Chapter 6- Proteins and Amino Acids
Proteins are made from 20 diff. amino acids, 9 of which are essential.
Each amino acid has an amino group, an acid group, a hydrogen atom, and a side group.
It is the side group that makes each amino acid unique.
The sequence of amino acids in each protein determines it unique shape and function.
A. Have unique side groups that result in differences in the size, shape, and electrical charge of an
Nonessential amino acids, are called
acids, are ones the body can create.
Nonessential amino acids include alanine, arginine, asparagines, aspartic acid, cysteine, glutamic
acid, glutamine, clycine, proline, serine, and tyrosine.
A. Essential amino acids, also called
indispensable amino acids
, must be supplied by the foods
Include histidine, isoeucine, leucine, lysine, methionine, phenyalanine, threonine, tryptophan, and
Conditionally essential amino acids refer to amino acids that are normally nonessential but
essential under certain conditions.
A. Amino acid chains are linked by peptide bonds in condensation reactions.
Dipeptides have two amino acids bonded together.
Tripeptides have three amino acids bonded together.
Polypeptides have more than 2 bonded.
Amino acid sequences are all different, which allows for a wide variety of possible sequences.
A. Protein Shapes
Hydrophilic side groups (water-loving) are attracted to water.
Hydrophobic side groups (water-hating) repel water.
Coiled and twisted chains help to provide stability.
Some carry and store materials.
Some require minerals for activation (ex. Hemoglobin and the mineral iron).
Protein denaturation is the uncoiling of protein that changes its ability to function.
Proteins can be denatured by heat and acid.
After a certain point, denaturation cannot be reversed.
Stomach acid (HCl) and enzymes facilitate the digestion of protein.
A. It is first denatured, then broken down to polypeptides.
The small intestine continues to break down protein into smaller peptides and amino acids so it
can be absorbed.
10. (see pg. 186 for chart diagram).