Topic outline

  • Year 12 Mocks

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    Mid A Level Mocks

  • Biological Molecules

    Monomers and polymers

    c   Monomers are the smaller units from which larger molecules are made.

    c   Polymers are molecules made from a large number of monomers joined together.

    c   Monosaccharides, amino acids and nucleotides are examples of monomers.

     

    Water

    c   Water is a major component of cells. It has several properties that are important in biology. In particular, water: is a metabolite, a solvent, has a high heat capacity, has a large latent heat of vaporisation and has strong cohesion between molecules.

     

    Lipids

    c   Triglycerides and phospholipids are two groups of lipid.

    c   A condensation reaction joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water.

    c   A hydrolysis reaction breaks a chemical bond between two molecules and involves the use of a water molecule.

    c   Triglycerides are formed by the condensation of one molecule of glycerol and three molecules of fatty acid (RCOOH) through the formation of an ester bond.

    c   The R-group of a fatty acid may be saturated or unsaturated.

    c   The structure of phospholipids, and how this structure relates to their properties.

    c   The emulsion test for lipids.

     

    Carbohydrates

    c   Glucose has two isomers, α -glucose and β –glucose.

    c   Monosaccharides, including glucose, galactose and fructose, are monomers from which larger carbohydrates are made.

    c   Condensation reactions produce disaccharides through the formation of glycosidic bonds. These include maltose, sucrose and lactose.

    c   Polysaccharides are formed by the condensation of many glucose units: Glycogen and starch are polysaccharides formed by condensation of α-glucose. Cellulose is formed by the condensation of β-glucose.

    c   Identify the biochemical tests for reducing sugars, non-reducing sugars and starch.

    c   Calibration curves can be used to provide quantitative data on the concentration of unknown starch solutions.

     

     

    Proteins

    c   The general structure of amino acids and how the only difference between amino acids in their side group

    c   The biuret test for proteins.

    c   Amino acids can be separated by Thin Layer Chromatography

    c   The formation of dipeptides and polypeptides through condensation of amino acids.

    c   The relationship between primary, secondary, tertiary and quaternary structure, and protein function.

    c   The role of hydrogen bonds, ionic bonds and disulphide bridges in the structure of proteins.

    c   The roles played by proteins.

     

     

    Enzymes

    c   Enzyme catalysis and activation energy.

    c   Calculate initial rate.

    c   The induced-fit model of enzyme action.

    c   Enzyme specificity linked to active site structure.

    c   The properties of an enzyme relate to the tertiary structure of its active site in the formation of an enzyme-substrate complex. 

    c   The effects of the following factors on the rate of enzyme controlled reactions – enzyme concentration, substrate concentration, concentration of competitive and of non-competitive inhibitors, pH and temperature.

    c   Required practical 1: Investigation into the effect of a named variable on the rate of anenzyme-controlled reaction

     

     

    DNA and RNA

    c   Deoxyribonucleic acid is important in all living cells, as it holds genetic information.

    c   DNA is a polymer of nucleotides formed by condensation, with phosphodiester bonds between nucleotides.

    c   Each nucleotide is formed from a deoxyribose, a nitrogen-containing organic base and a phosphate group.

    c   DNA is a double helix, held together by hydrogen bonds between complementary bases.

    c   Ribonucleic acid is important in all living cells, as it transfers genetic information from DNA to ribosomes.

    c   RNA is a polymer of nucleotides formed by condensation, with phosphodiester bonds between nucleotides.

    c   Each nucleotide is formed from a ribose, a nitrogen-containing organic base and a phosphate group.

    c   An RNA molecule is a relatively short polynucleotide chain.

    c   Ribosomes are formed from RNA and proteins.

     

    DNA replication

    c   The semi-conservative replication of DNA ensures geneticcontinuity between generations of cells.

    c   The process of semi-conservative replication of DNA, including the role of DNA polymerase.

     

    ATP

    c   A single molecule of ATP is a nucleotide derivative, formed from a molecule of ribose, a molecule of adenine and three phosphate groups.

    c   Hydrolysis of ATP to ADP and Pi is catalysed by the enzyme ATP hydrolase, and can be used to phosphorylate compounds or provide energy to energy-requiring cellular reactions.

    c   ATP is resynthesised from ADP and Pi by the enzyme ATP synthase, during photosynthesis or respiration.

     

    Inorganic ions

    c   Inorganic ions occur in solution in the cytoplasm and body fluids of organisms, some in high concentrations and others in very low concentrations.

    c   Each type of ion has a specific role, depending on its properties.

    c   Students should be able to recognise the role of ions in the following topics: hydrogen ions and pH; iron ions as a component of

    c   haemoglobin; sodium ions in the co-transport of glucose and amino acids; and phosphate ions as components of DNA and of ATP.

  • Cells

    Cells

    c   The structure of eukaryotic cells.

    c   Eukaryotic cells have adaptations to their function.

    c   The structure of prokaryotic, including the differences between prokaryotic and eukaryotic cells and the additional features of the cell which may be present.

    c   The structure of virus particles to include genetic material, capsid and attachment protein.

