Biology (Edexcel)

Biological Molecules: Water, Carbohydrates and Lipids

understand the importance of water as a solvent in transport, including its dipole nature · know the differences between monosaccharides, disaccharides and polysaccharides (glycogen, amylose, amylopectin); relate structures to roles in energy supply and storage (β-glucose and cellulose not required in this topic) · know how monosaccharides (glucose, fructose, galactose) join to form disaccharides (maltose, sucrose, lactose) and polysaccharides via condensation/glycosidic bonds, and how these split via hydrolysis · know how triglycerides are synthesised by ester bonds between glycerol and three fatty acids; saturated vs unsaturated lipids · CORE PRACTICAL 1: semi-quantitative Benedict's test for reducing sugars and iodine test for starch using colour standards

Mass Transport: the Mammalian Heart and Blood Vessels

understand why many animals need a heart and circulation (mass transport overcoming diffusion limits) · understand how the structures of capillaries, arteries and veins relate to their functions · know the cardiac cycle (atrial systole, ventricular systole, cardiac diastole) and the structure/operation of the mammalian heart, including major blood vessels (myogenic detail not required at IAS)

Haemoglobin and Oxygen Transport

understand the role of haemoglobin in transporting oxygen and carbon dioxide · understand the oxygen dissociation curve, the Bohr effect, and the significance of the higher oxygen affinity of fetal haemoglobin compared with adult haemoglobin

Atherosclerosis, Blood Clotting and Cardiovascular Disease

understand the course of events leading to atherosclerosis (endothelial dysfunction, inflammatory response, plaque formation, raised blood pressure) · understand the blood clotting process (thromboplastin, prothrombin → thrombin, fibrinogen → fibrin) and its role in CVD · know risk factors for CVD: genetics, diet, age, gender, high blood pressure, smoking, inactivity · understand the link between dietary antioxidants and CVD risk · CORE PRACTICAL 2: investigate the vitamin C content of food and drink

Health Data, Diet and CVD Treatment

analyse and interpret illness/mortality data to determine health risks; distinguish correlation from causation; recognise conflicting evidence · evaluate study design used to determine health risk factors (sample selection, sample size, validity, reliability) · understand why perceived risks often differ from actual risks (underestimation/overestimation in heart disease) · analyse data on blood cholesterol, HDL/LDL levels and the causal evidence linking cholesterol/LDL to CVD · understand how scientific knowledge of diet (BMI, waist-to-hip ratio, exercise, smoking) is used to reduce CHD risk · know the benefits and risks of CVD treatments (antihypertensives, statins, anticoagulants, platelet inhibitors)

Gas Exchange Surfaces and Fick's Law

know the properties of gas exchange surfaces (large surface area to volume ratio, thin surface, concentration gradient) · understand how the rate of diffusion depends on these properties and can be calculated using Fick's Law of Diffusion · understand how the mammalian lung is adapted for rapid gaseous exchange

Cell Membranes and Transport

know the structure and properties of cell membranes · understand how models such as the fluid mosaic model are interpretations of data on membrane structure and properties · CORE PRACTICAL 3: investigate membrane properties including the effects of alcohol and temperature on membrane permeability · understand osmosis in terms of free water movement through a partially permeable membrane down a water potential gradient · understand passive transport (diffusion, facilitated diffusion), active transport (ATP-driven, including endocytosis and exocytosis), and the roles of carrier and channel proteins

Proteins: Amino Acids, Bonds and Structure

know the basic structure of an amino acid (structures of specific amino acids are not required) · understand how polypeptides and proteins form via condensation/peptide bonds · understand how primary structure determines secondary and tertiary structure; differences between globular and fibrous proteins and the bonds involved · know the molecular structure of a globular and a fibrous protein (haemoglobin, collagen) and how their structures relate to their functions

Enzymes: Mechanism, Specificity and Kinetics

understand enzyme action and specificity in terms of three-dimensional structure · understand that enzymes are biological catalysts that lower activation energy · know that intracellular enzymes catalyse reactions inside cells and extracellular enzymes catalyse reactions outside cells · CORE PRACTICAL 4: investigate the effects of temperature, pH, enzyme concentration and substrate concentration on the initial rate of enzyme-catalysed reactions

