Biochem 2 Exam 2
Nutritionally non essential amino acids
-Alanine -asparagine -aspartic acid -cysteine -glutamic acid -glycine -hydroxyproline -proline -serine -tyrosine (Arginine)
Amino acids (can/cannot) be stored within tissues
?
Which of the following statements is true of eicosanoids? A) eicosanoids elicit their actions by bonding to their specific membrane receptor B) eicosanoids elicit their actions by binding to the specific nuclear receptors C) eicosanoids are derided from 20 carbon polyunsaturated fatty acids
A and C
Transamination reaction
A-amino group of an L-a-amino acid is transferred to the a-keto group of an a-keto acid
Amino acid+_______ -> a-ketoA + Glutamate
A-ketoglutarate
How bicarbonate used to form carbamoyl phosphate is activated in urea cycle reaction
ATP phosphorylates bicarbonate
In the urea cycle, the second nitrogen of urea enters the cycle in the form of which of the following metabolite?
Aspartate
Which compound contributes for the second nitrogen atom of urea
Aspartate
Which amino acids are dervided from oxaloacetate?
Aspartate-> methionine, lysine, threonine (Threonine->isoleucine)
Precursors for the biosynthesis of pyramiding ring system include: A) glycine and succinyl-CoA B) inosine and Aspartate C) Glutamate, NH3, and CO2 D) carbamoyl phosphate and Aspartate E)Glycine, glutamine, CO2, and Aspartate
Carbamoyl phosphate
Which compound is formed in the first reaction of urea cycle that captures the toxic ammonium ion
Carbamoyl phosphate
What is the rate limiting enzyme in urea biosynthesis
Carbamoyl phosphate synthetase I
What is the rate-limiting step of urea biosynthesis
Carbamoyl phosphate synthetase I?
Enzymatic cleavage of which membrane components releases arachidonic acid for eicosanoid biosynthesis
Carbon 2 of glycerol backbone
Enzyme and cofactor for transamination reaction
Enzyme: transaminase or aminotransferase Cofactor: pyridoxal phosphate
T/F Eicosanoids are composed of 20 carbon atoms containing four double bonds
False
Which of the following compounds can activate phospholipids A2 in order to release the precursor molecule for eicosanoid biosynthesis
Histamine
Activators of phospholipids
Histamines and ctokines
Which amino acid is derived from ribose-5-phosphate
Histidine
Which other amino acids are also deamination directly to produce ammonium ion
Histidine, serine, threonine, glutamine, asparagine
A defect in which enzyme can produce alcaptonuria
Homogentisate oxidase (AKA homogentisate 1,2 dioxygenase)
Which compound is accumulated in alcaptonuria
Homogentisate oxidation
Glutamate is___________to cellular membrane
Impermeable
The human genetic disease PKU can result from:
Inability to convert phenylalanine to tyrosine
What would happen to the activity of prostaglandin molecule if 15 hydroxyl group is oxidized to a ketone
Inactivate it
What would happen to the activity of prostaglandin molecule if the non ring portions of the dicarboxylic acids are oxidized at the beta carbon or w-position
Inactivate it
What would happen to the activity of prostaglandin molecules if the double bond at carbon 13 is reduced
Inactivate it
What are the general functions of leukotrienes
Induces contraction of the muscle lining the airways to the lungs
What is the effect of aspirin on prostaglandin biosynthesis
Irreversibly inactivates cyclooxygenase by transferring an Acetyl group to the serine hydroxyl group of the active cyclooxygenase enzyme
Main purpose of transamination reaction
Is to collect the amino groups from many different amino acids in the form of L glutamate
What is the metabolic significance of the action of dihydrofolate reductase enzyme catalyzed reaction?
It is blocking the regeneration of THF
What is the metabolic benefit of methionine synthase catalyzed conversion of homocysteine to methionine
It regenerates methylcobalamin and maintains a store of tetrahydrofolate
protein deficiency disease
Kwashiorkor
Which one of the following compounds is nutritionally essential dietary source of arachidonates in humans
Linoleate
At which cellular location is glutamate produced from oxidative deamination of amino acids
Liver?
