BIOCHEM AMINO ACID Flashcards
- Which among the following is the 21st amino
acid?
A. Selenagomesteine
B. Selenococysteine
C. Selenocysteine
D. Selenoprotein C
C. Selenocysteine
- Which among the following a.a. is
hydrophobic?
A. Arginine
B. Alanine
C. Asparagine
D. Aspartic acid
B. Alanine
- This is the nucleotide triplet that encodes
the 20 sets of L-α-amino acid?
A. Post-translational modification
B. Codon
C. Genetic code
D. UGA
B. Codon
- The condition is a result of a starchy rich
poor protein diet:
A. Kwashiorkor
B. Scurvy
C. Marasmus
D. Menkes syndrome
A. Kwashiorkor
- This condition is the result of both caloric
and specific amino acid intake is deficient:
A. Kwashiorkor B. Scurvy
C. Menkes Syndrome D. Marasmus
D. Marasmus
- Which of the following amino acid is the
smallest:
A. Alanine B. Aspartic acid
C. Glycine D. Leucine
C. Glycine
- Which of the following enzyme catalyzes
the transfer of the carbamoyl group of
carbamoyl phosphate to ornithine?
A. L-Ornithine transcarbamoylase
B. D-Ornithine transcarbamoylase
C. L-Transcarbamoyl ornithase
D. D-Transcarbamoyl ornithase
A. L-Ornithine transcarbamoylase
- Proline does not participate in
transamination:
A. True B. False
A. True
- The condition is characterized by a urine
sample that smells like burnt sugar:
A. Maple syrup urine disease
B. Burnt sugar urine syndrome
C. Syrup accumulation urine syndrome
D. Metabolic alkalosis
A. Maple syrup urine disease
_____________________ provide monomer units of the long polypeptide chains of proteins
L-α-Amino acids
________________ participate in the biosynthesis of porphyrins, purines, pyrimidines, and urea
L-α-Amino acids
therapeutic value of D-amino
acids
- antibiotics bacitracin and gramicidin A
- antitumor agent bleomycin
more than ______ amino acids occur in nature. Proteins are synthesized almost exclusively from the set of ______________________ encoded by nucleotide triplets called codons
300, 20 L-α-amino acids
All hydrophobic Amino Acids
Alanine
Isoleucine
Leucine
Methionine
Phenylalanine
Proline
Tryptophan
Tyrosine
Valine
*With the sole exception of glycine, the α-carbon of every amino acid is _______
chiral
all AA share the absolute configuration of ____________________ and thus are defined as L-α-amino acids
L- glyceraldehyde
*in mammals, the biochemical reactions of L-α-amino acids are catalyzed by enzymes that act exclusively on ___________
L-isomers
precursor of thyroid hormone
*Tyrosine
metabolized to
epinephrine, norepinephrine, and
dihydroxyphenylalanine (DOPA)
*Tyrosine and phenylalanine
neurotransmitter, precursor of γ-
aminobutyric acid (GABA)
*Glutamate
AA involved in urea biosynthesis
*Ornithine and citrulline
*Free __________ and __________ are found in human brain tissue
D-serine, D-aspartate
__________ and __________ are found in the cell walls of gram- positive bacteria
D-alanine, d-glutamate
an amino acid bears no net
charge
Isoelectric pH (pI)
solubility of amino acids reflects their _____________________
Ionic character
In aqueous solution, charged and uncharged forms of the ionizable weak acid groups ______________ and
__________ exist in dynamic protonic equilibrium:
—COOH, —NH3
both R—COOH and R—NH3 are ________ acids
weak
R—COOH is a far ________ acid than R—NH3
stronger
at ________________ (______), carboxyl groups exist almost entirely as R—COO- and amino groups predominantly as R—NH3
physiologic pH, pH 7.4
smallest amino acid; occurs where peptides bend sharply
glycine
The hydrophobic R groups
alanine, valine, leucine, and
isoleucine
The aromatic R groups
phenylalanine,
tyrosine, and tryptophan
number and order of the amino acid
residues in a polypeptide constitute its _________________________
primary structure
derivatives of the carboxy terminal aminoacyl residue
peptides
Nutritionally Essential Amino Acid
Arginine
Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Proline
Threonine
Tryptophan
Valine
Nutritionally Nonessential
Alanine
Asparagine
Aspartate
Cysteine
Glutamate
Glutamine
Glycine
Hydroxyproline
Hydroxylysine
Proline
Serine
Tyrosine
AA that are tissue aminotransferases and can reversibly interconvert all three amino acids and their corresponding α-keto acids
Valine, Leucine, & Isoleucine
present at the active site of several
human enzymes that catalyze redox
reactions
Selenocysteine
Impairments in human ___________
have been implicated in tumorigenesis and atherosclerosis
selenoproteins
The _________________ occupies a central position in protein and amino acid metabolism.
amino acid pool
→Each amino acid is ________________ via its own unique pathway, but the general scheme is the same for each
one.
degraded
General scheme for amino acid catabolism
→Removal of the amino group
→Use of nitrogen in synthesis of new nitrogen compounds
→Passage of nitrogen into the urea cycle
→Incorporation of the carbon atoms into compounds that
can enter the citric acid cycle
→Our bodies do not store __________________ compounds and
_______________ is toxic to cells.
nitrogen-containing, ammonia
→Amino nitrogen must either be incorporated into _____ and excreted,
or used in the synthesis of new ________________ compounds
urea, nitrogen-containing
→The ___________ atoms of amino acids are converted to compounds that can enter the citric acid cycle.
carbon
carbon atoms continue through the citric acid cycle to give ____ and _______ stored in ATP. About _________ of our energy is produced in this way.
