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Biology HL > B2.1 Membranes and membrane transport > Flashcards

B2.1 Membranes and membrane transport Flashcards

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1
Q

Function of lipid bilayers of phospholipids

A

basic structure of all cell membranes wich controls passage of substances going in and out.

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2
Q

Describe the layer of bilayer of phospholipids and the structure arrangement in membrane

( draw out and label areas within both sides of the plasma membrane)

A

Form bilayer in plasma membrane due to fatty acids which are hydrophobic in aqueous solutions.

Phosphate head - face outwards contacting the water

Hydrocarbon tail ( hydrophobic) - Fatty acids face inwards from the water

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3
Q

Describe the hydrophobic membrane core

A

never exposed to water, if solutes reach the hydrophobic tail they are drawn bac to aqueous solution outside membrane

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4
Q

Properties of hydrophobic membrane core

A

low permeability to hydrophilic molecules
( ions and polar molecules), cannot diffuse that easily

larger the molecule lower the permeable

smaller molecules can pass through the membrane more easily

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5
Q

Define simple diffusion

A

the net movement of particles from a region of high to low concentration gradient, down the concentration gradient

particles are in continuous random motion

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6
Q

Is energy required in simple diffusion?

A

No, it is a passive process

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7
Q

When can simple diffusion occur?

Give example

A

if phospholipid is permeable to the particles

non-polar molecules can pass through easily such as oxygen

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8
Q

Why are membrane proteins so diverse in struture and position?

A

so they can carry out their function correctly

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9
Q

Describe integral proteins ( draw out)

A

Embedded in hydrocarbon chains in the center of membrane

hydrophobic

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10
Q

Describe peripheral proteins ( draw out)

A

protein is anchord to membrane surface

hydrophilic surface

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11
Q

Define osmosis

A

net movement of water molecules from high to low concentration of water, down concentration gradient

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12
Q

Does osmosis require energy?

A

no it is a passitve process

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13
Q

Why can osmosis happen in all cells?

A

water molecules are small enough to pass through the phospholipid bilayer

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14
Q

Define aqauporin

A

water channels that greatly increases membranes permeability

allows water to pass through single file

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15
Q

what are some roles of the aquaporin?

A

prevents protons from passing through, due to positive charges in channel

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16
Q

Define channel proteins

A

transmembrane protein with pore connecting cytoplasm to aqueous solution (outside cell)

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17
Q

Why are channel proteins neccessary?

A

ions cannot pass easily between the phospholipid bilayers however diffusion of these particles is still possible with help of protein channels

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18
Q

What are the characteristis of protin channels?

A
  • diameter of pore and the chemical properties of protein channel ensures only one type of particle passes through

(e.g sodium ions or potassium ions not both)

particles can pass through both directions

  • cells can determine which hydrophilic substances diffuse in/out by different types of channel proteins placed in membrane.
  • permeability may temporary change, some channels can be opened/closed
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19
Q

What type of diffusion occurs if channel proteins are needed?

A

facilitated diffusion, since channel proteins are required for movement to occur

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20
Q

Does facilitated diffusion require energy?

A

no, passive process

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21
Q

Define pump protiens function

A

absorb substances even when concentration is higher inside than out, and pump substances out even when concentration is higher outside cell

against concentration gradient

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22
Q

Differences between pump proteins and channel proteins.

A
  1. use energy since it carries out active transport ( channel proteins don’t)
  2. particles can only move in one direction
    ( channel proteins can move particles in both)
  3. particles move against concentration gradient
    (particles in channel proteins move down concentration gradient)
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23
Q

How is energy retained for protein pumps to use?

A

Produces it’s own ATP through cell respiration

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24
Q

Characteristics of protein pump

A

each pump transfers only one specific type of particle across membrane

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25
Q

How is the characteristic of pump proteins helpful for cells?

A

it allows cells to control content of cytoplasm precisely

allows specific solutes required by cell to be absorbed even when going against concentration gradient

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26
Q

Describe how pump proteins are interconvertible between 2 conformations.

A

transported particle can enter pump from one side of membrane to reach binding site, pump protein changes into another conformation which allows ion and molecules to pass through to opposite side of membrane

then it returns to it’s original conformation
( energy is used when changing however reverse change does not require energy)

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27
Q

Describe what semi-permeable membrane means

A

allows passage of certain small solutes, and is freely permeable to solvent

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28
Q

Give an example of a diffusion that has a semi-permeable membrane

A

simple diffusion

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29
Q

Describe what selectively permeable membrane means.

