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.