Amino Acids Quiz Flashcards
Glycine (Gly)
Side chain: H
Non-polar, hydrophobic, optically inactive
Only achiral amino acid
Alanine (Ala)
Side chain: -CH3
Non-polar, hydrophobic
The simplest optically active AA. All other AAs build off alanine, A like the beginning of the alphabet.
Valine (Val)
Side chain: -CH(CH3)2
Non-polar, hydrophobic, branched chain is a V shape
Leucine (Leu)
Side chain: -CH2[CH(CH3)2]
Non-polar, hydrophobic, branched chain in shape of Y
Isoleucine (Ile)
Side chain: -CH(CH3)(C2H5)
Non-polar, hydrophobic, branched chain
An isomer of leucine
One branch is longer than the other
Proline (Pro)
Side chain: -CH2CH2CH2 (cyclic)
The only cyclic aliphatic
Non-polar, hydrophobic, locked geometry introduces kinks in structures
Cysteine (Cys)
Side chain: -CH2-SH
Cysteine has a sulfhydryl (SH) group
Polar, forms disulfide bonds
Methionine (Met)
Side chain: -(CH2)-S-(CH3)
Non-polar, hydrophobic, sulfur-containing
Start codon for protein synthesis
A methylated sulfur
Phenylalanine (Phe)
Side chain: -CH2(C6H5)
Non-polar, aromatic, hydrophobic
A benzene (or phenyl) ring attached to an alanine
F letter code like its name
Tryptophan (Trp)
Side chain: -indole ring
Non-polar, aromatic, hydrophobic
Largest side chain, two fused rings (double).
Tyrosine (Tyr)
Side chain: -CH2(C6H4OH)
Polar, aromatic, hydrophilic
A hydroxylated (OH) phenylalanine
Serine (Ser)
Side chain: -CH2OH
Polar, hydrophilic
A hydroxylated alanine
Threonine (Thr)
Side chain: -CH(OH)(CH3)
Polar, hydrophilic
Three parts (HAM): hydroxyl, alanine, methyl
Arginine (Arg)
Side chain: -(CH2)3-urea
Basic, hydrophilic, positively charged
Side chain has a urea (NH2-C (NH2+)(NH)) group (A pirates favorite AA, arginine).
Lysine (Lys)
Side chain: -(CH2)4-NH3+
Basic, hydrophilic, positively charged
Histidine (His)
Side chain: -CH2-(C3N2H4)+
Basic, hydrophilic, positively charged at low pH
Has an imidazole, an aromatic ring with two N atoms that can be protonated.
This allows His to act as a buffer that can accept or donate hydrogens when needed. Many active sites employ His to mediate reactions. His can also be used structurally in a salt bridge.
Aspartate (Asp)
Side chain: -CH2COOH
Acidic, hydrophilic, negatively charged
An acidic alanine
Glutamate (Glu)
Side chain: -CH2CH2COOH
Acidic, hydrophilic, negatively charged
A longer version of Aspartate
Asparagine (Asn)
Side chain: -CH2CONH2
Polar, hydrophilic
Amidated Aspartate
Glutamine (Gln)
Side chain: -CH2CH2CONH2
Polar, hydrophilic
All amino acids are composed of…
SAAC:
Side group (R)
Amino group (-NH2)
A-carbon
Carboxyl group (-COOH)
hydrophobic-amino acids are
non-polar
aromatic amino acids
tryptophan
phenylalanine
tyrosine
The neutral amino acids are
Qglutamine
Threonine
Serine
Ytyrosine
Nasparagine
Cysteine tyrosine
The basic amino acids (have basic side chains )are
His Lies Are: basic
histidine, lysine, arginine
Proline and glycine work together to….
Disrupt the secondary structure of proteins
Are known as a-helix breakers
Tyrosine and tryptophan
Eexhibit strong UV-light absorption at 280 nm
Phenylalanine absorbs at a much lower frequency
Proteins and peptides that contain either Tyr or Trp can be quantified by UV-Vis spectroscopy because they absorb light in the UV light spectrum
The acids–aspartate and glutamate–and bases—arginine, lysine and sometimes histidine
Form salt bridges
Interactions are stronger than hydrogen bonds, but weaker than disulfide bonds
Salt bridges are also found in the binding sites of proteins, often holding ligands for transport or substrates for enzymatic reactions.
Tyr and Cys
Behave like alcohols, but unlike Ser and Thr, can be deprotonated easily
PTM: Acetylation
Can occur on the side chain of lysine
The addition of ubiquitin, a protein, is done by acetylation. Ubiquitination is important for ubiquitin-mediated protein degradation, a method for flagging proteins for recycling.
Other types of acetylation are lipidations and prenylations on cysteine and N-terminal glycines.
PTM: Phosphorylation
Adds a -OPO3-2 to serine, threonine, tyrosine, histidine, arginine, or lysine.
This changes the electrostatics of the residue; neutral or basic AAs gain a -2 charge
Cells use phosphorylation as a method of signal transduction to activate or deactivate metabolic pathways.
PTM: Glycosylation
Adds a carbohydrate to an AA. Reported as Asn-X-Ser or Asn-X-Thr, where X is any residue
This sequence means that glycosylation will occur at a serine or threonine that is two residues away from an asparagine
All amino acids but ______ are chiral
glycine
19/20 are L amino acids that synthesize proteins except for
cysteine
The amino acid sequence of a protein is always presented in the __ to __ direction
N-terminus to C-terminus
Why is arginine’s side chain basic?
its positive charge is stabilized by resonance
Why is histidine’s side chain basic?
The N’s have a weak affinity for an H+ and are only partly positive at neutral pH
Acidic side chains
Aspartic acid
Glutamic acid
TSY in QTSYNC
can be phosphorylated (have -OH) group
