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BIOSCI 107 Part Two > Cell Processes: Transport Across Cell Membranes > Flashcards

Cell Processes: Transport Across Cell Membranes Flashcards

1
Q

What is non-mediated transport?

A

transport that doesn’t directly use a integral membrane transport protein (molecules are permeable across the hydrophobic core of phospholipid bilayer)

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2
Q

What is mediated transport?

A

transport that moves materials with the help of a transport protein

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3
Q

What is passive transport?

A

transport that moves substances down their concentration or electrochemical gradient with only their kinetic energy

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4
Q

What is active transport?

A

transport that uses energy to drive substances against their concentration or electrochemical gradients

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5
Q

What is vesicular transport?

A

transport that moves materials across membranes in small vesicles either by exocytosis or endocytosis

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6
Q

What is non-mediated transport important for?

A

absorption of nutrients – excretion of wastes

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7
Q

What type of molecules undergo non-mediated transport?

A

Nonpolar and hydrophobic molecules

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8
Q

Examples of molecules that undergo non-mediated transport

A

oxygen, carbon dioxide, nitrogen, fatty acids, steroids, small alcohols, ammonia and fat-soluble vitamins (A, E, D and K)

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9
Q

What is the function of ion channels?

A

mediate the movement of ions down their electrochemical gradient

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10
Q

What is formed in the centre of an ion channel and what is its functions

A

a water filled pore that shields the ions from the hydrophobic core of the lipid bilayer

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11
Q

Why is transport through the ion channel rapid?

A

ions do not bind to the channel pore (passive diffusion)

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12
Q

What determines what ions can pass through an ion channel (ionic selectivity)

A

certain amino acids lining the pore determine

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13
Q

What is ionic selectivity?

A

ion channels only allow certain ions to pass through

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14
Q

What is the result of channels being ion selective?

A

the channel can harness the energy stored in the different ion gradients

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15
Q

Why can ion channels NOT be open all the time?

A

it would get rid of the ion gradient

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16
Q

What do ion channels contain to control passage of ions

A

gates

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17
Q

Examples of stimuli that control channel gate opening and closing

A

voltage, ligand binding, cell volume (stretch), pH, phosphorylation

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18
Q

What is a patch clamp?

A

A sensitive voltage clamp method that permits the measurement of ionic currents flowing through individual ion channels

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19
Q

Number of ions that are able to diffuse through one ion channel per second

A

1 million

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20
Q

the current through a single ion channel

A

10^-12 amps

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21
Q

How does carrier mediated transport work?

A

The substrate to be transported directly interacts with the transporter protein

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22
Q

Is carrier mediated transport faster or slower than ion channels and why?

A

Slower because the transporter undergoes a conformational change

23
Q

What is the general function of carrier mediated transport?

A

to take one molecule from one side of the membrane to the other

24
Q

Carrier proteins exhibit these 4 properties

A

specificity, inhibition, competition, saturation

25
Q

Is carrier mediated transport active or passive?

A

it can be both

26
Q

What does saturation mean for carrier mediated transporters?

A

They have only a certain number of binding pockets so they cannot intake anymore molecules that their binding pockets allow

27
Q

Does increasing concentration increase uptake with carrier mediated transporters

A

To a point, eventually it will reach a point where uptake is saturated

28
Q

Name of protein that takes up glucose

A

Glucose transporter protein (GLuT)

29
Q

Amount of glucose in blood

A

5

30
Q

Process of glucose moving into a cell

A

Glucose BINDS to transport channel protein > changes conformational shape of protein > allowing it to go into cell

31
Q

Does glucose move down its concentration gradient in facilitated diffusion?

A

Yes

32
Q

What is glucose converted into in the cell by a kinase enzyme?

A

glucose-6-phosphate

33
Q

Why is glucose converted into glucose-6-phosphate

A

to maintain glucose concentration gradient

34
Q

What cells do Facilitated diffusion of glucose

A

Muscle, nervous, fat cells

35
Q

what is GluT NOT called

A

do not call this a glucose channel that is doing passive diffusion (it is a carrier protein, passive facilitated diffusion)

36
Q

What is active transport?

A

An energy requiring process that moves molecules and ions against their concentration or electrochemical gradients

37
Q

What is primary active transport?

A

A form of active transport in which energy is directly derived from the hydrolysis of ATP to make ion gradients

38
Q

How much cell energy is used on primary active transport?

A

30%

39
Q

What is secondary active transport?

A

A form of active transport in which energy is stored in an ionic concentration gradient is used to drive the active transport of a molecule against its gradient

40
Q

Process of Sodium and Potassium ATPase

A
  1. Na+ binds
  2. ATP is split and Na+ is pushed out of the cell
  3. K+ binds and phosphate is released
  4. K+ is pushed in
41
Q

With a Na/KATPase, how many Na+ are removed

A

3 Na+ ions are removed from the cell

42
Q

With a Na/KATPase, how many K+ are brought into a cell

A

2 K+ ions are brought into the cell

43
Q

What is the result of a Na/KATPase

A

pump generates a net current and is electrogenic

44
Q

What does electrogenic mean

A

producing a change in the electrical potential of a cell.

45
Q

Other examples of ATPase ion pumps

A

Ca/K ATPase (Muscle SR), H/K ATPase (stomach)

46
Q

What does a Na pump do

A

maintains a low concentration of Na+ and a high concentration of K+ in the cytosol

47
Q

What type of transport is a Na pump

A

primary active transport

48
Q

What is a Na ion concentration gradient important for (6)

A

Maintain resting membrane potential
Electrical excitability
Contraction of muscle
Maintenance of steady state cell volume
Uptake of nutrients via secondary active transporters
Maintenance of intracellular pH by secondary active transporters

49
Q

What is the pump-leak hypothesis

A

Na and K are continually leaking back into the cell down their respective gradients so the pump works continuously to maintain the ion gradient

50
Q

What type of transport are Na+ antiporter/exchangers

A

secondary active transport

51
Q

What do Na+ antiporter/exchangers do?

A

Allow Na+ ions to rush inwards and Ca2+ or H+ are pushed out

52
Q

What do Na+ symporter/cotransporters do?

A

Glucose or amino acids rush inward together with Na+ ions

53
Q

What are secondary active transporter powdered by?

A

Na+ gradient initially established by the Na pump

BIOSCI 107 Part Two (17 decks)

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