Question

Urea Cycle:

a. What is its main purpose?

b. Which 2 amino acids feed directly into the cycle?

c. What cellular location does it occur in?

d. Does it create or use ATP?

Answer 1

Urea cycle:-

The conversion of toxic ammonia to urea to get it detoxified by certain steps is urea cycle.

A)the main purpose of urea cycle is to convert the toxic ammonia produced by metabolism of amino acids (proteins) to urea which can be easily excreted.

B)In over all urea molecule had two amino groups which are derived from ammonia (NH3) and one from aspartate(R-NH2).

this ammonia is derived from glutamine which is seen in amino acid metabolism.

So,glutamine and aspartate feed into urea cycle by giving amino groups.

C)UREA SYNTHESIS is a five step process,which takes place both in mitochondria and cytosol.

But the first two enzymes are present in mitochondria only so first two steps in mitochondria and other steps in cytosol.

This whole process is seen in liver.

D)UREA CYCLE is irreversible and consumes 4 ATP but it doesn't create ATP.

two are utilised for synthesis of carbamoyl phosphate.

One ATP each is used in production of arginosuccinate.

Reaction:

NH4+, +CO2+ ASPARTATE + 3ATP------}UREA +FUMARATE +2ADP +2Pi +AMP +PPi