Biology — Cambridge A-Level

outline the hybridoma method for the production of monoclonal antibodies

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describe the sequence of events that occurs during a primary immune response with reference to the roles of: macrophages, B-lymphocytes, including plasma cells, T-lymphocytes, limited to T-helper cells and T-killer cells

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describe the roles of neuromuscular junctions, the T-tubule system and sarcoplasmic reticulum in stimulating contraction in striated muscle

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explain that transpiration involves the evaporation of water from the internal surfaces of leaves followed by diffusion of water vapour to the atmosphere

Transport Mechanisms

outline glycolysis as phosphorylation of glucose and the subsequent splitting of fructose 1,6-bisphosphate (6C) into two triose phosphate molecules (3C), which are then further oxidised to pyruvate (3C), with the production of ATP and reduced NAD

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explain why populations and species can become extinct as a result of: climate change, competition, hunting by humans, degradation and loss of habitats

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interpret absorption spectra of chloroplast pigments and action spectra for photosynthesis

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investigate the effect of changing surface area to volume ratio on diffusion using agar blocks of different sizes

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describe the types of interaction that hold protein molecules in shape: hydrophobic interactions, hydrogen bonding, ionic bonding, covalent bonding, including disulfide bonds

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explain that biodiversity can be assessed at different levels, including: the number and range of different ecosystems and habitats, the number of species and their relative abundance, the genetic variation within each species

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outline the following examples of selective breeding: the introduction of disease resistance to varieties of wheat and rice, inbreeding and hybridisation to produce vigorous, uniform varieties of maize, improving the milk yield of dairy cattle

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make annotated drawings of transverse sections of leaves from xerophytic plants to explain how they are adapted to reduce water loss by transpiration

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outline the mitotic cell cycle, including: interphase (growth in G1 and G2 phases and DNA replication in S phase), mitosis, cytokinesis

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recognise and draw red blood cells, monocytes, neutrophils and lymphocytes from microscope slides, photomicrographs and electron micrographs

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investigate the progress of enzyme-catalysed reactions by measuring rates of formation of products using catalase and rates of disappearance of substrate using amylase

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explain that gene editing is a form of genetic engineering involving the insertion, deletion or replacement of DNA at specific sites in the genome

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state that glucose, fructose and maltose are reducing sugars and that sucrose is a non-reducing sugar

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outline how microarrays are used in the analysis of genomes and in detecting mRNA in studies of gene expression

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investigate the difference in activity between an enzyme immobilised in alginate and the same enzyme free in solution, and state the advantages of using immobilised enzymes

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explain the role of the dominant allele, Le, that codes for a functional enzyme in the gibberellin synthesis pathway, and the recessive allele, le, that codes for a non-functional enzyme

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describe and draw the general structure of an amino acid and the formation and breakage of a peptide bond

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describe the roles of the hypothalamus, posterior pituitary gland, antidiuretic hormone (ADH), aquaporins and collecting ducts in osmoregulation

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describe and carry out a test to identify the presence of non-reducing sugars, using acid hydrolysis and Benedict’s solution

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interpret photomicrographs and diagrams of cells in different stages of meiosis and identify the main stages of meiosis

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explain the meanings of the terms haploid (n) and diploid (2n)

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state that the mammalian circulatory system is a closed double circulation consisting of a heart, blood and blood vessels including arteries, arterioles, capillaries, venules and veins

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outline the role of sensory receptor cells in detecting stimuli and stimulating the transmission of impulses in sensory neurones

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discuss the consequences of antibiotic resistance and the steps that can be taken to reduce its impact

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explain that stomata have daily rhythms of opening and closing

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explain how cholera, malaria, TB and HIV are transmitted

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interpret and construct genetic diagrams, including Punnett squares, to explain and predict the results of test crosses

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state that a gene mutation is a change in the sequence of base pairs in a DNA molecule that may result in an altered polypeptide

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describe and carry out investigations using redox indicators, including DCPIP and methylene blue, and a suspension of chloroplasts to determine the effects of light intensity and light wavelength on the rate of photosynthesis

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explain the relationship between genes, proteins and phenotype with respect to the: TYR gene, tyrosinase and albinism, HBB gene, haemoglobin and sickle cell anaemia, F8 gene, factor VIII and haemophilia, HTT gene, huntingtin and Huntington’s disease

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use Spearman’s rank correlation and Pearson’s linear correlation to analyse the relationships between two variables, including how biotic and abiotic factors affect the distribution and abundance of species (the formulae for these correlations will b

