at high temperatures?

Back 19

1. The enzyme has an active site where the reaction is catalysed. This is the right shape for the substrate molecule to fit into exactly - like a lock (active site) and key (substrate).
2. Each enzyme has a different shaped active site so it will only be the right shape for a specific substrate.
3. When the enzyme gets too hot the shape of the active site is changed so the substrate will no longer fit into it.

Front 20

1. What is the word equation for aerobic respiration?
2. Where does it occur?
3. How does the circulatory system facilitate respiration?
4. What is diffusion?

Back 20

1. Glucose + oxygen - carbon dioxide + water. Energy is released.
2. In the mitochondria of all cells.
3. Oxygen is carried from the lungs and glucose from the small intestine to respiring cells in the blood. Carbon dioxide is carried to the lungs in the blood.
4. The movement of particles from an area of high concentration to an area low concentration.

Front 21

1. What is the word equation for anaerobic respiration?
2. When and why does it occur?
3. Why do heart rate and breathing rate increase with exercise?
4. What is EPOC and why does it occur?

Back 21

1. Glucose - lactic acid
2. It occurs during intense exercise when we cannot supply enough oxygen to our muscles for aerobic respiration alone.
3. To supply more oxygen to muscles more quickly.
4. Excess post-exercise oxygen consumption occurs to provide oxygen for the breakdown of lactic acid that has built up due to anaerobic respiration being carried out.

Front 22

1. What is the word equation for photosynthesis?

2. How are leaves adapted for photosynthesis?

Back 22

1. Carbon dioxide + water -> glucose + oxygen
2. They have a large surface area; contain chlorophyll to absorb light to provide the energy for photosynthesis; and they have stomata (small holes) on the bottom layer to allow gas exchange to take place.

Front 23

1. What is a limiting factor?

2. Describe the effect of 3 limiting factors on photosynthesis.

Back 23

1. A factor that when in short supply will slow down a process such as photosynthesis.
2. Light: more light = more photosynthesis.
Carbon dioxide: more = more photosynthesis.
Temperature: higher = more photosynthesis.

Front 24

1. How does water get into the plant?
2. How does water move through the plant?
3. What is transpiration?
4. How does glucose move through the plant?
5. How are root hair cells adapted for osmosis?
6. How do mineral ions get into the plant?

Back 24

1. Through osmosis, moving from a high concentration in the soil to a low concentration in the root hair cells.
2. Through xylem vessels.
3. The process whereby water vapour lost through stomata in the leaves creates a suction force that pulls up water from the roots.
4. Through phloem vessels.
5. They have a large surface area.
6. By active transport - from low to high concentration. Energy is needed for this.

Front 25

1. Describe 4 different ways of studying the distribution of organisms in their environment.

2. What is systematic sampling and when would it be used?

Back 25

1. To collect animals or insects: sweep nets and pond nets; pooters and pitfall traps. To study plants: quadrats.
2. It is where samples are selected at regular intervals (e.g every metre along a line). It is used to investigate the effect of an environmental factor (e.g sunlight) on the population being studied.

Front 26

1. What are fossils?
2. How do they provide evidence for evolution?
3. Why are there gaps in the fossil record?
HIGHER ONLY
4. How does the pentadactyl limb provide evidence for evolution?

Back 26

1. The preserved remains of organisms that lived millions of years ago.
2. They show that organisms have changed gradually over long periods of time.
3. Because fossils only form under the right conditions; soft tissue doesn't form fossils; and some fossils may not have been found yet.
4. All vertebrates including fossil vertebrates have a similar limb structure (five fingers) which suggests that they all evolved from a common ancestor.

Front 27

1. What is growth?
2. What do percentile charts show?
3. How does plant growth differ from animal growth?

Back 27

1. An increase in size, length and mass.
2. The proportion of a population that is each size. Used to assess growth in babies. A baby in the 95th percentile is the same size or bigger than 95% of the population.
3. Plants grow throughout their lives whilst animals stop growing when they reach adulthood. Plants have stem cells (meristem) that can become any type of cell whilst animals have adult stem cells that can only become a limited number of cell types. Both grow by cell division and differentiation to form specialised cells. Plant cells also grow by elongation.

Front 28

1. What are the 4 components of blood?
2. What is the function of each component?
3. Compare the 3 types of blood vessel.

Back 28

1. Red blood cells, white blood cells, plasma and platelets.
2. Red blood cells carry oxygen; white blood cells fight disease; plasma carries dissolved substances (carbon dioxide and hormones) around the body; platelets are needed for blood clotting.
3. Veins have thin walls and large lumens to carry deoxygenated blood at a low pressure back to the heart; arteries have thick walls and small lumens to carry oxygenated blood from the heart to the rest of the body; capillaries have very thin walls to allow oxygen and carbon dioxide to diffuse easily between blood and respiring cells.

Front 29

1. What are cells, tissues, organs and organ systems?
2. Describe the flow of blood through the heart.
3. Why does the heart have valves?
4. Why is the wall of the left ventricle thicker than the right?

Back 29

1. Cells are the basic unit of living organisms, tissues are made up of cells of the same type; organs are made up of tissues that perform the same function; and organ systems are groups of organs that perform the same function.
2. Blood enters the right atrium through the vena cava; passes through a valve into the right ventricle; passes through another valve into the pulmonary artery, goes to the lungs to collect oxygen then travels back to the left atrium through the pulmonary vein. It passes through a valve into the left ventricle; through another valve into the aorta and then around the body.
3. Stop blood flowing backwards.
4. Because it has to pump blood further.

Front 30

1. Name the organs that make up the digestive system.
2. Describe the function of each organ.

Back 30

1. Mouth, oesophagus, stomach, pancreas, liver, gall bladder, small intestine, large intestine, anus.
2. Mouth: break down food. Oesophagus: transport food to stomach. Stomach: churns food up with stomach acid and enzymes to break it down. Pancreas: produces digestive enzymes. Liver: produces bile and processes digested food from the blood. Gall bladder: stores bile and releases it into the small intestine. Small intestine: complete the breakdown of food and absorbs soluble food molecules into the blood. Large intestine: reabsorbs water leaving waste material (faeces). Anus: waste material leaves the body.

Front 31

1. What are the 3 types of digestive enzyme and what do they do?
HIGHER ONLY
2. What are the 2 functions of bile?

Back 31

1. Carbohydrases (amylase) break down carbohydrates into sugars; proteases (pepsin) break down proteins into amino acids; and lipases break down fats into fatty acids and glycerol.
2. To emulsify (break down) fats and to neutralise stomach acid.

Front 32

HIGHER ONLY
1. What are villi?
2. How are they adapted for their function?

Back 32

1. Finger-like projections of the lining of the small intestine.
2. They have a large surface area so that food molecules can diffuse across more efficiently; a rich supply of capillaries so that food molecules can get into the blood easily and are moved away quickly to maintain a high concentration gradient; they have only a single cell thick wall so that the path for diffusion is shorter.

Front 33

1. What are probiotics?
What are prebiotics?
3. What are plant stanol esters?
4. Is there any evidence that they work?

Back 33

1.Foods that contain so called friendly bacteria.
2. Foods such as fruits and vegetables that promote the growth of friendly bacteria in the gut.
3. Oily substances found in plants that lower cholesterol levels.
4. There is evidence that prebiotics and plant stanol esters are beneficial but none for probiotics.