Which transamination amino acids do not participate in alpha amino group transfer
Lysine, threonine, proline, hydroxyproline
Both a protein deficiency and calorie deficiency disease
Marasmus
Which enzymes catalyze the release of arachidonic acid from membrane phospholipids
Membrane bound phospholipids A2 or phospholipids C
Defective degradation of which of the following amino acids causes hyperhomocysteinemia
Methionine
Enzyme that is responsible for the transfer with B12 (homocysteine to methionine)
Methionine synthase
Which of the following functional groups is transferred by S- adenosylmethionine (SAM) to produce epinephrine from norepinephrine
Methyl group (-CH3)
Which enzyme is required for the rearrangement of methyl group present in L-methylmalonyl-CoA to produce succinyl-CoA
Methyl malonyl CoA mutase
Which cellular location does glutamate dehydrogenase catalyze its specific reaction
Mitochondria
Which of the following enzymes is the rate limiting enzyme in urea biosynthesis
Mitochondrial carbamoyl phosphate synthetase I
At which cellular site the rate limiting enzyme of the urea cycle is localized
Mitochondrial matrix
Which nitrogen atoms of the tetrahydrofolate (THF) is bound to the one-carbon unit for its transfer to another molecule? Choose the correct pair.
N5 and/or N10
Pentose phosphate pathway important products
NADPH and ribose 5 phosphate
Which compound contributes for the first nitrogen atom of urea
NH4+
Dietary tryptophan deficiency could be one of the causes of
Niacin deficiency
Amino acid catabolism involves the breakdown of 20 amino acids all of which contain nitrogen but have different carbon skeletons. What overall strategy is used to deal with this problem
Nitrogen is removed by transamination to glutamate.
Tetrahydrofolate and its derivatives shuttle_____ between different substrates
One carbon units
Transaminases are specific for:
Only one pair of alpha amino and alpha keto acids
Which amino acid(s) is/are metabolites in the urea cycle, but is not used as a building blocks of protein
Ornithine and citrulline
Amino acid+_______ -> a-ketoA + Aspartate
Oxaloacetate
Which of the following compounds is produced in excessive quantities during defective glycine metabolism
Oxaloacetate
NADH and NADPH participate in which of the following type of reactions
Oxidation reduction reaction
Glutamate is metabolically converted to a-ketoglutarate and NH4+ by a process describes as:
Oxidative deamination
Which reaction is catalyzed by glutamate dehydrogenase enzyme
Oxidative deamination
A defect in what type of biochemical reaction is involved in the production of maple syrup urine disease
Oxidative?
Which is most oxidized? Which is the most reduced? A) Methyl B) methylene C) formyl
Oxidized-Formyl Reduced-methyl
Which prostaglandin isoform is used to biosynthesize thromboxanes
PGH2, causes vasoconstriction
2 major sources of NADPH
PPP and malic enzyme enzyme
The mechanism of action of eicosanoids mediated through their receptor activation
Paracrine and autocrine mechanisms
A defect in degradation of which amino acid can cause alcaptonuria?
Phenyalanine and tryosine
A defective degradation of which amino acid can cause phenylketonuria
Phenylalanine
Which amino acid is the precursor of tyrosine?
Phenylalanine
Which amino acids are derived from phosphoenolpyruvate and erythrose-4-phosphate
Phenylalanine, Tyrosine, & Tryptophan They produce the Aromatic Amino Acids
Which compounds are accumulated in blood during phenylketonuria (PKU)
Phenylketones (phenylalanine and phenylpyruvate)
Phospholipids that are used in / as a precursor for a precursor
Phosphatidyl-choline and phostidyl biphosphate
What two intermediates from carbohydrate metabolism are used to synthesize aromatic aa?
Phosphenolpyruvate (glycolysis) and erythrose 4 phosphate (PPP)
What are the activators of eiscosanoid biosynthesis
Phosphoglycerates?
