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BioSci107 Finals > Transport Across Cell Membranes > Flashcards

Transport Across Cell Membranes Flashcards

1
Q

5 types of transport across a plasma membrane

A
  1. Non-mediated transport
  2. Mediated transport
  3. Passive transport
  4. Active transport
  5. Vesicular transport
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2
Q

What does non-medicated transport do?

A

Does not directly use transport protein

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3
Q

What transport moves materials with help of a transport protein

A

Mediated transport

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4
Q

Passive transport moves…

A

Moves substances down their conc. gradient or electrochemical gradients with only their kinetic energy

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5
Q

What transport uses energy to drive substances against their conc. or electrochemical gradients

A

Active transport

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6
Q

What does vesicular transport do?

A

Move materials across membranes in small vesicles either by exocytosis or endocytosis

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7
Q

Non-mediated transport is diffusion through lipid bilayer… why is this transport type important?

A
  • Absorption of nutrients
  • Excretion of wastes
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8
Q

What are these examples of O2, CO2, N2, fatty acids, steroids, small alcohols, ammonia and fat-soluble vitamins (A, D, E, and K)

A

Nonpolar, hydrophobic molecules via non mediated transport

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9
Q

Diffusion requires gradient until reaches…

A

equilibrium

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10
Q

Ion channels form ___ filled pore that ____ the ions from the _____ core of the ___ bilayer

A

Ion channels form (water) filled pore that (shield) the ions from the (hydrophobic) core of the (lipid) bilayer

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11
Q

Water filled pores of ion channels are lined by…

A

Hydrophobic charged a.a

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12
Q

What makes the ion channel transport rapid

A

Ions don’t bind to channel pore

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13
Q

why are ions like “free diffusion”

A

through fluid filled pore

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14
Q

Name the 3 properties of channels

A
  1. Ionic selectivity
  2. Gating
  3. Electrical current
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15
Q

What determines the selectivity of the channel to ions

A

Specific amino acids lining the pore

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16
Q

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

A

Being selective to particular ions

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17
Q

What contains ion selectivity filter

A

Channel core

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18
Q

What do channel gates control

A

Opening and closing of the pore

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19
Q

What controls channel opening and closing

A

Different stimuli control the gate

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20
Q

Examples of stimuli that control gating

A
  1. Voltage
  2. Ligand binding
  3. Cell volume (stretch)
  4. pH
  5. phosphorylation
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21
Q

How to measure ion channel function

A

Patch clamp technique

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22
Q

How can current flowing through individual channel be recorded

A

Patch clamp technique

23
Q

What represents the opening and closing of single ion channels

A

Current fluctuations

24
Q

What do current fluctuations represent

A

Conformational changes in channel structure that are associated with channel gating

25
Q

The diffusion of over 1 ___ ions per ___ through a channel ____ a measurable current (~10-12 amp)

A

The diffusion of over 1 MILLION ions per SECOND through a channel GENERATES a measurable current (~10-12 amp)

26
Q

What is carried mediated transport

A

Mode of action

27
Q

What directly interacts with transporter protein in carrier mediated transport

A

Substrate to be transported

28
Q

Why does substrate to be transported interacts with transporter protein in carrier mediated transport

A

Transporter undergoes conformational change transport rates slower than those obtained for channels

29
Q

What are carrier mediated transport proteins have properties similar to…

A

enzymes

30
Q

What carrier mediated transport proteins exhibit

A
  1. Specificity
  2. Inhibition
  3. Competition
  4. Saturation (transport maximum)
31
Q

What transport proteins DON’T catalyse chemical reactions but mediate transport across cell membrane at faster than normal rate

A

Carrier mediated transport proteins

32
Q

Is mediated transport passive (facilitated) or active

A

Mediated transport is BOTH passive (facilitated) or active

33
Q

What display enzyme kinetics

A

Transporters

34
Q

How long does glucose transport occur in transporter saturation

A

Occurs until all binding sites are saturated

35
Q

3 steps of facilitated diffusion of glucose

A
  1. Glucose binds to transport protein (GLUT)
  2. Transport protein changes shape and glucose moves across cell membrane
  3. Kinase enzyme reduces glucose conc. inside cell by transforming glucose to glucose-6-phosphate
36
Q

What maintains conc. gradient for glucose entry

A

Conversion of glucose

37
Q

Define active transport

A

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

38
Q

What are the 2 forms of active transport

A
  1. Primary active transport
  2. Secondary active transport
39
Q

Primary active transport
- ___ is directly derived from ____ of ____
- A typical cell uses 30% of its ___ (__) on ___ active transport

A

Primary active transport
- (energy) is directly derived from (hydrolysis) of (ATP)
- A typical cell uses 30% of its (energy/ATP) on (primary) active transport

40
Q

What type of active transport “energy stored in an ionic conc. gradient used to drive active transport of a molecule against its gradient”

A

Secondary active transport

41
Q

What are the primary active transporters

A
  1. Na/KATPase
  2. Na pump
42
Q

4 steps of Na/KATPase transporters in primary active

A
  1. Na+ binding
  2. ATP split/Na+ pushed out
  3. K+ binding/Phosphate release
  4. K+ pushed in
43
Q

What Na/KATPase transporters do

A

3 Na+ ions removed from cell and 2 K+ ions brought into cell so pump generates net current and electrogenic

44
Q

Other examples of primary active transporters: Na/KATPase

A
  • Ca/K
  • ATPase (muscle SR)
  • H/K ATPase (stomach)
45
Q

What does Na pump maintain

A

Low concentration of Na+ and high conc. of K+ in cytosol

46
Q

What is difference in ion conc. important for…

A
  • Maintain resting membrane potential
  • Electrical excitability
  • Contraction of muscle
  • Maintenance of steady state cell vol.
  • Uptake of nutrients via secondary active transporters
  • Maintenance of intracellular pH by secondary active transporters
47
Q

What is pump-leak hypothesis

A

Na and K continually leaking back into cell down their respective gradients so pump works continuously

48
Q

Secondary active transport: ___ have many ___ active transporters which are powered by the ___ gradient initially established by the ___ pump

A

Secondary active transport: (cells) have many (secondary) active transporters which are powered by the (Na+) gradient initially established by the (Na) pump

49
Q

Why secondary active transport uses stored energy in ion gradients created by active transporters

A

To move other subst. against their own conc. gradient

50
Q

Do these secondary active transporters indirectly or directly use the energy obtained by hydrolysis of ATP

A

secondary active transporters INDIRECTLY use the energy obtained by hydrolysis of ATP

51
Q

What happens in Na+ antiporter or exchangers

A
  • Na+ ions rush inward
  • Ca2+ or H+ pushed out
52
Q

What happens in Na+ symporters or cotransporters

A

Glucose/a.a rush inward together with Na+ ions

53
Q

How is energy in ion gradients harnessed

A

Secondary active transporters use the energy store in ion gradients established by primary active transport

BioSci107 Finals (11 decks)

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