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Biology IB HL > B2.1 Membranes and Membrane Transport > Flashcards

B2.1 Membranes and Membrane Transport Flashcards

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1
Q

Phospholipids are amphipathic. Explain what this means

A

they have a hydrophilic head and and hydrophobic tail

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2
Q

Name another amphipathic lipid

A

cholesterol

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3
Q

what happens when phospholipids are placed in water

A

the hydrophilic phosphate heads orient towards the water and hydrophobic hydrophobic tails orient away from the water forming a PHOSPHOLIPID MONOLAYER

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4
Q

what are the 2 regions of a phospholipid bilayer

A

a hydrophobic core and a hydrophilic outer layer

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5
Q

what cannot pass through the hydrophobic region of the lipid bilayer barrier and why

A
  • large molecules because the hydrophobic region is tightly packed and has low permeability for them
    -polar molecules and ions as they are hydrophilic so will not interact
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6
Q

integral proteins

A

partially hydrophobic and embedded in phospholipid bilayer

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7
Q

peripheral proteins

A

hydrophilic and are attached to surface of integral proteins or to membrane with a a hydrocarbon chain

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8
Q

2 types of transport proteins

A

channel and carrier

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9
Q

what are channel proteins

A

form holes or pores where molecules travel through eg ions
some are gated

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10
Q

what do carrier proteins do

A

change shape to transport substance across the membrane

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11
Q

glycoproteins

A

act as cell markers/antigens for cell to cell recognition

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12
Q

what is simple diffusion

A

the net movement, due to random motion of molecules or ions, of a substance from a region of higher concentration to a region of lower concentration

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13
Q

molecules that move by simple diffusion

A

oxygen- diffuses into cells from capillaries surrounding- conc gradient by respiration
carbon dioxide- diffuses out of cells into surrounding capillaries

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14
Q

what does the rate of diffusion depend on

A

steepness of conc gradient
temperature
surface area
properties of molecules or ions

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15
Q

the higher the difference in conc across membrane…

A

higher the rate of diffusion

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16
Q

the higher the temperature

A

the higher the rate of diffusion because molecules have more kinetic energy so random movement of molecules is faster

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17
Q

the greater the surface area

A

the higher the rate of diffusion

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18
Q

the larger the molecule

A

the slower it diffuses because they require more energy to move

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19
Q

what can diffuse quickly

A

uncharged molecules - oxygen- as they can move directly across phospholipid bilayer
non polar molecules because they are soluble in the bilayer
smaller polar molecules- urea

20
Q

what is osmosis

A

the diffusion of water molecules from a region of lower solute concentration to a region of higher solute concentration, across a partially permeable membrane

21
Q

what channel proteins allow water to pass through membrane easily

A

aquaporins

22
Q

when does facilitated diffusion occur

A

when substances cross phospholipid bilayer with the help of channel and carrier proteins- passive and down a con gradient

23
Q

how does a carrier protein work

A

the substance that needs transporting attaches to binding site and the shape of the protein changes so it opens up to the other side of the membrane

24
Q

what is active transport

A

the movement of molecules and ions across a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration

25
Q

what does active transport require

A

carrier proteins- pumps which require energy from ATP from respiration to change shape

26
Q

how does the atp release energy

A

it is hydrolised

27
Q

what is selective permeability

A

ability of the membrane to differentiate between different types of molecules, only allowing some molecules through while blocking others

28
Q

what are glycoproteins

A

cell membrane proteins that have a carbohydrate chain attached on the extracellular side

29
Q

what are glycolipids

A

lipids with carbohydrate chains attached on the outer surface of cell membranes

30
Q

what does the carbohydrate chain allow for

A

enables them to act as receptor molecules so they can bind with substances at the surface

31
Q

label in fluid mosaic model

A

phospholipid bilayer
integral proteins
peripheral
glycoproteins
cholesterol

31
Q

receptor types

A

signalling- bind to hormones and neurotransmitters
involved in endocytosis
involved in cell adhesion so cells can attach to each other forming tissues
act as antigens for cell identification

32
Q

saturated fatty acids

A

they are straight so can pack closely together so have high mp- maintain stability

33
Q

unsaturated fatty acids

A

contain 1 or more double bonds
they have bends in the chain so cant pack together tightly so have lower mp and allow membranes to be fluid and flexible

34
Q

cholesterol importance

A

maintains membrane fluidity at low temp because it disrupts close packaging of phospholipids
increases membrane stability at high temp as it holds fatty acid tails together
acts as barrier

35
Q

what is the term for bulk transport into cells

A

endocytosis

36
Q

what is the term for bulk transport out of cells

A

exocytosis

37
Q

what does bulk transport require

A

energy and vesicles

38
Q

what happens during endocytosis

A

transports materials into cells and plasma membrane engulfs material forming a sac around it
eg, phagocytosis

39
Q

what happens during exocytosis

A

materials transported out of cells- releases and packaged into secretory vesicles that travel to surface and fuse with membrane and release contents outside cell

40
Q

what do sodium potassium pumps do

A

they move 3 sodium ions out of cells and 2 potassium ions into cell using 1 ATP molecule by moving ions against conc gradient via active transport

41
Q

what are sodium potassium pumps

A

integral proteins that generate an electrochemical gradient between the inside and outside of a nerve cell

42
Q

steps of sodium potassium pumps

A

3 sodium ions inside of axon bind to pump and ATP attaches so the pump opens to outside of axon
3 sodium ions released out, 2 potassium ions enter and bind to their sites
phosphate released so pump changes shape again

43
Q

what is cotransport

A

the coupled movement of substances across a cell membrane via a carrier protein
-facilitated diffusion and active transport

44
Q

example of cotransport

A

Reabsorption of glucose back into the blood is under the control of sodium-dependent glucose cotransporter proteins

45
Q

what are cams

A

cell adhesion molecules are integral proteins that protrude into extracellular environment

46
Q

why does cell adhesion need cams

A

involves the binding of CAMs to other cells or to the extra-cellular matrix

Biology IB HL (13 decks)

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