Calcium Ions (Ca²⁺) Are Present in the Endoplasmic Reticulum at Concentrations

question 78

Multiple Choice

Calcium ions (Ca²⁺) are present in the endoplasmic reticulum at concentrations 1,000 times higher than in the cytosol (the gel-like part of the cell outside organelles) . One protein on the endoplasmic reticulum membrane is devoted to allowing Ca²⁺ to move from the endoplasmic reticulum to the cytosol, and another protein moves Ca²⁺ from the cytosol to the endoplasmic reticulum. These processes are not trivial-Ca²⁺ released into the cytosol allows, for example, for muscle contraction and communication between nerve cells. In this pair of Ca²⁺ transport proteins, you would predict that the protein moving Ca²⁺ from the endoplasmic reticulum to the cytosol ________, and the protein that moves Ca²⁺ from cytosol to the endoplasmic reticulum ________.

• A) transports calcium slowly; transports calcium rapidly
• B) works without ATP; requires ATP
• C) requires ATP; works without ATP
• D) is large; is small
• E) is small; is large

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Definitions:

Required Reserve Ratio

The fraction of deposits that banks are required to hold in reserve and not lend out, as dictated by central banking authorities.

Excess Reserves

These are bank reserves held in excess of what is required by regulations, which can be lent out to generate income.

New Loans

Financial amounts borrowed by individuals, businesses, or governments, typically from banks or financial institutions, that have not previously existed in the market.

Required Reserve Ratio

The fraction of deposits that banks are mandated by the central bank to keep on hand as reserves, rather than loaning out.