3.1 - Plasma Membrane and Transport Flashcards
variety of protein molecules present in membrane structure (2)
- peripheral
- integral
phospholipid present in the plasma membrane
phosphatidylcholine
structure of phosphatidylcholine
one saturated and one unsaturated fatty acid with a kink (area of unsaturated fatty acid)
other molecules present in plasma membrane (apart from proteins and phospholipids) (2)
- steroids (e.g. cholesterol)
- glycolipids
role of steroids (e.g. cholesterol) and glycolipids in plasma membrane
give rigidity and provide support
term describing phospholipids having both hydrophobic/hydrophilic area
amphipathic
membrane protein functions (5)
- transporters
- ion channels
- anchors
- receptors
- enzymes
membrane protein transporter example and function (2)
- Na+ pump
- actively pumps Na+ out of cells and K+ in
membrane protein ion channel example and function (2)
- K+ leak channels
- allows K+ ions to leave cells, having major influence on cell excitability
membrane protein anchor example and function (2)
- integrins
- link intracellular actin filaments to extracellular matrix proteins
membrane protein receptor example and function (2)
- platelet-derived growth factor (PDGF) receptor
- binds extracellular PDGF, generating intracellular signals that cause cell growth and divide
membrane protein enzyme example and function (2)
- adenylyl cyclase
- catalyses production of small intracellular signalling molecule cyclic AMP in response to extracellular signals
which molecules can pass through plasma membrane via simple diffusion? (2)
- hydrophobic molecules
- non-polar small molecules
(very small amount of small uncharged polar molecules can also pass through)
types of transport proteins (3)
- channels
- transporters
- ATPase pumps
channel protein activation (3)
- polar substance more concentrated outside than inside cell
- binding of stimulus molecule causes pore to open
- polar substance can diffuse across membrane
natural state of channel proteins and why? (2)
- closed
- to maintain concentration gradients
aquaporins
highly specialised channel proteins that enable water to move quickly across membranes
function of aquaporin in kidney
allows blood to reclaim water from waste being produced
facilitated transport of glucose (3)
- glucose binds to carrier protein
- changes protein shape, releasing glucose inside cell
- carrier protein returns to original shape
GLUT4 glucose transporter activation (4)
- insulin binds to receptor
- signal cascade
- exocytosis
- glucose entry permitted
types of active transporters (3)
- uniporter
- symporter
- antiporter
uniporter role
transports one substance in one direction
symporter role
transports 2 different substances in same direction
antiporter role
transports 2 different substances in opposite directions
role of Na+/K+ pump
moves Na+ out using energy of ATP hydrolysis to establish concentration gradient of Na+
Na+/K+ pump activation (4)
- 3Na+ and 1 ATP bind to protein pump
- hydrolysis of ATP -> ADP and phosphorylates amino acid in pump protein
- shape change causes 2K+ to enter and bind to pump
- dephosphorylation of pump releases Pi causing 2K+ ions to be released to interior of cell returning pump to original form
Na+/glucose co-transporter (SGLT1) role in intestinal and renal proximal tubule (2)
- simultaneously transports 2Na+ and 1 glucose molecule into cell across plasma membrane
- Na+ moving with concentration gradient (established by Na+/K+ pump) drives transport of glucose against concentration gradient
role of Na/Ca2+ exchanger (NCX) in cardiac muscle cells
transports 3Na+ into cell in exchange for Ca2+ out
role of AE1 exchanger protein in erythrocyte membranes
(anion transporter)
exchanges Cl- for HCO3- in ratio 1:1, important for helping erythrocyte carry waste CO2
role of H+/oligopeptide (PepT) transporter in small intestine
couples movement of H+ across plasma membrane to transport dipeptides and tripeptides into cell against concentration gradient
