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BIO130 > Week 8 - Membrane Proteins and Transport (Part II) > Flashcards

Week 8 - Membrane Proteins and Transport (Part II) Flashcards

1
Q

What do multi-pass transmembrane proteins create and for what function?

A

They create a protein-lined path across the cell membrane; to transport polar and uncharged particles

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2
Q

Are transport proteins selective?

A

Yes; they transport a specific class of molecules.

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3
Q

What is passive transport?

A

Movement down the concentration gradient; does NOT require energy; uses channel proteins.

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4
Q

What is active transport?

A

Movement against the concentration gradient by transporter proteins; requires energy.

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5
Q

What are the 2 types of transport proteins?

A
  1. Channel proteins

2. Transporter proteins

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6
Q

What are channel proteins?

A

A type of transport protein; do NOT interact much or bind strongly to the transported molecule. Passive Transport only.

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7
Q

Do channel proteins change conformation?

A

They do not change conformation a lot.

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8
Q

What are transporter (a.k.a. carrier) proteins?

A

A type of transport protein; interact a lot with and bind to the transported molecule. Passive and Active transport.

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9
Q

Do carrier/transporter proteins change conformation?

A

Yes, they change to transport the solute across the membrane.

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10
Q

What is resting membrane potential?

A

Membrane potential is an electrical gradient aiding in transport.

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11
Q

What makes up the electrochemical gradient?

A

Concentration gradient + Membrane potential = Electrochemical gradient
The two gradient must be consider as they work against each other.

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12
Q

Are channel proteins hydrophilic or hydrophobic?

A

They are hydrophilic pores across a membrane.

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13
Q

Are channels or transporters faster at passive transport?

A

Channels are faster than transporters at passive transport as several molecules can pass through at once when open.

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14
Q

What are the two types of ion-channels?

A
  1. Non-gated ion channels

2. Gated ion channels

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15
Q

Example of a non-gated ion channel?

A

Always open; K+ leak channels that play a major role in resting membrane potential in animal cells.

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16
Q

What do gated-ion channels require to open?

A

Gated ion channels require signal to open; i.e. a chemical or electrical signal

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17
Q

What do larger and small fonts represent on membrane diagrams?

A

Large font = higher concentration

Small font = lower concentration

18
Q

What are 4 kinds of GATED ion channels?

A
  1. Voltage-gated
  2. Mechanically-gated
  3. Extracellular Ligand-gated
  4. Intracellular Ligand-gated
19
Q

What do voltage-gated ion channels require?

A

A change in voltage across the membrane; a.k.a. membrane polarization and depolarization

20
Q

What do mechanically-gated ion channels require?

A

Mechanical stress; i.e. opening if the plasma membrane is stretched.

21
Q

Extracellular v.s. Intracellular ligands examples?

A

Extracellular ligand: neurotransmitters

Intracellular ligand: ions, nucleotides

22
Q

Do Uniporters do passive or active transport?

A

Passive transport by a transporter via facilitated diffusion; transport is reversible

23
Q

What is an example of a uniporter and how does it function?

A

GLUT uniporter; transports glucose down the electrochemical gradient. Can work in both directions.

24
Q

What are 3 types of active transport?

A
  1. Co-transporters
  2. ATP-driven pumps (a.k.a. Pumps or ATPases)
  3. Light-driven pumps (i.e. bacteria)
25
Q

How do co-transporters move molecules?

A

They move one molecule down the gradient and one against the gradient.

26
Q

What is a symporter and what does it move?

A

An active transporter that move 2 molecules in the same direction.

27
Q

What is an antiporter and what does it move?

A

An active transporter that move 2 molecules in opposing directions.

28
Q

The free energy created from the co-transported ion moving down the electrochemical gradient does what?

A

Use the energy to transport the second molecule.

29
Q

In a Na+/Glucose symporter, what does moving Na+ down the electrochemical gradient do?

A

It provides energy to move glucose against the concentration gradient.

30
Q

What does cooperative binding of Na+ and glucose to a symporter lead to?

A

Leads to a conformational change in the protein.

31
Q

How is cytosolic pH (neutral) regulate?

A

Excess protons leak into the cell, produced by acid forming reactions; Na+ driven antiporters maintain pH.

32
Q

How does a Na+/H+ exchanger (antiporter) maintain cytosolic pH?

A

It responds to pH drops by increasing transporter activity; gets better at removing protons.

33
Q

How does a Na+/H+ exchanger (antiporter) move H+ out of the cell?

A

It uses the free energy stored in the Na+ electrochemical gradient to move the H+ out of the cell.

34
Q

As symporters and antiporters both use the sodium gradient to move molecules, what happens when the Na+ eventually gets equalized on both sides?

A

Na+/K+ pump (a transport ATPase) keeps the concentration different.

35
Q

What are P-type transport ATPases and what so they do?

A

P-type transport ATPases are ATP driven pumps that phosphorylate themselves to move molecules against the gradient.

36
Q

What does the Na+ gradient do?

A
  • transports nutrients into cells

- maintenance of pH and cell volume

37
Q

What are the 8 steps of the pumping cycle of the Na+/K+ pump?

A
  1. ATP bound to pump, 3 Na+ bind an open cytosolic pocket.
  2. Pocket closes preventing Na+ escape.
  3. ATP hydrolysis; pump phosphorylated, ADP released due to change in E1 conformation to E2 (phosphorylation).
  4. E2 binding pocket exposed on the extracellular side; 3 Na+ exit.
  5. 2K+ bind to E2.
  6. Pocket closes preventing K+ escape.
  7. Pump is de-phosphorylated.
  8. ATP bind to pump to return to E1 state and K+ is released into cytosol.
38
Q

What happens when ATP binds to an E2 conformation of Na/K pump?

A

It changes back to E1 conformation and K+ is released.

39
Q

During ATP hydrolysis, what happens when the Na/K pump is phosphorylated?

A

ADP is released and E1 conformation changes to E2.

40
Q

Which conformation of the Na/K pump has ATP bound to it?

A

The E1 conformation has bound ATP. Change to E2 requires the phosphorylation of this ATP to occur.

BIO130 (12 decks)

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