Lecture 2: Membrane Transport Mechanisms

Question 1

Which of the following transport mechanisms requires energy other than kinetic energy?

A. Osmosis
B. Diffusion
C. Active transport
D. Facilitated diffusion

Answer 1

C. Active transport

Question 2

Of the following ions, which is most concentrated in the extracellular environment?

A. Na+
B. K+
C. Cl-
D. Ca2+

Answer 2

A. Na+

Question 3

The sodium-potassium pump is an example of which of the following kinds of transport?

A. Diffusion
B. Primary Active Transport
C. Secondary Active Transport
D. Facilitated Diffusion

Answer 3

B. Primary Active Transport

Question 4

The sodium-glucose pump is an example of which of the following kinds of transport?

A. Diffusion
B. Primary Active Transport
C. Secondary Active Transport
D. Facilitated Diffusion

Answer 4

C. Secondary Active Transport

Question 5

The sodium-calcium pump is an example of which type of transport?

A. Diffusion
B. Primary Active Transport
C. Secondary Active Transport
D. Facilitated Diffusion

Answer 5

C. Secondary Active Transport

Question 6

Glucose transporters (GLUT) employ which of the following kinds of transport?

A. Diffusion
B. Primary Active Transport
C. Secondary Active Transport
D. Facilitated Diffusion

Answer 6

D. Facilitated Diffusion

Question 7

What is the function of the K+ Selectivity Filter and how does it work?

Answer 7

The filter is lined with carbonyl groups (attracted to water). Hydrated Na+ ions are smaller, so that when they pass through the filter, carbonyls can not successfully pull off H2O, so these molecules are too large to filter through. Carbonyls can dehydrate the K+ so that they pass through the filter.

Question 8

What makes secondary active transport unique if Na+ is travelling down it’s electrochemical gradient?

Answer 8

Secondary active transport requires ATP to set up the Na+ gradient initially, thus, ATP is used secondarily and active transport was used at some point.

Question 9

Sodium/Calcium antiporters move three sodium ions per calcium ion. Why does it take three sodium ions to move one calcium ion?

Answer 9

The calcium ion is more positive, larger, and has a larger electrochemical gradient that Na+ must overcome.

Question 10

Diffusion

Answer 10

Movement of particles from a region of high concentration to a region of low concentration; does NOT require outside energy

Question 11

Osmosis

Answer 11

Diffusion of water across a semipermeable membrane; does NOT require outside energy

Question 12

Facilitated Diffusion

Answer 12

Requires uniporter carrier proteins, occurs down an electrochemical gradient. Because it is carrier mediated it establishes stereospecificity; does NOT require external energy
ex: GLUT family

Question 13

Active Transport

Answer 13

Movement of particles against a concentration/electrochemical gradient; requires metabolic energy and carrier proteins

Question 14

Primary Active Transport

Answer 14

Use ATP directly; utilize ATPase transporters

Question 15

Secondary Active Transport

Answer 15

Energy is derived secondarily from concentration differences of molecular or ionic substances created originally by primary active transport; uses multiporters

At least one of the solutes moves down its electrochemical gradient while one or more of the other solutes moves up its electrochemical gradient

Question 16

Multiporters

Answer 16

carrier proteins that transport more than one substance at a time (includes symporters and antiporters)

Question 17

Symporters

Answer 17

Transport substances in same direction

Question 18

Antiporters

Answer 18

Transport substances in opposite directions

Question 19

Sodium-Potassium Pump

Answer 19

Example of Primary Active Transport: 2 K+ ions bind to outside of carrier protein, 3 Na+ bind to inside of carrier protein; ATPase is activated and moves both ions against their concentration gradient (3 Na+ out of the cell, 2 K+ into the cell)

Question 20

Sodium-Glucose Co-transport

Answer 20

Example of Secondary Active Transport: a sodium gradient is created by primary active transport; this energy is used to transport glucose inside the cell (against its concentration gradient); both substances moved inside the cell

Question 21

Sodium-Hydrogen and Sodium-Calcium Counter-Transport

Answer 21

Example of Secondary Active Transport: a sodium gradient is created by primary active transport; this energy is used to transport calcium or hydrogen against its concentration gradient (out of the cell) while sodium moves inside the cell