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Structure and Properties of Amino Acids and Proteins
Amino AcidsGeneral Features
Isomerism, Chirality and Optical RotationAmphoteric PropertiesAmino Acid Side ChainsAcid Base Characteristics of Amino Acids
Peptides and ProteinsLevels of Protein Structure
Primary StructureSecondary StructureTertiary and Quaternary Structures
How Protein Conformations are Stabilizing
General Amino Acid Features
-O OC
R
+H3N HC
= O O-C
R
NH3+H C
=
L - isomer D - isomer
Isomerism
Constitutional isomers, nonsuperimposable, mirror images(i.e. stereoisomers)
General Amino Acid Features
-O OC
R
+H3N HC
= O O-C
R
NH3+H C
=
R - clockwise
Chirality and the R, S system
S - counterclockwise
H < C < N < O
General Amino Acid Features
-O OC
R
+H3N HC
= O O-C
R
NH3+H C
=
L - isomer D - isomer
Amphoteric Properties
Zwitterions
ValineAlanine
Pyruvate
Nonpolar Hydrophobic Amino Acids
Isoleucine Leucine
Proline
Phenylalanine
Tryptophan
Tyrosine
Aromatic Amino Acids
Aspartic AcidOxaloacetate
Glutamic AcidA-ketoglutarate
Metabolic intermediatesMetabolic intermediates
HistidineArginine
Lysine
Positively Charged Amino Acids
Threonine
Asparagine
Methionine
SerineCysteine
Glutamine
Amino Acids with Uncharged R- groups (but vary in polarity)
Glycine
Essential amino acids
1. Humans can produce 10 of the 20 amino acids. The others must be supplied in the food. 2. Failure to obtain enough of even 1 of the 10 essential amino acids, those that we cannot
make, results in degradation cellular and noncellular proteins to obtain the one amino acid that is needed.
3. Unlike fat and starch, the human body does not store excess amino acids for later use—the amino acids must be in the food every day.
4. The 10 amino acids that we can produce are:
Alanine Asparagine Aspartic acid
Cysteine Glutamic acid Glutamine
Glycine Proline Serine
Tyrosine
Tyrosine is produced from phenylalanine, so if the diet is deficient in phenylalanine, tyrosine will be required as well.
Proline
The essential amino acids are:
Arginine Histidine Isoleucine
Leucine Lysine Methionine
Phenylalanine Threonine Tryptophan
Valine
These amino acids are REQUIRED in the diet.
They are INDISPENSABLE .