DNA Structure, Replication and the Genetic Code

know the basic structure of mononucleotides (deoxyribose or ribose + phosphate + base: thymine, uracil, adenine, cytosine or guanine) and the structure of DNA and RNA (polynucleotides linked by phosphodiester bonds) · know how complementary base pairing and hydrogen bonding form the DNA double helix · understand DNA replication and the role of DNA polymerase · understand how Meselson and Stahl's classic experiment supported the accepted theory of DNA replication · understand the nature of the genetic code (triplet, non-overlapping, degenerate); know that a gene is a base sequence on DNA coding for a polypeptide

Protein Synthesis and Mutations

understand protein synthesis (transcription and translation); roles of RNA polymerase, mRNA, tRNA, ribosomes, start and stop codons; the antisense template strand, codons on mRNA, anticodons on tRNA · understand how errors in DNA replication can give rise to mutations (substitution, insertion, deletion) · know that some mutations cause cancer or genetic disorders, but many have no observable effect

Inheritance, Genetic Screening and Ethics

understand the terms gene, allele, genotype, phenotype, recessive, dominant, codominance, homozygote, heterozygote · understand patterns of inheritance including monohybrid inheritance and genetic pedigree diagrams · understand sex linkage on the X chromosome (red-green colour blindness) · understand how the cystic fibrosis gene mutation impairs gaseous exchange, digestive and reproductive systems · understand uses of genetic screening (carrier identification, PGD, prenatal testing including amniocentesis and chorionic villus sampling) and the implications of prenatal screening · identify and discuss ethical and social issues relating to genetic screening (religious, moral and social viewpoints)

Cells, Tissues and Organ Systems

know that all living organisms are made of cells, sharing some common features · understand how the cells of multicellular organisms are organised into tissues, tissues into organs, and organs into organ systems

Eukaryotic Ultrastructure and Organelle Function

know the ultrastructure of eukaryotic cells: nucleus, nucleolus, ribosomes, rough and smooth ER, mitochondria, centrioles, lysosomes, Golgi apparatus · understand the function of each organelle listed above · understand the role of the rough ER and Golgi apparatus in protein transport, including formation of extracellular enzymes · recognise these organelles in electron microscope (EM) images

Prokaryotic Cells and Microscopy

know the ultrastructure of prokaryotic cells: cell wall, capsule, plasmid, flagellum, pili, ribosomes, circular DNA, and the function of each · know how magnification and resolution can be achieved using light and electron microscopy; understand the importance of staining specimens · CORE PRACTICAL 5: use a light microscope to make observations and labelled drawings of suitable animal cells; use a graticule to make measurements and understand scale

Meiosis, Gametes and Genetic Variation

know that a locus is the location of a gene on a chromosome; understand the linkage of genes on a chromosome · understand the role of meiosis in producing non-identical gametes via independent assortment in metaphase I and crossing over in prophase I (stage names of prophase not required) · understand how mammalian gametes are specialised for their functions (acrosome in sperm, zona pellucida in the egg)

Fertilisation in Mammals and Flowering Plants

know the process of fertilisation in mammals: acrosome reaction, cortical reaction, fusion of nuclei · know the process of fertilisation in flowering plants: pollen tube growth and fusion of nuclei

Mitosis and the Cell Cycle

understand the role of mitosis and the cell cycle in producing genetically identical daughter cells for growth and asexual reproduction · CORE PRACTICAL 6: prepare and stain a root tip squash to observe the stages of mitosis · calculate mitotic indices

Stem Cells and Differential Gene Expression

understand the terms stem cell, pluripotent, totipotent, morula and blastocyst; discuss societal uses of stem-cell knowledge in medical therapies · understand how cells become specialised through differential gene expression, producing active mRNA that drives synthesis of proteins controlling cell processes or structure · understand how one gene can give rise to more than one protein via post-transcriptional changes to mRNA

Phenotype, Epigenetics and Polygenic Inheritance

understand how phenotype results from the interaction of genotype and environment · know how epigenetic modification (DNA methylation, histone modification) can alter gene activation and be passed on following cell division · understand how phenotypes are affected by multiple alleles for the same gene, by polygenic inheritance, and by the environment, giving rise to continuous variation