Structure of arachidonic acid
Polyunsaturated (4 double bonds)
Paracrine actions
Synthesized and secreted from one kind of cells and act on other types of cells
Which compound is responsible for 1 carbon group transfer
THF, B12, SAM except for CO2(carried by biotin)
An amino acid that does NOT derive its carbon skeleton, at least in part, from a-ketoglutarate is:
Threonine
Which of the following amino acids are essential for humans
Threonine
Which enzymatic pathway is involved in the biosynthesis of thromboxanes
Thromboxane synthase
Vitamin B6 can participate in which of the following category of reactions
Transamination
What type of biochemical reaction oxidatively degrades amino acids to produce ammonium ion
Transamination
Which protein present within the intestinal epithelial cells delivers vitamin B12 into the blood circulation
Transcobalmin II
What are the 2 reactions B12 take part in
Transfer and rearrangement of methyl group
A defect in degradation of which amino acids can lead to Maple Syrup Urine disease?
Valine, leucine, and isoleucine (branch chain amino acids)
Which of the following compounds is needed for the rearrangement of the methyl group of L-methylmalonyl—CoA to form succinyl-CoA
Vitamin B12
Which of the following is required for the rearrangement of methyl group present in L-methylmalonyl-CoA to produce succinyl-CoA
Vitamin B12
Ketogenic amino acids are degraded to which of the following metabolites
acetyl CoA and acetoacetate
Autocrine actions
act on similar kind of cells or on the same cell from which these are synthesized & secreted
Which enzyme is involved for the conversion of glutamate to alanine
alanine aminotransferase
What happens when eicosanoids bind to their selective receptors A) adenylate cyclase activities are regulated B) G protein pathways are regulated C) Protein kinase pathways are regulated D) Calcium dependent pathways are regulated E) all of the above
all of the above
Eicosanoids are derived from the following precursor
arachidonic acid
Which fatty acid is the precursor of eicosanoids
arachidonic acid
which of the following amino acids is/are glucogenic?
asparagine, methionine, and valine
In the urea cycle, free NH4+ is coupled with carboxyphosphate to form:
carbamic acid
At which cellular site do these activators of eicosanoids bind and trigger their biosynthesis
cell membrane
What is one of the functions of prostacyclin
dilation of a blood vessel
In the urea cycle, ornithine transcarbamoylase catalyzes
formation of citrulline from ornithine and another reactant.
The human genetic disease phenylketonuria (PKU) can result from
inability to convert phenylalanine to tyrosine
The human genetic disease phenylketonuria (PKU) can result from:
inability to convert phenylalanine to tyrosine
Active forms of B12
methylcobalamin and 5-deoxyadenosylcobalamin
What is a transamination reaction?
movement of an amino group from one amino acid to the alpha keto acid (or amino acid carbon skeleton). The group that gains the amino group becomes an amino acid. The amino acid that loses the amino group becomes the carbon skeleton.
