Question

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; each word or phrase should be used only once.

Ca2+ can trigger biological effects in cells because an unstimulated cell has an extremely _______ concentration of free Ca2+ in the cytosol, compared with its concentration in the ________- space and in the nuclear, creating a steep electrochemical gradient. When Ca2+ enters the cytosol, it interacts with Ca2+-responsive proteins such as ______, which also binds diacylglycerol, and _______, which activates CaM-kinases.

Options:
a) low, extracellular, nuclear, calmodulin, protein kinase C
b) high, intracellular, endoplasmic reticulum, adenylyl cyclase, peroxisome
c) average, extracellular, endoplasmic reticulum, phospholipase C, protein kinase A
d) colorful, nuclear, peroxisome, adenylyl cyclase, protein kinase A

Answer 1

Calcium ions (Ca2+) create a steep electrochemical gradient between the cytosol and extracellular space due to their significantly lower concentration within the cell, leading to biological effects when interacting with proteins like protein kinase C and calmodulin.

Step-by-step explanation:

Ca2+ can trigger biological effects in cells because an unstimulated cell has an extremely low concentration of free Ca2+ in the cytosol, compared with its concentration in the extracellular space and in the nuclear, creating a steep electrochemical gradient. When Ca2+ enters the cytosol, it interacts with Ca2+-responsive proteins such as protein kinase C, which also binds diacylglycerol, and calmodulin, which activates CaM-kinases.