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BioSci107 Finals > Cell Membrane Structure and Function > Flashcards

Cell Membrane Structure and Function Flashcards

1
Q

what are the fundamental units of specialised functions in living organisms

A

cells

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2
Q

The cell membrane is a ____ 8nm, flexible and ____ barrier that _____ the cytoplasm of a cell

A

The cell membrane is a (thin), 8nm, flexible and (sturdy) barrier that (surrounds) the cytoplasm of a cell

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3
Q

Describe the membrane structure

A

Fluid mosaic model

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4
Q

What does this mean about the proteins of the membrane “sea of lipids in which proteins float like icebergs”

A

Proteins are free to move around

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5
Q

What type of bonds hold membrane proteins and lipids together?

A

hydrogen bonding

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6
Q

The membrane is 50% ___ and 50% ___

A

The membrane is 50% (lipid) and 50% (protein)

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7
Q

The lipid bilayer is a selectively permeable barrier for the entry/exit of…

A

The lipid bilayer is a selectively permeable barrier for the entry/exit of (polar substances)

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8
Q

What are gatekeepers in the membrane that regulate how things move across lipid barrier

A

Proteins

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9
Q

What are scattered among double row of phospholipid molecules (embedded in phospholipids)

A

Cholesterol & glycolipids

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10
Q

___ back-to-back layers of ___ types of ___ molecules

A

(2) back-to-back layers of (3) types of (lipid) molecules

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11
Q

cell membrane equation?

A

Cell membrane = proteins + (phospho)lipids

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12
Q

what acts as a barrier; isolates cells from their external environment

A

cell membrane

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13
Q

the membrane controls passage of subst. in/out of cells to allow for…
1. Maintain…
2. Spacial…
3. Control…
4. Develop…

A
  1. Maintain conc. gradient
  2. Spacial organisation of chemical/physical processes in cell
  3. Control uptake of nutrients + discharge of waste products + secretion of molecules
  4. Develop membrane potential
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14
Q

What comprises 75% lipids

A

Phospholipids

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15
Q

___ has 2 parallel layers of molecules

A

Phospholipid bilayer = 2 parallel layers of molecules

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16
Q

If a molecules has polar (charged) and nonpolar (uncharged) regions it is said to be…?

A

Amphipathic

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17
Q

how phospholipids orient themselves?

A

Spontaneously form stable bilayers, polar head exposed to water non-polar tails shielded in the interior

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18
Q

what provides highly impermeable barrier to passage of charged ions

A

hydrophobic core (fatty acid chains)

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19
Q

membranes are ___ structures and ___ can move around within the plane of the membrane ____

A

membranes are (fluid) structures and (lipids) can move around within the plane of the membrane (leaflet)

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20
Q

true or false
lipids often flip flop between membrane leaflets therefore lipid composition of leaflets can be symmetric

A

FALSE
lipids RARELY flip flop between membrane leaflets therefore lipid composition of leaflets can be ASYMMETRIC

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21
Q

membrane fluidity is determined by…

A
  • lipid tail length&raquo_space; longer tail = less fluid
  • # of double bonds&raquo_space; more double bonds = more fluidity
  • amount of cholesterol&raquo_space; more decreases fluidity
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22
Q

what proteins are amphipathic and stuck in lipid bilayer

A

integral transmembrane proteins

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23
Q

integral proteins have hydrophobic regions that span hydrophobic core of lipid bilayer
- what do these regions consist of?

A

non polar amino acids coiled into helices

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24
Q

where are peripheral proteins attached to membrane and are they removed easily?

A

inner or outer surface of membrane
removed easily

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25
Q

way to easily remove peripheral protein

A

exposure to salt treatment to break protein-protein bonds

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26
Q

how is membrane spanning protein attach to cytoskeleton and what for?

A

associated proteins; for bending shape of membrane

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27
Q

features of integral proteins

A
  1. amphipathic
  2. hydrophobic regions (non-polar amino acids coiled into helices) span hydrophobic core of lipid bilayer
  3. hydrophilic ends interact with aqueous solution
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28
Q

functions of membrane proteins

A
  • receptor proteins
  • cell identity markers
  • linkers
  • enzymes
  • ion channels
  • transporter proteins
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29
Q

what protein functions to “allow specific substance to move through water-filled pore”

A

Channel membrane protein

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30
Q

function of transporter membrane protein

A

Transport specific subst. across membrane by changing shape

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31
Q

x3 things permeability depends on

A
  1. shape
  2. charge
  3. lipid solubility
32
Q

what is governed by laws of diffusion

A

selective permeability

33
Q

The lipid bilayer is permeable to 3 things what are they?

A
  1. Nonpolar, uncharged molecules (O2, N2, Benzene)
  2. Lipid soluble molecules (steroids, fatty acids, some vitamins)
  3. Small uncharged polar molecules (H2O, urea, glycerol, CO2)
34
Q

The lipid bilayer is IMpermeable to 2 things what are they?

