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| Question | Answer |
| How common properties of a cell suggest a single evolutionary origin | - Mitochondria have characteristics that make them seem like a cell in their own right eg DNA/ribosomes - This suggests they at some point invated eukaryotic cells - Common features of cells- all surrounded by a plasma membrane - all perform metabolism |
| Prokaryotes vs Eukaryotes: Prokaryotes | - Always single celled, no nucleus - Classified into bacteria and archaea - Bacteria have a peptidoglycan cell wall, ribosomes, DNA (often circular) in tightly packed chrosomes |
| Prokaryotes vs Eukaryotes: Eukaryotes | - Can be single celled OR multicellular -ALL MULTICELLULAR ORGANISMS ARE EUKARYOTIC -Single cell eg: -Multicellular eg: - Contain a membrane-enclosed nucleus, containing DNA, except erythrocytes (RBCs) - Membrane-bound cytoplasmic orgsanelles - Cytoskeleton - Size of cells vary from 5-50mn |
| Eukaryotic organelles: Nucleus | - Diameter of a few Nm -Surrounded by a double membrane; the nuclear envelope that encloses the nucleoplasm -DNA packaged w/proteins to form chromosomes -Histones tightly pack DNA into the nucleus of the cell -Transcription happens here |
| Eukaryotic organelles: Endoplasmic reticulum | - Network of interconnecting closed membrane vesicles Types: -RER: rough ER. Studded w/ribosomes on the outside. Synthesis of proteins to be secreted. - SER: smooth Endoplasmic reticulum. Abundance/function depends on cell type. In liver release of glucose from glycogen. (detoxes organic compounds in the liver. - |
| Eukaryotic organelles: Golgi complex | - Stack of flattened membrane vesicles -2 sides, a cis region- pointing towards the nucleus- and a trans- pointing away from the nucleus- region -Directionality- proteins are modified here by enzymes and directed to the right places -Modified proteins leave the golgi body in vesicles, after which they go to their next destination; released by exocytosis or combined with lysosomes |
| Eukaryotic organelles: Lysosomes | - larger, membrane bound organelles, found in most animal cells - 'rubbish dumps of the cell' - macrophages in the immune system use lysosomes to digest bacteria - Acidic internal enviroment, as enzymes in the lysosome work best at this pH |
| Perioxosomes | - Oxidise fatty acids and toxic compounds to produce hydrogen peroxide - Fatty acid oxidation produces heat - Contain catalayse to breakdown hydrogen peroxide in order to protect cell |
| Eukaryotic organelles: Mitochondria | - Between 0.5 to 1 nm and 1-2 nm - Main site of ATP production in the cell, uses oxygen to do this - Uses lots of energy- up to 25% of the cell - Outer mitochondrial membrane is made up of 50/50 lipid and protein - Inner membrane is composed 20/80 lipid and protein. The inner membrane is folded into cristae that protrude into the central matrix. This increases, surface area to make the process more efficient. |
| Eukaryotic organelles: Cytosol | Packed with proteins in the form of the cytoskeleton |
| Subcellular fractination | Separation of different organelles in large numbers, used for biochemical study of cell function. - Cells must be physically disrupted, kept cold and in an isotonic solution. - Then centrifuged using differential velocity centrifugation- increased centrifugal force pellets increased centrifugal fractions - Equilibrium density centrifugation can purify this further; seperating according to density -Organelle specific tests can then be carried out eg catalyse for perioxosomes |
| What properties influence the behaviour of a cell in a centrifugal field? | - Each cell component's behaviour is expressed as the sedimentation constant- 's' (Svedberg units) - The behaviour of a cell component depends on it's volume, density and shape - So, a ribsosme of '70s' has a sedimentation constant of 70 svedberg units. |
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