Final Practice Exam Flashcards by Carl Gonzales

Tetrahydrobiopterin deficiency is caused by inborn errors impairing the biosynthesis of biopterin. One enzyme required for its biosynthesis is GTP cyclohydrolase 1 encoded by the GCH1 gene. Mutation of this gene may lead to a disease condition similar to:

Severe combined immune deficiency

Maple syrup urine disorder

PKU

Gout

PKU

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About enzymes and cofactors, which of the following statement is CORRECT?

Hydroxylation of phenylalanine to tyrosine requires tetrahydrofolate

Cytochrome P450-catalyzed oxidation uses heme as a cofactor, which is not a vitamin derivative

If a protein associates with an enzyme and modulates the enzyme activity, is is called a coenzyme

Biosynthesis of tetrabiopterin needs a vitamin precursor called biopterin

Cytochrome P450-catalyzed oxidation uses heme as a cofactor, which is not a vitamin derivative

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The potential causes of elevated levels of bilirubin or its derivates in blood (hyperbilirubinemia) include the following, EXCEPT for:

Liver failure, such as hepatitis (inflammation of liver) or liver car

Genetic defects of ALA synthase

Obstruction of bile duct caused by gallstone, inflammation, tumor, or other pathological changes

Hemolytic: e.g. increased breakdown of red blood cells

Genetic defects of ALA synthase

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About insulin, which of the following statement is NOT correct?

It is produced by pancreatic beta cells

Its target organs/tissues include liver, muscle and adipose

Its release is triggered by increased ATP production in B cells as a result of high blood glucose levels

It promotes both glycogenolysis and glycolysis to generate large amount of AlP in muscle

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Liver may supply other organs with fuel in the following forms, except for:

Ketone bodies

Free fatty acids

Glucose

Acetyl-CoA

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Lack of folic acids may cause metabolic consequence and clinical manifestation similar to the deficiency of vitamin:

B12

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The amino acid used for biosynthesis of serotonin is:

Histidine

Proline

Tryptophan

Tyrosine

Tryptophan

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Human cells may synthesize non-essential, proteinogenic amino acids, where the carbon skeletons (a-keto acids) may derive from the following pathways, except for:

Glycolysis and gluconeogenesis

Urea cycle

Beta oxidation of palmitate

TCA cycle

Beta oxidation of palmitate

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Two signaling molecules work together on the central nervous system to regulate our feeding behaviours. i.e. alpha-MSH and NYP. Generally, their effects are:

a-MSH inhibits whereas NYP stimulates food intake

a-MSH stimulates whereas NYP inhibits food intake

both stimulate food intake

both inhibit food intake

a-MSH inhibits whereas NYP stimulates food intake

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The biosynthesis of multiple neurotransmitters requires decarboxylation of amino acid precursors, a reaction may be directly impaired by the lack of vitamin:

B12

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Which of the following molecule is not one of the three polyamines used in packing newly synthesized DNA?

Spermine

Citrulline

Putrescine

Spermidine

Citrulline

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TCA cycle usually is stimulated by an increase of the following molecules, EXCEPT for:

Calcium

NADH

ADP

AMP

NADH

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S-Ado Met (SAM) serves as a methyl group donor in the following reactions, except for:

Protein methylation

Adrenaline biosynthesis

DNA methylation

Biosynthesis of polyamines

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Which of the following molecules IS NOT directly involved in the urea cycle?

Citrulline

Homocysteine

Ornithine

Aspartate

Homocysteine

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AMPK is considered intracellular energy sensor. Its activity is stimulated by an increase of

ATP

ADP

AMP

cAMP

AMP

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To culture cells defective in mitochondrial electron transfer chain, which of the following molecules is used to rescue the defective pyrimidine biosynthesis?

Guanine

Cytidine

Uridine

Thymidine

Uridine

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NADPH is important for the following biological processes, EXCEPT FOR:

Producing ATP via ETC

Participating in oxidative biosynthesis, such as in cholesterol biosynthesis

Preventing oxidative damage to cell structures

Participating in reductive biosynthesis, such as fatty acid biosynthesis

Producing ATP via ETC

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Biosynthesis of aspartate can be achieved by a transamination between:

Oxaloacetate and alanine

Oxaloacetate and asparagine

Oxaloacetate and glutamate

Oxaloacetate and glutamine

Oxaloacetate and glutamate

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About metabolites in TCA cycle, which statement is NOT correct?

