Question

Compared to the cytosol, which of the following is generally true about the lumen of the endoplasmic reticulum in our cells?

1) It has a higher pH.
2) It has a more reducing environment.
3) It has a much higher calcium ion concentration.
4) It has a higher density of ribosomes.
5) All of the above.

Answer 1

The lumen of the endoplasmic reticulum has a much higher calcium ion concentration compared to the cytosol.

Step-by-step explanation:

Compared to the cytosol, the lumen of the endoplasmic reticulum (ER) in our cells generally has a much higher calcium ion concentration. The ER, particularly the smooth endoplasmic reticulum (SER), is responsible for regulating the concentration of cellular calcium ions. The ER lumen does not have a more reducing environment, nor does it have a higher pH or a higher density of ribosomes. The rough endoplasmic reticulum (RER) is studded with ribosomes on the cytoplasmic surface, not inside the lumen. Therefore, the correct statement about the lumen of the ER is that it has a much higher calcium ion concentration (3).