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investigate the effects of immersing plant tissues in solutions of different water potentials, using the results to estimate the water potential of the tissues

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describe the distribution in the gas exchange system of cartilage, ciliated epithelium, goblet cells, squamous epithelium of alveoli, smooth muscle and capillaries

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explain why the energy yield from respiration in aerobic conditions is much greater than the energy yield from respiration in anaerobic conditions (a detailed account of the total yield of ATP from the aerobic respiration of glucose is not expected)

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state that Archaea and Bacteria are prokaryotes and that there are differences between them, limited to differences in membrane lipids, ribosomal RNA and composition of cell walls

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illustrate the principle that surface area to volume ratios decrease with increasing size by calculating surface areas and volumes of simple 3-D shapes (as shown in the Mathematical requirements)

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state that a polypeptide is coded for by a gene and that a gene is a sequence of nucleotides that forms part of a DNA molecule

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describe the features of ATP that make it suitable as the universal energy currency

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explain that, when oxygen is available, pyruvate enters mitochondria to take part in the link reaction

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explain that energy transferred as ATP and reduced NADP from the light-dependent stage is used during the light-independent stage (Calvin cycle) of photosynthesis to produce complex organic molecules

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relate the detailed structure of the Bowman’s capsule and proximal convoluted tubule to their functions in the formation of urine

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compare the structure of typical plant and animal cells

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explain how selection, the founder effect and genetic drift, including the bottleneck effect, may affect allele frequencies in populations

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describe and explain the oxygen dissociation curve of adult haemoglobin

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outline the main stages in the process of cell signalling leading to specific responses: secretion of specific chemicals (ligands) from cells, transport of ligands to target cells, binding of ligands to cell surface receptors on target cells

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explain that genetic engineering is the deliberate manipulation of genetic material to modify specific characteristics of an organism and that this may involve transferring a gene into an organism so that the gene is expressed

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relate the molecular structure of triglycerides to their functions in living organisms

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explain that genes to be transferred into an organism may be: extracted from the DNA of a donor organism, synthesised from the mRNA of a donor organism, synthesised chemically from nucleotides

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describe the rapid response of the Venus fly trap to stimulation of hairs on the lobes of modified leaves and explain how the closure of the trap is achieved

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describe how the information in DNA is used during transcription and translation to construct polypeptides, including the roles of: RNA polymerase, messenger RNA (mRNA), codons, transfer RNA (tRNA), anticodons, ribosomes

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explain why a promoter may have to be transferred into an organism as well as the desired gene

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describe and carry out a semi-quantitative Benedict’s test on a reducing sugar solution by standardising the test and using the results (time to first colour change or comparison to colour standards) to estimate the concentration

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explain that the random fusion of gametes at fertilisation produces genetically different individuals

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describe the structure and function of guard cells and explain the mechanism by which they open and close stomata

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describe and carry out investigations, using simple respirometers, to determine the RQ of germinating seeds or small invertebrates (e.g. blowfly larvae)

Energy – Determining the Respiratory Quotient (RQ) with Simple Respirometers

outline how genetic diseases can be treated with gene therapy, using the examples severe combined immunodeficiency (SCID) and inherited eye diseases

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discuss the ethical and social implications of using genetically modified organisms (GMOs) in food production

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describe the behaviour of chromosomes in plant and animal cells during meiosis and the associated behaviour of the nuclear envelope, the cell surface membrane and the spindle (names of the main stages of meiosis, but not the sub-divisions of prophase

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describe and explain the processes of simple diffusion, facilitated diffusion, osmosis, active transport, endocytosis and exocytosis

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describe and use suitable methods to assess the distribution and abundance of organisms in an area, limited to frame quadrats, line transects, belt transects and mark-release-recapture using the Lincoln index (the formula for the Lincoln index will b

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explain how hydrogen bonding of water molecules is involved with movement of water in the xylem by cohesion-tension in transpiration pull and by adhesion to cellulose in cell walls

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relate the molecular structure of antibodies to their functions

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explain mass flow in phloem sieve tubes down a hydrostatic pressure gradient from source to sink

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describe the role of abscisic acid in the closure of stomata during times of water stress, including the role of calcium ions as a second messenger

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describe and explain the formation of urine in the nephron, limited to: the formation of glomerular filtrate by ultrafiltration in the Bowman’s capsule, selective reabsorption in the proximal convoluted tubule