Oxaloacetate can be removed from the cycle to synthesize glucose, aspartate, and asparagine

Citrate can be transported to cytosol for biosynthesis of fatty acids and cholesterol

a-Ketoglutarate can be used to synthesize glutamate and glutamine

Fumarate can be used to synthesize heme and CoQ

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2-deoxy-2-(18F)fluoro-D-glucose is a glucose analog, with the positron-emitting radionuclide fluorine-18 substituted for the normal hydroxyl group at the C-2 position in the glucose molecule. This molecule is recognizable by glucose transporters and hexokinases, but the lack of 2-hydroxyl group (as in normal glucose) blocks its catabolism and leads to its intracellular accumulation. Thus, this molecule is commonly used in Positron-Emission Tomography (PET) in clinical radiology to detect tissues, such as neuronal tissues and cancers that accumulate this molecule. Its increased uptake in tumor cells is mainly based on the:

Warburg effect

Pasteur effect

Both

Neither

Both

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About vitamin B1 derived cofactor thiamine pyrophosphate (TPP), which of following statements is INCORRECT?

Required for pyruvate dehydrogenase complex

Required for transketolase activity

Required for transaldolase activity

Required for a-ketoglutarate dehydrogenase complex

Required for transaldolase activity

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In healthy person, after a good meal, which of the following transporters will be stimulated by insulin to translocate to the surface of adipocytes and myocytes?

Glut1

Glut2

Glut3

Glut4

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Which of the following statement about lipoproteins is NOT correct?

Chylomicrons are originated from intestinal mucosa cells, carrying ApoB48 on its surface

LDL transports cholesterol from liver to extrahepatic tissues; so it is considered bad lipoprotein

HDL transports cholesterol from liver to extrahepatic tissues, but less than LDL, thus being considered good lipoprotein.

Generally speaking, HDL/VLDL/LDL are all originated from liver, directly or indirectly

HDL transports cholesterol from liver to extrahepatic tissues, but less than LDL, thus being considered good lipoprotein.

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About beta-oxidation of fatty acids, which of the following is NOT correct:

One chain fatty acyl-CoA needs carnitine and translocase to enter the mitochondrion

Each beta-oxidation cycle releases 1 acetyl CoA, 1 NADPH, and 1 NADH

The translocation step is repressed by high levels of malonyl-CoA

Unsaturated fatty acids can also be completely oxidized

Each beta-oxidation cycle releases 1 acetyl CoA, 1 NADPH, and 1 NADH

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Eicosanoids serves as local hormones. Leukotrienes belong to the eicosanoids family of signaling molecules which are synthesized by: Neurons Hepatocytes White blood cells Red blood cells

White blood cells

The rate limiting enzyme of heme biosynthesis is ALA synthase. In hepatocytes, it is repressed by high levels of: Iron Glycine Heme Succinyl-CoA

Heme

Refer to Figure provided: the molecule generated from aspartate transamination with alpha-KG is: a b c d

To inhibit de novo biosynthesis of cholesterol, statin family drugs are developed to target HMG-COA synthase True False

False

The molecule Glutathione is: A tripeptide of glutamate, cysteine, and glycine, protecting cells from oxidative stress A byproduct of glutamate catabolism An enzyme involved in the biosynthesis of glutamate A methyl group donor in methylation reactions

A tripeptide of glutamate, cysteine, and glycine, protecting cells from oxidative stress

High level of ammonia in blood is toxic. Waste NH+ and amino group in skeletal muscles are transported to liver mainly in the form of: Alanine and glutamine Glutamate and arginine Glutamate and glutamine Asparagine and aspartate

Alanine and glutamine

Ornithine decarboxylase is an enzyme involved in the urea cycle True False

False

Oxidation of aromatic amino acids adds hydroxyl group to the ring. This type of reaction usually uses a cofactor: Tetrahydrofolate Tetrahydrobiopterin Heme PLP

Tetrahydrobiopterin

In the dynamics of phospholipids, phosphatidylethanolamine (PE) can be converted to phosphatylcholine (PC) by methylation True False

True

Acetylcholine is: A methyl group donor in methylation reactions An allosteric regulator of phospholipid biosynthesis A catabolic waste of phospholipid containing choline A neurotransmitter synthesized from acetyl-CoA and choline

A neurotransmitter synthesized from acetyl-CoA and choline

Under certain physiological conditions, nitric oxide synthases use arginine as substrate to produce nitric oxide (NO). NO binds to and activates the activity of a cytoplasmic enzyme to make: cGMP cCMP cAMP cUMP

cGMP

Beta-oxidation of fatty acids mainly occurs in: Golgi complex Mitochondria Nucleus Cytosol

Mitochondria

Glut2, like most metabolic enzymes, follows the Michaelis Menten kinetics. For such enzyme, determining the velocity vs. increasing substrate concentration (V vs. [S]), and plotting these data in a Lineweaver-Burk or double reciprocal plot results in a graph with: A bell-shaped curve A sine-shaped curve A straight line A hyperbolic curve

A straight line

Methyl group carried by tetrahydrofolate may come from the following molecules, except: Glycine Betaine Serine Glutamate

