Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

alevel biology ocr > membranes > Flashcards

membranes Flashcards

1
Q

what is the phospholipid bilayer made out of

A

phospholipids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the parts of the phospholipid

A

hydrophilic phosphate head (polar)

hydrophobic fatty acid tails
(non polar)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what type of interactions hold the bilayer together

A

weak hydrophobic interactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

how is the fluidity beneficial to cell membrane function

A

spontaneous breaking and reforming of membranes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

how thick is the bilayer

A

7.5 nm thick

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the impact of shorter fatty acid tails

A

increases fluidity, lots of double bonds= more sussepiltbe to KE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

explain the fluid mosaic model(3)

A

phospholipids create a viscous layer but are free to move.

proteins are embedded randomly in the bilayer the mosaic effect

they vary in shape and size and are globular so have a tertiary structure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are the 2 integral or intrinsic proteins

A

channel protein and carrier proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the different between intrinsic and extrinsic proteins

A

intrinsic proteins consist all the way through the phospholipid bilayer and extrinsic proteins do not

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is an example of an extrinsic protein in the bilayer

A

peripheral protein eg can act as receptors, can be enzymes
glycoprotein eg as a recognition site or for adhesion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is a peripheral/extrinsic protein

A

a protein that is temporarily attached to the bilayer by non covalent interactions and associate with one surface of the membrane. they can be present in either layer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is an integral protein

A

proteins that are permanently attached to the bilayer and span across it.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what are the 2 structures that transmembrane (integral) proteins could adopt

A

single helices/ helical bundles
or
beta barrels forming channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what effect does cholesterol have on the fluidity of the bilayer

A

more cholesterol makes it less fluid as the phospholipids become more tightly packed and so the permeability is also reduced so that very small water soluble molecules cannot freely cross. it immobilises the outer surface of the membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

describe a molecule of cholesterol

A

it is an amphipathic molecule. the OH group is polar and hydrophillic and so it aligns towards the phosphate heads.

the other bit is hydrophobic and so is situated within the fatty acid tails

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

why else is cholesterol useful in the bilayer

A

it separates phospholipid tails to prevent crystallisation of the membrane

helps to secure peripheral proteins by forming high density lipid rafts to anchor the protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

definition of diffusion

A

net movement of particles from a region of higher concentration to a region of lower concentration.
it will continue until all the particles are evenly dispersed (equilibrium)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

definition of bulk transport and an example

A

active movement of large molecules eg vesicle transport as too big to travel through a transport protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

definition of facilitated diffusion

A

passive movement of molecules across a cell membrane down a concentration gradient via the aid of a membrane protein.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

definition of active transport

A

movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

definition of osmosis

A

net movement (diffusion) of water across a partially permeable membrane from a region of high water potential to a region of low water potential

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

which transport processes are active and what does that mean

A

active means it requires energy. active transport and bulk transport are both active processes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what are the factors that effect the rate of diffusion (3)

A

temperature
molecular size eg if particle is bigger it takes more energy to move it
steepness of gradient

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

how and why does membrane thickness affect diffusion

A

the thinner the membrane the faster the diffusion as there is a shorter diffusion pathway

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

how and why does temperature affect the rate of diffusion

A

increased temperature makes diffusion faster as the thermal energy is converted to KE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

how and why does the concentration gradient affect the rate of diffusion

A

the steeper the gradient the faster the diffusion as particles are more likely to move from high to low conc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

how and why does surface area affect the rate of diffusion

A

a larger surface area to volume ratio means faster diffusion as there is more space (membrane) for diffusion to occur across

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what does net flow mean

A

the average flow as during diffusion particles move randomly but generaly h to l but some go the other way

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what cannot travel through the phospholipid bilayer (3)

A

ions as they have a charge
polar molecules
and large molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what are examples of molecules that are too large to pass through the bilayer

A

glucose, amino acids, nucleotides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

can water diffuse through the bilayer

A

although polar it is small enough to diffuse through the bilayer although it does so slowly

same for alcohols eg glyercol and ethanol

32
Q

what can diffuse through the bilayer

A

gases eg O2 and CO2
small hydrophobic molecules eg benzene
small polar molecules eg H2O and ethanol

33
Q

what is passive movement through the bilayer affected by

A

molecule size and molecules solubility in lipids

34
Q

what molecules use facilitated diffusion

A

molecules that are unable to freely cross the bilayer

35
Q

what structures are used in faciliatated diffusion

A

the transport proteins channel and carrier proteins

36
Q

what are carrier proteins (4)

A

they are integral glycoproteins that bind to a solute an undergo a conformational change (change in shape) to translocate the solute across the membrane

carrier proteins will only bind to a specific molecule

they can move molecules against the concentration gradient in the presence of ATP (active transport)

have a much slower rate of transport than channel proteins

37
Q

what are channel proteins (4)

