Exam 3 Flashcards
1
Q
Protein that is used to tag to identify proteins targeted for destruction
A
Ubiquitin (UB)
2
Q
Primary Proteolytic enzyme of the stomach?
A
pepsin
3
Q
Enzyme transfers alpha-amino group from amino acids to alpha-ketogluterate
A
Amino transferases (transaminases)
4
Q
This enzyme catalyzes an oxidative deamination and can either utilize NAD+ or NADP+
A
Glutamate Dehydrogenase
5
Q
Type of intermediates that forms between PLP and an amino acid
A
Schiff Base linkages
6
Q
Molecule that is form from excess NH4+ by ureotelic organims
A
Terrestrial vertebrates
-urea
7
Q
This product results when aspartate is transaminate with alpha-ketogluterate
A
OAA
8
Q
This methyl group donor is the product of the first step of methionine degradation
A
SAM
9
Q
This class of enzymes cleave most aromatic rings in biological systems
A
Oxidases
-dioxygneases
10
Q
This is the cofactor required by phenylalanine hydroxylase
A
biopterin
11
Q
The C terminal of glycine of Ubiquitin is covalently linked to ____ residues destined to be degraded
A
Lysine R group residues
12
Q
Ubiquitin tagged proteins are digested by the ___
A
Proteasome
13
Q
In the transamination reaction, pyridoxal phosphate is converted into ___ the first amnion acid is converted into a a-ketoacid
A
pyridoxamine phosphate
14
Q
The hydrolysis of arginine by arginase produces ornithine and___
A
Urea
15
Q
Nitrogen is transported from muscle to liver in the form of ___
A
Alanine or Glutamine
16
Q
Vitamin that plays a key role in amino acid degradation is____
A
Vitamine B6 or pyridoxine
17
Q
Serine dehydrates catalyzes the conversion of serine into NH4+ and ___
A
Pyruvate
18
Q
In the degradation of amino acids, the amino nitrogens can eventually become the amino group of
A
Glutamate
19
Q
In the first step of urea cycle, CO2 and NH4+ are converted into
A
Carbamoyl Phosphate
20
Q
The genetic deficiency of the enzyme ___ results in a condition referred to as maple syrup urine disease
A
branched chain A-keto acid dehydrogenase
21
Q
Surplus amino acids are ___
A
Neither Stored or excreted
-used as metabolic FUEL
22
Q
Which of the following is an allosteric activator of mammalian carbamoyl-phosphate synthetase?
- a-ketogluterate
- N-acetylaspartate
- N-acetylglutamate
- glutamine
- none of these
A
N-acetylglutamate
23
Q
The half life of a cytosolic protein is primarily determined by the
- length of protein chain
- amino terminal residue
- seqeucne at the carboxyl terminus
- all of the above
- none of the above
A
Amino terminal residue
24
Q
In the urea cycle, the second nitrogen of urea enters the cycle in the form of which of the following metabolites?
A
Aspartate
- other nitrogen is from NH3+
- C=O is from CO2 or HCO3-
25
The eukaryotic system for ubiquitination appears to have evolved form what prokaryotic precursor?
- a system for protein degradation and turnover
- a system for protein phosphorylation
- a system for coenzyme biosynthesis
- all of the above
- none of the above
a system for coenzyme biosynthesis
26
which amino acids can be directly deaminated to produce NH4+
Serine and Threonine
27
In urea cycle, free NH4+ is coupled with carboxyphoshpate to form
carbamic acid
28
which amino acids are metabolites in the urea cycle, but are not used as building blocks of proteins
Ornithine
| Citrulline
29
In the urea cycle the carbon skeleton of aspartate is preserved as
Fumurate
30
Four of the five enzymes in the urea cycle are evolutionary related to enzymes found in
- glucose transport
- electron transport chain
- nucleotide biosynthesis
- all of the above
- none of the above
Nucleotide biosynthesis
31
Ammoniotelic organisms excrete excess nitrogen as
Ammonium NH4+
32
Uricotelic organisms release nitrogen as
uric acid
33
Ketogenic amino acids are degraded to which of the following metabolites
- acetyl CoA
- acetoacetate
- pyruvate
- all of the above
- B and C
Acetyl CoA
| Acetoacetate
34
Which amino acids supply carbons for eventual entry intro metabolism as succinyl CoA
Met
Valine
Isoleucine
35
What is the function of the acidic enviroment in the stomach
causes dietary proteins to denature and unfold, making them more susceptible to hydrolytic degradation by pepsin
36
Why are four or more chains of ubiquimtin particularly effective as signal for degradation?
when several ubiquitin chains are attached to a target protein, they provide a unique surface for recognition for the proteasome.
