Membrane Transport

Question 1

How does downhill transport occur?

Answer 1

By diffusion, simple or facilitated, and required no input of metabolic energy

Question 2

How does uphill transport occur?

Answer 2

Primary or secondary active transport

Question 3

What is the difference between primary and secondary active transport?

Answer 3

Primary requires a direct input of energy, secondary uses indirect energy

Question 4

What is the only form of transport that is not carrier mediated?

Answer 4

Simple diffusion

Question 5

What are features of carrier-mediated transport?

Answer 5

Saturation, stereospecificity, and competition

Question 6

What is osmosis?

Answer 6

The flow of water across a semipermeable membrane from a solution with high concentration to a solution with low class concentration

Question 7

Will a potential difference affect the rate of diffusion of a non-electrolyte?

Answer 7

No

Question 8

Will a potential difference alter the rate of diffusion of a electrolyte?

Answer 8

Yes, it will alter the net rate of diffusion of a charged solute
(K+ will be slowed in a positive area and faster in a negative area)

Question 9

What is diffusion potential?

Answer 9

A potential difference across a membrane generated by a charged solute diffusing down its concentration gradient

Question 10

What is membrane permeability determined by?

Answer 10

Charge, polarity, size

Question 11

What are some examples of hydrophobic molecules?

Answer 11

O2, CO2, N2, steroid hormones

Question 12

What are some examples of small, uncharged polar molecules?

Answer 12

H2O, urea, glycerol, NH3

Question 13

List molecules groups from easiest to hardest to move across a membrane.

Answer 13

Hydrophobic molecules, small uncharged polar molecules, large uncharged polar molecules, ions

Question 14

How does low solute concentration affect facilitated diffusion?

Answer 14

Facilitiatated diffusion typically proceeds faster than simple diffusion

Question 15

How does high solute concentrations affect facilitated diffusion?

Answer 15

The membrane carrier proteins will become saturated and facilitated diffusion will level

Question 16

What are some examples of primary active transport?

Answer 16

Sodium/potassium pump, calcium pump, hydrogen/potassium pump

Question 17

Describe how secondary active transport works.

Answer 17

One solute moves down (downhill) its electrochemical gradient and the other solute moves up its electrochemical gradient (uphill)

Question 18

What is an example of facilitated diffusion?

Answer 18

The transport of d-glucose into skeletal muscle and adipose cells by the GLUT4 transporter

Question 19

What are the two types of secondary active transport?

Answer 19

Co-transport/symport and counter-transport/antiporter/exchange

Question 20

What is co-transport/symport?

Answer 20

A type of secondary active transport in which both solutes travel in the same direction

Question 21

Provide and example of co-transport/symport

Answer 21

Sodium and glucose binding to a transporter, and the transporter rotating and releasing both inside the cell

Question 22

What is counter-transport/antiport/exchange?

Answer 22

Secondary active transport where the solutes move in opposite directions

Question 23

Provide an example of counter-transport/antiport/exchange

Answer 23

Sodium moving down its gradient established by the sodium/potassium pump and calcium moving uphill

Question 24

How can you maintain osmotic balance?

Answer 24

Increase osmotic pressure on the external medium or continuously pump ions out to reduce the number of molecules in the cell and osmotic pressure

Question 25

What would happen to a RBC in a hypertonic, isotonic, hypotonic or very hypnotic solution?

Answer 25

Crenated, normal, swollen, lysed

Question 26

What is a channel?

Answer 26

Simple hole, often selective, often gated. May undergo conformational changes to open/close, but not for each substrate translocation reaction. Does not require energy input

Question 27

What does a carrier alter?

Answer 27

Accessibility to binding sites through conformational changes

Question 28

What is the ABC transporter superfamily?

Answer 28

2 highly conserved ATP binding cassette that fuel uphill substrate transport across cellular membrane through conformational changes

Question 29

How can cells becomes resistant to drugs?

Answer 29

Non-specific ABC transporters transport relatively hydrophobic molecules, most drugs are highly hydrophobic, cells that over-express an MDR protein can become resistant

Question 30

What is CFTR?

Answer 30

An ABC transporter activated by cAMP that’s a passive ATP-gated chloride channel. Chloride flows out, followed by sodium and water

Question 31

What are ion channels?

Answer 31

Pores that allow passive movement of ions across a membrane and can exploit ionic gradients to generate electrical signals

Question 32

If the concentrations are vastly different, the molecules will move _____, if the concentrations are similar, the molecules will move _____.

Answer 32

Quickly/slowly

Question 33

Sodium ions are usually more concentrated ___ of the cell, and potassium ions are usually more concentrated ____ of the cell.

Answer 33

Outside/inside