Cell Physiology 1 Flashcards
Lec 3 & 4 & 5
What are the components of the cell membrane?
- phospholipid bilayer. 2. membrane proteins. 3. membrane carbohydrates.
What is the phospholipid bilayer?
continuous layer around the cells. has carbs on external surface, proteins in the bilayer. its a barrier to water soluble substances (solutes that can easily dissolve in water). it lets lipid soluble molecules and small molecules like o2 and co2 pass though freely by simple diffusion.
What are the different kinds of membrane proteins?
a. transport proteins b. receptor proteins. c. enzymes d. joining proteins e. identifying proteins.
What are transport prots and what do they do? What are the two kinds?
they allow certain molecules to pass through the bilayer. so they allow passive transport that doesnt use energy, and secondary active transport. channel prots and carrier prots.
What do channel proteins do?
channel-mediated facilitated diffusion (passive transport using channels) of specific ions and water (osmosis). so forms a pore/channel in the membrane so that selected ions/mols can pass through. can be gated - opens and closes when signalled or non-gated - always open.
What do carrier proteins do?
allow carrier-mediated facilitated diffusion (passive transport using carriers) or active transport. bind to solute and help carry it across the membrane.
What are receptor proteins?
binding sites for signaling molecules ie ligands/chemical messengers like hormones and neurotransmitters. eg. glucose uptake - insulin binds to receptor on mm or adipose tissue and triggers more glucose transporters which increase glucose mvmt into blood from cells.
What are enzymes?
prots that control chemical reactions on outer or inner surfaces.
What are joining proteins?
anchor cell membrane o cytoskeleton or an adjacent cell. so join cells together. a. junctional prots btwn cells forming desmosomes, tight junctions, gap junctions. b. extracellular fibers
What are identifying proteins?
ex. major histocompatibility complex prots. are on the surface of all cells except for rbcs. they ID cell as self, so help immune syst. reco. foreign substances. will attack foreign bodies.
What are membrane carbohydrates?
glycoproteins and glycolipids on the exterior of bilayer. allow cells to reco other types of cells. ie sperm recognizes egg.
How does membrane transport affect homeostasis?
homeo relies on the ability of cells to maintain the composition of the intracellular and extracellular fluid and to move solutes and solvents across the cell membrane. so needing to maintain equilibrium and letting cells go where they need to go.
What is the difference btwn a solute and a solvent?
a solute is the substance dissolved in a solution (ions and molecules). a solvent is the substance that the solute is dissolved in ie water.
What are the two types of membrane transport (just list)?
passive transport, and active transport.
What is passive transport?
transport that doesnt require any energy (no ATP). its always mvmt down a concentration gradient, so solutes and solvents move from high to low. the greater the diff in conc (ie one side solute conc super high and one side super low), the more molecules that want to move (bc they want to be in equilibrium).
What are the types of passive transport (just list)?
simple diffusion, channel-mediated facilitated diffusion, carrier-mediated facilitated transport/diffusion, osmosis (solvent mvmt), bulk flow.
What is simple diffusion?
passive transport where solutes - specifically lipid soluble and small molecules like gases o2 and co2 - diffuse directly through the lipid bilayer. so down their conc grad from high to low.
What is channel-mediated facilitated diffusion?
passive transport where ions diffuse past bilayer bc of access granted by channel proteins. so solute moves freely through opening created by the channel.
What is carrier-mediated facilitated diffusion/transport?
passive or active transport where large, charged, or water soluble molecules diffuse through bilayer by binding to carrier protein that takes them so other side. so solute must bind to protein to pass.
What is osmosis?
water/solvent diffuses across semipermeable membrane due to water difference. so water moves bc theres a diff in water lvl on either side. water moves down its conc grad so form high to low (diffusion) via channels or across memb bilayer.
What is a dilute solution?
high [H2O], low [solute]
What is a concentrated solution?
low [H2O], high [solute]
What is osmotic pressure?
the pressure required to prevent water from moving across the semipermeable membrane due to osmosis (ie water wanting to go down its conc grad). so the pressure that S2 needs to exert to keep S1s water from coming over.
