Active transport Knowledge-Based Download PDF

Questions

1. 1.

   In secondary active transport, which type of carrier protein translocates two different solutes across a biological membrane in opposite directions?

   • A) An antiporter
   • B) A symporter
   • C) A uniporter
   • D) A ligand-gated channel
2. 2.

   During primary active transport, what specific event directly induces the conformational change in the carrier protein that allows it to translocate solutes against their gradient?

   • A) Allosteric binding of a cyclic nucleotide to the cytosolic regulatory domain
   • B) Covalent phosphorylation of the transport protein by a phosphate group from ATP
   • C) Proteolytic cleavage of an inhibitory peptide segment on the cytoplasmic side
   • D) Glycosylation of specific transmembrane residues facing the lipid bilayer
3. 3.

   In secondary active transport (cotransport), what directly powers the uphill movement of a solute against its electrochemical gradient?

   • A) The direct enzymatic hydrolysis of ATP by the transport protein itself
   • B) The downhill movement of a coupling ion along its pre-existing electrochemical gradient
   • C) The bulk osmotic flow of water molecules moving through channel proteins
   • D) The spontaneous passive diffusion of lipid-soluble molecules across the bilayer
4. 4.

   In animal cells, the sodium-potassium pump ($\text{Na}^+/\text{K}^+$ ATPase) directly utilizes energy from ATP hydrolysis to maintain resting membrane potential and cell volume. Which of the following describes the net movement of ions per ATP molecule consumed in this active transport mechanism?

   • A) Pumping 3 $\text{Na}^+$ ions into the cell and 2 $\text{K}^+$ ions out of the cell
   • B) Pumping 3 $\text{Na}^+$ ions out of the cell and 2 $\text{K}^+$ ions into the cell
   • C) Pumping 2 $\text{Na}^+$ ions out of the cell and 3 $\text{K}^+$ ions into the cell
   • D) Pumping equal numbers of $\text{Na}^+$ and $\text{K}^+$ ions into the cell down their concentration gradients
5. 5.

   Which of the following statements correctly describes a defining characteristic of primary active transport across a cell membrane?

   • A) It moves substances down their concentration gradient without consuming cellular energy.
   • B) It relies entirely on channel proteins that form open hydrophilic pores across the lipid bilayer.
   • C) It occurs spontaneously through simple diffusion directly across the hydrophobic core of the phospholipids.
   • D) It moves solute molecules against their concentration gradient using energy derived from ATP hydrolysis.