Which eicosanoid inhibits platelet aggregation
prostacyclin I2 (PGI2) also causes vasodilation
The coenzyme required for all transamination is derived from
pyridoxine (vitamin B6)
Which compound is required to produce alanine from glutamate in the glucose alanine cycle
pyruvate
What carb metabolite is used to synthesize histidine
ribose 5 phosphate
dUMP --> dTMP enzyme
thymidylate synthase (cancer can use this to synthesize)
In amino acid catabolism, the first reaction for many amino acids is a(n):
transamination requiring pyridoxal phosphate (PLP)
Surplus amino acids are:
used as metabolic fuel
If a persons urine contains unusually high concentrations of urea, which on of the following diets has he or she probably been eating recently
very low carbohydrate, very high protein
Nutritionally essential amino acids
-Histidine -isoleucine -leucine -lysine -methionine -phenylalanine -threonine -tryptophan -valine (Arginine- produced in body but gets degraded to produce urea)
Which reactions can inactivate prostaglandins and thromboxanes
-Oxidation of 15 OH group to ketone -double bond at C 13 is reduced -B-and w- oxidation of the non ring portions to do Carboxylase acids
What are eicosanoids and their general functions
-biosynthesize eicosanoid (20 C atoms) fatty acids -they form several isoforms of prostaglandins, thromboxanes, leokotrienes and lipoxins
What are the general functions of lipoxins
-induce chemotaxis -stimulate superoxide anion formation in leukocytes -activates adenylate cyclase cAMP protein kinase A systems -Binding of eicosanoids to simulators G protein subunit will amplify the stimulus through activation of adenylate cyclase -binding of eicosanoid to the inhibitory G protein subunit will decrease th effect by decreasing the activity of the adenylate cyclase which in turn will decrease cAMP synthesis
Mechanism by which glucocorticoids can suppress inflammatory responses
-inhibit or limit recruitment of leukocytes and monocytes/macrophages into inflamed area -inhibit or limit secretion of chemotactic factors or eicosanoids by these cells -suppress the transcription/translation of induce blue cyclo-oxygenate 2 enzyme (COX2) -inhibit or limit phospholipids A2 enzymes by inducing the synthesis of lipoproteins that block PLA2 activities
What are the general functions of prostaglandins
-regulate synthesis of cAMP -stimulate contraction of smooth muscle of the uterus during menstruation and labor -affect blood flow to specific organs -wake sleep cycle -affects responsiveness of certain fissure hormones such as epinephrine and glucagon -a third group prostaglandin elevates body temperature producing fever and cause inflammation and pain
What are the four major steps that remove the nitrogen of the amino acids to produce urea?
1.transamination 2.oxidative deamination 3.transportation of ammonia 4. reactions catalyzed by the enzymes of the urea cycle
Which enzymatic pathways are involved in the biosynthesis of lipoxins
15-lipoxygenase (15-LO) followed by 5-lipoxygenase (5-LO)
How many molecules of ATPs are required to produce carbamoyl phosphate in the first priming reaction of urea cycle
2 ATP
Which intermediate is produced when ATP and bicarbonate react before ammonium ion is captured in the first reaction of urea cycle
Carbamate?
Which conditions influence oxidative degradation of amino acids
Accumulation of amino acids?
What is the effect of non steroidal anti inflammatory drugs on prostaglandin biosynthesis
Acetaminophen and ibuprofen inhibit COX activity by competing for the substrate binding of COX where arachidonic acid binds as the substrate of COX normally
What are the general functions of thromboxanes
Act in formation of blood clots and reduction of blood flow to the site of the clot
Which two amino acids are the carriers of amino acid nitrogen from the muscle and other tissues to the liver?
Alanine and Glutamine
Which amino acids are derived from Pyruvate?
Alanine, Valine, Leucine, & Isoleucine (The Branch Chain Amino Acids)
_____, _____, and ______ are formed by one step transamination reactions
Alanine, asparagine, and glutamate
What is true about eicosanoids
All eicosanoids are derived for a 20 carbon polyunsaturated fatty acid
What happens when eicosanoids bind to their selective receptors? A) adenylate cyclase activities are regulated B) G protein pathways are regulated C) Protein kinase pathways are regulated D)Calcium dependent pathways are regulated E) all of the above
All of the above
What type of reaction is catalyzed by branch chain alpha keto acid dehydrogenase
Alpha keto acids are further oxidative Lee decarboxylate used to form corresponding acyl CoA derivatives
glucogenic amino acids
Amino acids such as alanine and glutamate that can be converted to glucose.
During amino acid metabolism glutamate releases its ____ group as ____ in the _____
Amino, ammonia, liver
Whcih enzyme catalyzes transamination reaction
Aminotransferase
Which of the following compounds generated from the oxidative metabolism of the amino acid nitrogen is the most toxic form and which one is the least toxic form? A) Ammonium ion B) urea
Ammonium ion is less toxic than urea
NADPH is the active form of which vitamin
B3- Niacin
A defect in which enzyme can cause maple syrup urine disease
Branch chain alpha keto acid dehydrogenase
Which enzymatic pathway is involved in the biosynthesis of prostaglandins
Cyclo-oxygenase pathway AKA prostaglandin peroxide synthase or prostaglandin H2 synthase
Which enzyme is blocked by aspirin
Cyclooxygenase
A defect in which enzyme is involved in the development of homocysteinema
Cystathione B synthase
Which enzymatic pathway is involved in the biosynthesis of epoxides
Cytochrome P-450 epoxygenase pathway
What is the major precursor of arachidonate
Dietary linoleic acid
What are common sources or precursors for non essential amino acid biosynthesis in human body?