A

allows passage of particular particles but not others

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30
Q

Give example of a diffusion that uses selectively permeable membrane

A

facilitated diffusion, active transport ( from the channel proteins and pump proteins)

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31
Q

What kind of permeability does the cell membrane have?

A

partially permeable, since it is both partly semi-permeable and partly selectively permeable

32
Q

Describe glycoproteins
(draw a glycoprotein in the membrane and label the carbohydrate part)

A

conjugated proteins with carbohydrates as the non-polypeptide component, it is embedded within the membrane

carbohydrte part is projecting out to exterior environment of cell

33
Q

Describe glycolipids

(draw structure of glycolipids and label it)

A

molecules consisting of carbohydrates linked to lipids, occurs in plasma membane of all eukaryotic cells

lipid part naturally fits in hydrophobic core membrane

not embedded in membrane

34
Q

What are the roles/ functions of glycolipids?

A
  • plays a role in cell recognition as it helps distinguish self and non-self cells
  • helps immune system as pathogens / foreign tisse can be recognized and destroyed
35
Q

Describe how saturated fatty acids affect the phospholipid bilayers fluidity.

( draw the saturated fatty acids)

A

straight chains which packs phospholipids tightly together, reducing the fluidity of membrane so substances pass through more difficultly

36
Q

Describe how unsaturated fatty acids affect affect the phospholipid bilayers fluidity.

(draw the unsaturated fatty acids)

A

one or more kins in their hydrocarbon chain making the phospholipids pack more loosely so the membrane is more fluid and permeable

37
Q

Why are relative amounts of saturated and unsaturated fatty acids regulated?

A

so that membranes remain fluid but not strong enough to prevent being perforated, permeable but not too porus

Ideal ratio depends on temperature the cell experiences

38
Q

How much do cholestrol make up in membrane?

A

20-40% of the lipids in membrane

39
Q

Describe the cholestrol molecule ( in animal cell)

Draw structure / position of cholestrol in the plasma membrane

A

most of the molecule is hydrophobic, attracted to hydrocarbon tails in centre of membrane, end has hydroxyl (-OH) group so is hydrophilic which is attracted to the phosphate head

40
Q

What does cholestrol help with?

A
  1. helps control fluidity of membrane

too fluid : less control over the type of substance pass through
too inflexible : restricted cell movement ( cell more likely to burst)

  1. Help maintain orderly arrangement of phospholipids
  • stabalizes membrane at high temps
  • ensures saturated fatty acids dont solidify at low temp
  • ensure peripheral proeins is anchored to membrane
41
Q

Define vesicles

A

small sac of membrane with a droplet of fluid inside ( spherical)

42
Q

What is the function of vesicles?

A

move substrates within cell, transporting their content then unmaking them ( continuous cycle)

43
Q

Define endocytosis

( draw out the steps of how vesicles are constructed)

A

vesicle made from the plasma membrane by pinching small piece of membrane inwards, containing material (water / solutes) that was outside the cell

44
Q

Does endocytosis require energy?

A

yes ( ATP is required)

45
Q

When is endocytosis used?

A

often vesicle contains larger molecules needed by cell that cannot pass the plasma membrane

used when :
content of vesicle needs to be moves or proteins in membrane needs to be moved

46
Q

Define exocytosis

(draw the structure of steps that the vesicle follows)

A

when vesicle has reached its destination, the vesicle will fuse with the plasma membrane, contents of plasma membrane are expelled ( the membrane flattens out again).

47
Q

What is exocytosis used for?

A

to expel waste products/unwanted materials and useful materials

48
Q

How are digestive enzymes secreted in a cell?

A

the polypeptide process in golgi apparatus are carried to plasma membrane in vesicle for exocytosis to occur ( content gets expelled outside the cell)

49
Q

How does exocytosis help the area of plasma membrane to increase in a growing cell?

A

phospholipids are synthesized then inserted into rough endoplasmic reticulum, ribosomes inside synthesize the membrane proteins, then vesicle buds off rough endoplasmic reticulum and move to plasma membrrane ( it’s destination), they fuse each increasing are of plasma membrane.

