What do carbs. do, and how come starch can be digested easily but cellulose cannot?

Question

What two general functions do carbohydrates carry out in cells?
Please be as detailed as possible while answering.

Why is it that, even though starch is easily digested by animals, cellulose is not?
Please be as detailed as possible while answering.

I will choose the best answer based on how helpful the comment was.

THANKYOU!!!!!!!!!!

Answer 1

Carbohydrates (sugars) have a number of major functions in cells. They are broken down into glucose. Glucose can then be phosphorylated to glucose-6-phosphate and enter glycolysis where it will ultimately result in 34-38 ATP (this number is debated).

Another fate of glucose is the pentose phosphate pathway. This is going to created 5-C ribose which can be used in construction of nucleic acids. NADPH is also a byproduct of this reaction, and is important in fatty acid synthesis.

Glucose can also be converted to glycogen for storage in the cell, via the enzyme glycogen synthase. This glycogen is then stimulated by insulin or epinephrine to signal whether nutrients are readily available (insulin, and thus storage can continue) or if the body is in a starved state (epinephrine, and thus glycogen phosphorylase enzyme breaks down the glycogen to glucose where it can carry out metabolic functions).

Humans can't digest cellulose because cellulose is a "pretty tough" molecule. This is because cellulose is formed from the beta-D-glucose molecules, which is very stable. We simply don't have the length in our digestive system to deal with this molecule. Starch on the other hand has specific enzymes in the digestive system (starch hyrdolase).

Answer 2

carbohydrates are the simplest macromolecule that can be used by the body. The body has enzymes which break it down to let the body utilize the different organic compounds. Starch is the storage carb in plants. Cellulose is the structural carb. We cant digest cellulose because it has a beta glycocidic link. We do not have the enzymes in our body to digest any structural carbohydrate from either plants nor animals. Only grazing animals and termites can break down beta glycosidic links. Carbohydrates are the main energy source for all living things. If it is not used, it is stored in the body or converted to a lipid called fat. In animals the storage carb is called glycogen and is stored in the organs and muscles, mostly in the liver. That's most of what I know. Hope that helped you out some.

Answer 3

Carbohydrates are used for energy and structure (in the case of plants which use cellulose and arthropods which have chitin). Carbohydrates are broken down into glucose in order to be apart of the process called cellular respiration ^_^

The structures of glucose, starch, and cellulose are different. Glucose and starch are sturctured in a matrix while cellulose is structured straight, like aligning chains. Thus, only some organisms can digest cellulose like termites...horses...it would cost too much energy to break down cellulose into glucose.

hope this helps at least some...

Answer 4

OK!

Carbohydrates serve as fuel or in fuel storage in metabolic pathways. They also have a structural role in cells, especially plant cells, but also in mammalian cells as moieties on glycoproteins.

Breakdown of larger carbohydrate polymers is dependent upon the action of enzymes. Cellulose monomers (β-glucose) are linked together through ß1→4 glycosidic bonds by condensation. This is in contrast to the α 1→4 glycosidic bonds present in other carbohydrates like starch. Humans and other mammals have amylase enzymes in the digestive system that readily break down the α 1→4 starch bonds into simple sugar for metabolic needs. However, such an enzyme is not present for breaking down the ß1→4 bonds in cellulose, so cellulose acts as indigestible bulk in the diet, as in bran. The exception is in ruminants, like cattle, which have multiple stomachs in which symbiotic bacteria break down the cellulose so that the simple sugars can be utilized by the mammal. Mammals also make their own starch, called glycogen, which is a storage form of glucose present in liver and muscle tissue.

Answer 5

Lets pretend I cut and pasted everything the rest did.

Animals CAN NOT breakdown Cellulose. No not even Horses. Bacteria can though. Ya need the enzyme to breakdown the structure.

Nothing to do with energy either. Its the need for the enzyme.