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 ________.

Question

Quizplus · Accepted Answer

CThe protein moving Ca²⁺ from the endoplasmic reticulum to the cytosol typically does so through a channel or transporter that allows calcium ions to flow down their concentration gradient, which does not require ATP (adenosine triphosphate) for energy. This process is passive and relies on the existing concentration gradient. On the other hand, moving Ca²⁺ from the cytosol back into the endoplasmic reticulum requires energy because it is moving against the concentration gradient. This process is typically carried out by a type of pump known as a Ca²⁺-ATPase, which uses ATP to actively transport calcium ions into the endoplasmic reticulum.

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