<span>Amino acids are the basic structural unit of all proteins. A 'free' amino acid (a single amino acid) always has:
an amino group -NH2,
a carboxyl group -COOH
a hydrogen -H
a chemical group or side chain -"R".
Since the amino acids (except glycine) have 4 different groups attached to the a-carbon, they are optically active stereoisomers (recall 23.101 Organic Chemistry) although only L-isomers are found in proteins.
At a neutral pH, both the amino and the carboxyl groups are ionised, giving what is termed the zwitterionic</span>
The correct answer is: [D]: "receives venous blood from the lower extremity" .
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<span>The Nerve is a tissue that carries messages throughout our bodies. </span>
<span>The answer is : movement, reproduction, obtaining food and oxygen, and body structure</span>
We live long lives compared to a lot of animals, we are at the top of the food chain, we are omnivores and have a larger variety of foods we can eat that’ll nurture our bodies
