NS 132 Exam #2 Review Outline
Protein Composition and Structure
Proteins are chains of ____amino acids_____________________________.
Amino acids are the "building blocks" of proteins; each block is joined together by a peptide bond.
Proteins can be made up of hundreds or thousands of amino acids; small proteins are called "peptides" or
"polypeptides" (a peptide is a protein). Proteins can be enzymes, hormones, transporters, antibodies,
carriers, cellular pumps, and receptors (and other things), and they form part of many structures (bone,
There are ____20
_____ different amino acids and about 100,000 different proteins in the human body.
9 amino acids are essential or indispensable.
This means they must be obtained from the diet.
Amino acids are composed of carbon, hydrogen, oxygen, and ____nitrogen
_____(and sometimes sulfur).
that distinguishes protein from the other macronutrients.
The body is constantly synthesizing and breaking down proteins to carry out the many functions required.
The sequence for proteins is carried in DNA; DNA tells the body how to make the proteins it needs.
One gene carries the "code" for one protein.
amino acid sequence
A protein's shape (e.g., whether it's coiled or folded, how it's coiled or folded) determines its function.
Protein Digestion and Absorption
Proteins cannot be absorbed whole; they are broken down by enzymes into
Proteins are denatured; this exposes certain sections of the protein, making them available for interaction.
occurs during digestion by
acids in the stomach and small intestine
can also occur by heat - as in cooking - and by alcohol, bases, and the salts of heavy metals).
In the stomach
: Acid and protease begin to denature proteins.
In the small intestine
: Proteases continue to denature proteins until they are reduced to the absorbable units.
REVIEW THE TEXT for a succinct summary of the fate of an amino acid in digestion.
in our diets is to provide us with the essential amino acids we CAN'T make and
provide a source of nitrogen for the amino acids the body can make. Each cell in the body has an amino
acid "pool" with amino acids supplied both by the diet and by the body's own production.
List of protein functions:
Blood clotting factors
Blood transport proteins (e.g., iron, hemoglobin)
Structural components (e.g., muscle, bone matrix, cell membranes, connective tissue)
Maintain fluid balance
by attracting and retaining fluid in the blood via osmosis.