CEE 2 - BIOCHEM Amino Acids

General Structure of Amino Acids

• More than ___ amino acids have been described

• Only __ are commonly found in mammalian proteins

300, 20

Except for proline, each amino acid has:

• A carboxyl group (COOH)

• An amino group (NH2)

• A distinctive side chain (R-group)

Except for ____, each amino acid has:

• A carboxyl group (COOH)

• An amino group (NH2)

• A distinctive side chain (R-group)

proline

Which part of amino acid is an acid (can donate a proton)

carboxyl group (COOH)

Which part of amino acid is a base (can accept a proton)

amino group (NH2)

Which part of amino acid dictates the function of the amino acid in the protein

distinctive side chain (R-group)

Abbreviations of Phenylalanine

Phe, F

Abbreviations of Histidine

His, H

Abbreviations of Isoleucine

Ile, I

Abbreviations of Methionine

Met, M

Abbreviations of Serine

Ser, S

Abbreviations of Valine

Val, V

Abbreviations of Glycine

Gly, G

Abbreviations of Alanine

Ala, A

Abbreviations of Leucine

Leu, L

Abbreviations of Proline

Pro, P

Abbreviations of Threonine

Thr, T

Abbreviations of Arginine

Arg, R

Abbreviations of Asparagine

Asn, N

Abbreviations of Aspartic acid

Asp, D

Abbreviations of Glutamic acid

Glu, E

Abbreviations of Tyrosine

Tyr, Y

Abbreviations of Tryptophan

Trp, W

Abbreviations of Lysine

Lys, L

Abbreviations of Glutamine

Gln, Q

This is the simplest amino acid, with just a hydrogen atom as its side chain.

Glycine

This amino acid is unique due to its cyclic structure that incorporates the amino nitrogen, restricting flexibility.

Proline

These amino acids have alkyl side chains of varying lengths, contributing to the hydrophobic core of proteins. ALKYL CONTAINING AAs

Valine, Alanine, Leucine, Isoleucine

Sulfur containing AAs

Cysteine, Methionine

This amino acid has a thiol group, making it reactive and prone to forming disulfide bonds, which are crucial for protein stability

Cysteine

This amino acid contains a sulfur atom within a thioether group

Methionine

Aromatic AAs

Tryptophan, Phenylalanine, Tyrosine

Aromatic AA: The side chain is an indole ring, consists a benzene ring fused to a nitrogen-containing pyrrole ring.

Tryptophan

Aromatic AA: Has a benzyl side chain.

Phenylalanine

Aromatic AA: The phenol side chain is polar.

Tyrosine

Alcohol containing AAs

Serine, Threonine

These both contain hydroxyl groups, which are often involved in phosphorylation.

Serine, Threonine

Amide containing AAs

Asparagine, Glutamine

These contain amide groups that do not gain or lose protons, remaining neutral in charge and often involved in hydrogen bonding.

Asparagine, Glutamine

Acidic AAs

Aspartic acid, Glutamic acid

These amino acids have carboxyl groups in their side chains, which lose protons and become negatively charged.

Aspartic acid, Glutamic acid

Basic AAs

Histidine, Arginine, Lysine

Basic AA: This AA contains an imidazole ring

Histidine

Basic AA: This AA contains a guanidinium group.

Arginine

Basic AA: This AA has a terminal primary amino group.