Plant Cell Structure and Ultrastructure

know the structure and ultrastructure of plant cells including cell wall, chloroplast, amyloplast, vacuole, tonoplast, plasmodesmata, pits and middle lamella; compare with animal cells · understand the function of each plant-cell structure listed above · recognise plant organelles in electron microscope (EM) images

Cellulose, Plant Fibres and Plant Tissue Microscopy

understand the structure and function of starch and cellulose, including the role of hydrogen bonds between β-glucose molecules in cellulose microfibrils · understand how the arrangement of cellulose microfibrils and secondary thickening in plant cell walls contributes to the physical properties of xylem vessels and sclerenchyma fibres · know the similarities and differences between sclerenchyma fibres (support), xylem vessels (support and water/mineral transport) and phloem (translocation of organic solutes), and their positions in the stem · CORE PRACTICAL 7: use a light microscope to make labelled plan diagrams of transverse sections of roots, stems and leaves; identify sclerenchyma fibres, phloem, sieve tubes and xylem vessels

Plant Fibres for Sustainability; Water and Inorganic Ions

understand how the uses of plant fibres and starch may contribute to sustainability, including plant-based replacements for oil-based plastics · understand the importance of water and inorganic ions (nitrate, calcium, magnesium) to plants · CORE PRACTICAL 8: determine the tensile strength of plant fibres

Plants as Drug Sources and the History of Drug Testing

understand the conditions required for bacterial growth · know that substances derived from plants can have antimicrobial and other therapeutic properties · CORE PRACTICAL 9: investigate the antimicrobial properties of plants, including aseptic techniques for the safe handling of bacteria · understand the development of drug testing from historic to contemporary protocols, including William Withering's digitalis soup, double-blind trials, placebos and three-phased testing

Classification and the Three-Domain System

understand that classification organises the variety of life using phenotypic and genotypic differences, built around the species concept · understand the importance of critical evaluation of new data by the scientific community, leading to new taxonomic groupings based on molecular evidence (three-domain system: Archaea, Bacteria, Eukarya) · know that, over time, the variety of life has become extensive but is now being threatened by human activity

Biodiversity and How It Is Measured

understand the terms biodiversity and endemism · know how biodiversity within a habitat is measured using species richness, and within a species using genetic diversity via the heterozygosity index = number of heterozygotes / number of individuals · understand how biodiversity is compared between habitats using the index of diversity D = N(N−1) / Σn(n−1)

Niches, Hardy-Weinberg and Reproductive Isolation

understand the concept of niche; discuss adaptations of organisms (behavioural, anatomical, physiological) · understand how the Hardy-Weinberg equation tracks allele frequency changes in a population over time · understand that changes in allele frequency arise from mutation and natural selection · understand that reproductive isolation can lead to accumulation of different genetic information in populations and the formation of new species

Conservation: Zoos and Seed Banks

evaluate the methods used by zoos and seed banks in conserving endangered species and their genetic diversity, including scientific research, captive breeding programmes, reintroduction programmes and education

Planning an Experiment

identify the apparatus, dependent and independent variables, and controlled variables required for an investigation · describe how to measure variables using appropriate instruments and correct techniques; identify health and safety issues · discuss repeat readings, sources of uncertainty/systematic error and how to reduce them · comment on the wider implications of biology (benefits/risks) and its social, environmental and historical context

Implementation and Measurements

comment on the number of readings, range of measurements and significant figures · check inconsistent readings (e.g. points not on the line of a graph) · comment on how the experiment may be improved, including by using additional apparatus to reduce errors

Processing Results

perform calculations using the correct number of significant figures; use the correct units throughout · plot results on a graph using an appropriate scale; comment on the relationship obtained · determine the relationship between two variables, or a constant from a graph (e.g. via the gradient using a large triangle) · suggest realistic modifications to reduce errors and improve the experiment; discuss uncertainties qualitatively and quantitatively

Photosynthesis Overview and ATP

understand the overall reaction of photosynthesis: light energy splits water, hydrogen is stored in glucose by combination with CO₂, and O₂ is released to the atmosphere · understand how photophosphorylation of ADP requires energy, and that hydrolysis of ATP provides an immediate supply of energy for biological processes

