Cell activity

Cells
1. Animal cells
  1. Nucleus, to control the activities of the cell
    1. Contains chromosomes which carry genes that control the characteristics of the body
    2. Different forms of genes are called alleles
  2. Cytoplasm, in which most of the chemical reactions take place
  3. The cell membrane controls passage of substances into and out of the cell
  4. Mitochondria, where most of the energy is released in respiration
  5. Ribosomes, where protein synthesis occurs
2. Plant cells
  1. Chloroplasts, which absorb light energy to make food
    1. Contain chlorophyll
  2. A permanent vacuole filled with cell sap
  3. A cell wall made of cellulose, which strengthens and supports the cell
3. Other cells
  1. Bacteria
    1. No nucleus - instead genetic material is arranged in plasmids
  2. Yeast
    1. A single celled organism
Movement of substances in and out of cells
1. Diffusion
  1. Spreading of the particles of any substance in solution
  2. Results in a net movement of particles from a region of high concentration to a low concentration
  3. The greater the difference in concentration, the faster the rate of diffusion
2. Osmosis
  1. Movement of water across a partially permeable membrane
  2. Moves from an area of high concentration to an area of low concentration
3. Definitions
  1. Isotonic: if two solutions have the same concentration
  2. Hypertonic: the solution which is more concentrated
  3. Hypotonic: the solution which is more dilute
  4. Turgid plant cells: rigid plant cells with lots of water
  5. Plasmolysed plant cells: shrunken plant cells with little water
4. Cells use active transport to absorb substances across partially permeable membranes against the concentration gradient.
  1. This requires energy from respiration
5. Efficiency of exchange can be increased by
  1. Having a large surface area
  2. Having a thin surface
  3. Having an efficient blood supply
  4. Being ventilated
Cell division
1. Meosis
  1. Cell divides to form sex cells/gametes
  2. Cell divides twice to form four gametes, each with a single set of chromosomes
  3. Gametes join at fertilisation and this newly form cell divides by mitosis to form many cells, becoming an organism
2. Mitosis
  1. The cell divides once to produce two genetically identical daughter cells
3. Cell division is essential for growth and repair in an organism
4. Plants can differentiate cells throughout their lives, however animals are unable to

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	Created by kate.siena almost 11 years ago