PUMPS (SITES FOR ATPase)

A Pump or ion transporter is a transmembrane protein that moves ions across a plasma membrane against their concentration gradient through active transport.
They utilized energy to transport ions
The primary transporters are enzymes that convert energy from various sources including ATP sunlight and other redox -reaction to potential energy which is stored in an electrochemical gradient.
This potential energy is then used by secondary transporters including ion carrier and ion channel;
A active transport pump may be uni-porter or anti-porter
ATP dependent ion pumps are grouped into classes based on transport mechanisms as well as genetic and structural homology.
All ATP powered pumps are transmembrane proteins with one or more binding sites.
ATP located on the cytosolic face of the membrane .
These proteins are commonly called ATPase
The ATP hydrolyzed into ADP and Pi and the energy is used to move ions or other molecule uphill against an electrochemical gradient

Types of Pumps

There are four types/ Classes (P,V,F, and ABC) of ATP powered pumps.
In these three classes (P,F, and V) transports ions only.
where as ABC superfamily transport small molecules.

P- Class Pumps (ATP powered Pump)

These are found in plasma membrane of plant fungi and bacteria
All P class ion pump posses two identical catalytic α sub-unit that contain an ATP binding site and an β sub-unit that usually have regulatory function.
During the transport process α sub-unit is phosphorylated (hence the name “P” Class) and the transported ions through the phosphorylated sub-unit.
They included

(i) Na+K+ATPase

It is present in plasma membrane of most animal cell
These are antiport ion pumps
They catalyze ATP dependent Transport of Na+ out of a cell in exchange for K+ entering the cell.

(ii) H+- K+ ATPase

These are involved in acid secretion in the stomach
These are antiport pump
They catalyzed ATP dependent transport of H+ out of the gastric parietal ell (to ward the stomach lumen) in exchange for K+ entering the cell

(iii) Ca 2+ ATPase

It is present in the endoplasmic reticulum (E.R.) and plasma membrane of many cells.
This catalyzes ATP dependent transport of Ca2+ away from the cytosol into the E.R. lumen or out of the cell.
These pumps are antiporters transporting protons in the opposite direction.
Ca2+ ATPase pump function to keep cytosolic Ca2+ conc low. allowing Ca2+ to serve as a signal.

V -Classes pump

All V-class ATPase transport only H+ ions
These proton pumps present in the membranes of lysosomes, endosomes and plant vacuoles functions to acidify the lumen of these organelles.
These V. Class proton pumps contain two domain a-cytosolic hydrophilic domain (V1) and a transmembrane domain (V0) with multiple subunits in each domain.
Binding and hydrolysis of ATP by the β subunits in (V1) provide the energy for pumping of H+ ions through the proton- conducting channel formed by the “C” and “a” subunit in V0.
V class proton pumps are not phosphorylated and dephosphorylated during proton transport.
V Class pumps generally function to maintain the low pH of plant vacuoles and lysosome and other acidic vesicles in animal cells by pumping protons from the cytosolic to the exoplasmic face of the membrane against a proton electrochemical gradient.

F Class Pump

The structures of F-class and V-class ion pumps are similar to one another but unrelated to and more complicated than P-class pumps.
F- class pumps contain several different transmembrane and cytosolic subunits.
All known F pumps transport only protons, in a process that does not involve a phosphoprotein intermediate.
F-class pumps are found in bacterial plasma membranes and in mitochondria and chloroplasts. In contrast to V pumps, they generally function to power the synthesis of ATP from ADP and Pi by movement of protons from the exoplasmic to the cytosolic face of the membrane down the proton electrochemical gradient.
Because of their importance in ATP synthesis in chloroplasts and mitochondria, F-class proton
pumps, commonly called ATP synthases.

