GCSE Science B3 Living and Growing Revision List

B3A Molecules of Life

  • Recall that respiration occurs in the mitochondria providing energy for life processes.
  • Identify the mitochondria in an animal cell.
  • Recall that chromosomes in the nucleus:
    • carry coded information in the form of genes
    • are made of a molecule called DNA.

 

  • Recall that the information in genes is in the form of coded instructions called the genetic code.
  • Understand that the genetic code controls cell activity and consequently some characteristics of the organism.
  • Recall that DNA controls the production of different proteins.
  • Recall that proteins are needed for the growth and repair of cells.
  • Recall that the structure of DNA was first worked out by two scientists called Watson and Crick.(helped by Rosalind Franklin)
  • Describe chromosomes as long, coiled molecules of DNA, divided up into regions called genes.
  • Describe the structure of DNA as two strands coiled to form a double helix, each strand containing chemicals called bases, of which there are four different types, with cross links between the strands formed by pairs of bases.
  • Explain why liver and muscle cells have large numbers of mitochondria.
  • Know that each gene:
    • contains a different sequence of bases
    • codes for a particular protein.

 

  • Know that proteins are made in the cytoplasm and understand why a copy of the gene is needed: the gene itself cannot leave the nucleus.
  • Know that (HL):
    • some structures in cells, such as ribosomes, are too small to be seen with the light microscope
    • ribosomes are in the cytoplasm and are the site of protein synthesis.

 

  • Describe how Watson and Crick used data from other scientists to build a model of DNA, to include:
    • X-ray data showing that there were two chains include: wound in a helix,
    • data indicating that the bases occurred in pairs.

 

  • Be able to describe the complementary base pairings: A – T and G – C.(HL)
  • Know that the four bases of DNA are A, T, C and G (full names will not be required).(HL)
  • Explain how protein structure is determined by the DNA base code, to include:(HL)
    • the base sequence determines amino acid sequence
    • each amino acid is coded for by a sequence of 3 bases.

 

  • Explain how DNA controls cell function by controlling the production of proteins, some of which are enzymes.(HL)
  • Explain how the code needed to produce a protein is carried from the DNA to the ribosomes by a molecule called mRNA.(HL)
  • Explain why new discoveries, such as Watson and Crick’s, are not accepted or rewarded immediately, to include(HL)
    • the importance of other scientists repeating or testing the work.

 

B3B Proteins and mutations

  • Know some examples of proteins to include:
    • collagen
    • insulin
    • haemoglobin.

 

  • Be able to describe enzymes as:
    • proteins
    • molecules that speed up a chemical reaction
    • c) working best at a particular temperature.

 

  • Know that different cells and different organisms will produce different proteins.
  • Understand that enzymes have active sites that substrate molecules fit into when a reaction takes place.
  • Understand that mutations occur spontaneously but can be made to occur more often by radiation or chemicals.
  • Describe gene mutations as changes to genes.

 

  • Understand that mutations are often harmful but may be beneficial or have no effect.
  • Be able to describe gene mutations as changes to genes.
  • Be able to recognise that proteins are made of long chains of amino acids.
  • Explain the specificity of enzymes in terms of the enzyme function ‘lock and key’ mechanism.
  • Explain how each protein has its own number and sequence of amino acids, which results in differently shaped molecules, which have different functions.

 

  • Be able to describe some functions of proteins, to include:
    • structural (limited to collagen)
    • hormones (limited to insulin)
    • carrier molecules (limited to haemoglobin)
    • enzymes.

 

  • Be able to describe enzymes as:
    • biological catalysts
    • catalysing chemical reactions occurring in living cells: respiration, photosynthesis and protein synthesis
    • having a high specificity for their substrate

 

  • Explain how enzyme activity is affected by pH and temperature, to include:(HL)
    • lower collision rates at low temperatures
    • denaturing at extremes of pH and high temperatures
    • denaturing as an irreversible change inhibiting enzyme function
    • denaturing changing the shape of the active site.

