Membrane Transport

Question 1

Process in solutions where molecules move from a high concentration to a low concentration:

Answer 1

Diffusion

Question 2

Transport that is diffusion driven, so materials move only from high concentration to lower concentration and don’t require outside energy:

Answer 2

Passive Transport

Question 3

An energy-requiring process that moves at least one molecule from a low concentration to a higher concentration:

Answer 3

Active Transport

Question 4

What is big diff between active and passive transport?

Answer 4

Active transport moves at least one molecule from a low concentration to a higher concentration.

Question 5

Primary energy source for active transport:

Answer 5

ATP

Question 6

Pumps that move two molecules in the same direction across a membrane are called:

Answer 6

symports

Question 7

Pumps that move two molecules in opposite directions across a membrane are called:

Answer 7

antiports

Question 8

Electroneutral pumps:

Answer 8

Their action does not result in a net change in charge

Question 9

Electrogenic:

Answer 9

their action changes the charge across the membrane as a result of their action.

Question 10

A glucose transporter in blood cells that simply lets glucose diffuse into cells and no energy is required for that particular transporter is an example of:

Answer 10

Passive transport.

Question 11

P-type ATP-using transport systems use this molecule as a covalent intermediate in their mechanism of action during calcium sequestration.

Answer 11

phosphoaspartate

Question 12

Mechanism of the Ca/ATPase pump (steps 1 through 3):

Answer 12

1) binding of ATP and the relevant ions (calcium, in this case)
2) transfer of phosphate from the ATP to the protein (making phosphorylaspartate)
3) conformational change in the protein causing movement of the ions across the membrane

Question 13

Mechanism of the Ca/ATPase pump (steps 4 through 5):

Answer 13

4) hydrolysis of the phosphate from an asparatic acid side chain in the protein
5) a second conformational change to bring the protein back to its original state

Question 14

Is Ca/ATPase a symport or antiport?

Answer 14

Symport

Question 15

Example of active transport not requiring ATP but concentration gradient of carrier molecule (H+) instead:

Answer 15

lactose permease (lactose is carried into the cell using the gradient of protons (higher outside than in). Bacteria use this to bring in lactose.

Question 16

Example of active transport not requiring ATP but using electrical forces that drive ions into the cell:

Answer 16

Na/glucose pump that uses the tendency of Na to move from outside the cell to inside the cell as the driving force.

Question 17

Na/glucose and lactose permease pumps are referred to as:

Answer 17

Secondary transporters.

Question 18

Heart muscle has an antiport pump that pumps calcium out of the cell using a sodium gradient.
How does it do this?

Answer 18

Sodium moves in (wants to move in because Na/K ATPase is pumping it out) and calcium moves out.

Question 19

What inhibits Na/K ATPase, thus reducing the proton gradient? What is this used for as a treatment?

Answer 19

Digitoxigenin. It causes the heart muscle to contract more forcefully and can be used to treat heart failure.

Question 20

ABC transporters are transporters proteins that use what to move molecules?

Answer 20

ATP

Question 21

Example of ABC transporter is the Multidrug Resistance Protein involved in the resistance of cancer cells to chemotherapy agents. (chemo doesn’t work)
What are the 5 steps of this mechanism?

Answer 21

• Protein binds to the compound
• Conformational change in the protein that allows ATP to bind. -Protein ‘everts’ (moves opening from one side of the membrane to other).
• Moves the bound compound to the outside of the cell.
• ATP is hydrolyzed to change the protein to evert back to its original conformation.

Question 22

Nerve cells use the gradient of what to transmit signals?

Answer 22

Na and K built up by the Na/K

Question 23

In nerve transmission, special “gates” open and close to allow what to diffuse into the nerve cells and what to diffuse out?

Answer 23

Na diffuses into the nerve cells and K diffuses out of the nerve cells.

Question 24

5 step mechanism for nerve transmission:

Answer 24

1. Na gates open
2. Na flows causing change in gradient.
3. K gates open and Na gates close
4. K flows out, overcompensating for voltage change.
5. K gates close then original voltage recovers.

Question 25

How does the signal in nerve transmission move from one junction to another?

Answer 25

When Na is in the cell, it diffuses down to the next Na gate before it can be pumped out. This changes voltage and triggers the mechanism to occur again and signal moves along.

Question 26

Describe the components of this wavelike signal:

Answer 26

• wave of sodium arrives at the end of the cell and causes synaptic vesicles to fuse with the end of the nerve cell.
• This causes release of contents into synaptic cleft.
• receptors at next nerve cell are stimulated and same response occurs.