-if one chain is lost, the protein is still targeted fro degradation
37
What is the 26S proteosome
Composed of
- a 20S catalytic core composed of a dimer of 14 subunits
- 2 19S subunit cap each end of the barrel-shaped core
Multisubunit core protease requires ATP to digest ubiquiniated proteins
-peptide is denatured then digested to peptide fragemetns
38
What are some types of enzyme catalyzed reactions that require pyridoxal phosphate as a coenzyme
transamination
- decarboxylation
- deamination
- racemizations
- aldol cleavages
- some elimination and replacement rxns
39
Describe the glucose alanine cycle and its significance in amino acid metabolism
During prolonged exercise and fasting muscles use branched chains amino acids as fuel
- this degradation takes place in the muscle, but conversion to urea is not possible in this tissue thus Is transported to liver is required
- The amino nitrogen is removed by transamination to produce glutamate
- glutatmate then transaminases with pyruvate to produce alanine which enters blood and transported to liver
- In liver alanine Is converted to pyruvate and the urea is metabolized to urea
- pyruvate is converted to glucose via gluconeogenesisand glucose is transported back to muscle via bloodstream
40
What type of damage occurs f there is a defect in the urea cycle?
defect in cycle causes hyperammonemia (large amount of NH4+)
- genetic defects become obvious immediately
- after lethargy and vomiting begins, coma and brain damage follow, most likely due to the high levels of glu and gln in the brain
41
the original source of nitrogen found in amino acids?
Atmospheric nitrogen
42
The process of converting N2 to NH3 is called
Nitrogen fixation
43
A common biochemical strategy by which ammonia can be generated for use within the same enzyme
Glutamine hydrolysis
44
a versatile carrier of one carbon unit is
THF-tetrahydrofolate
45
Methylcobalamine is derived from vitamin?
B12
46
An activated form of ribose phosphate?
PRPP
47
Glycine condenses with succinylcholine CoA in the first step of?
Porphyrin
48
a vasodilator derived from histidine?
Histamine
49
__ are made up of amino acid building blocks?
proteins
50
How many ATP molecules are hydrolyzed for each N2 reduced?
At least 16
51
The alpha amino group found in most amino acids comes from __ by a transamination reaction
Glutamate
52
Glutamine synthetase adds NH3+ to
glutamate to produce glutamine
53
Glutamate is the precursor for amino acids glutamine, proline and?
arginine
54
What can THF carry?
Methyl
methylene
formyl units
55
Homocysteine is an intermediate in the synthesis of what 2 amino acids?
cysteine
| methionine
56
What enzyme is regulated by cumulative feedback inhibition?
Glutamine Synthase
57
What enzyme contains a selenium analogue of cysteine?
Glutathionine peroxidase
58
Amino acid synthesis is generally regulated by?
Feedback and allosteric enzyme regulation
59
Organisms capable of carrying out reduction of atmospheric nitrogen include?
some bacteria and archaea
60
The ATP-binding region of nitrogen-fixating reductase is an?
P loop NTPase family
61
The carbon skeletons for amino acids are intermediates found in?
Glycolysis
Citric acid cycle
Pentose phospahte pathway?
62
This amino acid is high levels correlated with the damage of cells lining the blood vessels
homocysteine
63
Essential Amino acids are synthesized by?
plants and microorganisms(bacteria)
64
This amino acid is added to indole to form tryptophan
Serine
65
Chorismate is a precursor to what amino acids?
aromatic amino acids
| Tyr, Phe, Trp
66
How may have feedback inhibition processes evolved?
Linking specific regulator domains to catalytic domains
67
An example of a reaction controlled by enzyme multiplicity is
phosphorylation of aspartate by aspartokinases
68
Tyrosine is a precursor to the molecules:
- melanin
- epinephrine
- serotonin
Melanin
| epinephrine
69
Tryptophan is a precursor for the neurotransmitter?
