Cellular Functions

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Cellular Functions

CORE TOPIC 1: CELLULAR FUNCTIONS
Learning Outcomes: (a) Describe and interpret drawings and photographs of typical animal and plant cells as seen under the electron microscope, recognising the following membrane systems and organelles: rough and smooth endoplasmic reticulum, Golgi body, mitochondria, ribosomes, lysosomes, chloroplasts, cell surface membrane, nuclear envelope, centrioles, nucleus and nucleolus. (b) Outline the functions of the membrane systems and organelles listed in (a). (c) Describe the formation and breakage of a glycosidic bond. (d) Analyse the molecular structure of a triglyceride and a phospholipid, and relate these structures to their functions in living organisms. (e) Describe the structure of an amino acid and the formation and breakage of a peptide bond. (f) Explain the meaning of the terms primary structure, secondary structure, tertiary structure and quaternary structure of proteins, and describe the types of bonding (hydrogen, ionic, disulfide and hydrophobic interactions) which hold the molecule in shape. (g) Analyse the molecular structure of a dimeric enzyme with a quaternary structure e.g. viral/HIV protease, as an example of a globular protein, and of collagen as an example of a fibrous protein, and relate these structures to their functions. (h) Explain the mode of action of enzymes in terms of an active site, enzyme/substrate complex, lowering of activation energy and enzyme specificity. (i) Follow the time course of an enzyme-catalysed reaction by measuring rates of formation of products (e.g. using catalase) or rate of disappearance of substrate (e.g. using amylase). (j) Investigate and explain the effects of temperature, pH, enzyme concentration and substrate concentration on the rate of enzyme catalysed reactions, and explain these effects. (k) Explain the effects of competitive and non-competitive inhibitors on the rate of enzyme activity. (l) Explain the importance of mitosis in growth, repair and asexual reproduction. (m) Explain the need for the production of genetically identical cells and fine control of replication. (n) Explain how uncontrolled cell division can result in cancer, and identify factors which can increase the chances of cancerous growth. (o) Describe with the aid of diagrams, the behaviour of chromosomes during the mitotic cell cycle and the associated behaviour of the nuclear envelope, cell membrane and centrioles. (Names of the main stages are expected) (p) Explain what is meant by homologous pairs of chromosomes. (q) Describe, with the aid of diagrams, the behaviour of chromosomes during meiosis, and the associated behaviour of the nuclear envelope, cell membrane and centrioles. (Names of the main stages are expected, but not the sub-divisions of prophase)

The Cell Theory
The cell is the basic unit of life, the basic unit of structure and function in living organisms as it is the building block of structures in living organisms and the functioning unit of life. It is derived from pre-existing cells by division and contains genetic material. General functions of cell include taking in raw materials, extracting useful energy from the materials, synthesising its own molecules, growing in an organised manner, responding to stimuli from the surrounding, and reproducing itself.

Compare Animal and Plant cell
Animal Plant Cell surface membrane – defines the boundary of a cell, retains its contents and regulates the movement of substances in and out. (ref. Core Topic 6) Nucleus – contains the genetic material that directs cellular activities. Cytoplasm – semi-fluid mixture of the cytosol and organelles. Organelles include ribosomes, endoplasmic reticulum, golgi apparatus, mitochondria, vacuoles, and cytoskeleton. Lysosomes Cell wall and plasmodesmata Centrioles Plastid e.g. chloroplast Flagella and cilia Large central vacuole and tonoplast 1

Cellular Functions

(a) Nucleus
The nucleus is spherical or ovoid in shape with an average...
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