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cell membranes Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

why do cell membranes have to be partially permeable ?

A

they have to allow substances in to be used and let substances out in order for normal function of the cell to continue

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2
Q

what are 6 roles of the cell membrane?

A

separates cell components from external environment.
regulates transport of substances in and out of the cell.
may contain enzymes involves in a metabolic pathway that are bound to the membrane.
has antigens, allows immune system to recognise the cell and not attack it.
may release chemicals to signal to other cells and could contain receptors to receive chemical signals from other cells.
site of chemical reactions

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3
Q

what is the role of membranes around organelles?

A

to separate contents of the organelle from the cytoplasm

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4
Q

what does the fluid mosaic model explain about the membrane ?

A

how cell membrane is dynamic and interacts with the cells environment

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5
Q

what is the structure of cholesterol?

A

it is polar, has hydrophilic group at one end and attracts the polar head of the phospholipids
the rest of it is hydrophobic and attracts the hydrophobic fatty acid tails on the phospholipid

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6
Q

what is the function of cholesterol in the membrane?

A

increases mechanical strength and flexibility of the plasma membrane so it is less likly to get damaged. it maintains fluidity

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7
Q

how does cholesterol maintain fluidity of the membrane at low temps?

A

At low temperatures, by preventing the fatty acid tails of the membrane lipids from packing too closely together, helps to maintain the proper spacing between the lipid molecules and allows the membrane to remain flexible and functional

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8
Q

how does cholesterol maintain fluidity of the membrane at high temps?

A

At high temperatures, the lipid bilayer can become too fluid, which can also impair its function. Cholesterol stops the movement of the fatty acid tails of the membrane lipids

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9
Q

what is an integral protein?

A

a protein in the cell membrane that is fully embedded into the membrane from one side to the other

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10
Q

what is a channel protein?

A

an integral protein filled with water to allow water soluble substances to diffuses through. it is lined with hydrophillic AA and has hydrophobic AA on the outdside which interact with the fatty acid tails

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11
Q

name 2 types of integral proteins in the cell membranes?

A

carrier and channel proteins

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12
Q

what is a peripheral protein?

A

just is on one side of the membrane or the other

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13
Q

what is a carrier protein?

A

it is an integral protein which goes through a conformational change to transferre molecules from one side of the membrane to another, it used energy

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14
Q

what is a glycolax ?

A

a carbohydrate chain attached to either a lipid(glycolipid) or a protein(glycoprotein)

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15
Q

what are the roles of a glycoprotein?

A

allows cells to attach to each other, form antigens and act as receptors for hormones

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16
Q

what are the roles of peripheral proteins?

A

structural, enzymes or receptors for molecules such as hormones

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17
Q

what are the roles of a glycolipid?

A

allows for cell regognition when 2 clls come into contact with eachother, form antigens

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18
Q

what is the definition of diffusion?

A

the movement of molecules from an area of high concentration of that molecule to a low concentration

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19
Q

what is the definition of facilitated diffusion?

A

movement of molecules from an area of high concntration to low across a partially permeable membrane via integral/ transmembrane proteins

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20
Q

do either types of diffusion require energy?

A

no

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21
Q

where do water molecules diffuse through in the cell membrane?

A

specific channels called aquaporins for only water molecules

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22
Q

why can’t water molecules travel through the bilayer ?

A

they are polar and insoluble in lipids so cant diffuse through the lipid bilayer

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23
Q

how is a concentration gradient maintained?

A

molecules that pass into the cell will heighten the concentration gradient in the cell so diffusion rate will slow down and that is not what the cell wants. so by these molecules then diffusing into organelles it increases the concentration gradient

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24
Q

what are the 5 factors affecting simple diffusion?

A

temperature, diffusion distance, surface area, size of diffusing molecule and concentration gradient

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25
Q

how does temperature affect the rate of diffusion? and why

A

as temperature increases the rate increases due to molecules having more kinetic energy

26
Q

how does size of the diffusion molecule affect the rate of diffusion?

A

as size increases, rate decreases as it is harder to get around

27
Q

what type of a molecule is required to use facillitated diffusion in protein channels? and why

A

a small polar one that is insolubel in lipids, because they cant interact with the lipid bilayer so they have to diffuse through a protein channel

28
Q

how does suface area affect the rate of diffusion?

A

as surface area increases, diffusion increases as there is physically more space for the site of diffusion

29
Q

what is a high water potential in terms of water and solute?

