Question

When proteins are catabolized, the waste product is ___________ (the main component of mammalian urine).

. Sun (UV) exposure causes adjacent ________ in the DNA of your skin to form a covalent dimer (which causes mutations during replication).

Answer 1

1. Protein is mainly composed of nitroge. In the mitochondria of human liver the protein is catabolized. Protein then breaks down into amino acids which the transported to various tissues , organs and some of them again goes for the polymerization of protein to form the new protein. The amino acid then catabolised to ammonia . But ammonia is a toxic agent in human. Further amonia is transformed to urea by the urea cycle and goes to kidney for filtration. Kidney filters the urea and it excreates from body through urine.

So the right answer is UREA , the main component of mammalian urine specialy in human.

2. Exposure to the sun uv lights causes many disease specialy cancer when mutation occur. The sun UV penetrates the epidermis of the skin and form the pyrimidine dimer.

In our DNA there are 4 base viz Adenine, Guanine, Cytosine and Thymine. The UV rays formed the pyrimidine dimer in the Thymine or cytosine. These causes the formation of cyclobutane pyrimidine dimer (CPD) .CPD has mutagenic effect. This CPD causes misreading during replication , resulting mutation in DNA.

So the right answer is PYRIMIDINE DIMER OF THYMINE OR CYTOCINE.