Serotonin
70
Hyperammonemia
Inherited disease
-elevated levels of ammonium in blood
-
caused by:
- lack/reduced synthesis of carbamyl phosphate
- lack/reduced activity of the four enzymes of urea synthesis
71
How is chirality of the alpha carbon amino acid establish?
a specific transaminase is responsible for the proper stereochemistry
-most of these transaminases have come from common ancestor
72
Describe the process and proteins involved in nitrogen fixation
1) Electrons are provided by ferredoxin and transferred to reductase and then nitrognease
- reaction is driven by thehydrolysis of ATP
73
What is the major difference between the amino acid biosynthetic capacity of prokaryotic organisms and humans?
Microorganisms can make most of the amino acids, humans can't
74
How does herbicide glyphosphate work?
GLyphosphate (round up) acts by inhibiting the enzyme critical to synthesis of the aromatic amino acid intermediate 5-enolpyruvateshikimate 3-P
-intermediate chorismate is critical to the ssynthesis of the essential amino acids
75
What is catalytic substrate channeling?
Channeling increases the catalytic rate
- prevents the loss of an intermediate
- intermediate is passed from active site to active site without releasing the intermediate
Ex: synthesis of tryptophan, indole is channeled to prevent its loss during the reaction
76
which nucleotide is themes common "energy Currency"
ATP
77
assembly of a compound from simpler molecules is known as a ___ pathway
De novo
78
Assembly of a compound from PRPP and a base is known as a ___ pathway
Salvage
79
A purine or pyrimidine linked to a sugar is a ___
nucleoside
80
a purine or pyrimidine linked to a sugar and to a phosphate ester is a?
nucleotide
81
CTP is formed by the amination of?
UTP
82
the intermediate between insinuate and guanylate is?
xanthylate
83
the methyl donor to make TMP is?
N5,N10 Methylene THF
84
High levels of urate cause this disease?
Gout
85
Final product of purine degradation is?
Urate
86
What are the two nucleotides that can serve as energy currency in certain biomolecule paths?
ATP and GTP
87
In ___ biosynthesis, the base is assembled first and then attached to ribose
Pyrimidine
88
Scaffolds for the ring systems in nucleotides are from the amino acids
glycine and aspartate
89
Fluorouracil actas as an analog of?
dUMP
90
Dihydrofolate reductase is an excellent target for anticancer drugs because it is critical in the synthesis of ?
thymidylate
91
The commited step in purine nucleotide biosynthesis is the conversion of?
PRPP to phosphoribosylamine
92
some individuals with a deficiency in the enzyme adenine diaminase exhibit?
SCID
| -severe combined immunodeficiency
93
The source of NH2 groups in synthesis in nucleotides?
- Aspartate
- glutamine
- Glycine
Aspartate and glutamine
94
In de novo synthesis the pyrimidine ring is assemble using
- bicarbonate
- aspartate
- glutamine
ALL 3!
95
They synthesis of CTP from UTP requires?
glutamine and ATP
96
Which enzyme in nucleotide biosynthesis pathways, use a substrate channeling mechanism?
Glutamine Phosphoribosyl Amidotransferaes.
97
The displacing nucleophile in pyrimidine synthesis is typically?
Ammonia or an amino group
98
The ultimate reductant in synthesis of deoxyribonucleotides?
NADPH
99
What amino acid side chain in thymidylate synthase activates the ring of dUMP making C5 a good nucleophile?
cysteine
100
What is/are the competitive inhibitors of dihydrofolate redutase
Amniopterin
| Methotexrate
101
Allopurinol
used to treat gout
| -inhibitor of the enzyme xanthine oxdiase
102
Given the function of nucleotides, would you expect their synthesis to be simple or complex and diverse?
Simple as these molecule were important early in the evolutionary period
- a fw reactions were utilized and small metabolic pathway differences developed accompanied by the need to make different nucleotides
103
Describe the reaction by which carbamoyl phsoate synthetase acquires ammonia to make carbamoyl phoshate
component of the enzyme hydrolyzes glutamine, forming glutamate and ammonia
104
What is the approximate rate change the enzyme orotidylate decarboxylase; decarboxylates orotidylate to form UMP?
the reaction would rarely occur without a catalyst
-approximately once per 78 million years
-
With the enzyme it occurs once per second and the net change is 1x10^17 fold
105
Why do purine salvage pathway save the cell energy?
free purine can be attached to PRPP in a single step to form nucleoside monophosphate