ABC (ATP binding Cassette) transporter

These catalyze trans-membrane movement of organic compounds including amphipathic lipids and drugs.
It is organized by four core domains.
These domain consist of two transmembrane (T) domain and two cytosolic (A) domain.
The two T domain alternate b/w an inward and outward facing orientation.
This alternation is powered by the hydrolysis of ATP.
ATP bind to A sub-unit and it is then hydrolyzed to power the alternation.
These four domain can be present in four separate polypeptides.

E.g.

CUT 1 (Carbohydrate uptake Transporter 1)
PAAT (polar amino acid uptake transporter )
PepT, PhoT

MCQs on Pumps (ATPase Sites)

1. What is the primary function of an ATP-powered pump?

A) Passive transport of ions
B) Movement of ions against their concentration gradient
C) Diffusion of ions along the electrochemical gradient
D) Production of glucose

✅ Answer: B) Movement of ions against their concentration gradient

2. Which of the following is NOT a function of ATP-powered pumps?

A) Transporting ions across membranes
B) Generating electrochemical gradients
C) Facilitating passive diffusion
D) Converting ATP energy into ion movement

✅ Answer: C) Facilitating passive diffusion

3. What is the main energy source for primary transporters?

A) Diffusion
B) ATP hydrolysis
C) Osmosis
D) Facilitated diffusion

✅ Answer: B) ATP hydrolysis

4. Which of the following classes of ATP-powered pumps transport only ions?

A) P, F, and V
B) ABC and P
C) ABC and F
D) F and ABC

✅ Answer: A) P, F, and V

5. Why are P-class pumps named so?

A) They transport phosphorus
B) Their α-subunit undergoes phosphorylation
C) They are found in plant cells
D) They require proton gradients for function

✅ Answer: B) Their α-subunit undergoes phosphorylation

6. Which ion pump is responsible for maintaining resting membrane potential in animal cells?

A) H+ ATPase
B) Na+/K+ ATPase
C) Ca2+ ATPase
D) F-Class ATP synthase

✅ Answer: B) Na+/K+ ATPase

7. The H+/K+ ATPase pump is primarily involved in which function?

A) Nerve impulse transmission
B) Muscle contraction
C) Acid secretion in the stomach
D) Oxygen transport in blood

✅ Answer: C) Acid secretion in the stomach

8. Which ATP-powered pump is present in the endoplasmic reticulum and regulates calcium levels?

A) Na+/K+ ATPase
B) H+/K+ ATPase
C) Ca2+ ATPase
D) ABC Transporter

✅ Answer: C) Ca2+ ATPase

9. What is the main function of V-class pumps?

A) Transport of protons (H+) to acidify organelles
B) Pumping sodium ions across membranes
C) ATP synthesis in mitochondria
D) Transport of small organic molecules

✅ Answer: A) Transport of protons (H+) to acidify organelles

10. Which organelles contain V-class pumps to maintain acidic environments?

A) Mitochondria and chloroplasts
B) Lysosomes and vacuoles
C) Ribosomes and nucleus
D) Golgi apparatus and rough ER

✅ Answer: B) Lysosomes and vacuoles

11. What is the primary role of F-class pumps?

A) Proton transport to maintain acidic pH
B) ATP synthesis in mitochondria and chloroplasts
C) Drug transport across membranes
D) Sodium-potassium exchange

✅ Answer: B) ATP synthesis in mitochondria and chloroplasts

12. Which of the following is a unique feature of ABC transporters?

A) They transport only ions
B) They use ATP to move small organic molecules
C) They undergo phosphorylation
D) They synthesize ATP

✅ Answer: B) They use ATP to move small organic molecules

13. How many core domains do ABC transporters have?

A) Two
B) Three
C) Four
D) Five

✅ Answer: C) Four

14. Which of the following is an example of an ABC transporter?

A) Na+/K+ ATPase
B) H+/K+ ATPase
C) CUT1 (Carbohydrate uptake Transporter 1)
D) V-class ATPase

✅ Answer: C) CUT1 (Carbohydrate uptake Transporter 1)