     

    Methods of study cells

    c   The principles and limitations of optical microscopes, transmission electron microscopes and scanning electron microscopes.

    c   The difference between magnification and resolution.

    c   Measuring (and drawing to scale) the size of an object viewed with an optical microscope and calculation of magnification.

    c   Principles of cell fractionation and ultracentrifugation as used to separate cell components.

     

     

    Transport across cell membranes

    c   The fluid mosaic model of cell membranes, including the arrangement of phospholipids, proteins, glycoproteins and glycolipids.

    c   The role of cholesterol.

    c   Required practical 4: Investigation into the effect of a named variable on the permeability of cell-surface membranes.

    c   Movement of molecules and ions with concentration gradients by simple diffusion or facilitated diffusion.

    c   The movement of water across partially permeable membranes by osmosis.

    c   The concepts of water potential and hypotonic, hypertonic and isotonic solutions.

    c   Required practical 3: Production of a dilution series of a solute to produce a calibration curve with which to identify the water potential of plant tissue.

    c   Movement of molecules and ions against concentration gradients by active transport.

    c   Movement of molecules and ions against concentration gradients by co-transport.

    c   The adaptations of cells for rapid transport across internal and external membranes.

     

    All cells arise from other cells

    c   Not all cells in multicellular organisms retain the ability to divide.

    c   The cell cycle involves DNA replication followed by mitosis.

    c   The behaviour of chromosomes during interphase and the stages of mitosis. 

    c   The role of spindle fibres.

    c   Required practical 2: Preparation of stained squashes of cells from plant root tips; set-up and use of an optical microscope to identify the stages of mitosis in these stained squashes and calculation of a mitotic index.

    c   Uncontrolled cell division can lead to the formation of tumours and of cancers. 

    c   Many cancer treatments are directed at controlling the rate of cell division.

    c   Binary fission in prokaryotic cells.

    c   Viruses do not undergo cell division but replicate by injection of their nucleic acid into host cells.

     

    Cell recognition and the immune system

    c   Describe the main defence mechanisms of the body

    c   Phagocytosis of pathogens. The subsequent destruction of ingested pathogens by lysozymes.

    c   Antigens and Antibodies

    c   The definition of antigens.

    c   These molecules allow the immune system to identify pathogens, cells from other individuals, abnormal body cells and toxins.

    c   The definition of an antibody.

    c   The structure of an antibody.

    c   The formation of antigen-antibody complexes and the subsequent destruction of pathogens.

    c   The response of T lymphocytes to a foreign antigen (the cellular response).

    c   The role of antigen-presenting cells in the cellular response.

    c   The role of T helper cells (TH cells) in stimulating cytotoxic Tcells (TC cells), B cells and phagocytes.

    c   The response of B lymphocytes to a foreign antigen, clonal selection and the release of monoclonal antibodies (the humoral response).

    c   The roles of plasma cells and of memory cells in producing primary and secondary immune responses.

    c   The effect of antigen variability on disease and disease prevention.

    c   The differences between active and passive immunity.

    c   The use of vaccines to provide protection for individuals and populations against disease.

    c   The concept of herd immunity.

    c   Ethical issues associated with the use of vaccines.

    c   Structure of the human immunodeficiency virus (HIV) and its replication in helper T cells.

    c   How HIV causes the symptoms of AIDS. 

    c   Why antibiotics are ineffective against viruses.

    c   The use of monoclonal antibodies in: targeting medication at particular cell types, medical diagnosis, and ELISA.

    c   Ethical issues associated with the use of monoclonal antibodies.

     

  • Exchange and mass transport

    Surface area to volume ratio

    c   The relationship between the size or structure of an organism and its surface area to volume ratio.

    c   Changes to body shape and the development of systems as adaptations that facilitate exchange as this ratio reduces.

     

    Gas exchange

    c   Adaptations of gas exchange surfaces, shown by insect tracheal systems.

    c   Structural and functional compromises between gas exchange and the limitation of water loss shown by terrestrial insects.

    c   Adaptations of gas exchange surfaces, shown by fish gills.

    c   Required practical 5: Dissection of animal or plant respiratory system or mass transport system or of an organ within such a system

    c   The gross structure of the human gas exchange system.

    c   Ventilation and the exchange of gases in the lungs. 

    c   The mechanism of breathing.

    c   The essential features of the alveolar epithelium as a gas exchange surface.

    c   Lung diseases and the risk factors associated with them.

     

    c   Adaptations of gas exchange surfaces in leaves of dicotyledonous plants (mesophyll and stomata).

    c   Structural and functional compromises between gas exchange and the limitation of water loss shown by xerophytic plants.

