2.5 biological membranes Flashcards

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1
Q

state the role of membranes

A

partially permeable barriers between the cell and its environment, between organelles and
the cytoplasm and within organelles
sites of chemical reactions
sites of cell communication (receptors, cell signalling, cell reconition).

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2
Q

what is the fluid mosaic model

A

model that shows arrangement of biological membranes

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3
Q

name the components in the fluid mosaic model

A

phospholipid
intrinsic proteins(carrier,channel)
extrinsic proteins
glycoproteins
glycolipids
cholesterol

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4
Q

what is a micelle

A

one layer of phospholipids, creates sphere shape

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5
Q

whats a bilayer

A

two layers of phospholipids

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6
Q

describe channel proteins

A

have pores that act as channels to allow ions to pass through

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7
Q

describe carrier proteins

A

change shape using ATP to carry specific molecules across membrane

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8
Q

describe extrinsic proteins

A

found on the surface
provides mechanical support and act as cell receptors for hormones etc.

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9
Q

describe glycolipids

A

carbohydrate chain attached to phosholipid
role in cell recognition and act as cell markers or antigens

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10
Q

describe glycoproteins

A

carbohydrate chain attached to protein molecule
receptors for chemical signals/hormones/toxins
role in cell adhesion

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11
Q

describe cholesterol

A

4 carbon based rings in fatty acid tail layer
provides mechanical stability and flexibility
restricts movement of membrane etc

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12
Q

how does cholesterol affect membrane permeability

A

buffers the effect of lower temperature by preventing phospholipids getting too close = prevents reduction in fluidity

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13
Q

what is simple diffusion

A

the net movement of particles down a concentration gradient from an area of higher conc. to lower conc.

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14
Q

what molecules does simple diffusion allow to cross membranes

A

small polar or non polar

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15
Q

what is facilitated diffusion

A

diffusion using proteins (carrier or channel)

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16
Q

what molecules does facilitated diffusion allow to cross membranes

A

large or polar molecules

17
Q

what factors affect the rate of simple diffusion (+facilitated diffusion)

A

conc. gradient
temperature
surface area
diffusion distance
+more intrinsic proteins

18
Q

what is passive transport

A

no energy needed from ATP

19
Q

how do molecules move down/up concentration gradients

A

kinetic energy

20
Q

what do active transport require

A

energy needed from ATP

21
Q

what is active transport

A

movement of substances against their concentration gradient using ATP and carrier proteins

22
Q

what is bulk transport and name two examples

A

transport of large molecules too large to pass through membrane
endo and exocytosis

23
Q

what is endocytosis

A

bulk transport of molecules into the cell
segment of membrane surrounds and encloses particle into a vesicle

24
Q

name the different ways of endocytosis and what they move

A

phagocytosis - solids
phinocytosis - liquids

25
Q

what is osmosis

A

net movement of water molecules down their water potential gradient across a partially permeable membrane

26
Q

what is water potential

A

the tendency of water molecules to diffuse/move from one region to another

27
Q

what is the highest water potential

A

pure water 0kPa

28
Q

what is osmotic concentration

A

the amount of dissolved solutes in a solution

29
Q

what do a higher and lower osmotic concentration do to the water potential

A

higher osmotic conc= lower water potential = concentrated solution
lower osmotic conc= higher water potential = dilute solution

30
Q

what is a hypertonic solution

A

has a higher osmotic conc. to the inside of cell so water moves out of cell and shrinks

31
Q

what is an isotonic solution

A

an equal osmitic/ water potential conc. inside and outside of cell

32
Q

what is a hypotonic solution

A

has a lower osmotic concentration to inside the cell so water moves in and cells expand

33
Q

what factors affect membrane structure and permeability

A

temperature
solvents

34
Q

how does increasing temperature affect membranes

A

increased temp = more kinetic energy = molecules move faster = permeability/ fluidity increases

35
Q

how does a drop in temperature affect membranes

A

saturated fatty acids become compressed= unsaturated fatty acids with kinks = maintain fluidity

36
Q

how does temperature below freezing pint affect membranes

A

water freezes = expands = pierces/ forces apart closely packaged rigid layer = permeability increases

37
Q

what determines membrane fluidity at cold temperatures

A

proportions of unsaturated and saturated fatty acids

38
Q

how does a solvent affect membranes

A

organic solvents (acetone, ethanol) will damage membranes = dissolve lipids

39
Q

how does increasing temperature affect proteins in membranes and permeability

A

vibrates more= breaks hydrogen and ionic bonds = tertiary structure changes/ denatures = more permeable