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 _______A___________ concentration of free Ca2+ in the cytosol, compared with its concentration in the ______B____________ space and in the ______C____________, creating a steep electrochemical gradient. When Ca2+ enters the cytosol, it interacts with Ca2+-responsive proteins such as ______D____________, which also binds diacylglycerol, and ________E__________, which activates CaM-kinases.

average
extracellular
nuclear
phosopholipase C
protein kinase C
low
peroxisome
high
Ca2+
adenylyl cyclase
protein kinase A
intracellular
endoplasmic reticulum
calmodulin
colorful

Answer 1

In an unstimulated cell, the cytosol has a very low free Ca2+ concentration compared to the extracellular space and endoplasmic reticulum, creating a strong gradient. Upon Ca2+ entry, it binds to proteins like protein kinase C and calmodulin to elicit cellular responses.

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 endoplasmic reticulum, 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.