     

    Digestion and absorption

    c   The purpose of digestion.

    c   Digestion in mammals of:

    • carbohydrates by amylases and disaccharidases
    • lipids by lipase
    • proteins by endopeptidases, exopeptidases and dipeptidases.

    c   The role of bile salts.

    c   Co-transport mechanisms and the role of micelles in the absorption of the products of digestion by cells lining the ileum.

     

    Mass transport in animals

    c   The general pattern of blood circulation in a mammal.

    c   The quaternary structure of haemoglobins.

    c   The role of haemoglobin in the loading, transport and unloading of oxygen.

    c   The cooperative nature of oxygen binding, with the binding of the first oxygen molecule making the binding of subsequent oxygen molecules easier.

    c   The effects of carbon dioxide concentration on oxygen dissociation (Bohr effect).

    c   Many animals are adapted to their environment by possessing different types of haemoglobin with different oxygen transport properties.

     

    c   The gross structure of the human heart.

    c   Required practical 5: Dissection of animal or plant respiratory system or mass transport system or of an organ within such a system

    c   Pressure and volume changes and associated valve movements during the cardiac cycle that maintain a unidirectional flow of blood.

    c   The structure of arteries, arterioles and veins in relation to their function.

    c   The structure of capillaries and the importance of capillary beds as exchange surfaces. 

    c   The formation of tissue fluid and its return to the circulatory system

    c   Cardiovascular disease (CVD) and associated risk factors.

     

    Mass transport in plants

    c   Xylem as the tissue that transports water in the stem and leaves of plants. 

    c   The cohesion-tension theory of water transport in the xylem.

    c   The use of a potometer to measure transpiration

    c   Phloem as the tissue that transports organic substances in plants.

    c   The mass flow hypothesis for the mechanism of translocation.

    c   Investigating transport in plants using tracers and ringing experiments.

  • Genetic information, variation and relationships between organisms

    DNA, genes and chromosomes

    c   Eukaryotic cells have chromosomes of linear DNA associated with histones. 

    c   Prokaryotic cells contain short, circular DNA that is not associated with histones.

    c   Mitochondria and chloroplasts contain DNA like that of prokaryotes.

    c   Genes as regions of DNA, occupying a fixed locus, coding for the amino acid sequence of a polypeptide or a functional RNA

    c   DNA is a triplet code which is universal, non-overlapping and degenerate.

    c   Much of eukaryotic DNA does not code for polypeptides. There are non-coding regions of multiple base repeats between genes. There are also introns within genes which separate coding sequences (exons).

     

    Protein synthesis

    c   The concept of the genome and the proteome.

    c   The structure of molecules of mRNA

    c   The process of transcription in prokaryotes to produce mRNA.

    c   The process of transcription in eukaryotes to produce pre-mRNA which is subsequently spliced.

    c   The process of translation.

    c   The roles of ribosomes, tRNA and ATP.

    c   The structure of molecules of tRNA.

    c   The structure of molecules of tRNA.

     

    c   Gene mutations arise spontaneously during DNA replication and include base deletion and base substitution.

    c   The degeneracy of the genetic code means that not all base substitutions cause a change in the amino acid sequence.

    c   Mutagenic agents can increase the risk of gene mutation.

     

    Meiosis

    c   Meiosis produces daughter cells produces genetically unique daughter cells. 

    c   The process of meiosis involves two nuclear divisions and forms four haploid daughter cells.

    c   Independent segregation and crossing over result in genetically different daughter cells.

    c   Mutations in the number of chromosomes can arise spontaneously by chromosome non-disjunction during meiosis.

     

    Genetic diversity and adaptation

    c   The concept of genetic diversity.

    c   The principles of natural selection in the evolution of populations (including random mutation, reproductive success, inheritance of the beneficial allele and increasing allele frequency in the next generation).

    c   Natural selection results in species that are better adapted to their environment. This included anatomical, physiological or behavioural adaptations.

    c   Directional selection, exemplified by antibiotic resistance in bacteria, and stabilising selection, exemplified by human birth weights.

    c   Required practical 6: Use of aseptic techniques to investigate the effect of anti-microbial substances on microbial growth

     

    Species and taxonomy

    c   The concept of a species.

    c   Courtship behaviour as a necessary precursor to successful mating. 

    c   The role of courtship in species recognition.

    c   Phylogenetic classification is based on evolutionary origins and relationships.

    c   The hierarchical nature of classification into taxonomic ranks.

    c   The binomial identification of species based on its genes and species.

    c   Advances in immunology and genome sequencing help to clarify evolutionary relationships between organisms.

    c   Genetic diversity within, or between species, can be made by comparing the frequency of characteristics, the base sequences of DNA or mRNA, or the amino acid sequences of proteins.

     

    Biodiversity within a community

    c   The concepts of biodiversity, species richness and index of diversity.

    c   Calculation of the index of diversity (d).

    c   Farming techniques reduce biodiversity. The balance between conservation and farming.

    c   Quantitative investigations of variation within a species involve:

    • collecting data from random samples
    • calculating a mean value of the collected data and the standard deviation of that mean
    • interpreting mean values and their standard deviations