3.5.3 Active Transport: Ion Pumps and Cotransport

Question 1

active transport

Answer 1

• Living cells often require the uptake of molecules that are scarce in their environment. Cells must expend energy in order to transport material against its concentration gradient
• The process of active transport requires the expenditure of energy in the form of ATP by the cell.
• Two types of active transport are ion pumps and cotransport. Ion pumps involve the transport of ions against their concentration gradient resulting in a charge differential across the membrane. Cotransport is the coupled passage of two different solutes across
  the membrane

Question 2

ion pumps

Answer 2

• also called electrogenic pumps, to transport ions
  against their concentration gradient. The result is a differential charge across the cell membrane. The differential charge is a form of stored energy that the cell can use to fuel energy requiring (endergonic) processes.

Question 3

cotransport

Answer 3

• a cell expends energy to pump ions against their
  concentration gradient. The ions are then used like markers, tagging molecules for transport. In this example, cells pump hydrogen against a concentration gradient. The hydrogen ions bind with important molecules that are then transported into the cell. The hydrogen ions act like a key opening a door and enabling the transport of molecules across the membrane.

Question 4

An ion pump in a cell membrane uses ATP to

Answer 4

• store energy

Question 5

Which one of the following processes does not employ the use of a transport protein?

Answer 5

• osmosis

Question 6

How do the cells of the thyroid obtain iodine to produce thyroxin?

Answer 6

• Iodine is relatively rare in the blood and so is actively pumped into the thyroid.

Question 7

__________ is the situation when there is no net movement of molecules because a balance has been achieved.

Answer 7

• Equilibrium

Question 8

Which of the following statements concerning cotransport is not true?

a. Cotransport does not necessarily involve the transport of more than one substance.
b. An expenditure of ATP is needed to drive the transport process.
c. Cotransport requires the use of transport proteins.
d. A substance moves against its concentration gradient in the absence of ATP.

Answer 8

• d. A substance moves against its concentration gradient in the absence of ATP.