The transport of an ion across a membrane against its concentration gradient can
ID: 94713 • Letter: T
Question
The transport of an ion across a membrane against its concentration gradient can be accomplished by: A) the co-transport of another ion down its concentration gradient. B) the synthesis of ATP. C) the antiport of an ion against its concentration gradient. D) the opening of a channel specific for the ion. E) proteolytic removal of an inactivating domain on the transporter Calmodulin is a: A) nonspecific kinase. B) protein that binds Ca^2+. C) second messenger. D) protein channel that facilitates the influx of Ca^2+. E) G-protein. What is true about the (Na^+ - K^+)-ATPase transporter? A) three potassium ions bind to the cytostolic face of the transporter in the E_1 state B) GTP binds to it and is hydrolyzed to form GDP and a high energy phosphorylated glutamyl residue C) formation of the high-energy phosphorylated glutamyl residue triggers a conformational shift from the E_1 form to the E_2 form D) bound Na^+ ions are released from the E_2 state to the extracellular medium, and two potassium ions are bound to the dephosphorylated E_2 E) phosphate hydrolysis of the E_2 state releases potassium ions to the cytosol and results in rearrangement to the E_1 state.Explanation / Answer
8) A. The cotransport of another ion down its concentration gradient. because of the difference in environment across the membrane, it is important to transport a molecule from a region of low concentration to a region of higher concentration. Movement up a concentration gradient cannot occur passively, it have need of a mechanism to take the process. The mechanism can be influenced directly by the chemical breakdown of ATP to ADP and phosphate or it can be influenced by other molecules moving down a concentration gradient.
9) B. Protein that binds Ca2+ . Calmodulin is an abbreviation for calcium-modulated protein. It is a multifunctional intermediate calcium-binding messenger protein expressed in all eukaryotic cells. It is an intracellular target of the secondary messenger Ca2+, and the binding of Ca2+ is involved for the activation of Calmodulin.
10) E. Phosphate hydrolysis of the E2 state releases potassium ions to the cytosol and results in rearrangement to the E1 state.
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