HW #3 chapter 3 61-72 (11-14) Flashcards
Why are amino acid side chains so important?
A classification scheme for amino acids can be based on the properties of their side chains. Two particularly important criteria are the polar or nonpolar nature of the side chain and the presence of an acidic or basic group in the side chain.
Why is it important to specify the three dimensional structure of amino acids?
The amino acids that are the monomer units of proteins have a general structure in common with an amino group and a carboxyl group bonded to the same carbon atom. The nature of the side chains which are referred to as R groups is the basis of the differences among amino acids. Except for glycine amino acids can exist in two forms, designated L and D. These two stereoisomers are non superimposable mirror images of each other. The amino acids found in proteins are of the L form but some D amino acids occur in nature.
Which amino acids have nonpolar side chains?
One group of amino acids has nonpolar side chains. The side chains are mostly aliphatic or aromatic hydrocarbons or their derivatives.
Which amino acids have electrically neutral polar side chains?
A second group of amino acids has side chains that contain electronegative atoms such as oxygen, nitrogen, and sulfur.
Which amino acids have carboxyl groups in there side chains?
Two amino acids, glutamic acid and aspartic acid have carboxyl groups in their side chains.
Which amino acids have basic side chains?
Three amino acids histidine, lysine, and arginine have basic side chains.
Which amino acids are found less commonly in proteins?
Some amino acids are found only in a few proteins. They are formed from the common ones after the protein has been synthesized in the cell.
What happens when we titrate an amino acid?
In free amino acids at neutral pH the carboxylate group is negatively charged (acidic) and the amino group is positively charged.
