A Number of Systems for Pumping Across Membranes Are Powered

question 25

Multiple Choice

A number of systems for pumping across membranes are powered by ATP. Such ATP-powered pumps are often called ATPases although they don't often hydrolyze ATP unless they are simultaneously transporting ions. Small increases in calcium ions in the cytosol trigger a number of different intracellular reactions, so the cells must keep the calcium concentration quite low. Muscle cells also transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (SR) . If a muscle cell cytosol has a free calcium ion concentration of 10-⁷ in a resting cell, while the concentration in the SR can be 10-², then how is the ATPase acting?

• A)The ATP must be powering an inflow of calcium from the outside of the cell into the SR.
• B)ATP must be transferring Pi to the SR to enable this to occur.
• C)ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient.
• D)The calcium ions must be diffusing back into the SR along the concentration gradient.
• E)The route of calcium ions must be from SR to the cytosol, to the cell's environment.

---

Definitions:

Climate Change

The significant and lasting changes in the statistical distribution of weather patterns over periods ranging from decades to millions of years.

Intertropical Convergence Zone

The region near the equator where the northeast and southeast trade winds converge, often leading to thunderstorms and heavy precipitation.

Maximum Solar Radiation

Refers to the highest amount of solar energy received by a specific area over a period, affecting climate and weather patterns.

Subtropics

Regions of the Earth located immediately north and south of the tropics, characterized by hot summers, mild winters, and relatively high humidity.