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biology > Cell Membranes > Flashcards

Cell Membranes Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what is a plasma membrane

A

a membrane on the outside of a cell controlling what enters and leaves the cell

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2
Q

how are substances transported

A

osmosis, diffusion and active transport through the partially permeable membrane

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3
Q

what functions does the plasma membrane have

A

cell recognition (allows immune system to recognise it), cell signalling and substance movement

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4
Q

what are the functions of intracellular membranes

A

compartmentalisation, vesicles, substance movement

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5
Q

what is compartmentalisation

A

where the regions of a cell are split up this increases the rate of metabolic reactions

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6
Q

what is the fluid-mosaic model

A

represents the parts of a cell membrane the phospholipids being the fluid part as they continuously move and the proteins being the mosaic

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7
Q

why is a bilayer created

A

the hydrophobic tails face inwards to get away from the water with the heads facing the opposite way

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8
Q

why are water soluble substances stopped

A

the centre is hydrophobic making them repel water soluble substances

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9
Q

what does cholesterol do

A

located within the phospholipids it makes them pack tightly keeping the stability of the membrane

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10
Q

which proteins help ions into the cell

A

channel proteins and carrier proteins assist molecules that wouldn’t be able to get into the cell otherwise e.g. ions

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11
Q

what do glycolipids and glycoproteins do

A

stabilise membrane (hydrogen bonding), cell signalling (acts as an antigen), receptor cell

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12
Q

what are ‘membrane bound receptors’

A

proteins in the cell membrane which pick up signals

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13
Q

what does a complimentary receptor mean

A

the receptor is specific to the shape of the messenger molecule

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14
Q

what effect does a low temperature have on membranes

A

low temps-packed too closely together deforming carrier and channel proteins, very rigid due to low phospholipid movement

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15
Q

what effect does a normal temperature have on membranes

A

normal temperatures- allow phospholipids to gain kinetic energy and therefore it is less rigid and partially permeable

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16
Q

what effect does a high temperature have on membranes

A

a high temperautre increaes the kinetic energy too much as water begins to expand, therefore deforming the cell membrane making it more permeable

17
Q

how does changing the solvent affect membranes

A

surrounding membranes in a solvent like ethanol would increase the permability as there strucutre would dissolve therefore deform

18
Q

what is a passive process

A

it requires no energy

19
Q

what is diffusion

A

net movement of particles from a high concentration to a low concentration

20
Q

what molecules diffuse easiest

A

small non polar molecules

21
Q

what process does water use

A

osmosis

22
Q

what factors affect the rate of diffusion

A

concentration gradient, surface area,temperature and diffusion distance

23
Q

what is facilitated diffusion

A

where larger/polar molecules use carrier and channel proteins, also a passive process, they use a molecule as a signal to allow the shape to change and open

24
Q

what is active transport

A

`a molecule attaches to a carrier protein which changes its shape. it uses energy and goes against the concentration gradient. e.g. sodium-potassium pump (in plasma membranes)

25
Q

`what is endocytosis

A

when molecules need to enter the cell but are too large to go through the bilayer they invaginate the molecule turning it into a vesicle and then it can move along the cytoskeleton. It uses energy.

26
Q

what is exocytosis

A

when vesicles containing waste from the cell fuse to the plasma membrane and release their content it also uses energy

27
Q

what is water potential

A

how likely it is for a solution to perform osmosis (pure water has the highest water potential)

28
Q

what is a hypotonic solution

A

solution has a higher water potential than the cell so water moves into the cell

29
Q

what is a isotonic solution

A

the cell and the soltution have equal water potential

30
Q

what is a hypertonic solution

A

one that has a lower water potential so does not gain any water

biology (10 decks)

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