 

  • Describe how changing temperature and pH, away from the optimum, will change the rate of reaction of an enzyme-catalysed reaction.
  • Calculate and interpret the Q10 value for a reaction of over a 10°C interval, given graphical or numerical data, using the formula:(HL)
    • Q10 = rate at higher temperature / rate at lower temperature

 

  • Know that gene mutations may lead to the production of different proteins.(HL)
  • Understand that only some of the full set of genes are used in any one cell; some genes are switched off.(HL)
  • Understand that the genes switched on determine the functions of a cell.(HL)
  • Explain how changes to genes alter, or prevent the production of the protein which is normally made.(HL)

B3C Respiration

  • Know and use the word equation for aerobic respiration:
    glucose + oxygen → carbon dioxide + water
  • Recognise that the energy provided by respiration is needed for all life processes in plants and in animals.
  • Be able to describe examples of life processes that require energy from respiration, to include:
    • muscle contraction
    • protein synthesis
    • control of body temperature in mammals.

 

  • Know and use the symbol equation for aerobic respiration: C6H12O6 + 6O2 → 6CO2 + 6H2O
  • Be able to analyse given data from a pulse rate experiment.
  • Describe an experiment to measure resting pulse rate and recovery time after exercise.
  • Explain why breathing and pulse rates increase during exercise.

 

  • Use data from experiments to compare respiration rates, to include:
    • increased oxygen consumption
    • increased carbon dioxide production.

 

  • Calculate the respiratory quotient (RQ) using the formula (data provided):
    • RQ = carbon dioxide produced / oxygen used

 

  • Know that respiration results in the production of ATP and that ATP is used as the energy source for many processes in cells.(HL)
  • Explain how the rate of oxygen consumption can be used as an estimate of metabolic rate because aerobic respiration requires oxygen.(HL)
  • Explain why the rate of respiration is influenced by changes in temperature and pH.(HL)
  • Explain why anaerobic respiration takes place during hard exercise in addition to aerobic respiration.
  • Know that this produces lactic acid which accumulates in muscles causing pain and fatigue.
  • Know and use the word equation for anaerobic respiration which releases energy:
    • glucose → lactic acid

 

  • Understand that anaerobic respiration releases much less energy per glucose molecule than aerobic respiration.
  • Explain fatigue in terms of lactic acid build up (oxygen debt) and how this is removed during recovery, to include:(HL)
    • hard exercise causing lack of oxygen in cells
    • the incomplete breakdown of glucose
    • continued panting replacing oxygen allowing aerobic respiration
    • increased heart rate ensuring that blood carries lactic acid away to the liver.

 

B3D Cell Division

  • Explain why the chromosomes have to be copied to produce new cells for growth.
  • Know that most body cells contain chromosomes in matching pairs.
  • Be able to describe the difference between simple organisms which are unicellular and more complex organisms which are multicellular.
  • Know that this type of cell division is also needed for:
    • replacement of worn out cells
    • repair to damaged tissue
    • asexual reproduction

 

  • Explain why sperm cells are produced in large numbers to increase the chance of fertilisation.
  • Understand that in sexual reproduction to produce a unique individual half the genes come from each parent.
  • Know that gametes have half the number of chromosomes of body cells.
  • Explain the advantages of being multicellular:
    • allows organism to be larger
    • allows for cell differentiation
    • allows organism to be more complex.

 

  • Know that in sexual reproduction gametes join in fertilisation.
  • Explain why becoming multicellular requires the development of specialised organ systems, limited to:(HL)
    • communication between cells
    • supplying the cells with nutrients
    • controlling exchanges with the environment.

 

  • Explain why DNA replication must take place before cells divide.
  • Know that in mammals, body cells are diploid (two copies of each chromosome).
  • Explain why these new cells are genetically identical.
  • Know that new cells for growth are produced by mitosis.
  • Be able to describe how, prior to mitosis, DNA replication occurs, to include:(HL)
    • ‘unzipping’ to form single strands
    • new double strands forming by complementary base pairing.

 

  • Be able to describe how in mitosis the chromosomes:(HL)
    • line up along the centre of the cell
    • they then divide
    • the copies move to opposite poles of the cell.

 

  • Be able to describe gametes as haploid (contain one chromosome from each pair).
  • Know that gametes are produced by meiosis.
  • Explain why fertilisation results in genetic variation, limited to:
    • gametes combine to form a diploid zygote
    • genes on the chromosomes combine to control the characteristics of the zygote.

 

  • Explain how the structure of a sperm cell is adapted to its function, to include:
    • many mitochondria to provide energy
    • an acrosome that releases enzymes to digest the egg membrane.

