16402997
Description
Flashcards by Alice Hathaway, updated more than 1 year ago
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Created by Alice Hathaway
over 5 years ago
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| Question | Answer |
| Needs for transport | Maintain homeostasis Keep solutes within defined limits e.g. proteins structure impacted by pH Specific mechanisms for selective transport |
| Intracellular ionic concentrations | Extremely low H+ Very low Ca2+ Low Mg2+ Fairly low Na+ High K+ |
| Solutes in trade and communication | Solutes for growth and maintenance imported and waste exported Export for wall synthesis/ hormones and other agents Cells use transport systems to move across membrane |
| Volume regulation | Regulate volume through solute movement - water follows by osmosis |
| Compartmentation | Areas of specialised function need own environment different to cytoplasm Vacuole pH3 |
| Vesicle mediated transport | components retrieved, recycled or broken down New components in place Endocytosis = pinch of membrane. Import of solids = phagocytosis, liquids = pinocytosis Exocytosis =addition of new components by fusion |
| Receptor mediated endocytosis | More selective. Cholesterol, growth regulator, iron binding proteins |
| How does this occur? | Specific protein adapter complex interacts with clathrin after specific tetra peptide sequence binds with protein adapter Clathrin spontaneously polymerises to form coated puts of invaginated membrane below plasma Protein adapter associates with free end of heavy chain - receptors localised above pits or diffuse into pit region after conformational change when bind to ligand or their solute Invagination continues until clathrin coated vesicles form In cytosol, clathrin and adaptors released and recycled, catalysed by chaperone |
| Clathrin | 3 heavy chains and 3 light chains From triskelion |
| Cholesterol - unloading the cargo | insoluble - transported as water-soluble LDL Core of cholesterol ester linked to fatty acids surrounded by phospholipids and unesterised cholesterols Embedded is specific protein to allow recognition by LDL receptor |
| How uptakes? | Uncoated vesicle fuses with CURL - lower pH cause dissociation of LDL from receptor receptor embedded in CURL extensions, bud as transport vesicles and taken to the membrane Some transport LDL in lumen, fuse to lysosome. Separated by hydrolytic enzymes |
| Exocytosis | Fusion of vesicle to plasma membrane to release cargo or insert protein Seed germination - highly exocytotic - aleurone cells release alpha amylase to hydrolyse starch supply Marine diatom - able to secrete calcium coccolith - equivalent of human exocytosing tyre |
| Transmembrane transport basics | More lipid soluble, more permeable Passive - down concentration gradient for net movement. increases entropy by dissipating gradient |
| Protein mediated transport | Hydrophilic, charge, large polar Passive (facilitated diffusion) - electrochemical gradient. electrical and chemical gradients can be additive (Na+) or oppose (K+) Active transport -> Carrier, energy from ATP, against gradient |
| Energetics of solutes with no charge | Only consider concentration different Exergonic = down concentration gradient If positive, ATP needed to decrease free energy Et equilibrium, concentration equal hence Keq =1 |
| Energetics of charged solutes | Influence of membrane potential Influx of cations favoured NERNST or Goldman equation If know Em and find solution concentration different to predicted by NERST, know must be active |
| Membrane potentials | Animal = -80mV Plant & Bacteria= -150mV Fungi = -250mV |
| Partition coefficient | In lipid mediated transport Amount dissolving in test lipid/ amount dissolving in water Amount in test lipid equivalent to hydrophobic core |
| Rate limiting | Core viscosity - slows movement Best in liquid crystal state |
| Notable lipid transport | Ethanol movement for anaerobic respiration of plants and fungi Lipid soluble vulnerable to hydrophobic pollutants from industrial activities |
| Protein mediated transport | Protein undergoes conformational change Substate same chemical state, but different compartment Highly specific Inhibited by similar structures Rate of reaction quicker - protein lowers Ea Saturation kinetics Driven chemical potential gradient of solute Not intrinsically vectorial - direction depends on gradient |
| Carriers | Lower Ea of transport Binding cause conformational change - stop further binding. release at other face trigger return to normal Cotransport |
| Channel | Fastest 10^6-10^8/ sec Smaller conformational change Hydrophilic pore |
| Fungi adaptations | Phosphorylate glucose as soon as reach cytoplasm to prevent gradient reversal |
| Ion transport | Varied specificity of channels - size and residues lining pore determine Gate controlled via +ve charge amino acid residues - voltage sensory. Phosphorylation or cAMP Channels rapid where needed - nerve/ muscle Plants - K+ to close stomata |
| Patch clamp electrophysiology | ion movement generates electrical current Glass electrode pushed against to isolate tiny currents mreasures Increase of 1Pa for less than 1 sec. 10^-2 moles pass |
| Ionophores | Bacterial peptides, secreted to kill competing bacteria Shuttle within membrane Valinomycin has K+ in centre - hydrophobic outside to allow transport through Bacteria have beta barrel porins for passive transport |
| Water movements | Diffusion Bulk flow - down pressure gradient Osmosis - high energy to low energy |
| Water potential | WP = solute potential + pressure potential + gravity effect (only if above 5m) |
| Why water potential causes movement of water | Adding solutes increases entropy - WP more negative Solute potential = -RTcs (Cs mole concentration solute per litre water) Pressure potential - negative pressure decreases water potential - walled cells- protoplast against inflexible wall and wall pushes back with equal force |
| Osmosis in action | No significant pressure difference if no wall Hypotonic, water moves into cell as higher water potential outside Isotonic = same water potential inside and outside so no net movement Hypertonic = water moves out as lower water potential outside |
| Growth of walled cells | Loosening of wall needed Accumulates solute for water to enter Antibiotics weaken walls |
| How water goes through membrane | Aquaporins Regulated by phosphorylation and ADH Osmosis combination of through membrane and bulk flow through aquaporins |
| Active transport | Energy input form ATP to move against gradient Primary = ATP directly used to power Secondary = energy from gradient Specific, saturation kinetics, solutes can be accumulated against gradient |
| Primary active transport | Hydrolysis coupled to trnasport ATP high energy bond to overcome phosphate repulsion -31kjmol-1 released to decrease Gibbs free energy to make negative |
| P Type ATPase | Eukaryotic cell function. phosphorylated intermediate - Na+/K+ ATPase 2K+ in/ 3Na+ out to maintain below toxic 1/2 ATP on this Phosphorylation releases Na+, removal of P binds K+- conformational change Plants - H+ transactor. 1H+ per ATP. Maintain pH gradient for cell function |
| V Type ATPase | H+ translocating pumps - ubiquitous in eukaryotes endomembranes - vacuole, vesicles, endosomes Acidification of compartment. ATP drives. V0 integral domain, peripheral V1 domain |
| Secondary active transport | Cotransport of glucose - Na+ chemical gradient symports glucose in with Na+ Chemical gradient brings one down and one against gradient Symport = same direction Antiport = opposite |
| F type ATPase | Use transport mechanism to synthesis ATP Plasma bacteria membrane/ inner mitochondrial membrane/ thylakoid membrane H+ pumped across membrane, chemiosmosis back down gradient stimulates ATP synthesis similarity supports endosymbiosis |
| Structure of ATPase | Sequential H+ binding and release at weak acidic residuals changes electrostatic attraction, rotation by epsilon gamma shaft 3 beta and 3 alpha subunits - beta involved in ATP formation Each 120 degree rotation causes conformational change and release of ATP |
| Membranes and signalling | Signalling ligand recognised by specific transmembrane protein receptors - specific and sensitive Response without ligand crossing Ligand binding causes conformational change in receptor - functionally linked to cytoplasmic protein and initiate next reactions |
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