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describe and explain the steps involved in the polymerase chain reaction (PCR) to clone and amplify DNA, including the role of Taq polymerase

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describe the external and internal structure of the mammalian heart

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describe the relationship between the structure and function of mitochondria using diagrams and electron micrographs

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describe the molecular structure of the polysaccharide cellulose and outline how the arrangement of cellulose molecules contributes to the function of plant cell walls

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describe the ultrastructure of striated muscle with reference to sarcomere structure using electron micrographs and diagrams

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draw and label xylem vessel elements, phloem sieve tube elements and companion cells from microscope slides, photomicrographs and electron micrographs

Structure of Transport Tissues

state that all viruses are non-cellular structures with a nucleic acid core (either DNA or RNA) and a capsid made of protein, and that some viruses have an outer envelope made of phospholipids

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describe and explain how gel electrophoresis is used to separate DNA fragments of different lengths

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state that triglycerides are non-polar hydrophobic molecules and describe the molecular structure of triglycerides with reference to fatty acids (saturated and unsaturated), glycerol and the formation of ester bonds

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describe the differences between structural genes and regulatory genes and the differences between repressible enzymes and inducible enzymes

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describe the role of NAD and FAD in transferring hydrogen to carriers in the inner mitochondrial membrane

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explain the principles of operation of test strips and biosensors for measuring the concentration of glucose in blood and urine, with reference to glucose oxidase and peroxidase enzymes

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explain the movement of water between cells and solutions in terms of water potential and explain the different effects of the movement of water on plant cells and animal cells (knowledge of solute potential and pressure potential is not expected)

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outline reasons for the need to maintain biodiversity

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describe the functions of ciliated epithelial cells, goblet cells and mucous glands in maintaining the health of the gas exchange system

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describe the formation of a glycosidic bond by condensation, with reference to disaccharides, including sucrose, and polysaccharides

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explain the need for a reduction division during meiosis in the production of gametes

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investigate simple diffusion and osmosis using plant tissue and non-living materials, including dialysis (Visking) tubing and agar

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explain how rice is adapted to grow with its roots submerged in water, limited to the development of aerenchyma in roots, ethanol fermentation in roots and faster growth of stems

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explain how companion cells transfer assimilates to phloem sieve tubes, with reference to proton pumps and cotransporter proteins

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explain the importance of mitosis in the production of genetically identical daughter cells during: growth of multicellular organisms, replacement of damaged or dead cells, repair of tissues by cell replacement, asexual reproduction

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describe the structure of a molecule of collagen as an example of a fibrous protein, and the arrangement of collagen molecules to form collagen fibres

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state that water is the main component of blood and tissue fluid and relate the properties of water to its role in transport in mammals, limited to solvent action and high specific heat capacity

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compare the features of the nervous system and the endocrine system

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outline key structural features of a prokaryotic cell as found in a typical bacterium, including: unicellular, generally 1–5 µm diameter, peptidoglycan cell walls, circular DNA, 70S ribosomes, absence of organelles surrounded by double membranes

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describe the cardiac cycle, with reference to the relationship between blood pressure changes during systole and diastole and the opening and closing of valves

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explain that during photophosphorylation: energetic electrons release energy as they pass through the electron transport chain (details of carriers are not expected), the released energy is used to transfer protons across the thylakoid membrane, prot

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explain that reactions in the Krebs cycle involve decarboxylation and dehydrogenation and the reduction of the coenzymes NAD and FAD

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outline the Krebs cycle, explaining that oxaloacetate (4C) acts as an acceptor of the 2C fragment from acetyl coenzyme A to form citrate (6C), which is converted back to oxaloacetate in a series of small steps

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outline the three main stages of the Calvin cycle: rubisco catalyses the fixation of carbon dioxide by combination with a molecule of ribulose bisphosphate (RuBP), a 5C compound, to yield two molecules of glycerate 3-phosphate (GP), a 3C compound, GP

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describe the differences between active immunity and passive immunity and between natural immunity and artificial immunity

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explain how gibberellin activates genes by causing the breakdown of DELLA protein repressors, which normally inhibit factors that promote transcription

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describe the principle of the universal genetic code in which different triplets of DNA bases either code for specific amino acids or correspond to start and stop codons

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describe the principles of cell signalling using the example of the control of blood glucose concentration by glucagon, limited to: binding of hormone to cell surface receptor causing conformational change, activation of G-protein leading to stimulat

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state that ATP is synthesised by: transfer of phosphate in substrate-linked reactions, chemiosmosis in membranes of mitochondria and chloroplasts

