Question

How does an animal cell react when there is no glucose available to carry out cellular respiration

Answer 1

It breaks down polysaccharides such as starch. The next step is to metabolize fats and proteins.

Answer 2

Answer: First, the cell breaks down polysaccharides such as glycogen. After that, it metabolizes fats and proteins.

Explanation:

Cellular respiration is a set of reactions that convert chemical energy from nutrients into adenosine triphosphate (ATP) which is an energy carrier molecule. The cells use cellular respiration to convert glucose into energy, and in addition, waste products are released.  When there is no glucosa available to do this, the organisms uses glycogen, which is a polymer consisting of a large number of glucose units joined together by glycosidic bonds.

Glycogen is broken down into glucose units, which is now available to be used during cellular respiration. But, when there's no glycogen either, the body metabolizes fats or proteins. Amino acids and fats can be converted into various intermediates of cellular respiration allowing them to slip into the pathway. Once these molecules enter the pathway, there is no difference where they came from, because they go through the remaining steps.

There are also metabolic processes that break down fats into fatty acids and glycerol. Fatty acids are changed into acetyl CoA molecules, which enters the Kreb's Cycle. While. glycerol is changed into an intermediate product of glycolysis, so it also enters the cellular respiration pathway.

On the other hand, to metabolize amino acids, they must have their amino group removed. Proteins are first broken down to amino acids by various enzymes. This step makes ammonia as a waste product, and it is converted to urea and removed from the body in urine.  After that, different amino acids enter the cellular respiration pathways at different stages.