11/17/2014 Medical Physiology Transport Physiology Steven Grassl

Question 1

Define active transport.

Answer 1

Movement of solute across a membrane UP its concentration gradient (from low [] to high [])

Question 2

______ transport is defined as movement of solute from a place of high electrochemical potential on one side of a membrane to a place of low electrochemical potential on the other.

Answer 2

Passive

Question 3

T/F: In no instance would a passive transport mechanism mediate net transport of a charged solute in a direction across the cell membrane that opposed both the chemical and electrical driving forces acting on the ion.

Answer 3

True

Question 4

What is the most important distinguishing feature of active transport versus passive transport?

Answer 4

Active transport can generate and maintain an electrochemical or chemical potential difference across a membrane.

Question 5

Give an example of a non-equilibrium steady state.

Answer 5

Na/K ATPase

Question 6

How are uncharged solute differences classified?

Answer 6

As chemical potentials. For example, glucose is uncharged, so there can be no voltage difference across a membrane, only a chemical difference.

Question 7

Ion transporters, antiporters and symporters all mediate what kind of transport?

Answer 7

Active transport

Question 8

Channels and uniporters generally mediate what kind of transport?

Answer 8

Passive

Question 9

What bonds are broken to drive active transport?

Answer 9

Phosphate bonds of ATP

Question 10

In epithelial cells such as in the kidney and intestine, different secondary active _____ mediate concentrative, intracellular accumulation of solutes such as glucose, amino acids, vitamins, mono and dicarboxylates etc.

Answer 10

symporters

Question 11

Name the two types of secondary active transport.

Answer 11

1. Cotransport - symporter 2. Countertransport - antiporter

Question 12

Name the primary active transport method.

Answer 12

Pump

Question 13

Solute potential equilibrium and net zero differential across the membrane occurs in:

Answer 13

Passive transport

Question 14

In secondary active transport, what does secondary mean?

Answer 14

The mode of transport is indirectly dependent on the hydrolysis of ATP and a primary active transport process

Question 15

Which is a faster mode of transport, channels or carrier-mediated transport?

Answer 15

Channels, by many orders of magnitude

Question 16

How is the steady state distribution of Na and K maintained?

Answer 16

Active transport of ATPase, and leak channels that move Na in and K out (opposite the direction of the pump)

Question 17

How many Na ions are transported into the cell via the Na/K ATPase?

Answer 17

NONE! The Na/K pump moves 3 Na OUT of the cell and 2 K IN to the cell

Question 18

What is the shape of the slope of a graph of simple diffusion?

Answer 18

Straight line, linear relationship between [X] and Jx (transport rate, aka Vx)

Question 19

What is the shape of the slope of a graph of carrier-mediated or facilitated diffusion?

Answer 19

Asymptotic, determined by [X] where higher [X] eventually levels off at Vmax (or Jmax)

Question 20

In facilitated diffusion/Michelis Menton kinetics, when does [X] = Km?

Answer 20

At 1/2Vmax

Question 21

What is Vmax?

Answer 21

The maximal transport rate achievable in carrier-mediated or facilitated diffusion (Michelis Menton kinetics)

Question 22

T/F: The interaction of a substrate with a transporter may or may not result in the transport of of the substrate across the membrane.

Answer 22

True. Sometimes the transport can be inhibited.

Question 23

Amiloride specifically inhibits what?

Answer 23

The epithelial Na channel and the epithelial Na/H exchanger

Question 24

What is phloridzin?

Answer 24

Phloridzin is a non-transported chemical analog of glucose. It inhibits the glucose-Na cotransporter.

Question 25

T/F: Phloridzin inhibits both the Na/glucose cotransporter and the Na/succinate cotransporter.

Answer 25

FALSE. Phloridzin only inhibits the Na/glucose cotransporter.

Question 26

What is transport stoichiometry?

Answer 26

The number of substrate molecules transported across a membrane in one complete cycle.

Question 27

What is the stoichiometric coupling or the Na/glucose cotransporter?

Answer 27

1:1, both Na and glucose moving the same direction across the membrane

Question 28

Define electrogenicity.

Answer 28

A property that describes the membrane potential difference as well as the substrate concentration difference

Question 29

Define acidosis at the level of the ion transporter.

Answer 29

Na in for H out (excess of acid in blood)

Question 30

Define alkalosis at the level of the ion transporter.

Answer 30

HCO3- out for Cl- in (excess of base in blood)