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describe the role of chloroplast pigments (chlorophyll a, chlorophyll b, carotene and xanthophyll) in light absorption in thylakoids

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state that light intensity, carbon dioxide concentration and temperature are examples of limiting factors of photosynthesis

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explain how the structure of muscular arteries, elastic arteries, veins and capillaries are each related to their functions

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state that infectious diseases are caused by pathogens and are transmissible

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explain that vaccines contain antigens that stimulate immune responses to provide long-term immunity

Antibodies and \cdot accination

describe and interpret photomicrographs, electron micrographs and drawings of typical plant and animal cells

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state that Calvin cycle intermediates are used to produce other molecules, limited to GP to produce some amino acids and TP to produce carbohydrates, lipids and amino acids

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draw cells from microscope slides and photomicrographs

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describe the functions of the main blood vessels of the pulmonary and systemic circulations, limited to pulmonary artery, pulmonary vein, aorta and vena cava

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describe the roles of phospholipids, cholesterol, glycolipids, proteins and glycoproteins in cell surface membranes, with reference to stability, fluidity, permeability, transport (carrier proteins and channel proteins), cell signalling (cell surface

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describe the functions of cartilage, smooth muscle, elastic fibres and squamous epithelium in the gas exchange system

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explain what is meant by homologous pairs of chromosomes

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outline the role in conservation of the International Union for Conservation of Nature (IUCN) and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES)

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state the functions of tissue fluid and describe the formation of tissue fluid in a capillary network

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state that the respiratory quotient (RQ) is the ratio of the number of molecules of carbon dioxide produced to the number of molecules of oxygen taken in, as a result of respiration

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calculate RQ values of different respiratory substrates from equations for respiration

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explain that, in eukaryotes, the RNA molecule formed following transcription (primary transcript) is modified by the removal of non-coding sequences (introns) and the joining together of coding sequences (exons) to form mRNA

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describe the structure of an RNA molecule, using the example of messenger RNA (mRNA)

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explain, with examples, that phenotypic variation is due to genetic factors or environmental factors or a combination of genetic and environmental factors

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use the t-test to compare the means of two different samples (the formula for the t-test will be provided, as shown in the Mathematical requirements)

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state that globular proteins are generally soluble and have physiological roles and fibrous proteins are generally insoluble and have structural roles

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describe the structure of the human kidney, limited to: fibrous capsule, cortex, medulla, renal pelvis, ureter, branches of the renal artery and renal vein

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explain that crossing over and random orientation (independent assortment) of pairs of homologous chromosomes and sister chromatids during meiosis produces genetically different gametes

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describe methods of assisted reproduction used in the conservation of endangered mammals, limited to IVF, embryo transfer and surrogacy

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describe and explain changes to the membrane potential of neurones, including: how the resting potential is maintained, the events that occur during an action potential, how the resting potential is restored during the refractory period

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state that transcription factors are proteins that bind to DNA and are involved in the control of gene expression in eukaryotes by decreasing or increasing the rate of transcription

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outline the characteristic features of the kingdoms Protoctista, Fungi, Plantae and Animalia

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describe the distribution of xylem and phloem in transverse sections of stems, roots and leaves of herbaceous dicotyledonous plants

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describe the role of red blood cells in transporting oxygen and carbon dioxide with reference to the roles of: haemoglobin, carbonic anhydrase, the formation of haemoglobinic acid, the formation of carbaminohaemoglobin

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explain that in non-cyclic photophosphorylation: photosystem I (PSI) and photosystem II (PSII) are both involved, photoactivation of chlorophyll occurs, the oxygen-evolving complex catalyses the photolysis of water, ATP and reduced NADP are synthesis

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describe the classification of organisms in the Eukarya domain into the taxonomic hierarchy of kingdom, phylum, class, order, family, genus and species

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state that enzymes are globular proteins that catalyse reactions inside cells (intracellular enzymes) or are secreted to catalyse reactions outside cells (extracellular enzymes)

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discuss how DNA sequence data can show evolutionary relationships between species

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describe the structure of a cholinergic synapse and explain how it functions, including the role of calcium ions

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explain how speciation may occur as a result of genetic isolation by: geographical separation (allopatric speciation), ecological and behavioural separation (sympatric speciation)

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outline the benefits of using databases that provide information about nucleotide sequences of genes and genomes, and amino acid sequences of proteins and protein structures

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describe the mode of action of phagocytes (macrophages and neutrophils)