Glutamate

Ribonucleotide reductase is regulated allosterically. Its primary regulatory sites may bind to either dATP or ATP: dATP activates; ATP inhibits Both dATP and ATP activates its activity ATP activates; dATP inhibits Both dATP and ATP inhibits its activity

ATP activates; dATP inhibits

Regarding prostaglandin biosynthesis. which statement is INCORRECT? PLA2 is the enzyme that releases arachidonate from phospholipids Products of this pathway promote inflammation, allergy, pain and thrombosis. Fatty acid synthase (FAS) in human cells is responsible for the biosynthesis of the substrates Cyclooxygenase (COX) is the key enzyme. which oxidizes the substrate arachidonate

Fatty acid synthase (FAS) in human cells is responsible for the biosynthesis of the substrates

Biomolecules that can be derived from phenylalanine include the following molecules except for: Histamine Dopamine Norepinephrine Epinephrine

Histamine

To use methionine as precursor to synthesize cysteine, we need another amino acid as substrate, which is: Serine Glycine Alanine Aspartate

Serine

For de novo synthesis of purines, the rate limiting enzyme is glutamine-PRPP amidotransferase. Which of the following molecules will NOT repress its activity? AMP IMP GMP UMP

UMP

Substrates for the biosynthesis of the pyrimidine ring include: Glutamine, CO2, and aspartate Glycine, succinyl-CoA, and CO2 Glutamine, glutamate, and aspartate Glutamate, glycine, CO2, and aspartate

Glutamine, CO2, and aspartate

Hepatocytes increase glucose uptake in response to increase in blood glucose levels. Consequently, high levels of G-6P in hepatocytes thermodynamically favors the formation of pentose-phosphate and stimulates the activity of a transcription factor called ChREBP/Mlx. Based on the logics we have discussed during the course, the genes stimulated by the transcription factor are most likely to: Facilitate the mobilization of triacylglycerol Facilitate the gluconeogenesis Facilitate the synthesis of fatty acids and cholesterol Promote the beta-oxidation of fatty acids

Facilitate the synthesis of fatty acids and cholesterol

Regarding nucleotides, nucleosides, and nitrogenous bases, which statement is INCORRECT: A nucleoside contains a nitrogenous base and a ribose The key difference between NTP and dNTP is the oxidation state of the ribose A nucleotide contains a nucleoside, with a phosphate at C3 or C5 position of the ribose furanose ring The key difference between NTP and dNTP is the oxidation state of the nitrogenous base

The key difference between NTP and dNTP is the oxidation state of the nitrogenous base

Refer to Figure provide: The molecule serves as substrate for malic enzyme in cytosol to generate NADPH is: a b c d

Catabolism of dATP requires adenosine deaminase to remove the amino group to form hypoxanthine. Adenosine deaminase deficiency (ADA) may cause the following except for: Lack of other dNTPs blocks T/B cell proliferation in response to microbial infection, causing severe combined immune deficiency (SCID) syndrome Accumulation of dATP, which allosterically inhibits ribonucleotide reductase activity Accumulated dATP forms crystals, damaging joints, causing gout Accumulation of adenosine, which inhibits purine biosynthesis and reduces level of guanidine

Accumulated dATP forms crystals, damaging joints, causing gout

Which of the following molecules is NOT directly involved in the biochemical reactions of cholesterol biosynthesis? Choline Isoprene Mevalonate HMG-CoA

Choline

The rate limiting step of fatty acid biosynthesis is: Citrate exporting out of mitochondria Citrate cleavage in cytosol Acetyl-CoA carboxylation Condensing enzyme activity of FAS

Acetyl-CoA carboxylation

Under starvation, which of the following carbon sources is unlikely a major source for anaplerosis: Pyruvate from glycolysis Glutamate and glutamine from breakdown of proteins Glycerol from catabolism of phospholipids Carbon skeleton from the degradation of pyrimidine

Pyruvate from glycolysis

When oxygen is not available, glycolysis of three GLUCOSE MOLECULES TO FORM LACTATE MOLECULES will have a net gain of: 6 ATP 8 ATP 16 ATP 32 ATP

6 ATP 2 ATP per molecule of glucose in lactate fermentation

In methylation reactions, two most commonly used DIRECT donors of methyl groups are: Methionine and homocysteine Arginine and lysine Serine and glycine Methyl-tetrahydrofolate and S-adenosyl-methionine (S-Ado-Met)

Methyl-tetrahydrofolate and S-adenosyl-methionine (S-Ado-Met)

About catabolism of pyrimidines, which statement is correct? Eventually disposed in the form of bile salts for excretion via bile duct Eventually disposed in the form of CO2 and urea Eventually converted to uric acid for excretion via the urinary system Eventually disposed in the form of isoprene

