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Biology > Cells b > Flashcards

Cells b Flashcards

1
Q

role of the cell membrane

A

acts as a barrier between cell and the environment and controls what enters and leaves the cell

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2
Q

what does fluid mosaic structure mean?

A

it shows how phospholipid molecules form a continuous bilayer
it is fluid as phospholipids are flexible and constantly moving
it is mosaic because proteins imbedded vary in shape/ size/ pattern

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3
Q

what does cholesterol do in membranes?

A

gives stability
makes membranes less fluid (bind to phospholipid tails so restrict movement)
prevents leakage of water and dissolved ions
maintain shape of animal cells

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4
Q

what do glycoproteins do in membranes?

A

recognition sites
help cells attach to form tissues

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5
Q

what do glycolipids do in membranes?

A

recognition sites
maintain stability of membrane
help attach cells
cell surface receptors

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6
Q

what are protein receptor sites?

A

allow other proteins to attach due to complimentary shape
send signals

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7
Q

what do channel proteins do?

A

allow water soluble ions to diffuse by facilitated diffusion

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8
Q

what do carrier proteins do?

A

bind to ions/molecules to change their shape- active transport

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9
Q

does a low temp increase or decrease permeability? why?

A

increase as ice crystals may form and pierce the membranes
but
rigid as phospholipids dont have much energy

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10
Q

permeability of a membrane at 0-40 degrees

A

partially permeable as phospholipids can move. increases as phospholipids gain more energy

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11
Q

does a high temp increase or decrease permeability of membrane?

A

increase as bilayer begins to break down
water moves in which puts pressure on membrane
channel and carrier proteins deform so cant control what enters/leaves and permeability increases

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12
Q

what is simple diffusion and examples of things that do this

A

molecules passing straight through the membrane
eg oxygen and carbon dioxide

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12
Q

what is diffusion?

A

net movement of particles from area of higher concentration to an area of lower concentration. passive

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13
Q

what is facilitated diffusion and examples of things that do this

A

large/charged particles diffusing through carrier/channel proteins
still down conc gradient
eg larger molecules (amino acids, glucose), charged particles (ions, polar molecules)

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14
Q

why cant larger molecules simply diffuse?
why cant charged particles simply diffuse?

A

too big so diffuse slowly
they are water soluble and centre centre of bilayer is hydrophobic so diffuse slowly

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15
Q

carrier proteins job and how they do this

A

move large molecules across membranes
1) large molecule attaches (diff protein for diff molecule)
2) protein changes shape
3) released on opposite side of membrane

16
Q

channel proteins job

A

form pores in membrane for charged particles to diffuse through
diff protein for diff particle

17
Q

what does rate of simple diffusion depend on?

A

conc gradient- higher means faster but slows over time as reach equilibrium
thickness of exchange surface- thinner means faster (shorter path to travel)
surface area- larger means faster eg microvilli increase sa by about 600x so more particles exchanged in same time

18
Q

what does rate of facilitated diffusion depend on?

A

conc gradient- higher means faster until equilibrium reached
number of channel/ carrier proteins- once all in use, rate cant increase so more proteins means faster

19
Q

what are aquaporins?

A

channel proteins that allow facilitated diffusion of water through cell membranes. some kidney cells have lots
they allow cell to reabsorb a lot of water otherwise excreted

20
Q

what is osmosis?

A

(net) movement of water molecules from an area of higher water potential to an area of lower water potential across a partially permeable membrane

21
Q

what is water potential? units?

A

potential/ likelihood of water molecules to diffuse into or out of a solution
KPa

22
Q

does pure water have a high or low water potential? what happens as you add more solute?

A

highest water potential
it decreases/ becomes more negative

23
Q

what is isotonic?

A

two solutions having the same water potential

24
Q

what is hypertonic?

A

total molecular conc of dissolved solute particles is greater than that of another cell

25
Q

what is hypotonic?

A

total molecular conc of dissolved solute particles is less than that of another solution

26
Q

what does the rate of osmosis depend on?

A

water potential gradient- higher means faster
thickness of exchange surface- thinner means faster
surface area- larger means faster

27
Q

what happens to a cell in a hypotonic solution? what is turgor?

A

net movement is into cell so cells w/o walls lyse
plant cells have walls so prevent breaking- turgor pressure is pressure pushing against wall

28
Q

what happens to cells in hypertonic solutions? what is plasmolysis?

A

water inside the cell flows out so cells lose water and cant divide/ function
plasmolysis is cell shrinking away from cell wall can be reversed
cells w/o cell walls shrink resulting in dehydrated cells can be reversed

29
Q

what is active transport?

A

movement of particles from an area of lower concentration to an area of higher concentration using energy

30
Q

similarity between facilitated diffusion and active transport

A

both use carrier proteins

31
Q

differences between active transport and facilitated diffusion

A

against/ down conc gradient
requires energy (ATP)/ doesn’t

32
Q

what are cotransporters?

A

type of carrier protein that binds 2 molecules at a time
the conc gradient of one is used to move other against its own conc gradient

33
Q

factors affecting rate of active transport

A

speed of individual carrier proteins
number of carrier proteins present
rate of respiration/ availability of ATP

34
Q

why does cotransport take place?

A

diffusion creates an equilibrium so not all available glucose/ amino acids would be able to pass out of body

35
Q

what is cotransport?

A

indirect active transport
glucose and amino acid molecules being drawn into cells with sodium ions

36
Q

describe the sodium-potassium pump

A

1) Na ions actively transport out of epithelial by sodium potassium pump (carrier protein)
2) maintains higher conc in lumen than the epithelial cells
3) Na ions diffuse into epithelial cell through carrier protein and carry glucose/ amino acids with them. Na diffuses, glucose/ amino acids go against conc gradient
4) glucose/ amino acids pass to blood plasma by facilitated diffusion using carrier proteins

Biology (11 decks)

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