Amino Acids Flashcards
Each amino acid has at least two pKas:
- amino group attached to central alpha C
- carboxylic acid group attached to central alpha C
- R group/side chain
R groups are the only…
difference between the 20 amino acids
Amino acids are monomers of…
polypeptide/protein molecules
Protein shape and function are determined by…
sequence in which amino acids are linked together and the interactions with the side chains
Side chains and their position relative to the adjacent/nearby chain from another amino acid determine…
shape and function of protein
Sequence of amino acids are also known as…
primary structure of proteins
Longer side chains leads to the molecule becoming more…
hydrophobic
Examples of uncharged polar side chains:
- Glutamine (Glu)
- Tyrosine (Tyr)
- Cysteine (Cys)
- Serine (Ser)
- Threonine (Thr)
- Asparagine (Asn)
Examples of charged polar side chains:
- Lysine (Lys)
- Arginine (Arg)
- Histidine (His)
- Aspartic acid (Asp)
- Glutamic acid (Glu)
Histidine is often used in…
acid/base enzyme reactions due to pKa close to neutrality
Lysine and Arginine side chains are always…
positive at physiological pH
Aspartic and Glutamic acid are the only amino acids w/…
negative charge at physiological pH
- often termed aspartate and glutamate due to negative charge
Carboxylic acid (COOH) and amine group (NH3+) remains protonated at…
pH at or below their own pKa
Zwitterionic molecules have…
net charge of 0
Isoelectric point (pl) is the point where…
net charge is equal to 0
pl = [pKa1 + pKa2]/2
If pH is above the pKa…
group is deprotonated
If pH is below/equal to the pKa…
group is protonated
Changes in charge on amino acids are important b/c…
- can make amino acid inactive
- disrupt protein structure/function
- alter E levels of protein
- keep reaction from occurring
Fully protonated amino acid would have a _____ pH
low
Fully deprotonated amino acid would have exist at pH…
above pKa of amino group on side chain
T/F: amino acids are optically active
T
Why are amino acids optically active?
- rotate the plane of polarized light
- asymmetric
- result from chiral C
- are enantiomers
Dextrorotatory (D form) amino acids are…
on the right side
Levorotatory (L form) amino acids are…
on the left side
T/F: all amino acids incorporated by organisms in proteins are of the D form
F, they’re of the L form
Modified amino acids are…
amino acids that are modified after incorporation into a protein
5-HTP (5-hydroxytryptophan):
- derivative of amino acids
- used to treat neurological problems associated w/ PKU and depression
- ex: serotonin and melatonin
Serotonin is a:
neurotransmitter that doesn’t cross blood brain barrier
Serotonin is involved in regulation of:
- mood
- sleep
- vomiting
- sexuality
- appetite
Serotonin is associated w/…
- depression
- migraines
- bipolar-disorder
- anxiety
Precursor of serotonin:
Trp and 5HTP
Ecstasy is thought to cause…
a mass release of 5 HT
Levels of serotonin are controlled by…
- MAO inhibitor: stops breakdown of neurotransmitters
- reuptake inhibitors
Melatonin regulates…
circadian cycle
Melatonin can prevent…
hyperphosphorylation of tau
DOPA (L-dihydroxyphenylalanine) is a drug that is used to treat…
Parkinson’s
Examples of DOPA (L-dihydroxyphenylalanine) are…
- epinephrine
- norepinephrine
Epinephrine is involved in…
stress action
Action of epinephrine:
- binds to multiple receptors
- participates in adenylate cyclase pathway that breaks down glycogen
Norepi is involved in…
- ADD/ADHD
- depression
- replenishing catecholamine stores
T/F: tyrosine and cysteine carry a positive charge
F, they don’t carry a charge
What is the side chain of cysteine in its reduced form?
SH
When cysteine participates in a disulfide bonds w/ another cysteine amino acid, the side chain turns into its…
oxidized form (S-S)
Which amino acids are hydrophobic?
- gly
- ala
- val
- leu
- ile
- pro
- phe
- met
- trp
Which amino acids are hydrophilic?
- lys
- arg
- his
- asp
- glu
- ser
- thr
- tyr
- gln
Cysteine has a side chain that…
ionizes
Amino acids that are ionizable:
- arg
- asp
- cys
- glu
- his
- lys
- tyr
Functional group on side chain of lysine:
NH3+
Functional group on side chain of arginine:
guanidino
Functional group on side chain of histidine:
imidazole ring
Functional group on side chain of glutamate:
COOH
Functional group on side chain of aspartate:
COOH
How are disulfide bonds formed?
oxidation between pairs of cysteine side chains
What reduces disulfide bonds?
dithiotheritol (DTT)
What oxidizes disulfide bonds?
cysteine
