Amino Acids

What is the general structure of an amino acid?

α-carbon attached to

-carboxyl group

-amino group

-hydrogen

-R group.

What part of an amino acid determines its unique properties?

R group / side chain.

Which amino acid has H as its R group?

Glycine.

Which amino acid is the only achiral standard amino acid? Why?

Glycine — its α-carbon has two hydrogens.

Which amino acid has a CH₃ side chain?

Alanine.

Which amino acids have branched hydrocarbon side chains and are easy to confuse structurally?

Valine, leucine, isoleucine.

Which amino acid has a side chain that loops back and binds to its amino nitrogen?

Proline.

What structural feature makes proline unique?

It has a secondary amine; its nitrogen is bonded to two carbons.

Which amino acid contains an -SH group?

Cysteine.

Which amino acid contains a thioether?

Methionine.

Which amino acid contains an imidazole ring?

Histidine.

Which amino acid contains a guanidinium group?

Arginine.

Which amino acid contains an indole ring?

Tryptophan.

Which amino acid is basically phenylalanine with an -OH added to the aromatic ring?

Tyrosine.

Which amino acid has a CH₂OH side chain?

Serine.

Which amino acid resembles serine but has an additional methyl group?

Threonine.

What is the approximate pKa of the amino group?

9.8.

What is the approximate pKa of the carboxyl group?

2.2.

At physiologic/neutral pH, what is the carboxyl group predominantly present as?

COO⁻.

At physiologic/neutral pH, what is the amino group predominantly present as?

NH₃⁺.

What is a zwitterion?

A molecule containing both positive and negative charges but having no net charge overall.

What does pH > pKa generally mean?

The group is predominantly deprotonated.

What does pH < pKa generally mean?

The group is predominantly protonated.

What charge do aspartic acid and glutamic acid usually carry at physiologic pH?

Negative.

What is the side-chain charge of arginine at physiologic pH?

Positive.

What is important about histidine's side-chain pKa around 6?

pKa close to physiologic pH

protonation state change around biologically relevant pH values.

Which amino acids are classified as aliphatic, nonpolar/hydrophobic?

Alanine, valine, leucine, isoleucine, proline,

What are the aromatic amino acids?

Phenylalanine, tryptophan, tyrosine.

Which aromatic amino acid is hydrophobic and essentially has a phenyl ring?

Phenylalanine.

Which aromatic amino acid is somewhat hydrophilic because it contains an OH group?

Tyrosine.

Which amino acids are acidic/anionic?

Aspartic acid and glutamic acid.

What is the amide derivative of aspartic acid?

Asparagine.

What is the amide derivative of glutamic acid?

Glutamine.

What are the basic positive/cationic amino acids?

lysine, arginine, histidine.

What is the approximate side-chain pKa of histidine?

6.

What is the approximate side-chain pKa of arginine?

12.5.

Which basic amino acid is commonly acetylated or methylated?

Lysine.

Which amino acids contain sulfur?

Cysteine and methionine.

What is cysteine's -SH group called?

A thiol / sulfhydryl group.

What bond can form between two cysteine residues?

A disulfide bond.

What is the oxidized disulfide-linked form of two cysteines called?

Cystine.

In plasma, cysteine is transported primarily in what form?

Cystine.

Which amino acid acts as the starting amino acid during translation of a new protein?

Methionine.

Which amino acids are common targets for phosphorylation?

Serine, threonine, tyrosine.

Which amino acid is a site for N-linked glycosylation?

Asparagine.

Which amino acids commonly undergo O-linked glycosylation?

Serine and threonine.

What is arginine a precursor for?

Nitric oxide.

What major physiologic effect does nitric oxide produce?

Vasodilation.

Tyrosine is a precursor for which major molecules?

Thyroid hormones, dopamine, norepinephrine, epinephrine.

What two compounds is tryptophan required for synthesis?

Serotonin and melatonin.

What is the major excitatory neurotransmitter?

Glutamate.

Which stereoisomer of amino acids is overwhelmingly used in biological proteins?

L-amino acids.

What D-amino acid is found in bacterial cell walls?

D-alanine.

Why might D-amino acids be incorporated into peptide/protein drugs?

-increase resistance to enzymatic degradation,

-increasing metabolic stability

-potentially extending half-life.

Non-Essential amino acids

Alanine

Asaparagine

Aspartic Acid

Glutamic Acid

Essential Amino Acids

Lysine

Histidine

Methionine

Phenylalanine

Threnonine

Tryptophan

Isoleucine

Leucine

Valine

Very Loudly I Try To Practice My Lesson History

Polar, Uncharged

Serine

Threonine

Asparagine

Glutamine

Tyrosine

So Thirsty Asaparagus Grapes Tangerines

Nonpolar Uncharged Hydrophobic

Valine

Alanine

Leucine

Proline

Isoleucine

Tryptophan

Phenylalanine

Methionine

Cystine

Valine And Leucine Prepare Icecream Try Phinking Mint Chocolate

Basic / Cationic

Lysine

Arginine

Histidine

Little Amazing Hair

Acidic Anionic

Aspartic Acid

Glutamic Acid