Digestion of endogenous proteins and peptides (~70 g/day) Dietary proteins after digestion and absorption of the resulting amino acids (~100 g/day) Intracellular protein turnover or degradation (~230 g/day)
Biochemical activity of thiamin pyrophosphate can be prevented via the activation of
Dihydrofolate reductase
Enzyme for Folate to THF
Dihydrofolate reductase
What are the chemical characteristics of prostaglandins
Five carbon ring originating from the chain of arachidonic acid and produced by almost all mammalian cells EXCEPT red blood cells
What is the source of a THF
Folate
Deficiency of which vitamin interrupts DNA methylation?
Folic acid
Which enzyme oxidatively deaminates glutamate to produce ammonium ion and alpha ketoglutarate
Glutamate dehydrogenase
Why is it necessary to convert glutamate to alanine and glutamine
Glutamate is impermeable to the cell membrane
Which amino acids are dervided from a-ketoglutarate?
Glutamate-> glutamine, proline, and arginine
Glutamine synthetase converts ____ to ___, whereas glutamte synthase converts ___ to ____
Glutamate; glutamine ; a-ketoglutarate; glutamate
Which amino acid is the final carrier of nitrogen from all amino acids oxidatively metabolized in the liver before it is the biochemically processed to generate urea
Glutamate?
Which enzyme is required to generate glutamate from glutamine in liver tissue
Glutaminase (liver mitochondria)
Which enzyme is required to convert glutamate to glutamine
Glutamine synthetase?
Which enzyme is required to synthesize glutamine from glutamate
Glutamine synthetase?
Backbone of eicosanoids
Glycerol
Which enzyme is involved in the defective metabolism of glycine that leads to primary oxaluria type I
Glycine transaminase (also B6 deficiency)
What are the major sources of vitamin B12
Gut bacteria and meat
Classify eicosnaoids
Prostaglandins, thrombocytes, leukotrienes, lipoxins
What is the cofactor for transamination reaction
Pyridoxal phosphate (vitamin B6)
Amino acid+_______ <-> a-ketoA + Alanine
Pyruvate
Serine or cysteine many enter the citric acid cycle as Acetyl coa after conversion to:
Pyruvate
How do we activate folic acid that is the source of THF
Reduction process to make dihyrdofolate
What is the fate of the nitrogen skeleton of an amino acid when it is degraded oxidatively
Removal of amino acid nitrogen as ammonia
What willl happen to the biosynthesis of SAM if there is a deficiency in THF and B12
SAM will not synthesize
The cofactor for transaminayion reaction is attached to the enzyme via:
Schiff base linkage to lysine residue
Which amino acids are dervided from 3 phosphoglycerate?
Serine-> cysteine and glycine
What are the chemical characteristics of thromboxanes?
Six member ring containing ether
Which of the following compounds can release arachidonic acid
Some membrane bound phospholipids
Which of these amino acids are both ketogenic and glucogenic? 1. Isoleucine 2. Valine 3. Histidine 4. Arginine 5. Tyrosine A) 1 and 5 B) 1, 3, and 5 C) 2 and 4 D) 2, 3, and 4 E) 2, 4, and 5
isoleucine and tyrosine ALSO (tryptophan and phenylalanine)
Which of the following compounds is nutritionally essential dietary source of arachidonates in humans
linoleate
Which plant product is the precursor of arachidonic acid
linoleate
Urea synthesis in mammals takes place primarily in tissues of the
liver
Which substance is not involved in the production of urea from NH4+ via the urea cycle
malate
