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chapter 7- membrane structure and function Flashcards

1
Q

what is an amphipathic molecule and example

A

a molecule that has both a hydrophilic and hydrophobic region
phospholipid

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2
Q

why are membranes considered fluid

A

because the proteins and lipids move laterally through the membrane

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3
Q

what moves and how does it move in a membrane

A

phospholipids and proteins move side to side fast
but they wont flip upside down because it would require going through the hydrophobic/hydrophilic portions (hard to cross)

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4
Q

how does temperature affect the fluidity of the membrane

A

lower temperature = solid membrane
higher temperature = more fluid/liquid

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5
Q

how is the temperature at which a membrane solidifies determined

A

based on the types of lipids in it

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6
Q

why should a membrane be fluid

A

it needs to be to work properly

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7
Q

which membrane it more fluid:
lots of unsaturated fatty acids or lots of saturated fatty acids

A

unsaturated as the kinks in the fatty acids prevent the packing of molecules

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8
Q

what does cholesterol do regarding membranes at different temperatures

A

at warm temperatures it restrains the phospholipid movement (stops membrane from being too fluid)
at cool temperatures it prevents packing (keeps membrane fluid)

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9
Q

what is the reason for the difference in membrane lipid composition (evolution)

A

adaptation to different environmental conditions
(ability to change lipid composition as temperature changes evolved in organisms that live where temperature varies)

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10
Q

what are integral proteins

A

proteins that are imbedded into the membrane (through the hydrophobic middle)

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11
Q

characteristics of integral proteins

A

they have hydrophobic sections made up of nonpolar amino acids/R groups and hydrophilic/polar sections that touch the inside and outside of the cell

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12
Q

what are integral proteins also called

A

transmembrane proteins

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13
Q

what are peripheral proteins

A

proteins that are bound to the surface of the membrane or to integral proteins

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14
Q

what are the six major functions of membrane proteins

A

transport
enzymatic activity
signal transduction
cell-cell recognition
intercellular joining
attachment to cytoskeleton and extracellular matrix

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15
Q

what are the two types of membrane carbohydrates

A

glycolipids (sugar + lipid)
glycoproteins (sugar + protein)

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16
Q

what is the role of membrane carbs in cell recognition

A

cells recognize each other by binding to surface molecules, often carbs and recognizing foreign glyco-lipids/proteins

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17
Q

what builds the membrane

A

the ER and golgi

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18
Q

what does selective permeability mean

A

allows some substances to cross more easily than others

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19
Q

what passes through the membrane and what does not

A

hydrophobic molecules pass through easily while hydrophilic molecules do not or pass through slowly

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20
Q

what facilitates the movement of hydrophilic molecules across the membrane

A

transport

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21
Q

what are the types of transport proteins

A

channel and carrier

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22
Q

what are the types of channel proteins

A

aquaporins
ion channels

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23
Q

how do ion channels work

A

they have a hydrophilic channel that allows polar molecules to pass (ions)

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24
Q

what are gated channels

A

ion channels that open or close in response to a stimulus

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25
Q

how do aquaporins work

A

channel that allows water to pass through

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26
Q

are transport proteins specific

A

yes they are specific to the substance that they move (and sometimes related substances)

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27
Q

what are carrier proteins

A

proteins that bind molecules and change shape to shuttle them across the membrane

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28
Q

what is diffusion

A

tendency for molecules to spread out evenly into available space

29
Q

how does diffusion work

A

substances diffuse down their concentration gradient (high concentration to low)
spontaneous

30
Q

what kind of transport is diffusion

A

passive

31
Q

what does passive transport mean

A

substance moves with no energy being used from the cell

32
Q

what is osmosis

A

diffusion of water across a selectively permeable membrane

33
Q

how does water diffuse in osmosis

A

moves from region of lower solute concentration to a region of higher solute concentration until they are equal

34
Q

what is the formula for solute concentration/osmolarity

A

molarity x number of ionized particles (van hoff i)