A
30
Q

what happens to bigger molecules in faccilitated diffusion?

A

they will bind to transmembrane carrier proteins which goes through a conformational change to allow the molecule into the cell

31
Q

what is the definition of osmosis?

A

the net movement of water from a high water potential to an area of low water potential via a partially permeable membrane

32
Q

what is a high water potential in terms of water and solute?

A

dilute solution- less solute more water

33
Q

what is water potential units?

A

kilo-pascals (KPa)

34
Q

what is the definition of water potential?

A

the tendency of water to diffuse from one region to another

35
Q

when and why does cytosis occur?

A

when a cell is in an environment of higher water potential than in the cell so water will diffuse in, so the cell will swell and burst because the cell membrane breaks

36
Q

why will the inside of cells have a lower water potential?

A

lots of different substances are in cells so it is not 100 percent water

37
Q

what happens as a result of a hypotonic external environment in an animal cell?

A

cytosis

38
Q

what happens as a result of a hypertonic external environment in an animal cell?

A

crenation

39
Q

what happens as a result of a hypotonic external environment in an plant cell?

A

cell becomes turgid

40
Q

what happens as a result of a hypertonic external environment in an plant cell?

A

plasmolosis

41
Q

what does hypotonic mean?

A

the solution outside of the cell has a lower solute concentration/or a higher water potential

42
Q

what happens in a hypotonic environment to the cell in terms of water movement?

A

water moves into the cell

43
Q

what does hypertonic mean?

A

when the solution outside the cell has a high solute concentration/lower water potential

44
Q

what does isotonic mean?

A

solution has same solute concentration inside and outside of the cell

45
Q

what happens in a hypertonic environment to the cell in terms of water movement?

A

water moves out of the cell

46
Q

what happens in a isotonic environment to the cell in terms of water movement?

A

no net movement because movement of water molecules into and out of the cell happens at the same rate

47
Q

how do plant cells become turgid?

A

in a hypotonic environment water is drawn in via osmosis. water enters vacuole so volume of cell increases but the cell wall stops it from bursting so now the cell is turgid

48
Q

what is crenation?

A

when the external environment to the cell has a lower water concentration therfore water will move out of the cell so it shrivels and shrinks

49
Q

how does a plant cell become plasmolysed?

A

in a hypertonic environment water is drawn out so water leaves the vacuole and volume decreases. the contents of the cell shrink and pulls away from the cell wall - now plasmolysed or flaccid

50
Q

what is the definition of active transport?

A

movement of molecules through a cell membrane from low concentration to high, uses energy and protein carriers

51
Q

how do protein carriers work in active transport?

A

there is a site that the molecule will bind to and another site that ATP binds to and is hydrolysed to supply it with energy to go through a conformational change

52
Q

what is endocytosis?

A

form of bulk transport (larger molecules) are brought into cells

53
Q

what is exocytosis?

A

form of bulk transport out of cells

54
Q

what are the 2 types of endocytosis?

A

phagocytosis and pino(endo)cytosis

55
Q

what is phagocytosis?

A

the intake of solid matter by a cell, it forms a vesicle around solid. requires energy to move vesicle along cytoskeleton

56
Q

what is pinocytosis?

A

intake of liquids by a cell, requires energy

57
Q

how does exocytosis occur?

A

a vesicle containing matter to be secreted is moved towards the plasma membrane and fuses with it, then the fused site opend and releases its contents outside of cell

58
Q

how does a low temprature affect membrane fluidity?

A

saturated fatty acid tails become compressed making the membrane rigid. however unsaturated tails becaome compressed and their tails push against each other which maintains fluidity

59
Q

what factors affect the fluidity of the membrane at different teperature?

A

proportions of unsaturated to saturated because the more saturated the less compressed and therefore more fluid and more unsaturater the more compressed and less fluid
cholesterol will buffer then effect of temperature on fluidity

60
Q

how does a higher temperature (not too hot) affect the membrane?

A

phospholipids have more kinetic energy and will vibrate more so fluididty and permeability will increase

61
Q

what consequence is there if a membrane gets too fluid?

A

effectivness of the barrier to polar molecules reduces so permeability increases maybe more so than desired

62
Q

if temperature gets too high, what effects does this have on the membrane?

A

proteins whithin the membrane will denature which will disrupt the structure of it and it will no longer form an effective barrier

Biology (12 decks)

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