 

  • Explain why, in meiosis, the chromosome number is halved and each cell is genetically different, to include(HL)
    • one chromosome from each pair separate to opposite poles of the cell in the first division
    • chromosomes divide and the copies move to opposite poles of the cell in the second division.

 

B3E The circulatory system

  • Be able to describe the functions of components of the blood:
    • red blood cells
    • white blood cells
    • platelets.

 

  • Know that the blood moves around the body in:
    • arteries
    • veins
    • capillaries.

 

  • Be able to describe the functions of the heart in the pumping of blood, to include:
    • the right side of the heart pumping blood to the lungs
    • the left side of the heart pumping blood to the rest of the body.

 

  • Know that blood in arteries is under higher pressure than blood in the veins.
  • Explain, in terms of pressure difference, why blood flows from one area to another.
  • Explain how the structure of a red blood cell is adapted to its function: size, shape, contains haemoglobin, lack of nucleus.
  • Describe the function of plasma.
  • Explain how the structure of a red blood cell is adapted to its function in terms of the small size providing a large surface area to volume ratio.(HL)
  • Describe how haemoglobin in red blood cells reacts with oxygen in the lungs to form oxyhaemoglobin and how the reverse of this reaction happens in the tissues(HL)

 

  • Describe how the parts of the circulatory system work together to bring about the transport of substances around the body, to include:
    • arteries transporting blood away from the heart
    • veins transporting blood to the heart
    • capillaries exchanging materials with tissues.

 

  • Explain how the adaptations of arteries, veins and capillaries relate to their functions, to include:(HL)
    • thick muscular and elastic wall in arteries
    • large lumen and presence of valves in veins
    • permeability of capillaries.

 

  • Identify the names and positions of the parts of the heart and describe their functions, to include:
    • left and right ventricles to pump blood
    • left and right atria to receive blood
    • semilunar, tricuspid and bicuspid valves to prevent backflow
    • four main blood vessels of the heart.

 

  • Explain why the left ventricle has a thicker muscle wall than the right ventricle.
  1. Explain the advantage of the double circulatory system in mammals, to include:(HL)
    • higher pressures
    • therefore greater rate of flow to the tissues.

B4F Growth and development

  • Describe the functions of parts of a plant cell to include:
    • vacuole, containing cell sap and providing support
    • the cell wall, made of cellulose to provide support.

 

  • Describe how to make a stained slide of an onion cell.
  • Understand that bacterial cells are smaller and simpler than plant and animal cells.
  • Know that growth can be measured as an increase in height, wet mass or dry mass.
  • Interpret data on a typical growth curve for an individual.

 

  • Describe the process of growth as cell division followed by cells becoming specialised.
  • Know that the process of cells becoming specialised is called differentiation.
  • Understand that animals grow in the early stages of their lives whereas plants grow continually.
  • Understand that all parts of an animal are involved in growth whereas plants grow at specific parts of the plant.
  • Identify simple differences between bacterial cells and plant and animal cells.

 

  • Know that bacterial cells lack:
    • a ‘true’ nucleus
    • mitochondria
    • chloroplasts

 

  • Describe the difference between the arrangement of DNA in a bacterial cell and a plant/animal cell, to include:(HL)
    • presence/absence of a nucleus
    • single circular strand/chromosomes.

 

  • Know that dry mass is the best measure of growth.
  • Be able to interpret data on increase in mass (including wet and dry mass).
  • Be able to describe the main phases of a typical growth curve.

 

  • Be able to explain the advantages and disadvantages of measuring growth by:(HL)
    • length
    • wet mass
    • dry mass.

 

  • Be able to explain the difference between adult and embryonic stem cells.(HL)
  • Discuss issues arising from stem cell research in animals.
  • Know that stem cells can be obtained from embryonic tissue and could potentially be used to treat medical conditions.
  • Know that undifferentiated cells called stem cells can develop into different cells, tissues and organs.
  • Be able to explain why the growth of parts of an organism may differ from the growth rate of the whole organism.(HL)
  • Know that in human growth there are two phases of rapid growth, one just after birth and the other in adolescence.

