AMINO ACIDS Flashcards
are the most abundant and functionally diverse molecules in living systems.
Proteins
direct and regulate metabolism in the body, whereas contractile proteins in muscle permit movement.
Enzymes and polypeptide hormones:
have a carboxyl group, a primary amino group (except for proline, which has a secondary amino group), and a distinctive side chain (“R group”) bonded to the α-carbon atom
Amino Acids
is the result of the hydrophobicity of the nonpolar R groups, which act much like droplets of oil that coalesce in an aqueous environment.
hydrophobic effect
its side chain and α-amino N form a rigid, five-membered ring structure.
has a secondary (rather than a primary) amino group.
It is frequently referred to as an “imino acid.”
Proline
Two disulfide-linked cysteines are referred to as
cystine
is the only amino acid with a side chain that can ionize within the physiologic pH range.
Histidine
is a solution that resists change in pH following the addition of an acid or base.
Buffers
is the linear sequence of amino acids in a protein. It is determined by the DNA sequence of the gene that codes for the protein.
PRIMARY STRUCTURE OF PROTEINS
is the formation of regular arrangements of amino acids that are located near each other in the linear sequence.
SECONDARY STRUCTURE OF PROTEINS
-the most common of the helices
spiral structure, tightly packed, coiled polypeptide backbone core, with the side chains of the component amino acids
a-Helix
–surfaces of β-sheets appear “pleated”
β-strands are often visualized as broad arrows
β-Sheet
reverse the direction of a polypeptide chain, helping it form a compact, globular shape.
β-Bends (reverse turns, β-turns)
- refers both to the folding of domains (the basic units of structure and function), and to the final arrangement of domains in the polypeptide.
TERTIARY STRUCTURE OF GLOBULAR PROTEINS
involves non-random, ordered pathways
Protein folding
results in the unfolding and disorganization of a protein’s secondary and tertiary structures without the hydrolysis of peptide bonds.
Denaturation of proteins
is the three-dimensional arrangement of multiple protein subunits.
QUATERNARY STRUCTURE OF PROTEINS
accumulation of these insoluble, spontaneously aggregating proteins, called amyloids (Parkinson, Huntington, and Alzheimer disease).
Amyloid disease