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state that some mineral ions and organic compounds can be transported within plants dissolved in water

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describe the breakage of a glycosidic bond in polysaccharides and disaccharides by hydrolysis, with reference to the non-reducing sugar test

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interpret photomicrographs, diagrams and microscope slides of cells in different stages of the mitotic cell cycle and identify the main stages of mitosis

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investigate and explain the effects of the following factors on the rate of enzyme-catalysed reactions: temperature, pH (using buffer solutions), enzyme concentration, substrate concentration, inhibitor concentration

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explain that in cyclic photophosphorylation: only photosystem I (PSI) is involved, photoactivation of chlorophyll occurs, ATP is synthesised

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use the chi-squared test to test the significance of differences between observed and expected results (the formula for the chi-squared test will be provided, as shown in the Mathematical requirements)

The roles of genes in determining the phenotype

outline the role of telomeres in preventing the loss of genes from the ends of chromosomes during DNA replication

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relate the structure of haemoglobin to its function, including the importance of iron in the haem group

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discuss the meaning of the term species, limited to the biological species concept, morphological species concept and ecological species concept

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explain the differences in the thickness of the walls of the: atria and ventricles, left ventricle and right ventricle

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outline how penicillin acts on bacteria and why antibiotics do not affect viruses

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outline the roles of zoos, botanic gardens, conserved areas (including national parks and marine parks), ‘frozen zoos’ and seed banks, in the conservation of endangered species

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describe and use chromatography to separate and identify chloroplast pigments (reference should be made to Rf values in identification of chloroplast pigments)

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recognise organelles and other cell structures found in eukaryotic cells and outline their structures and functions, limited to: cell surface membrane, nucleus, nuclear envelope and nucleolus, rough endoplasmic reticulum, smooth endoplasmic reticulum

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explain reasons for controlling invasive alien species

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explain the roles of restriction endonucleases, DNA ligase, plasmids, DNA polymerase and reverse transcriptase in the transfer of a gene into an organism

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explain that during oxidative phosphorylation: hydrogen atoms split into protons and energetic electrons, energetic electrons release energy as they pass through the electron transport chain (details of carriers are not expected), the released energy

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explain how vaccination programmes can help to control the spread of infectious diseases

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outline how viruses are classified, limited to the type of nucleic acid (RNA or DNA) and whether this is single stranded or double stranded

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recognise cartilage, ciliated epithelium, goblet cells, squamous epithelium of alveoli, smooth muscle and capillaries in microscope slides, photomicrographs and electron micrographs

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Identify, in diagrams, photomicrographs and electron micrographs, the parts of a nephron and its associated blood vessels and structures, limited to: glomerulus, Bowman’s capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, c

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outline the need for energy in living organisms, as illustrated by active transport, movement and anabolic reactions, such as those occurring in DNA replication and protein synthesis

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use the Hardy–Weinberg principle to calculate allele and genotype frequencies in populations and state the conditions when this principle can be applied (the two equations for the Hardy–Weinberg principle will be provided, as shown in the Mathematica

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describe the link reaction, including the role of coenzyme A in the transfer of acetyl (2C) groups

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state that cyclic photophosphorylation and non-cyclic photophosphorylation occur during the light-dependent stage of photosynthesis

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describe the structure of nucleotides, including the phosphorylated nucleotide ATP (structural formulae are not expected)

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state that cells use ATP from respiration for energy-requiring processes

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explain how uncontrolled cell division can result in the formation of a tumour

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explain that natural selection occurs because populations have the capacity to produce many offspring that compete for resources; in the ‘struggle for existence’, individuals that are best adapted are most likely to survive to reproduce and pass on t

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State where each of the four stages in aerobic respiration occurs in eukaryotic cells: glycolysis in the cytoplasm, link reaction in the mitochondrial matrix, Krebs cycle in the mitochondrial matrix, oxidative phosphorylation on the inner membrane of

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define resolution and magnification and explain the differences between these terms, with reference to light microscopy and electron microscopy

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make temporary preparations of cellular material suitable for viewing with a light microscope

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explain the relative energy values of carbohydrates, lipids and proteins as respiratory substrates

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explain what is meant by discontinuous variation and continuous variation

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explain the importance of the refractory period in determining the frequency of impulses

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explain that a gene mutation is a result of substitution or deletion or insertion of nucleotides in DNA and outline how each of these types of mutation may affect the polypeptide produced

