Biochemistry- Amino Acids and Proteins Flashcards
Tryptophan is a precursor for what neurotransmitter?
serotonin
The reaction of tryptophan to serotonin requires what vitamin as a cofactor?
B6- pyrodoxine
Tryptophan can also be turned into what molecule?
Niacin
Phenylkeonturia is a genetic inability (lack of phenylalanine hydroxylase) to convert phenylalanine into what aminoacid?
Tyrosine
Tyrosine is the precursor for which 2 neurotransmitters and what is the intermediate substance produced?
Norepi, and Epinephrine
Dopamine intermediate
What is the rate-limiting enzyme for the production of L-DOPA (and therefore catecholamines in general) from tyrosine?
Tyrosine hydroxylase
What inhibits and promotes the activity of tyrosine hydroxylase?
Promotes: cold, stress
Inhibits: Norepi
What vitamin is needed as a cofactor for the production of Norepi from dopamine?
Vitamin C
What is the name of the enzyme that breakdown Norepi and epinephrine?
Monoamineoxidase (MAO)
What is the breakdown product of MAOs action of norepi and epic?
vanillmandelic acid (VMA)
What are the 3 branched chain amino acids?
BCAAs: valine, isoleucine, leucine
Post-translational modification of proline and lycine to form hydroxylycine and hydroxyproline in collagen formation requires what vitamin?
Vitamin C
Which are the only 3 amino acids that can be posttranvslationally modified by phosphorylation?
serine, threonine, tyrosine
Acetylcholine is formed from what amino acid?
Serine
GABA (gamma amino butyric acid) is formed from what amino acid?
Glutamate/ Glutamic acid
The reaction of glutamic acid to GABA requires what vitamin as a cofactor?
B6 (pyrodoxine)
Histamine is formed from what amino acid?
Histadine
Which amino acid is the main methyl donor in the body?
Methionine
What are the 6 amino acids that can be catabolized by skeletal muscle?
Valine Leucine Isoleucine Aspartic acid Asparagine Glutamin Acid
What are the 3 amino acids that make up the tripeptide glutathione?
Cysteine, Glycine and glutamic acid
What are the 2 initial precursors for heme synthesis?
Glycine and succinyl CoA
What amino acid is the main transporter of nitrogen (ammonia) in the blood?
Glutamine
Alanine can be converted into what substance?
Pyruvate
What amino acid is a major component of actin and myosin? What form does it take?
Histadine in the form of 3-methyl histadine
What type of bond holds together the amino sequence of peptides?
covalent
what are the only 2 sulphur containing amino acids?
cysteine, methionine
What 2 bonds hold a secondary protein structure?
disulfide, weak covalent bonds
3D folding is seen is which level of protein structure?
tertiary
2 or more single polypeptide chains bonded by weak bonds is called what?
quaternary structure
Heme molecule is an example of what type of protein structure?
quaternary
2 cysteine resides can form what type of bond
disulfide
a water soluble protein is known as what?
globular, hydrophilic
What kinds of bonds make up secondary structure?
salt bridges, hydrophobic interactions, hydrogen bonds…
Atoms that share 1 or more electrons are bonded by what type of bond?
covalent
What are the 9 essential amino acids?
Threonine, Valine, Tryptophan, Phenylalanine, Isoleucine, Methionine, Histadine, Alanine, Leucine, Lysine
(PVT TIM HALL)
The removal of an alpha amino group from an amino acid is the first stage in amino acid catabolism and is known as what?
Transamination
Catabolism of amino acids uses what 2 types of reaction?
oxidative deamination, transamination
The effect of transamination reactions is to collect the amino groups from all the other amino acids in the form of only on amino acid- which one?
glutamate
Transaminases require what vitamin as a cofactor?
B6 (pyrodoxine)
Alph ketoglutarate in the alphketo acid for what amino acid?
glutamate
Oxaloacetate is the alphaketo acid for what amino acid?
aspartate
Pyruvate is the alphketo acid for what amino acid?
Alanine
Conversion of an amino acid into its alphaketo acid with the release of ammonia is what type of reaction?
oxidative deamination
Where does oxidative deamination occur?
in the liver and kidneys
In what part of the cell does oxidative deamination occur?
mitochondria
What is the main amino acid to undergo oxidative deamination?
glutamate
What is the main enzyme in oxidative deamination?
glutamine dehydrogenase
Which amino acid is present in the blood in the highest levels?
Glutamine- it is the major carrier of amino groups so toxic nitrogen can be carried in a non-toxic form from extra hepatic tissues to the liver
Glutamine synthetase is the enzyme that catalyzes the reaction of glutamate into glutamine. It’s levels are especially high in which tissues? Why?
brain- it’s especially sensitive to ammonia
Which amino acid transfers ammonia from the muscle to the liver?
alanine
Urea is formed from what 2 molecules?
CO2 and ammonia
Where does the urea cycle take place?
liver
How is the urea cycle regulated?
substrate availability ie- dietary protein
Where do the 2 nitrogen atoms in urea come from?
ammonia, aspartate
Which Krebs cycle intermediate is produced by the urea cycle?
fumarate
what are the 4 major constituents of urine?
urea, ammonia, creatinine, uric acid
What is the role of HCl in protein digestion?
denatures the protein and provides optimal pH for pepsinogen conversion to active pepsin
What enzyme has optimum activity at pH2?
pepsinogen/pepsin
What 3 aromatic amino acids have their peptide bonds hydrolyzed by pepsin?
Tyrosine, phenylalanine, tryptophan
Enterokinase is the enzyme that activates which zymogen released by the pancreas?
trypsinogen
Which enzyme activates all other enzymes released by the pancreas?
trypsin
What is the overall fate of proteins that we eat?
form free amino acids and enter the liver via the portal blood system
What is the role of brush border enzymes in protein digestion?
break down smaller peptides to release free amino acids that a readily absorbed
Which bonds need to be broken for a peptide to become denatured?
weak and disulfide bonds (secondary structure)
