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MCAT biochem > biological membranes > Flashcards

biological membranes Flashcards

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MCAT flashcards
1
Q

fluid mosaic model

A

describes the structure of the plasma membrane
-lipids and proteins diffuse freely
- lipid bilayer

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2
Q

lipid bilayer

A

two layers of phospholipids with polar heads facing environment and hydrophobic FA tails facing internal space

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3
Q

what force is PRIMARILY responsible for the formation of the lipid bilayer

A

hydrophobic interactions

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4
Q

other forces that contribute to the lipid bilayer

A

van der walls, hydrogen bonding, noncovalent

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5
Q

lipid rafts

A

held together by large amounts of cholesterol and high concentrations of sphingomyelins and diffuse in lipid bilayer to INCREASE FLUIDITY OF THE MEMBRANE and regulate signaling processes

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6
Q

cholesterol effect on memrbane at HIGH TEMPERATURES

A

decreases fluidity

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7
Q

cholesterol effect on membranes at LOW TEMPERATURES

A

increases fluidity

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8
Q

cholesterol effect on membranes at LOW TEMPERATURES

A

increases fluidity

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9
Q

purpose of unsaturated fatty acids in the plasma membrane

A

promote fluidity by preventing the tails from stacking as happens with saturated fatty acids

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10
Q

which direction in the membrane are phospholipids mobile

A

horizontal

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11
Q

flippases

A

allow phospholipids to shift from one face of the membrane to another (energetically costly)

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12
Q

3 main classes of lipids in the plasma membrane

A
  1. phospholipids –> major component
  2. sterols –> cholesterol
  3. glycolipids –> signalling
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13
Q

sphingosine

A

lipid with a sphingosone backbone instead of glycerol

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14
Q

which orientation are unsaturated fatty acids in the plasma membrane almost always?

A

cis

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15
Q

embedded proteins

A

proteins on the interior or exterior surface of the membrane but do not span it

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16
Q

transmembrane/ integral proteins

A

membrane spanning protein with a hydrophobic and hydrophilic region
major examples: GPCR and ion channels

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17
Q

peripheral proteins

A

attatched to integral protein or associate with peripheral region of the membrane

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18
Q

lipid anchored proteins

A

covalently bound to a small lipid molecule and anchored to protein within the membrane without the protein physically coming into contact with the membrane
- g proteins

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19
Q

majority of glycosylations are

A

O linked
- bound to a serine or a threonine

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20
Q

N glycosylations

A

bount to N on asparagine

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21
Q

o glycosylations

A

o linked to serine or threonine

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22
Q

example of glycoproteins

A

ABO blood system

23
Q

liposomes

A

lipid bilayers enclosing a spherical space , derived in lab

24
Q

how are liposomes formed in lab

A
  1. suspend lipid in aqueous solution
  2. agitate mixture –> results in a vesicle
25
Q

micelle

A

aggregate composed of a single layer of lipids with hydrophobic tails pointed toward the interior

26
Q

micelles vs liposomes

A

liposomes are double membranes and micelles are single membranes

27
Q

simple diffusion

A

nonpolar, small, uncharged particles can pass through membrane without facilitation down their concentration gradients
ex: O2 and CO2 for gas/waste exchange , water, ethanol, urea

28
Q

osmosis

A

special form of simple diffusion that applies specifically to solvents (water)
- THE SOLVENT MOVES (WATER ) NOT THE SOLUTE
Water moves from high to low concentration of solute via simple diffusion to equalize the solute concentrations

29
Q

isotonic solution

A

extracellular space has the same solute concentration as the intracellular space

30
Q

hypotonic solution

A

solution has a lower concentration of solute than the intracellular space
- EC has more water than IC

31
Q

hypertonic solution

A

solution has a higher concentration of solute than the cell

32
Q

what happens when a cell is placed in a hypotonic solution

A

water rushes from solution into the cell and causes cell burst
–> cytolysis

33
Q

what happens when a cell is placed in a hypertonic solution

A

water moves from the cell into the EC and causes cell shrinkage
- plasmolysis

34
Q

when is equillibrium reached during osmosis

A

when hydrostatic pressure of water becomes large enough that it prevents more net osmosis from occuring
–> pressure is osmotic pressure

35
Q

osmotic pressure eqn

A

π = iMRT
m is concetration of solute
R is gas constant
t is time in kelvin
i is number of particles that result from a substance being placed into a solution (nacl would be 2, glucose would be 1 )

35
Q

osmotic pressure eqn

A

π = iMRT
m is concetration of solute
R is gas constant
t is time in kelvin
i is number of particles that result from a substance being placed into a solution (nacl would be 2, glucose would be 1 )

36
Q

what kind of property is osmotic pressure

A

colligative because it depends on solute concentration

37
Q

facillitated diffusion

A

trasport from high to low concentration using a transport protein

38
Q

aquaporins

A

specifically transport water

39
Q

ion channels

A

facillitate diffusion of ions

40
Q

active transport

A

energy is used (ATP) to force molecules against their concentration gradients

41
Q

primary active tranport

A

energy is used to pump against concentration gradient

42
Q

secondary active transport

A

energy to pump against graident is stored in an electrochemical gradient

43
Q

example of primary transport enzymes

A

atpases: hydrolyze atp to pump things
Na/K atpase

44
Q

what does na/K atpase do

A

uses atp to pump 3 na out of cell and 2 k into cell

45
Q

what kind of active transport is used in ETC

A

primary active transport
redox reations harnessed via NADH e- and FADH2 and translocate H+

46
Q

cotransport

A

secondary transport: relies on electrochemical differences to couple transport

47
Q

antiporters

A

secondary transporters that transport 2 molecules in opposite directiosn. one is going with its gradient and the other isnt
EX: sodium calcium transport

48
Q

symport

A

both molecules are sent in the same direction, one is going in the direction of its gradient and the other is not
SLGLT –> glucose and 2 na into cell

49
Q

is endocytosis active or passive transport

A

active, requires energy to do pinocytosis and phagocytosis

50
Q

early endosomes

A

pass molecules of interest onto late endosomes and recycle material back to the plasma membrane

51
Q

late endosomes

A

pass material onto lysozome

52
Q

lysozomes

A

final component of endocytic pathway
- hydrolytic compartment of the cell
- breaks down waste products
- highly acidic (4.8).

53
Q

constitutive exocytosis

A

preformed regularly by all cells to release material to the EC to deliver membrane proteins to the plasma membrane

MCAT biochem (11 decks)

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