Topic 4
- Created by: Sailing26880
- Created on: 12-04-18 12:11
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- Topic 4
- Endocytosis and Exocytosis
- En- Phaagocytosis: solid substances, sometimes whole organisms are taken into a cell through in folding of the surface membrane
- En- Pinocytosis: similar to phagocytosis but infoldngs in the membrane much smaller so transports liquids
- Exo- reverse of endocytosis, vesicules and vacuoles move towards the surface membrane fuse with it and release the contents to outside the cell
- Xylem and Phloem
- Mass flow hypothesis: dissolved sucrose moves in phloem by means of pressure gradients between source and sinks
- mass flow of the phloem towards sink when hydrostatic pressure is lower due to the sucrose
- Uptake and loss of water
- Mass flow hypothesis: dissolved sucrose moves in phloem by means of pressure gradients between source and sinks
- Gas Exchange
- Mammals Alveoli have a large surface area
- Insects Tracheae from spiracles, into tracheoles then organs
- Plants gained and lossed through the concentration of potassium ions
- Fish counter current flow
- Surface Area to Volume Ratio
- Small Organisms
- High SA-V ratio diffusion is adequate as diffusion over a short distance
- Large Organisms
- Low SA-V ratio diffusion is not adequate so have evolved organs for gas exchange
- Rate of diffusion
- Small Organisms
- Heart and Blood
- Heart and blood vessels
- Single and double circulation
- CARDIAC CYCLE - diastole (relaxed); pressure increases in atrium so AV opens; systole of atrium; then ventricle systole; AV close SL open
- Control of the heartbeat; SAN impulses across walls of atrium, AVN through Bundle of His, Purkyne fibers.
- Pressure changes and ECG
- BLOOD CLOTTING:
- Platelets form and plug and release clotting factors including thromboplastin
- Prothrombin > active from thrombin, catalysed through thromboplastin
- Thrombin acts on soluble fibrogen into insoluble fibrin forming a mesh to cover the wound
- Platelets and blood called get trapped in mesh forming in a blood clot
- Thrombin acts on soluble fibrogen into insoluble fibrin forming a mesh to cover the wound
- Prothrombin > active from thrombin, catalysed through thromboplastin
- Platelets form and plug and release clotting factors including thromboplastin
- Haemoglobin: Bohr Effect, when levels of CO2 are high as the tissues Hb bind with O2 less well so Hb gives O2 up more easily
- Cell Surface Membrane
- Glycoproteins and glycolipids often act as receptors and antigens, they are lipids or proteins with a carbohydrate chain attached
- Passive Movement
- Diffusion: small non charged molecules can diffuse through the lipid bilayer of the cell surface membrane. high to low conc
- Facilitated diffusion: large charged or polar molecules move thrugh a channel in the bilayer known as carrier proteins.
- Osmosis: the diffusion of water
- the turgor pressure is that of the inside of the cells, so plants cells should be turgid and ridged
- Water potential = turgor pressure+ osmotic potential
- Turgor pressure= hydrostatic pressure caused by the cell contents pushing against the cell wall
- Osmotic potential= the potential of water to move out of a solution across a partially permeable membrane
- water potential= measure for water to move out of a solution by osmosis
- Osmotic potential= the potential of water to move out of a solution across a partially permeable membrane
- Turgor pressure= hydrostatic pressure caused by the cell contents pushing against the cell wall
- Active Transport
- 1- proteins in the membrane act as carriers (specific to the molecule)
- 2- the release of energy from the hydrolysis of ATP causes a change of shape in the carrier protein moving the molecule from one side to the other
- 3- the protein then returns to its original shape (passively) to allow more molecules to enter.
- 2- the release of energy from the hydrolysis of ATP causes a change of shape in the carrier protein moving the molecule from one side to the other
- 1- proteins in the membrane act as carriers (specific to the molecule)
- Tissue Fluid and Formation
- Derived from blood and contain everything that plasma does but no proteins and platelets, l
- Lymph is derived from tissue fluid and is similar but has a lower concentration of nutrients
- Endocytosis and Exocytosis
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