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MC Biochem 2 > Exam 3 > Flashcards

Exam 3 Flashcards

1
Q

Protein that is used to tag to identify proteins targeted for destruction

A

Ubiquitin (UB)

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2
Q

Primary Proteolytic enzyme of the stomach?

A

pepsin

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3
Q

Enzyme transfers alpha-amino group from amino acids to alpha-ketogluterate

A

Amino transferases (transaminases)

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4
Q

This enzyme catalyzes an oxidative deamination and can either utilize NAD+ or NADP+

A

Glutamate Dehydrogenase

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5
Q

Type of intermediates that forms between PLP and an amino acid

A

Schiff Base linkages

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6
Q

Molecule that is form from excess NH4+ by ureotelic organims

A

Terrestrial vertebrates

-urea

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7
Q

This product results when aspartate is transaminate with alpha-ketogluterate

A

OAA

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8
Q

This methyl group donor is the product of the first step of methionine degradation

A

SAM

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9
Q

This class of enzymes cleave most aromatic rings in biological systems

A

Oxidases

-dioxygneases

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10
Q

This is the cofactor required by phenylalanine hydroxylase

A

biopterin

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11
Q

The C terminal of glycine of Ubiquitin is covalently linked to ____ residues destined to be degraded

A

Lysine R group residues

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12
Q

Ubiquitin tagged proteins are digested by the ___

A

Proteasome

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13
Q

In the transamination reaction, pyridoxal phosphate is converted into ___ the first amnion acid is converted into a a-ketoacid

A

pyridoxamine phosphate

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14
Q

The hydrolysis of arginine by arginase produces ornithine and___

A

Urea

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15
Q

Nitrogen is transported from muscle to liver in the form of ___

A

Alanine or Glutamine

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16
Q

Vitamin that plays a key role in amino acid degradation is____

A

Vitamine B6 or pyridoxine

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17
Q

Serine dehydrates catalyzes the conversion of serine into NH4+ and ___

A

Pyruvate

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18
Q

In the degradation of amino acids, the amino nitrogens can eventually become the amino group of

A

Glutamate

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19
Q

In the first step of urea cycle, CO2 and NH4+ are converted into

A

Carbamoyl Phosphate

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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

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21
Q

Surplus amino acids are ___

A

Neither Stored or excreted

-used as metabolic FUEL

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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

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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

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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-
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25
Q

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

a system for coenzyme biosynthesis

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26
Q

which amino acids can be directly deaminated to produce NH4+

A

Serine and Threonine

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27
Q

In urea cycle, free NH4+ is coupled with carboxyphoshpate to form

A

carbamic acid

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28
Q

which amino acids are metabolites in the urea cycle, but are not used as building blocks of proteins

A

Ornithine

Citrulline

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29
Q

In the urea cycle the carbon skeleton of aspartate is preserved as

A

Fumurate

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30
Q

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
A

Nucleotide biosynthesis

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31
Q

Ammoniotelic organisms excrete excess nitrogen as

A

Ammonium NH4+

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32
Q

Uricotelic organisms release nitrogen as

A

uric acid

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33
Q

Ketogenic amino acids are degraded to which of the following metabolites

  • acetyl CoA
  • acetoacetate
  • pyruvate
  • all of the above
  • B and C
A

Acetyl CoA

Acetoacetate

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34
Q

Which amino acids supply carbons for eventual entry intro metabolism as succinyl CoA

A

Met
Valine
Isoleucine

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35
Q

What is the function of the acidic enviroment in the stomach

A

causes dietary proteins to denature and unfold, making them more susceptible to hydrolytic degradation by pepsin

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36
Q

Why are four or more chains of ubiquimtin particularly effective as signal for degradation?

A

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

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37
Q

What is the 26S proteosome

A

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

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38
Q

What are some types of enzyme catalyzed reactions that require pyridoxal phosphate as a coenzyme

A

transamination

  • decarboxylation
  • deamination
  • racemizations
  • aldol cleavages
  • some elimination and replacement rxns
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39
Q

Describe the glucose alanine cycle and its significance in amino acid metabolism

A

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
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40
Q

What type of damage occurs f there is a defect in the urea cycle?

A

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
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41
Q

the original source of nitrogen found in amino acids?

A

Atmospheric nitrogen

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42
Q

The process of converting N2 to NH3 is called

A

Nitrogen fixation

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43
Q

A common biochemical strategy by which ammonia can be generated for use within the same enzyme

A

Glutamine hydrolysis

44
Q

a versatile carrier of one carbon unit is

A

THF-tetrahydrofolate

45
Q

Methylcobalamine is derived from vitamin?

A

B12

46
Q

An activated form of ribose phosphate?

A

PRPP

47
Q

Glycine condenses with succinylcholine CoA in the first step of?

A

Porphyrin

48
Q

a vasodilator derived from histidine?

A

Histamine

49
Q

__ are made up of amino acid building blocks?

A

proteins

50
Q

How many ATP molecules are hydrolyzed for each N2 reduced?

A

At least 16

51
Q

The alpha amino group found in most amino acids comes from __ by a transamination reaction

A

Glutamate

52
Q

Glutamine synthetase adds NH3+ to

A

glutamate to produce glutamine

53
Q

Glutamate is the precursor for amino acids glutamine, proline and?

A

arginine

54
Q

What can THF carry?

A

Methyl
methylene
formyl units

55
Q

Homocysteine is an intermediate in the synthesis of what 2 amino acids?