CO2, energy, 10–20%
→If not needed immediately for energy, the carbon- carrying intermediates enter storage as ___________, _______, or _____________.
triacylglycerols, glycogen, ketone bodies
→In ____________________, the amino group of the amino
acid and the keto group of an α-keto acid
change.
transamination
→A number of ___________ enzymes are responsible for “transporting” an amino group from one molecule to another.
→Most are specific for ______________ as the amino group acceptor and work with several amino acids.
→The α-ketoglutarate is converted to ___________, and the amino acid is converted to an ______________________.
transaminase, α-ketoglutarate, glutamate, α-keto acid
is a key reaction in many
biochemical pathways.
→Transamination
→Transamination reactions are _____________ and go easily in
either direction, depending on the
concentrations of the reactants.
reversible
Conversion of an amino acid —NH2 group to an α-keto group, with removal of NH4
+.
→Oxidative deamination:
_____________________ is highly toxic to living things and must be eliminated in a way that does no harm.
→Ammonia
_______________ are able to excrete ammonia through their
gills directly into their watery surroundings.
→Fish
→Mammals must find other ways to get rid of ammonia, and must first convert ammonia, in solution as ammonium ion, to nontoxic urea via
the _______________
urea cycle.
→The conversion of ammonium ion to urea takes place in the _______________
liver.
→From the Liver, urea is transported to the ___________ and transferred to _______ for excretion.
kidneys, urine
→Ammonium ion, bicarbonate ion, and ATP combine to form ___________________ in the
mitochondrial matrix.
carbamoyl phosphate
The Urea Cycle
→The first step of the urea cycle transfers the carbamoyl group, H2NC=O, from carbamoyl phosphate to ___________, an amino acid not found in proteins, to give ___________, another nonprotein amino acid.
ornithine, citrulline
The Urea Cycle
→Both nitrogen atoms destined for elimination as urea are now bonded to the same carbon atom in ____________
argininosuccinate.
The Urea Cycle
→Step 3 cleaves argininosuccinate into two pieces: _________, an amino acid, and ______________, which is an
intermediate in the citric acid cycle.
→In Step 4 the hydrolysis of _________ takes place to give urea and regenerate the reactant in Step 1 of the cycle,
____________
arginine, fumarate, arginine, ornithine.
→Amino acids that are converted to acetoacetyl- CoA or acetyl-CoA enter the ________________ pathway, and are called __________________________
ketogenesis, ketogenic amino acids.
→Those amino acids that proceed by way of oxaloacetate to the _____________________ pathway
are known as ______________________
gluconeogenesis, glucogenic amino acids.
amino acids Post-translation allows them to perform _________________
specific functions
Carrier of ammonia and of the carbons of pyruvate from skeletal
muscle to liver via the Cori Cycle
Alanine
Constitutes a major fraction of free amino acids in plasma (together
with glycine)
Alanine
Carrier of nitrogen atoms in urea biosynthesis
Guanidino group is incorporated into creatinine
Arginine
Following conversion to ornithine, the carbon skeleton serves as a
precursor of the polyamines putrescine and spermine
Arginine
biosynthesis of coenzyme A 🡪
reacting with pantothenate to form
4-phosphopantothenoylcysteine
CYSTEINE
incorporated into creatine
GLYCINE
entire glycine molecule becomes atoms
4, 5, and 7 of the __________
purines
biogenic amine; functions in allergic
reactions and gastric secretion
histamine
Catalyzed by histidine decarboxylase
HISTIDINE
principal source of methyl
groups in the body
S-adenosylmethionine
catalyzed by methionine
adenosyltransferase (MAT)
METHIONINE
precursor of peptidyl selenocysteine
SERINE
genetic defects in cystathionine β-
synthase (PLP dependent)
homocystinuria
potent vasoconstrictor and
stimulator of smooth muscle
contraction
serotonin
■ regulate the activity of
certain enzymes of lipid
and carbohydrate
metabolism and proteins
■ signal transduction
cascades
Phosphoserine, Phosphothreonine,
and Phosphotyrosine
■ occur in mitochondria
■ catalyzed by dimethyl
glycine dehydrogenase
■ may also arise from
methylation of glycine
(GNMT)
■ important sources of one-
carbon units
SARCOSINE
inhibitory neurotransmitter
γ-Aminobutyrate