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state that within a chloroplast, the thylakoids (thylakoid membranes and thylakoid spaces), which occur in stacks called grana, are the site of the light-dependent stage and the stroma is the site of the light-independent stage

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define the term recombinant DNA

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state the role of covalent bonds in joining smaller molecules together to form polymers

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state that assimilates dissolved in water, such as sucrose and amino acids, move from sources to sinks in phloem sieve tubes

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describe the chloride shift and explain the importance of the chloride shift

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compare the structure of a prokaryotic cell as found in a typical bacterium with the structures of typical eukaryotic cells in plants and animals

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explain genetic control of protein production in a prokaryote using the lac operon (knowledge of the role of cAMP is not expected)

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describe the sequence of events that results in an action potential in a sensory neurone, using a chemoreceptor cell in a human taste bud as an example

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describe and carry out the Benedict’s test for reducing sugars, the iodine test for starch, the emulsion test for lipids and the biuret test for proteins

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explain how negative feedback control mechanisms regulate blood glucose concentration, with reference to the effects of insulin on muscle cells and liver cells and the effect of glucagon on liver cells

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discuss the biological, social and economic factors that need to be considered in the prevention and control of cholera, malaria, TB and HIV (details of the life cycle of the malarial parasite are not expected)

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describe the structure of the human gas exchange system, limited to: lungs, trachea, bronchi, bronchioles, alveoli, capillary network

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interpret and construct genetic diagrams, including Punnett squares, to explain and predict the results of dihybrid crosses that involve autosomal linkage and epistasis (knowledge of the expected ratios for different types of epistasis is not expecte

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relate the structure of xylem vessel elements, phloem sieve tube elements and companion cells to their functions

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explain the genetic basis of discontinuous variation and continuous variation

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define the terms ecosystem and niche

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relate the structures of collagen molecules and collagen fibres to their function

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describe the semi-conservative replication of DNA during the S phase of the cell cycle, including: the roles of DNA polymerase and DNA ligase (knowledge of other enzymes in DNA replication in cells and different types of DNA polymerase is not expecte

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describe and carry out investigations using whole plants, including aquatic plants, to determine the effects of light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis

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describe the transport of water from the soil to the xylem through the: apoplast pathway, including reference to lignin and cellulose, symplast pathway, including reference to the endodermis, Casparian strip and suberin

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use Simpson’s index of diversity (D) to calculate the biodiversity of an area, and state the significance of different values of D (the formula for Simpson’s index of diversity will be provided, as shown in the Mathematical requirements)

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discuss the social and ethical considerations of using genetic screening and gene therapy in medicine

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calculate magnifications of images and actual sizes of specimens from drawings, photomicrographs and electron micrographs (scanning and transmission)

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describe the arrangement of cholesterol, glycolipids and glycoproteins in cell surface membranes

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outline respiration in anaerobic conditions in mammals (lactate fermentation) and in yeast cells (ethanol fermentation)

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describe the role of gibberellin in the germination of barley (see 16.3.4)

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describe the classification of organisms into three domains: Archaea, Bacteria and Eukarya

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explain the role of memory cells in the secondary immune response and in long-term immunity

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outline how bacteria become resistant to antibiotics as an example of natural selection

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define the terms monomer, polymer, macromolecule, monosaccharide, disaccharide and polysaccharide

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explain the mode of action of enzymes in terms of an active site, enzyme–substrate complex, lowering of activation energy and enzyme specificity, including the lock-and-key hypothesis and the induced-fit hypothesis

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explain what is meant by an antigen (see 4.1.3) and state the difference between self antigens and non-self antigens

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describe the structure and function of a sensory neurone and a motor neurone and state that intermediate neurones connect sensory neurones and motor neurones

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explain the role of auxin in elongation growth by stimulating proton pumping to acidify cell walls

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explain that stomata respond to changes in environmental conditions by opening and closing and that regulation of stomatal aperture balances the need for carbon dioxide uptake by diffusion with the need to minimise water loss by transpiration

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explain what is meant by homeostasis and the importance of homeostasis in mammals

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outline the advantages of genetic screening, using the examples of breast cancer (BRCA1 and BRCA2), Huntington’s disease and cystic fibrosis

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describe the fluid mosaic model of membrane structure with reference to the hydrophobic and hydrophilic interactions that account for the formation of the phospholipid bilayer and the arrangement of proteins

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explain the sliding filament model of muscular contraction including the roles of troponin, tropomyosin, calcium ions and ATP

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describe the role of plasma in the transport of carbon dioxide