A

cysteine

methionine

56
Q

What enzyme is regulated by cumulative feedback inhibition?

A

Glutamine Synthase

57
Q

What enzyme contains a selenium analogue of cysteine?

A

Glutathionine peroxidase

58
Q

Amino acid synthesis is generally regulated by?

A

Feedback and allosteric enzyme regulation

59
Q

Organisms capable of carrying out reduction of atmospheric nitrogen include?

A

some bacteria and archaea

60
Q

The ATP-binding region of nitrogen-fixating reductase is an?

A

P loop NTPase family

61
Q

The carbon skeletons for amino acids are intermediates found in?

A

Glycolysis
Citric acid cycle
Pentose phospahte pathway?

62
Q

This amino acid is high levels correlated with the damage of cells lining the blood vessels

A

homocysteine

63
Q

Essential Amino acids are synthesized by?

A

plants and microorganisms(bacteria)

64
Q

This amino acid is added to indole to form tryptophan

A

Serine

65
Q

Chorismate is a precursor to what amino acids?

A

aromatic amino acids

Tyr, Phe, Trp

66
Q

How may have feedback inhibition processes evolved?

A

Linking specific regulator domains to catalytic domains

67
Q

An example of a reaction controlled by enzyme multiplicity is

A

phosphorylation of aspartate by aspartokinases

68
Q

Tyrosine is a precursor to the molecules:

  • melanin
  • epinephrine
  • serotonin
A

Melanin

epinephrine

69
Q

Tryptophan is a precursor for the neurotransmitter?

A

Serotonin

70
Q

Hyperammonemia

A

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
Q

How is chirality of the alpha carbon amino acid establish?

A

a specific transaminase is responsible for the proper stereochemistry
-most of these transaminases have come from common ancestor

72
Q

Describe the process and proteins involved in nitrogen fixation

A

1) Electrons are provided by ferredoxin and transferred to reductase and then nitrognease
- reaction is driven by thehydrolysis of ATP

73
Q

What is the major difference between the amino acid biosynthetic capacity of prokaryotic organisms and humans?

A

Microorganisms can make most of the amino acids, humans can’t

74
Q

How does herbicide glyphosphate work?

A

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
Q

What is catalytic substrate channeling?

A

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
Q

which nucleotide is themes common “energy Currency”

A

ATP

77
Q

assembly of a compound from simpler molecules is known as a ___ pathway

A

De novo

78
Q

Assembly of a compound from PRPP and a base is known as a ___ pathway

A

Salvage

79
Q

A purine or pyrimidine linked to a sugar is a ___

A

nucleoside

80
Q

a purine or pyrimidine linked to a sugar and to a phosphate ester is a?

A

nucleotide

81
Q

CTP is formed by the amination of?

A

UTP

82
Q

the intermediate between insinuate and guanylate is?

A

xanthylate

83
Q

the methyl donor to make TMP is?

A

N5,N10 Methylene THF

84
Q

High levels of urate cause this disease?

A

Gout

85
Q

Final product of purine degradation is?

A

Urate

86
Q

What are the two nucleotides that can serve as energy currency in certain biomolecule paths?

A

ATP and GTP

87
Q

In ___ biosynthesis, the base is assembled first and then attached to ribose

A

Pyrimidine

88
Q

Scaffolds for the ring systems in nucleotides are from the amino acids

A

glycine and aspartate

89
Q

Fluorouracil actas as an analog of?

A

dUMP

90
Q

Dihydrofolate reductase is an excellent target for anticancer drugs because it is critical in the synthesis of ?

A

thymidylate

91
Q

The commited step in purine nucleotide biosynthesis is the conversion of?

A

PRPP to phosphoribosylamine

92
Q

some individuals with a deficiency in the enzyme adenine diaminase exhibit?

A

SCID

-severe combined immunodeficiency

93
Q

The source of NH2 groups in synthesis in nucleotides?

  • Aspartate
  • glutamine
  • Glycine
A

Aspartate and glutamine

94
Q

In de novo synthesis the pyrimidine ring is assemble using

  • bicarbonate
  • aspartate
  • glutamine
A

ALL 3!

95
Q

They synthesis of CTP from UTP requires?

A

glutamine and ATP

96
Q

Which enzyme in nucleotide biosynthesis pathways, use a substrate channeling mechanism?

A

Glutamine Phosphoribosyl Amidotransferaes.

97
Q

The displacing nucleophile in pyrimidine synthesis is typically?

A

Ammonia or an amino group

98
Q

The ultimate reductant in synthesis of deoxyribonucleotides?

A

NADPH

99
Q

What amino acid side chain in thymidylate synthase activates the ring of dUMP making C5 a good nucleophile?

A

cysteine

100
Q

What is/are the competitive inhibitors of dihydrofolate redutase

A

Amniopterin

Methotexrate

101
Q

Allopurinol

A

used to treat gout

-inhibitor of the enzyme xanthine oxdiase

102
Q

Given the function of nucleotides, would you expect their synthesis to be simple or complex and diverse?

A

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
Q

Describe the reaction by which carbamoyl phsoate synthetase acquires ammonia to make carbamoyl phoshate

A

component of the enzyme hydrolyzes glutamine, forming glutamate and ammonia

104
Q

What is the approximate rate change the enzyme orotidylate decarboxylase; decarboxylates orotidylate to form UMP?

A

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
Q

Why do purine salvage pathway save the cell energy?

A

free purine can be attached to PRPP in a single step to form nucleoside monophosphate

MC Biochem 2 (31 decks)

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