Active Transport

Question 1

A cell uses transport protein to move a substance against its concentration gradient

Answer 1

Active Transport

Question 2

Involves the use of carrier proteins (called protein pumps due to their use of energy)

Answer 2

Active transport

Question 3

What happens in active transport? (Sodium-potassium pump)

Answer 3

Three sodium ions (Na-) from the inside bind to the protein channel and change the shape of the channel, which then drives the ions to move outward.

The new shape has a high affinity for potassium (K+) ions, so two bind to the channel and change its shape again, launching the potassium inward.

The cycle repeats.

Question 4

The electrochemical gradient moves from

Answer 4

From an area of lower concentration to an area of higher concentration.

Question 4

How do carrier proteins work? (first)

Answer 4

A specific solute will bind to the protein pump on one side of the membrane

Question 4

The interior of the cell is more negatively charged, while the exterior is more positively charged

Answer 4

Electrical/Voltage gradient

Question 5

How do transport proteins work? (second)

Answer 5

The hydrolysis of ATP (to ADP + Pi) causes a conformational change in the protein pump

Question 6

How do transport proteins work? (third)

Answer 6

The solute molecule is consequently translocated across the membrane (against the gradient) and released

Question 7

Energy used by the gradient may be generated by

Answer 7

• primary active transport
• secondary active transport

Question 8

The direct hydrolysis of ATP. Uses membrane proteins called “pumps”

Answer 8

Primary Active Transport

Question 9

Indirectly coupling transport with another molecule that is moving along its gradient. Uses energy from the electrochemical gradient. Also called cotransport

Answer 9

Secondary Active Transport

Question 10

Types of Carrier Proteins

Answer 10

• Uniport
• Symport
• Antiport

Question 11

Uniport proteins

Answer 11

Transports a single type of molecule/ion in one direction

Question 12

Symport proteins

Answer 12

Transport two molecules or ions in the same direction

Question 13

Antiport proteins

Answer 13

Transports two molecules/ions in the opposite directions

Question 14

Examples of protein pumps

Answer 14

• Na+- K+ ATPase - carries sodium and potassium ions
• H+-K+ ATPase - carries hydrogen and potassium ions
• Ca2+ ATPase – carries calcium ions only
• H+ ATPase - carries hydrogen ions only

Question 15

Which side of the cell membrane holds more negative charges?

Answer 15

The inside of the cell holds more negative charges and vice versa

Question 16

It uses energy released in ATP hydrolysis to move sodium ions (Na+) out of the cell and potassium (K+) inside the cell

Answer 16

Sodium-potassium pump

Question 17

____ Sodium (Na+) ions move ___ of the cell, while ____ potassium (K+) ions move ____ of the cell

Answer 17

3 Sodium ions - outside of the cell
2 Potassium ions - inside the cell

Question 18

What happens when sodium-potassium pumps remain at rest?

Answer 18

They expel sodium ions from the nerve cell, while potassium ions are accumulated within.

Question 19

What happens when sodium-potassium pumps’ neurons fire?

Answer 19

Their ions swap locations via facilitated diffusion via sodium and potassium channels

Question 20

Sodium-potassium pumps (extended)

Answer 20

1. Three sodium ions bind to intracellular sites on the sodium-potassium pump
2. A phosphate group is transferred to the pump via the hydrolysis of ATP
3. The pump undergoes a conformational change, translocating sodium across the membrane
4. The conformational change exposes two potassium binding sites on the extracellular surface of the pump
5. The phosphate group is released which causes the pump to return to its original conformation
6. This translocate the potassium across the membrane, completing the ion exchange