Lysine

Hydrophobic/Nonpolar Alipathic AA

G, P, (Sulfur: LAVI), M

Hydrophobic/Nonpolar AA (not alkyl and sulfur)

Glycine, Proline

Hydrophobic/Nonpolar AA alkyl

Valine, Alanine, Leucine, Isoleucine

Hydrophobic/Nonpolar AA sulfur

Methionine

Hydrophobic/Nonpolar AA Aromatic

Tryptophan, Phenylalanine

Hydrophilic/Polar AA uncharged all

S,T,N,Q,Y,C

Hydrophilic/Polar AA uncharged alcohol

Serine, Threonine

Hydrophilic/Polar AA uncharged amide

Aspargine, Glutamine

Hydrophilic/Polar AA uncharged Aromatic

Tyrosine

Hydrophilic/Polar AA uncharged sulfur

Cysteine

Hydrophilic/Polar AA charged

D,E,H,R,K

Hydrophilic/Polar AA charged acidic

Aspartic acid, Glutamic acid

Hydrophilic/Polar AA charged basic

Histidine, Arginine, Lysine

C skeleton can be converted to ketone bodies or their precursors (example: Acetyl CoA, acetoacetate)

Exclusively ketogenic

Exclusively Ketogenic examples

LK

C skeleton can be converted to precursor of gluconeogenesis (example: Pyruvate, Intermediates of Krebs such as alpha ketogluconate, succinyl CoA, Fumarate, OOA)

Exclusively Glucogenic

Exclusively Glucogenic examples

Other AAs

Both Ketogenic and Glucogenic

TWIFY

AAs that can be synthesized in the body

Non-essential AAs

Non-essential AAs examples

Other AAs

AAs that Cannot be synthesized in the body and must be obtained in the diet

Essential AAs

Essential AAs examples

FHM LV TWIRK

AAs Can be synthesized in the body but not always in sufficient quantities.

Semi-essential AAs

Semi-essential AAs examples

R

Has the smallest side chain; only achiral(Superimposable) amino acid among the 20 AAs

Glycine

Used in the first step of heme synthesis

Glycine + Succiny/ CoA → 8-ALA

Glycine

Used in synthesis of purines and creatine

Glycine

Conjugated to bile acids, drugs, and other metabolites

Glycine

Major inhibitory neurotransmitter in the spinal cord or CNS

Glycine

Branched-chain amino acids whose metabolites accumulate in maple syrup urine disease

Valine,Isoleucine, Leucine

maple syrup urine disease can be detected in?

Newborn screening test

Accumulates in phenylketonuria

Phenylalanine

Precursor of tyrosine

Phenylalanine

Has the largest side chain

Tryptophan

Precursor for melatonin, serotonin, and niacin

Tryptophan

Source of methyl groups in metabolism:

Involved in transfer of methyl groups as S-adenosylmethionine (SAM)

Methionine

Precursor of homocysteine and cysteine

Methionine

Precursor of Carnitine

Methionine

• Contain a polar hydroxyl group

• Site for O-linked glycosylation and phosphorylation of proteins

Serine, Threonine, Tyrosine

Precursor of thyroxine and and melanin

Tyrosine

Precursor of Dopamine, Norepinephrine, and Epinephrine

Tyrosine

Have a carbonyl group and an amide group that can also form hydrogen bonds

Asparagine, Glutamine

is the site for N-linked glycosylation of proteins

Asparagine

is deaminated by glutaminase resulting in the formation of ammonia, and is a major carrier of nitrogen to the liver from peripheral tissues

Glutamine

• Contains a sulfhydryl group that is an active part of many enzymes

• Participates in the biosynthesis of coenzyme A

Cysteine

Two cysteines can be connected by a covalent disulfide bond to form__

cystine

Disulfide bonds formed by ___ residues causes kinking of hair. Disruption of these bonds (using heat) may straighten hair temporarily.

cystine

• Negatively charged at neutral pH because of the carboxylate group

• Participate in ionic interactions

• Serve as proton donors

Aspartate, Glutamate

is the precursor for GABA and glutathione

Glutamate

is the major excitatory neurotransmitter of the CNS.

Glutamate

___is the major inhibitory neurotransmitter of the BRAIN.

GABA

___is the major inhibitory neurotransmitter of the SPINE

Glycine

proton acceptors

Histidine, Arginine, Lysine

At neutral pH these AAs are positively charged

Arginine, Lysine

At neutral pH these AAs have no charge,weak base

Histidine