15. What powers the alternation of transmembrane domains in ABC transporters?

A) Osmosis
B) ATP hydrolysis
C) Passive diffusion
D) Sodium-potassium pump

✅ Answer: B) ATP hydrolysis

16. Which of the following ATP-powered pumps does NOT involve phosphorylation during transport?

A) P-class pumps
B) V-class pumps
C) F-class pumps
D) ABC transporters

✅ Answer: B) V-class pumps

17. The Na+/K+ ATPase pump moves sodium and potassium ions in what ratio?

A) 2 Na+ out, 2 K+ in
B) 3 Na+ out, 2 K+ in
C) 2 Na+ out, 3 K+ in
D) 1 Na+ out, 1 K+ in

✅ Answer: B) 3 Na+ out, 2 K+ in

18. Which ATPase is involved in muscle contraction by regulating calcium levels?

A) Na+/K+ ATPase
B) H+/K+ ATPase
C) Ca2+ ATPase
D) ABC Transporter

✅ Answer: C) Ca2+ ATPase

19. Which of the following correctly describes an antiporter pump?

A) Moves two different ions in the same direction
B) Moves one type of ion in one direction
C) Moves two different ions in opposite directions
D) Uses facilitated diffusion instead of active transport

✅ Answer: C) Moves two different ions in opposite directions

20. Where are F-class ATP synthases primarily found?

A) Plasma membrane of bacteria
B) Inner mitochondrial membrane
C) Thylakoid membrane of chloroplasts
D) All of the above

✅ Answer: D) All of the above

21. Which of the following is NOT a function of the ABC transporter superfamily?

A) Drug resistance in bacteria
B) Lipid transport
C) Proton transport
D) Transport of amino acids and sugars

✅ Answer: C) Proton transport

22. In which cellular organelle does the V-class proton pump function to lower pH?

A) Mitochondria
B) Lysosome
C) Ribosome
D) Nucleus

✅ Answer: B) Lysosome

23. Which subunit of the F-class ATP synthase is responsible for ATP synthesis?

A) α-subunit
B) β-subunit
C) γ-subunit
D) ε-subunit

✅ Answer: B) β-subunit

24. What distinguishes the ABC transporters from other ATP-powered pumps?

A) They do not transport ions
B) They work only in mitochondria
C) They move molecules like lipids and drugs
D) They do not hydrolyze ATP

✅ Answer: C) They move molecules like lipids and drugs

25. What is the main role of the P-class Na+/K+ ATPase pump?

A) Secretion of gastric acid
B) Maintenance of resting membrane potential
C) ATP synthesis in mitochondria
D) Transport of carbohydrates

✅ Answer: B) Maintenance of resting membrane potential

26. How does the Ca2+ ATPase pump contribute to muscle relaxation?

A) Pumps calcium ions into mitochondria
B) Pumps calcium out of the cytosol into the sarcoplasmic reticulum
C) Inhibits ATP hydrolysis
D) Reduces sodium ion concentration

✅ Answer: B) Pumps calcium out of the cytosol into the sarcoplasmic reticulum

27. What is the primary function of V-class pumps in plant cells?

A) ATP synthesis
B) Protein transport
C) Acidification of vacuoles
D) Regulation of membrane fluidity

✅ Answer: C) Acidification of vacuoles

28. Which ATPase is responsible for the movement of protons across the mitochondrial membrane to generate ATP?

A) Na+/K+ ATPase
B) F-Class ATP synthase
C) Ca2+ ATPase
D) ABC Transporter

✅ Answer: B) F-Class ATP synthase

29. What drives the movement of protons through the F-class ATP synthase?

A) ATP hydrolysis
B) Sodium gradient
C) Proton electrochemical gradient
D) Direct phosphorylation

✅ Answer: C) Proton electrochemical gradient

30. What is the function of the transmembrane domains in ABC transporters?

A) Hydrolyze ATP
B) Bind transported molecules
C) Synthesize ATP
D) Regulate sodium-potassium balance

✅ Answer: B) Bind transported molecules