50
Q

Define the function of an ion channel

A

allows specific ions to pass across a membrane in either direction with net movement from high to low concentration of ions

51
Q

What type of diffusion occurs in ion channels

A

facilitated diffusion
(no energy required)

52
Q

Where are ion channels useful?

A

in neurons inside a nerve cell

53
Q

How does ion channels know when to open and close the pores?

A

there is a voltage across membrane, which is an imbalance of positive/negative charges across membrane

54
Q

When do sodium channel open?

A

when their are more positive charges outside the neuron (axon) than inside.

55
Q

When do potassium channel open?

A

when more positive charges are inside the axon( neuron) than compared to outside.

56
Q

Draw a diagram of a voltage-gated potassium channel

when closed, opened then closed again by ball and chain

( include diagrams)

A
  1. closed because net positive charge is higher outside axon ( make sure positive charges are drawn outside axon)
  2. the charges on the pores moves upwards as the pore turns and opens up ( make sure the positive charges are drawn inside axon)
  3. the ball fits inside the pore closing flow of potassiums out of the axon, label the 4 subunits and extra globular proteins for the ball and the amino acids for the flexible chain.
57
Q

Define sodium and potassium channels

A

channels that only allow either sodium ions or potassium ions to pass but not both

58
Q

how wide is a potassium channel

A

0.3 nanometers wide

59
Q

what happens when potasssium ions are dissolved

A

they become bonded to shell of water molecules, making them too large to pass through pore.

60
Q

how does dissolved potassium ions pass through pores?

A

bond between potassium and surrounding water molecules needs to be broken, after potassium ion passes through pore it can be associated with a shell of water molecules.

61
Q

can sodium ions shed their shell of water molecules

A

no, sodium ions are too small to form bonds with amino acids within the pore

62
Q

an example of the use of sodium + potassium chan nels

A

nicotinic acetylcholine receptors

  1. both nicotine + acetylcoline binds to a receptor
  2. there are 5 transmembrane subunits for acetylcholine
  3. binding site of 2 subunits for acetylcholine causes conformational change ( pore opens betwen the 5 subunits and cations such as sodium can pass)

pore in receptor closes

sodium then diffuses into postsynaptic neuron which changes its voltage

the voltage gated sodium channel then opens

63
Q

define acetylcholine

A

a neurotransmitter in many synapses

64
Q

what must there be for neurons to convey a nerve impulse?

A

there must be a concentration gradient of sodium and potassium ions across membrane.

65
Q

How many ATP is used each time sodium-potassium pump process occurs once?

A

one ATP

66
Q

describe how the sodium-potassium pump works

(draw the diagram)

A
  1. 3 sodium ion enters from interior side and attatched to the binding site of the sodium/potassium pump
  2. ATP transfers a phosphate group to pump, causing pump to change shape ( closes the interior side and opens up on exterior side), sodium ions exit on the exterior side, increasing concentration outside neuron.
  3. 2 potassium ions enters and attach to binding site ( reducing concentration of potassium ions outside), binding causes conformational change (closing pump on exterior side but opening it on interior side)
  4. potassium exists on the interior side, increasing potassium concentration inside
67
Q

Define the function of sodium-dependent glucose cotransporters

A

transferring a sodium ion and a glucose molecule together across plasma membrane into cell

68
Q

why can glucose molecule move against concentration gradient

A

if the sodium is moving down its concentration gradient

69
Q

What does glucose absorption into cell depend on?

A

on the sodium ion concentration being greater outside than inside the cell.

Concentration is maintained by active transport of sodium ions out of cell

70
Q

Why is sodium-dependent glucose cotransporters secondary active transport?

A

because the process depends on energy however is not directly used by the co-transporter

71
Q

where does the sodium potassium pump, pump sodium ions towards

A

pump sodium ions from inner side of cell to the outer side towards nearby blood capillaries

72
Q

Define CAMs

A

cell-adhesion molecule
(typically proteins)

73
Q

What are cells in tissue linked by?

(draw the diagram)

A

cell to cell junctions which depends on CAMs

head of CAM is in cytoplasm ( look on notes for right diagram)

74
Q

What happens when the same time of CAM presented in both cells bind together?

A

builds a group of the same type

75
Q

what happens when CAMs of cells are different

A

then an asymmetrical junction is formed.

76
Q

what do some type of junctions prevent?

A

prevents extracellular movement of substances in a tissue

other types facilitate it

has major roles in immune system

Biology HL (1 decks)

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