Exam 2 Active Transport

Question 1

Two important characteristics of transporters

Answer 1

1. Traffic drugs in/out of cells

2. Important drug targets

Question 2

Movement of nonpolar stuff down the electrochemical gradient that involves desolvation and has a high activation barrier

Answer 2

Simple diffusion

Question 3

Protein assisted movement down electrochemical gradient

Answer 3

Facilitated diffusion

Question 4

Protein assisted, energy requiring transport against electrochemical gradient that is often coupled with ATP hydrolysis

Answer 4

Active transport

Question 5

Type of protein that are very specific for ions and substrate molecules. Catalyzation rates are well below diffusion, and they also display saturation kinetics

Answer 5

Transporters

Question 6

Type of protein that shows moderate specificity for ions, and are not saturable with an ion substrate. They allow a much faster rate of diffusion than protein transporters

Answer 6

Channels

Question 7

What is ion movement dictated by in protein channels?

Answer 7

Electochemical gradient

Question 8

What do transporters rely on to determine specificity of correct ions?

Answer 8

Size and electrostatic criteria

Question 9

Both ions move through the membrane in the same direction from a low concentration to a high concentration

Answer 9

Symport (secondary active)

Question 10

One ion moves from high to low concentration in one direction, while another ion moves from low to high concentration in the other direction

Answer 10

Antiport (secondary active)

Question 11

ATP is used to move an ion from low to high concentration

Answer 11

Primary active transport

Question 12

A protein transporter moves an ion from high to low concentration without ATP use

Answer 12

Facilitated diffusion

Question 13

Measure of transmembrane electrogradients

Answer 13

Vm

Question 14

Vm > 0

Answer 14

High charge differentials

Question 15

Vm < 0

Answer 15

Low charge differentials

Question 16

What does the spontaneous movement of ions depend on? (2)

Answer 16

1. Difference in solute concentration

2. Vm

Question 17

What is the benefit of using a protein carrier when moving a polar molecule across the membrane?

Answer 17

A hydration shell is usually formed around a polar molecule. This shell has to be removed when it passively diffuses through the lipid portion of the membrane; however, when a transporter is used, the hydration layer is removed easier and saves free energy expenditure

Question 18

How many more times efficient is glucose transport by a transporter, than by diffusion?

Answer 18

50,000 times

Question 19

A simple glucose uptake uniporter

Answer 19

GLUT 1

Question 20

An insulin-responsive glucose transporter

Answer 20

GLUT 4

Question 21

A glucose transporter that responds to large intracellular glucose due to glycogenolysis and can transport it out of the cell (puts glucose into the blood stream)

Answer 21

GLUT 2

Question 22

Pathology of Type II Diabetes

Answer 22

Insulin binding causing endosomes harboring GLUT 4 to fuse with cell membrane, that results in an increased glucose uptake into the cell. Deficiencies in this signaling pathway cause GLUT 4 to be trapped in endosomes and prevents fusion to the membrane (GLUT 4 transporter isn’t brought back to surface of cell)

Question 23

What are two characteristics of active transport

Answer 23

1. Some source of energy

2. Movement of a solute against its gradient

Question 24

Movement of a solute against it’s gradient, coupled with ATP hydrolysis

Answer 24

Primary active transport

Question 25

Movement of one solute against its gradient and one solvent down its gradient, where the movement of solute down the gradient supplies energy for this process

Answer 25

Secondary active transport

Question 26

Class of ATPase where cation transport proteins are phosphorylated by ATP. These include Na+/K+ ATPases and H+ ATPases, and are inhibited by vandium ions since they resemble phosphate

Answer 26

P-type ATPases

Question 27

Type of ATPase that transports Ca++ ions

Answer 27

Sarcoplasmic/Endoplasmic c-Reticulum Calcium ATPase

(SERCA) pump

Question 28

What class of molecules inhibit Na+/K+ ATPase

Answer 28

Cardiac glycosides (digoxin an digitoxin)

Question 29

What happens when cardiac glycosides such as digoxin and digitoxin inhibit Na+/K+ ATPase in patients with heart failure?

Answer 29

It increases intracellular Ca++ levels, which leads to increased stroke volume by making the heart work (contract) harder

Question 30

ATPase that acidifies intracellular compartments in organisms that are between pH 3 and 6.

Answer 30

V-Type ATPases

Question 31

ATPase that catalyzes uphill proton movement. They are energy coupling ATPases with the ATP synthase of the mitochondria being the best example

Answer 31

F-Type ATPases

Question 32

Transporters that pump a variety of chemicals outside of the cell, such as proteins, amino acids, bile salts, metals, lipids, and sterols

Answer 32

ABC transporters

Question 33

What was the first cloned ABC protein

Answer 33

Gene for MDR1/p glycoprotein which gave colchicine resistant hamsters, resistance to structurally unrelated drugs… hence MDR1 = Multi-drug-resistant 1

Question 34

What is the role of MDR1/P glycoprotein? (historically)

Answer 34

Pump xenobiotics out of healthy cells

Question 35

Where are MDR1/P glycoproteins present in the body?

Answer 35

Brain, placenta, testis, retina

Question 36

What makes P glycoprotein special (specifically the evolution of the gene)

Answer 36

Protects CNS of adults and infants from a variety of structurally diverse chemicals (promiscuous substrate)

Question 37

P glycoprotein is displays _________ transport.

Answer 37

Active transport

Question 38

P glycoprotein issue in cancer patients

Answer 38

P glycoprotein can become OVEREXPRESSED in cancer cells after exposure to chemotherapeutic agents, which means it pumps out anticancer drugs so they can’t accumulate inside the cell. This necessitates the use of different drug treatments to overcome resistance