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describe the molecular structure of phospholipids with reference to their hydrophilic (polar) phosphate heads and hydrophobic (non-polar) fatty acid tails

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describe the molecular structure of the polysaccharides starch (amylose and amylopectin) and glycogen and relate their structures to their functions in living organisms

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outline the use of a colorimeter for measuring the progress of enzyme-catalysed reactions that involve colour changes

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describe gas exchange between air in the alveoli and blood in the capillaries

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recognise trachea, bronchi, bronchioles and alveoli in microscope slides, photomicrographs and electron micrographs and make plan diagrams of transverse sections of the walls of the trachea and bronchus

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explain how hydrogen bonding occurs between water molecules and relate the properties of water to its roles in living organisms, limited to solvent action, high specific heat capacity and latent heat of vaporisation

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outline the principles of using monoclonal antibodies in the diagnosis of disease and in the treatment of disease

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explain the principles of homeostasis in terms of internal and external stimuli, receptors, coordination systems (nervous system and endocrine system), effectors (muscles and glands) and negative feedback

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explain how gene expression may be confirmed by the use of marker genes coding for fluorescent products

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explain how environmental factors can act as stabilising, disruptive and directional forces of natural selection

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describe the principles of selective breeding (artificial selection)

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describe and carry out investigations using simple respirometers to determine the effect of temperature on the rate of respiration

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explain that genetic engineering may help to solve the global demand for food by improving the quality and productivity of farmed animals and crop plants, using the examples of GM salmon, herbicide resistance in soybean and insect resistance in cotto

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describe the structure of a chromosome, limited to: DNA, histone proteins, sister chromatids, centromere, telomeres

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explain the importance of random sampling in determining the biodiversity of an area

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explain the advantages of using recombinant human proteins to treat disease, using the examples insulin, factor VIII and adenosine deaminase

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explain the effects of changes in light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis

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state that the strand of a DNA molecule that is used in transcription is called the transcribed or template strand and that the other strand is called the non-transcribed strand

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explain the terms gene, locus, allele, dominant, recessive, codominant, linkage, test cross, F1, F2, phenotype, genotype, homozygous and heterozygous

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describe the relationship between the structure of chloroplasts, as shown in diagrams and electron micrographs, and their function

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explain the effects of reversible inhibitors, both competitive and non-competitive, on enzyme activity

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describe and draw the ring forms of α-glucose and β-glucose

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explain that the maximum rate of reaction (Vmax) is used to derive the Michaelis–Menten constant (Km), which is used to compare the affinity of different enzymes for their substrates

Factors that Affect Enzyme Action

explain the meaning of the terms primary structure, secondary structure, tertiary structure and quaternary structure of proteins

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state that urea is produced in the liver from the deamination of excess amino acids

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use Spearman’s rank correlation and Pearson’s linear correlation to analyse the relationships between two variables, including how biotic and abiotic factors affect the distribution and abundance of species (the formulae for these correlations will b

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explain that in non-cyclic photophosphorylation: photosystem I (PSI) and photosystem II (PSII) are both involved, photoactivation of chlorophyll occurs, the oxygen-evolving complex catalyses the photolysis of water, ATP and reduced NADP are synthesis

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explain that during photophosphorylation: energetic electrons release energy as they pass through the electron transport chain (details of carriers are not expected), the released energy is used to transfer protons across the thylakoid membrane, prot

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Identify, in diagrams, photomicrographs and electron micrographs, the parts of a nephron and its associated blood vessels and structures, limited to: glomerulus, Bowman’s capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, c

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outline the theory of evolution as a process leading to the formation of new species from pre-existing species over time, as a result of changes to gene pools from generation to generation

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use an eyepiece graticule and stage micrometer scale to make measurements and use the appropriate units, millimetre (mm), micrometre (µm) and nanometre (nm)

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describe the features of the endocrine system with reference to the hormones ADH, glucagon and insulin (see 14.1.8, 14.1.9 and 14.1.10)

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State where each of the four stages in aerobic respiration occurs in eukaryotic cells: glycolysis in the cytoplasm, link reaction in the mitochondrial matrix, Krebs cycle in the mitochondrial matrix, oxidative phosphorylation on the inner membrane of

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explain that genetic engineering may help to solve the global demand for food by improving the quality and productivity of farmed animals and crop plants, using the examples of GM salmon, herbicide resistance in soybean and insect resistance in cotto

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explain the importance of the oxygen dissociation curve at partial pressures of oxygen in the lungs and in respiring tissues