A
  1. Large uncharged polar molecules (glucose, a.a)
  2. Ions (Na+, K+, Cl-, Ca2+, H+)
35
Q

what do membrane proteins mediate

A

transport of subst. across the membrane that can’t penetrate hydrophobic core of lipid bilayer

36
Q

Membrane proteins ____ the transport of substance across the membrane that ____ permeate the ______ core of the lipid bilayer

A

Membrane proteins (mediate) the transport of substance across the membrane that (CAN’T) permeate the (hydrophobic core) of the lipid bilayer

37
Q

Define diffusion

A

Net diffusion from high concentration to low concentration

38
Q

Aim of diffusion

A

To redistribute so substances maintain equilibrium

39
Q

what way along gradient do molecules move in diffusion

A

area of high concentration to area of low concentration

40
Q

what is the “random mixing of particles in a solution as a result of the particle’s kinetic energy”

A

simple diffusion

41
Q

Principles of diffusion (things that affect diffusion rate)

A
  • greater difference in conc. between 2 sides of membrane = faster rate
  • higher temp = faster rate
  • larger subst. = slower rate
  • increase SA = faster rate
  • increase diffusion distance = slower rate
42
Q

physical consequences of diffusion

A
  1. diffusion rate sets limit on size of cells
  2. increase diffusion = increase membrane area available
  3. membrane thickness > thicker membrane = slower rate
  4. very fast over small distances
43
Q

define concentration gradient

A

non charged molecules diffuse down their concentration gradients

44
Q

what does a selectively permeable membrane enable

A

difference in conc. across membrane to be established

45
Q

define electrical gradient

A

ions will be influenced by membrane potential in addition to their concentration gradient

46
Q

what are movement of ions influenced by

A

electrochemical gradient

47
Q

what do membranes mimic and why?

A

membranes mimic capacitors
- can separate + store charge

48
Q

___ use ~30% of resting energy to maintain ___ and ___ gradients

A

(cells) use ~30% of resting energy to maintain (conc.) and (electrical) gradients

49
Q

what do conc. and electrical gradients represent

A

stored energy

50
Q

Na+ ion gradient: ___ Na+ conc. in extracellular fluid&raquo_space; to ___ Na+ conc. in cytoplasm

A

Na+ ion gradient: (HIGH) Na+ conc. in extracellular fluid&raquo_space; to (LOW) Na+ conc. in cytoplasm

51
Q

K+ ion gradient: ___ K+ conc. in extracellular fluid&raquo_space; to ___ K+ conc. in cytoplasm

A

K+ ion gradient: (LOW) K+ conc. in extracellular fluid&raquo_space; to (HIGH) K+ conc. in cytoplasm

52
Q

Cl- ion gradient ___ ways: ___/___ Cl- conc. in extracellular fluid&raquo_space; to ___/___ Cl- conc. in cytoplasm

A

Cl- ion gradient BOTH ways: HIGH/LOW Cl- conc. in extracellular fluid&raquo_space; to HIGH/LOW Cl- conc. in cytoplasm

53
Q

what are ions influenced by in their gradients

A

membrane potential and ion conc. gradient

54
Q

why are ion gradients kept up

A

to harness energy stored in ion gradients

55
Q

define osmosis

A

net movement of H2O through a selectively permeable membrane from area of HIGH to LOW conc.

56
Q

true or false
“osmosis occurs if membrane is permeable to H2O but not to certain solutes”

A

TRUE

57
Q

how can osmotic H2O movement be prevented by opposing force?

A

hydrostatic pressure (osmotic pressure of solution)

58
Q

what is osmotic pressure of solution

A

colligative property > depends on # and not types of particles in solution

59
Q

what is osmolarity calculated in/

A

Osmol

60
Q

membrane permeability to water (Pw) equation

A

Pw = Pd + Pf

61
Q

what is Pd

A

through lipid bilayer
- small
- mercury insensitive
- temp dependent (lipid fluidity)

62
Q

what is Pf

A

through water channel
- large
- mercury sensitive
- temp independent

63
Q

what is mediated by aquaporins (9 isoforms)

A

Pf

64
Q

cells have different ___ because they express different ___ ___

A

cells have different (Pw) because they express different (aquaporin) (isoforms)

65
Q

true or false
“different aquaporin = same permeability”

A

FALSE
“DIFFERENT aquaporin = DIFFERENT permeability”

66
Q

what is osmotic pressure

A

the pressure applied to a solution to prevent the inward flow of H2O across a semi-permeable membrane

67
Q

same osmolarity

A

isosmotic

68
Q

lower osmolarity

A

hyposomotic

69
Q

higher osmolarity

A

hyperosmotic

70
Q

define tonicity

A

effect solution has on cell volume

71
Q

what does tonicity depend on

A

membrane permeability of solute

72
Q

True or false
“osmolarity of solution DOESN’T always indicate effect on cell vol.”

A

TRUE
osmolarity and tonicity NOT always the same thing

73
Q

isotonic solution

A

no change in cell vol

74
Q

hypotonic solution

A

cell swells = cell lysis (haemolysis)

75
Q

hypertonic solution

A

cell shrinks (crenation)

BioSci107 Finals (11 decks)

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