35
Q

what is tonicity

A

ability of a surrounding solution to make a cell gain or lose water

36
Q

what is an isotonic solution

A

solution’s solute concentration is the same as the cell’s concentration (no water movement)

37
Q

what is a hypertonic solution

A

solution’s solute concentration is higher than the cell’s (water moves out of the cell)

38
Q

what is a hypotonic solution

A

solution’s solute concentration is lower than cell’s (water moves in the cell)

39
Q

when an animal cell is placed into isotonic, hypertonic and hypotonic solutions what happens to it

A

isotonic: normal
hypertonic: shrivel
hypotonic: swell

40
Q

what is osmoregulation

A

control of solute concentrations and water balance

41
Q

what is different for plant cells regarding osmosis

A

they have cell walls which allow them to have better water balance

42
Q

when a plant cell is placed into isotonic, hypertonic and hypotonic solutions what happens to it

A

isotonic: flaccid (limp)
hypertonic: plasmolysis (dead)
hypotonic: turgid (firm)

43
Q

what happens during plasmolysis

A

plant cell loses water, plasma membrane pulls away from cell wall and causes plant to wilt

44
Q

what is facilitated diffusion

A

transport proteins aid the passive movement of molecules across the membrane

45
Q

what is active transport and characteristics

A

moving of substances against their concentration gradient, requires energy, performed by specific proteins embedded in membrane

46
Q

what is a type of active transport system

A

sodium-potassium pump

47
Q

what are the 6 steps of the sodium-potassium pump

A
  1. sodium in the cell binds to the pump
  2. binding of sodium stimulates the attachment of a phosphate group to the pump (using atp)
  3. the attachment of P group leads to the pump changing shape and releasing the sodium to the outside
  4. new shape attracts and binds potassium from the outside which triggers the release of the P group (inside)
  5. losing P group restores the original shape
  6. potassium is released
48
Q

what is phosphorylation

A

attachment of a phosphate group to a molecule of ion

49
Q

how much energy does one cycle of the sodium-potassium pump take

A

one ATP molecule

50
Q

how many sodiums are taken out and potassiums taken in

A

3 sodiums and 2 potassiums

51
Q

what is membrane potential

A

voltage difference across a membrane

52
Q

how is voltage created in a membrane

A

by the differences in the distribution of + and - charged ions across a membrane

53
Q

what is the electrochemical gradient

A

chemical force (ion’s concentration gradient) and electrical force (effect of membrane potential on ion’s movement)

54
Q

what does the electrochemical gradient do

A

diffuses ions across the membrane

55
Q

what is an electrogenic pump and example

A

a transport protein that generates voltage across a membrane
sodium-potassium pump

56
Q

what is the main electrogenic pump for plants fungi and bacteria

A

proton pump (pumps out H+)

57
Q

what is another function of the electrogenic pump

A

store energy that can be used for cellular work

58
Q

what is cotransport

A

when the transport of one solute indirectly drives the transport of other solutes
active transport driven by concentration gradient

59
Q

what is bulk transport

A

large molecules crossing membrane using vesicles

60
Q

does bulk transport require energy

A

yes

61
Q

what is exocytosis

A

transport vesicles migrating to the membrane then fusing with it and releasing their contents outside

62
Q

what is endocytosis

A

cell taking in macromolecules by forming vesicles from the membrane

63
Q

what are the three types of endocytosis

A

phagocytosis
pinocytosis
receptor-mediated endocytosis

64
Q

what is phagocytosis

A

when a cell engulfs a particle into a vacuole
vacuole then fuses with lysosome to be digested

65
Q

what is pinocytosis

A

extracellular fluid in gulped into tiny vesicles

66
Q

what is receptor-mediated endocytosis*

A

molecule or ion binding to a receptor triggers the formation of a vesicle

67
Q

what do humans use receptor-mediated endocytosis for*

A

to take in cholesterol using LDL receptors

68
Q

how is cholesterol found in blood*

A

in particles called low-density lipoproteins (LDL)

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