The Light-Dependent Reactions

understand the light-dependent reactions of photosynthesis: light excites electrons in chlorophyll; the role of these electrons in generating ATP, reducing NADP in cyclic and non-cyclic photophosphorylation, and producing O₂ via photolysis of water

The Light-Independent Reactions and the Calvin Cycle

understand the light-independent reactions as reduction of CO₂ using the products of the light-dependent reactions (carbon fixation in the Calvin cycle, roles of GP, GALP, RuBP and RUBISCO) · know that the products are simple sugars used by plants, animals and other organisms in respiration and the synthesis of polysaccharides, amino acids, proteins, lipids and nucleic acids

Chloroplasts, Pigments and Chromatography

understand the structure of chloroplasts in relation to their role in photosynthesis · understand the terms absorption spectrum and action spectrum · understand how chloroplast pigments can be separated using chromatography and identified using R+f values · CORE PRACTICAL 10: investigate the effects of light intensity, light wavelength, temperature and CO₂ availability on the rate of photosynthesis using a suitable aquatic plant

Productivity and Trophic Transfers

understand the relationship between gross primary productivity (GPP), net primary productivity (NPP) and plant respiration (R); calculate NPP · know how to calculate the efficiency of biomass and energy transfers between trophic levels

Populations, Communities, Niches and Habitats

understand the terms population, community, habitat and ecosystem · understand that the numbers and distribution of organisms in a habitat are controlled by biotic and abiotic factors · understand how the concept of niche accounts for distribution and abundance of organisms in a habitat · CORE PRACTICAL 11: study the ecology of a habitat using quadrats and transects; measure relevant abiotic factors

Succession and Climax Communities

understand the stages of succession from colonisation to the formation of a climax community

Evidence and Causes of Climate Change

understand the different types of evidence for climate change and its causes, including records of CO₂ levels, temperature records, pollen in peat bogs and dendrochronology; recognise correlations vs causal relationships · understand the causes of anthropogenic climate change, including the role of greenhouse gases in the greenhouse effect · understand how knowledge of the carbon cycle can be applied to methods that reduce atmospheric CO₂ · understand that data can be extrapolated to make predictions used in models of future climate change, and that these models have limitations

Climate Change Effects on Organisms and Enzyme Activity

understand the effects of climate change (changing rainfall, seasonal cycles) on plants and animals (distribution, development, lifecycles) · understand the effect of temperature on the rate of enzyme activity and its impact on plants, animals and microorganisms, including Q₁₀ · CORE PRACTICAL 12: investigate the effects of temperature on the development of organisms (e.g. seedling growth or brine shrimp hatch rates), with ethical use of organisms

Evolution, Speciation and Conservation Responses

understand how evolution (changes in allele frequency) can come about through gene mutation and natural selection · understand how isolation reduces gene flow between populations, leading to allopatric or sympatric speciation · understand how scientific conclusions on controversial issues (climate change actions, human contribution) can depend on who is reaching the conclusions · understand how reforestation and the use of sustainable resources (including biofuels) manage the conflict between human needs and conservation

Culturing Microorganisms and Measuring Growth

understand the principles and techniques involved in culturing microorganisms using aseptic technique · understand methods of measuring microbial growth: cell counts, dilution plating, mass and optical methods (turbidity) · understand the phases of a bacterial growth curve (lag, exponential, stationary, death); calculate exponential growth-rate constants · CORE PRACTICAL 13: investigate the rate of growth of microorganisms in a liquid culture, with safe and ethical use of organisms

Bacteria vs Viruses; Lytic vs Latent Cycles

compare bacteria and viruses (nucleic acid, capsid structure, envelope) with reference to Ebola virus, tobacco mosaic virus, human immunodeficiency virus, and lambda phage · understand the terms lytic and latency

Pathogens, Infection Routes and Barriers

understand how Mycobacterium tuberculosis and human immunodeficiency virus infect human cells, causing symptoms that may result in death · know the major routes pathogens may take when entering the body · understand the role of physical/chemical barriers protecting the body from infection: skin, stomach acid, gut and skin flora