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draw plan diagrams of transverse sections of stems, roots and leaves of herbaceous dicotyledonous plants from microscope slides and photomicrographs

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describe the behaviour of chromosomes in plant and animal cells during the mitotic cell cycle and the associated behaviour of the nuclear envelope, the cell surface membrane and the spindle (names of the main stages of mitosis are expected: prophase,

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state that the bases adenine and guanine are purines with a double ring structure, and that the bases cytosine, thymine and uracil are pyrimidines with a single ring structure (structural formulae for bases are not expected)

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use the Hardy–Weinberg principle to calculate allele and genotype frequencies in populations and state the conditions when this principle can be applied (the two equations for the Hardy–Weinberg principle will be provided, as shown in the Mathematica

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interpret and construct genetic diagrams, including Punnett squares, to explain and predict the results of dihybrid crosses that involve autosomal linkage and epistasis (knowledge of the expected ratios for different types of epistasis is not expecte

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recognise organelles and other cell structures found in eukaryotic cells and outline their structures and functions, limited to: cell surface membrane, nucleus, nuclear envelope and nucleolus, rough endoplasmic reticulum, smooth endoplasmic reticulum

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describe the behaviour of chromosomes in plant and animal cells during meiosis and the associated behaviour of the nuclear envelope, the cell surface membrane and the spindle (names of the main stages of meiosis, but not the sub-divisions of prophase

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describe the structure of a molecule of haemoglobin as an example of a globular protein, including the formation of its quaternary structure from two alpha (α) chains (α–globin), two beta (β) chains (β–globin) and a haem group

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describe the Bohr shift and explain the importance of the Bohr shift

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explain that natural selection occurs because populations have the capacity to produce many offspring that compete for resources; in the ‘struggle for existence’, individuals that are best adapted are most likely to survive to reproduce and pass on t

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describe the structure of a DNA molecule as a double helix, including: the importance of complementary base pairing between the 5′ to 3′ strand and the 3′ to 5′ strand (antiparallel strands), differences in hydrogen bonding between C–G and A–T base p

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explain the roles of the sinoatrial node, the atrioventricular node and the Purkyne tissue in the cardiac cycle (knowledge of nervous and hormonal control is not expected)

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outline the three main stages of the Calvin cycle: rubisco catalyses the fixation of carbon dioxide by combination with a molecule of ribulose bisphosphate (RuBP), a 5C compound, to yield two molecules of glycerate 3-phosphate (GP), a 3C compound, GP

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describe and carry out investigations using redox indicators, including DCPIP and methylene blue, to determine the effects of temperature and substrate concentration on the rate of respiration of yeast

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explain that during oxidative phosphorylation: hydrogen atoms split into protons and energetic electrons, energetic electrons release energy as they pass through the electron transport chain (details of carriers are not expected), the released energy

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describe the semi-conservative replication of DNA during the S phase of the cell cycle, including: the roles of DNA polymerase and DNA ligase (knowledge of other enzymes in DNA replication in cells and different types of DNA polymerase is not expecte

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describe and use suitable methods to assess the distribution and abundance of organisms in an area, limited to frame quadrats, line transects, belt transects and mark-release-recapture using the Lincoln index (the formula for the Lincoln index will b

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describe the principles of cell signalling using the example of the control of blood glucose concentration by glucagon, limited to: binding of hormone to cell surface receptor causing conformational change, activation of G-protein leading to stimulat

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describe and explain the rapid transmission of an impulse in a myelinated neurone with reference to saltatory conduction

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describe the roles of phospholipids, cholesterol, glycolipids, proteins and glycoproteins in cell surface membranes, with reference to stability, fluidity, permeability, transport (carrier proteins and channel proteins), cell signalling (cell surface

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interpret and construct genetic diagrams, including Punnett squares, to explain and predict the results of monohybrid crosses and dihybrid crosses that involve dominance, codominance, multiple alleles and sex linkage

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recognise arteries, veins and capillaries from microscope slides, photomicrographs and electron micrographs and make plan diagrams showing the structure of arteries and veins in transverse section (TS) and longitudinal section (LS)

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outline the role of stem cells in cell replacement and tissue repair by mitosis

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state the name and type of pathogen that causes each of the following diseases: cholera – caused by the bacterium Vibrio cholerae, malaria – caused by the protoctists Plasmodium falciparum, Plasmodium malariae, Plasmodium ovale and Plasmodium vivax,

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