A

integral lipoproteins which contain a water filled pore with a fixed shape. charged substances may cross from one side of the membrane to the other via these pores.

they are ion selective and most are gated to regulate the passage of ions in response to a certain stimuli.

cannot move molecules against a concentration gradient so are not used in AT

have a much faster rate of transport than carrier proteins

38
Q

what is a feature of integral proteins that allows them to be held in place

A

they are made of amino acids with Rgroups that are hydrophobic on the external surface so that they interact with the hydrophobic core of the bilayer to hold them in place

39
Q

what integral protein uses facilitated diffusion

A

carrier proteins

40
Q

what is the function of the glycolipids

A

cell markers/antigens that are used for recognition by the immune system as self or foreign

41
Q

what is the structure of extrinsic proteins

A

hydrophilic Rgroups on outer layer surface interacting with polar heads of phospholipids

42
Q

what is the function of integral glycoproteins

A

cell adhesion in some tissues and chemical sign receptors

43
Q

what are glycolipids

A

lipids with attached carb chains

44
Q

what are glycoproteins

A

carbohydtrate attached on a lipid with varying shape and length

45
Q

why are cells microscopic

A

so that there is a larger SA to volume ratio so that more product/whatever can be produceed

46
Q

when does diffusion stop

A

when equlibirum is reached

47
Q

why is diffusion described as passive

A

as no extra metabolic energy is needed as the cell already has the energy it needs to move

48
Q

what does ficks law state

A

that the rate of diffusion is proportional to the surface area x difference in concentration over the length of diffusion path (mem thickness)

49
Q

what is the difference between dialysis tubing and cell membranes

A

dialysis doesnt have transort proteins

50
Q

examples of when active transport is used in a cell

A

minerals into root hair cell
in the intestines to get nutrients into the blood
in the loop of henley

51
Q

what is endocytosis + eg

A

invagination of membrane and forms vesicles which pinches off and moves into cytoplasm

phagocytosis

52
Q

what is exocytosis

A

vesicles formed at golgi move towards and fuse with plasma membrane and the contents are released

53
Q

why is atp required for endo and exocytosis

A

to move vesicles along cytoskeleton (motor proteins)
change the shape of cells and engulf materials
fusion of the vesicles and membrane

54
Q

compare and contrast facilitated diffusion and active transport

A

compare: both require a protein (carrier), both the protein changes shape.

contrast: high to low and passive vs low to high and active

55
Q

what are the roles of membranes (5)

A

communication/cell signalling

control of transport
site of chemical reactions
anchorage/cell to cell joining

compartmentalisation

56
Q

what is NOT a role of membranes

A

to provide shape and support for cell shape

57
Q

what is compartmentalisation

A

to separate different conditions or to isolate substances eg lysosomes, enzymes, creating a cell

58
Q

what is cell signaling

A
59
Q

what does crynated mean

A

for a cell to shrivel up

60
Q

what to say instead of water concentration

A

water potential

61
Q

what is a solute

A

substance dissolved in a solvent to form a solution

62
Q

what does concentration mean

A

mass of solute in a given volume of aqueous solution

63
Q

what does hypotonic mean

A

that a substance has LOWER solute THAN another = HIGH WATER POTENTIAL

64
Q

what does hypertonic mean

A

HIGHER solute than another substance = LOWER WATER POTENTIAL

65
Q

what does isotonic mean

A

the same water potential

66
Q

what are the units for water potential

A

kilopascals (kPa)

67
Q

what is the water potential of pure water

A

0kPa

68
Q

what is the effect of solutes on water potential

A

solute lowers water potential (kPa can go negative)
decreased ability to move freely due to reduced energy to move.

69
Q

talk about animal cells and water potential

A

will never have 0kPa and will always have a negative wp
water potential=solute potential

70
Q

what is the symbol for wp, sp, pp

A

wp=psi
sp=psi s
pp=psi p

71
Q

talk about water potential in plant cells

A

water potential= solute potential + pressure potential

plant cells can have a wp of 0kPa but only turgid cells because they create the pressure, the psi s and psi p will cancel out

72
Q

how are red blood cells stored before donation

A

in an isotonic solution

73
Q

what happens when the the wp of a solution is hypotonic to inside a rbc

A

the net movement of water will enter the cell and it will swell and eventually burst (lysis), the contents including haemoglobin will be released

74
Q

what will happen is a solution is hypertonic to inside a rbc

A

water will leave the cell causing the cell to shrink and be shrivelled (crynation), haemoglobin will be more concentrated and so the rbc will appear darker

75
Q
A
76
Q

what is an amphipathic molecule, give 2 examples

A

a molecule that has hydrophobic and hydrophillic parts. eg phospholipids and cholesterol

alevel biology ocr (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions