11.1 Antibody production and vaccination

Cells & pathogens

• The surface of cells of an organism has unique molecules.
• Pathogens can be species-specific or can cross species barriers.

Antibody production involves the following:

• B lymphocytes are activated by T lymphocytes in mammals.
• Activated B lymphocytes multiply to form clones of plasma cells and memory cells (giving immunity).
• Plasma cells secrete antibodies which aid the destruction of pathogens.
• Other white blood cells release histamine in response to allergens which causes allergic symptoms.

Vaccination and monoclonal antibodies

• Vaccines contain antigens that trigger an immune response without causing the disease.
• Fusion of a tumour cell with an antibody-producing plasma cell creates a hybridoma cell.
• Monoclonal antibodies are produced by hybridoma cells
• Monoclonal antibodies to HCG are used in pregnancy test kits.

11.2 Movement

Skeletons and muscles

• Bones and exoskeletons (e.g. insect legs) provide anchorage for muscles and act as levers.
• Synovial joints allow certain movements but not others.
• Muscles work in antagonistic pairs.

Muscle contraction

• Skeletal muscle fibres are multinucleate and contain
  • specialised endoplasmic reticulum
  • many myofibrils
  • made up of contractile sarcomeres.
• The sliding of actin and myosin filaments causes contraction.
• Contraction requires ATP hydrolysis and cross bridge formation
• Calcium ions and the proteins tropomyosin and troponin control muscle contractions.

11.3 The Kidney and osmoregulation

Control of water balances in different animals

• Some animals are osmoconformers - their cells have solute concentration equal to their environment (eg. marine invertebrates)
• Vertebrates and insects are osmoregulators. (so are some single cells, eg.Amoeba)
• Insects have malpighian tubules but vertebrates have kidneys to carry out osmoregulation and remove nitrogenous wastes.
• The type of nitrogenous waste in animals is correlated with evolutionary history and habitat.

Kidney structure & function

• The differences in composition of blood in the renal artery & the renal vein.
• Ultrafiltration helped by the ultrastructure of the glomerulus and Bowman’s capsule.
• Selective reabsorption of useful substances by active transport in the proximal convoluted tubule.
• The loop of Henle maintains hypertonic conditions in the medulla.
• ADH controls reabsorption of water in the collecting duct.

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• The length of the loop of Henle is positively correlated with the need for water conservation in animals.

11.4 Sexual Reproduction

Gametogenesis

• Similarities in spermatogenesis and oogenesis include mitosis, cell growth, two divisions of meiosis and differentiation.
• Students need to be able to annotate diagrams of seminiferous tubule and ovary to showing these details.
• Differences between the processes in spermatogenesis and oogenesis are the different numbers of gametes produced and the different amounts of cytoplasm in these gametes.
• Annotation of diagrams of mature sperm and egg to indicate functions.

Fertilization

• Fertilization in animals can be internal or external.
• Fertilization involves the acrosome reaction, fusion of the plasma membrane of the egg and sperm and the cortical reaction. (mechanisms that prevent polyspermy)

Early growth of the embryo

• Implantation of the blastocyst in the endometrium is essential for the continuation of pregnancy.
• HCG stimulates the ovary to secrete progesterone during early pregnancy.
• The placenta facilitates the exchange of materials between the mother and fetus.
• Estrogen and progesterone are secreted by the placenta once it has formed.
• Birth is mediated by positive feedback involving estrogen and oxytocin.