Non-Specific Immune Response

understand the non-specific responses to infection: inflammation, lysozyme action, interferon and phagocytosis

Specific Immunity: B Cells and T Cells

understand the roles of antigens and antibodies in the body's immune response, including plasma cells, macrophages and antigen-presenting cells · understand the differences between B cells (B memory and B effector) and T cells (T helper, T killer, T memory) in the host's immune response

Immunity Types, Evolutionary Arms Race and Antibiotic Resistance

understand how individuals develop immunity (natural, artificial, active and passive) · understand how the evolutionary arms race between pathogens and hosts is supported by pathogen evasion mechanisms · understand the difference between bacteriostatic and bactericidal antibiotics · CORE PRACTICAL 14: investigate the effect of different antibiotics on bacteria · know how understanding the contributory causes of hospital-acquired infections has led to codes of practice on antibiotic prescription and infection control

Microbes in Decomposition and the Carbon Cycle

know the role of microorganisms in the decomposition of organic matter and the recycling of carbon

Gene Technology: PCR, Gel Electrophoresis and DNA Profiling

know how DNA can be amplified using the polymerase chain reaction (PCR) · know how gel electrophoresis separates DNA fragments of different length · understand how DNA profiling is used for identification and determining genetic relationships between organisms (plants and animals)

Forensic Biology: Determining Time of Death

understand how to determine the time of death of a mammal by examining the extent of decomposition, the stage of succession, forensic entomology, body temperature and degree of muscle contraction

Respiration Overview and Glycolysis

understand the overall reaction of aerobic respiration: splitting of respiratory substrate to release CO₂ and reuniting hydrogen with atmospheric oxygen, releasing large amounts of energy · understand that respiration is a stepped process, each step controlled and catalysed by a specific intracellular enzyme (names of enzymes not required) · understand the role of glycolysis in aerobic and anaerobic respiration: phosphorylation of hexoses, ATP production by substrate-level phosphorylation, reduced coenzyme, pyruvate and lactate (intermediate compound names not required)

The Link Reaction and the Krebs Cycle

understand the role of the link reaction and the Krebs cycle in the complete oxidation of glucose, formation of CO₂ by decarboxylation, ATP by substrate-level phosphorylation, and reduced NAD/FAD by dehydrogenation (other compound names not required); locate these steps in mitochondria vs glycolysis in the cytoplasm

Oxidative Phosphorylation and ATP Synthase

understand how ATP is synthesised by oxidative phosphorylation associated with the electron transport chain in mitochondria, including the role of chemiosmosis and ATP synthase

Anaerobic Respiration, RQ and Respirometry

understand what happens to lactate after anaerobic respiration in animals · understand the term respiratory quotient (RQ) · CORE PRACTICAL 15: use an artificial hydrogen carrier (redox indicator) to investigate respiration in yeast · CORE PRACTICAL 16: use a simple respirometer to determine the rate of respiration and RQ of a suitable material (e.g. germinating seeds or small invertebrates)

Muscles and the Skeleton

know how muscles, tendons, the skeleton and ligaments interact to enable movement, including antagonistic muscle pairs, extensors and flexors · know the structure of a mammalian skeletal muscle fibre; differences between fast and slow twitch fibres

Sliding Filament Theory of Muscle Contraction

understand the process of skeletal muscle contraction in terms of the sliding filament theory, including the roles of actin, myosin, troponin, tropomyosin, calcium ions (Ca²⁺), ATP and ATPase

Cardiac Muscle, ECGs and Cardiac Output

know the myogenic nature of cardiac muscle · understand how the normal electrical activity of the heart coordinates the heartbeat (SAN, AVN, bundle of His, Purkyne fibres) · understand how ECGs can aid in the diagnosis of abnormal heart rhythms · calculate cardiac output

Ventilation, Exercise and Adrenaline

understand how variations in ventilation and cardiac output enable rapid O₂ delivery and CO₂ removal, including control by the cardiovascular control centre and the ventilation centre in the medulla oblongata · understand the role of adrenaline in the fight-or-flight response · CORE PRACTICAL 17: investigate the effects of exercise on tidal volume, breathing rate, respiratory minute ventilation, and oxygen consumption using data from spirometer traces