 

  • Be able to explain why plant growth differs from animal growth, to include:
    • animals tend to grow to a finite size but many plants can grow continuously
    • plant cell division is mainly restricted to areas called meristems
    • cell enlargement is the main method by which plants gain height
    • many plant cells retain the ability to differentiate but most animal cells lose it at an early stage.

 

B3G New genes for old

  • Describe the process of selective breeding as involving the:
    • selection of desired characteristics
    • cross breeding
    • selection of suitable offspring over many generations

 

  • Be able to explain how selective breeding can contribute to improved agricultural yields.
  • Know that:
    • selected genes can be artificially transferred from one living organism to another
    • this transfer of genes is called genetic engineering or genetic modification
    • the transfer of genes can produce organisms with different characteristics.

 

  • Recognise that a selective breeding programme may lead to inbreeding, which can cause health problems within the species.
  • Recognise that in the future it may be possible to use genetic engineering to change a person’s genes and cure certain disorders.
  • Identify features of plants and animals that might be selected for in a genetic engineering programme.
  • Be able to explain how a selective breeding programme may reduce the gene pool leading to problems of inbreeding, to include:(HT)
    • accumulation of harmful recessive characteristics
    • reduction in variation

 

  • risks – inserted genes may have unexpected harmful effects.
  • advantage – organisms with desired features are produced rapidly
  • Explain some potential advantages and risks of genetic engineering:
  • Describe, in outline only, some examples of genetic engineering:
    • taking the genes from carrots that control beta-carotene production and putting them into rice.
      Humans can then convert the beta-carotene from rice into Vitamin A (solving the problem of parts of the world relying on rice but lacking vitamin A)
    • the production of human insulin by genetically engineered bacteria
    • transferring resistance to herbicides, frost damage or disease to crop plants

 

  • Be able to discuss the ethical issues involved in genetic modification.
  • Understand the principles of genetic engineering, to include:(HT)
    • selection of desired characteristics
    • isolation of genes responsible
    • insertion of the genes into other organisms
    • replication of these organisms.

 

  • Know that changing a person’s genes in an attempt to cure disorders is called gene therapy.
  • Know that gene therapy could involve body cells or gametes.(HT)
  • Be able to explain why gene therapy involving gametes is controversial.(HT)

B3H Cloning

  • Know that:
    • cloning is an example of asexual reproduction
    • cloning produces genetically identical copies (clones).

 

  • Know that Dolly the sheep was the first mammal cloned from an adult.
  • Be able to recognise that identical twins are naturally occurring clones.
  • Be able to recognise that plants grown from cuttings or tissue culture are clones.
  • Be able to describe how spider plants, potatoes and strawberries reproduce asexually.

 

  • Be able to describe how to take a cutting.
  • Understand that Dolly the sheep was produced by the process of nuclear transfer and that nuclear transfer involves placing the nucleus of a body cell into an egg cell.

 

  • Be able to describe some possible uses of cloning, limited to:
    • mass producing animals with desirable characteristics
    • producing animals that have been genetically engineered to provide human products
    • producing human embryos to supply stem cells for therapy

 

  • Understand the ethical dilemmas concerning human cloning.
  • Describe in outline the cloning technique used to produce Dolly, to include:(HL)
    • nucleus removed from an egg cell
    • egg cell nucleus replaced with the nucleus from an udder cell
    • egg cell given an electric shock to make it divide
    • embryo implanted into a surrogate mother sheep
    • embryo grows into a clone of the sheep from which the udder cell came.

 

  • Describe the benefits and risks of using cloning technology.(HL)
  • Explain the possible implications of using genetically modified animals to supply replacement organs for humans.(HL)

 

  • Explain why cloning plants is easier than cloning animals: many plant cells retain ability to differentiate unlike animal cells which usually lose this ability at an early stage.(HL)
  • Describe the advantages and disadvantages associated with the commercial use of cloned plants:
    • advantage – can be sure of the characteristics of the plant since all plants will be genetically identical
    • advantage – it is possible to mass produce plants that may be difficult to grow from seed
    • disadvantage – if plants become susceptible to disease or to change in environmental conditions then all plants will be affected
    • disadvantage – lack of genetic variation.

 

  • Describe plant cloning by tissue culture, to include:(HL)
    • selection for characteristics
    • large number of small pieces of tissue
    • aseptic technique
    • use of suitable growth medium and conditions.