What is osmotic pressure determined by?
solute concentration. if its pure water (ie no solutes) there is no OP. the greater the solute conc the greater the OP.
Where does water move depending on the OP?
water moves from low OP to high OP, bc low OP= high water conc and high OP= low water conc, and we know that water diffuses from high to low concentration.
What is the OP if both solutions are pure water?
OP is 0 bc there is no conc grad for water mols and therefore no pressure is required to prevent water mvmt. water is still moving but there is no net mvmt.
What is the OP if both solutions have the same concentration of solutes?
the OP of both solutions is equal but not zero. so theres still pressure bc there;s solute, but its the same amount.
If the OP is high what is the concentration of the solution?
high OP = high [solute], low [h2o]. bc more pressure is needed to prevent water from other solution going down conc grad into this solution.
If the OP is low what is the concentration of the solution?
low OP = high[h2o], low [solute]. bc minimal pressure is needed bc water wants to go from high to low so doesnt want to come into this solution where the water is already high.
What is tonicity and what does it depend on?
the response of a cell immersed in a solution. depends on solute conc (and permeability of memb to solute).
What are the classifications of tonicity (just list)?
hypotonic, hypertonic, and isotonic
What is a hypotonic solution?
cell is a ‘hungry hippo’ and takes in too much water causing it to swell. this happens bc the ECF has lower OP then the ICF (cell). and we know water moves from low OP to high OP, in other words from high [h2o] to low [h2o]. too much swelling can cause a rupture = lysis (in rbcs called hemolysis).
What is a hypertonic solution?
cell is ‘hyper and sweats’ so loses too much water causing it to shrivel/shrink. this happens bc the ICF (cell) has low OP and the ECF has high OP, in other words the water goes down its conc grad from high conc in cell to low conc outside.
What is a isotonic solution?
‘same’ where theres no change bc the ECF and ICF have equal osmotic pressures. most cells in human body have solute concentrations that are equal to a 0.9% saline solution.
What are the practical uses of tonicity to reduce a brain edema?
edema is swelling in the brain, so if we inject a 10% sucrose solution which is hypertonic, the swelling will decrease in the cells bc the OP is higher outside the cell, so water will want to move to it.
What is bulk flow?
passive transport thats the mvmt of fluid and solutes due to a pressure gradient (high pressure to low pressure). uses hydrostatic pressure.
What is hydrostatic pressure?
the pressure of a fluid pressing against a hard surface.
What is an active transport process?
require energy (ATP) to move ions/molecules against their concentration gradient (low to high).
What are the types of active processes (just list)?
active transport, and vesicular transport.
What is active transport? list its two types?
substances move against their conc grad, always protein carrier-mediated. type one is primary active transport. type two is secondary active transport.
What is primary active transport?
a molecular pump breaks down ATP and uses it directly so that it can actively transport ions against their conc grads. example is the Na/K ATPase pump which pumps 3 Na out of the cell and 2 K into the cell per ATP (against their gradients). this forms a conc grad for Na/electron concentration gradient bc now theres even more Na outside cell and even more K inside cell which makes inside the cell negative and outside positive. Summary: pump uses ATP, moves 3 Na and 2 K against conc grad, establishes Na conc grad.
What is secondary active transport?
example; glucose absorption by nterocytes. step 1: conc grad established by ATPase pump which uses atp directly (so cant do secondary transport without primary) so use of atp is indirect in secondary. step 2: Na binds to a carrier protein bc it wants to go down its conc grad, and glucose hitches a ride onto that carrier protein and they are cotransported into the cell. (Na going down its conc grad allows glucose to be transported in against its conc grad)
What is vesicular transport?
substance is surrounded by a membrane within the cell that moves across the memb ie a vesicle. vesicle mvmt across memb is fueled by atp.
What are the types of vesicular transport (list)?
endocytosis, and exocytosis.
What is endocytosis?
movement into a cell. two diff kinds; phagocytosis - large items into cell ie bacteria. pinocytosis - fluids into cell.
What is exocytosis?
movement out of the cell. vesicles contain hormones, nt, enzymes, etc. fuse with cell memb releasing contents into ECF.