Feedback Control and Homeostasis

understand negative feedback and positive feedback control · understand the principle of negative feedback in maintaining systems within narrow limits · understand homeostasis and its importance in maintaining dynamic equilibrium during exercise, including the role of the hypothalamus in thermoregulation

The Mammalian Kidney, Urea and Osmoregulation

know the gross and microscopic structure of the mammalian kidney · understand how urea is produced from excess amino acids in the liver (ornithine cycle detail not required) and removed by ultrafiltration · understand selective reabsorption in the proximal tubule and how the loop of Henle acts as a countercurrent multiplier to increase water reabsorption · understand how the pituitary, osmoreceptors in the hypothalamus, and ADH bring about negative feedback control of plasma concentration and blood volume

Hormones and Gene Expression Control

understand how genes can be switched on and off by DNA transcription factors, including the role of peptide hormones acting extracellularly vs steroid hormones acting intracellularly

Neurones and Reflex Arcs

know the structure and function of sensory, relay and motor neurones, including Schwann cells and myelination · understand how the nervous system can cause effectors to respond to a stimulus · know the structure and function of a spinal reflex arc, including grey matter and white matter of the spinal cord

Action Potentials and Saltatory Conduction

understand how a nerve impulse (action potential) is conducted along an axon, including changes in membrane permeability to sodium and potassium ions · understand the role of myelination in saltatory conduction

Synapses and the Pupil Reflex

know the structure and function of synapses in nerve impulse transmission, including the role of neurotransmitters and acetylcholine · understand how the pupil dilates and contracts

Drugs Affecting Nerve Impulse Transmission

understand how drugs affect nerve impulse transmission, illustrated by nicotine, lidocaine, cobra venom alpha toxin, L-DOPA for Parkinson's disease, and MDMA (ecstasy)

Vision: Rods, Rhodopsin and Action Potentials

understand how the nervous system detects stimuli, with reference to rods in the mammalian retina, the roles of rhodopsin, opsin, retinal, sodium ions, cation channels, and hyperpolarisation of rod cells in forming action potentials in the optic neurones

Habituation and Plant Hormones

understand the term habituation · understand how phytochrome, auxin (IAA) and gibberellins bring about responses in plants, including their effects on transcription · CORE PRACTICAL 18: investigate the production of amylase in germinating cereal grains

The Mammalian Nervous System and the Brain

know that the mammalian nervous system consists of the central and peripheral nervous systems · understand how coordination in animals is brought about through nervous and hormonal control · know the location and main functions of the cerebral hemispheres, hypothalamus, pituitary gland, cerebellum and medulla oblongata

Brain Imaging and Neurological Disease

understand how MRI, fMRI, PET and CT are used in medical diagnosis and investigation of brain structure and function · understand how imbalances in naturally-occurring brain chemicals contribute to ill health (dopamine in Parkinson's, serotonin in depression) and to the development of new drugs

Recombinant DNA, GMOs and Their Risks

know how drugs can be produced using genetically modified organisms (plants, animals and microorganisms) · understand how recombinant DNA can be produced, including the roles of restriction endonucleases and DNA ligase · understand how recombinant DNA can be inserted into other cells · understand the risks and benefits associated with the use of genetically modified organisms

Microarrays and Bioinformatics

know how microarrays can be used to identify active genes · understand the term bioinformatics

Planning Whole Investigations

plan a complete experimental investigation to test a hypothesis, including apparatus, variables, control, safety, and how the data will be used · identify sources of uncertainty and systematic error; discuss how to reduce or eliminate them · comment on the wider implications and context (social/environmental/historical) of the investigation

Practical Techniques for Units 4 and 5

apply techniques from Unit 4 (photosynthesis rates, ecological sampling, microbial growth, antibiotic testing) and Unit 5 (respiration, kidney/spirometry, microscopy) to novel contexts · evaluate the choice of apparatus and method for the technique in use

Synoptic Data Analysis and Evaluation

process and analyse data using appropriate mathematical skills, including ratios, exponential and logarithmic functions, and statistical tests · evaluate results and conclusions with reference to measurement uncertainties and errors; suggest realistic modifications · draw together evidence from multiple topics to answer synoptic questions