Eventually disposed in the form of CO2 and urea

In humans, the major form of nitrogen excretion is: Creatine Ammonia Urea Uric acid

Urea

The biochemical nature of nucleotide reductation is to: Remove an oxygen atom at C3 of the ribose furanose Remove an oxygen atom at C2 of the ribose furanose Introduce a hydroxyl group at C3 of the ribose furanose Introduce a hydroxyl group at C2 of the ribose furanose

Remove an oxygen atom at C2 of the ribose furanose

About nitric oxide (NO), which of the following statements is NOT correct? It can be a hormone or a neurotransmitter, depending on cell origin and mode of release After synthesis by hepatocytes, it travels long distance to regulate neuron and heart function It binds a cytosolic receptor, which produces cGMP as second messenger More than one isoenzyme of NO synthase catalyzes its biosynthesis on different cell types

After synthesis by hepatocytes, it travels long distance to regulate neuron and heart function

Refer to fig provided: The molecule directly generated by the urea cycle and returned to TCA cycle is: a b c d

One amino acid may serve as the substrate to contribute both carbon and nitrogen for the biosynthesis of another amino acid. Which one of the following amino acids can be used as such a substrate to synthesize proline? Glutamate Histidine Serine Aspartate

Glutamate

The general outline of mobilization and utilization of endogenous TAG may include the following except for: Insulin activates lipase on white adipose tissue (adipocytes), which releases fatty acids Translocation of long chain acyl-CoA to mitochondria, a carnitine acyl-CoA transferase dependent process Beta-oxidation in mitochondria, resulting cleavage by thiolase to form acetyl-CoA Biochemical activation of free fatty acid by ATP to form acyl-CoA in the cytosol

Insulin activates lipase on white adipose tissue (adipocytes), which releases fatty acids

Catabolism of odd-numbered fatty acids, some amino acids and other biomolecules may create propionyl-CoA or alpha-keto-butyrate. To completely oxidize these metabolites. In addition to the common vitamins B2, B5, and B3 based cofactors, we need special cofactors derived from: Vitamin B7 only Vitamin B12 only Vitamin B9 and B12 Vitamins B7 and B12

Vitamins B7 and B12

In catabolism of amino acids with non-alpha amino group such as glutamine and asparagine, the non-alpha amino group is usually removed by: Oxidative deamination Hydrolysis Dehydration initiated deamination Transamination

Hydrolysis

For hepatocytes, the major type of glucose transporter is: Glut3 Glut1 Glut4 Glut2

Glut2

Biosynthesis of dNTP is critical for DNA replication in proliferating cells. One step in the synthetic pathway is to reduce the ribose of nucleotides catalyzed by ribonucleotide reductase. Which of the following is the substrate for this reaction? Ribose phosphate NMP NDP NTP

NDP

In the biosynthesis of the pyrimidine, the first synthesized pyrimidine is: Cytosine Adenosine Thymine Uracil

Uracil

In addition to form acetvl-CoA, other metabolic fates of pyruvate include the following, except for: Reduction by lactate dehydrogenase to form lactate Carboxylation by pyruvate carboxylase to form oxaloacetate Transamination by GPT to form alanine Phosphorylation by pyruvate kinase to form phosphoenolpyruvate

Phosphorylation by pyruvate kinase to form phosphoenolpyruvate

Maple syrup disease is caused by the defective catabolism of: Methionine, homocysteine, and cysteine Tryptophan and histidine Phenylalanine, tyrosine, & tryptophan Leucine, isoleucine, and valine

Leucine, isoleucine, and valine

Isotope tracing is a technique commonly used in metabolic study. If 14C labelled acetoacetate is used to culture neuronal cells, the isotope 14C is likely be detectable in the following molecules, except for: Alpha-ketoglutarate Pyruvate Cholesterol Oxaloacetate

Cholesterol

The major regulatory factor of pentose phosphate pathway (PPP) is the cytosolic level of: Pentose phosphate NADH NADPH ATP

NADPH

In human cell biochemistry, isoprene is also a required substrate for the biosynthesis of ubiquinol and lipoic acid True False

True

Refer to Figure provided: The substrate for ETC complex II is: a b c d

Cholesterol is the precursor for the following important molecules, except for: Testosterone Ubiquinol Estrogen Glucocortisol

Ubiquinol

Leptin and adiponectin are two hormones released by fat tissues which regulate the body fat homeostasis. Which of the following statement is correct? Both stimulates the catabolism of fat Adiponectin releases following fat mass increases, which stimulates food intake as a positive physiological feedback Both inhibits the catabolism of fat Leptin increases when fat mass increases, which inhibits food intake as a negative physiological feedback

Leptin increases when fat mass increases, which inhibits food intake as a negative physiological feedback

TCA cycle usually is repressed by an increase of the following factors, EXCEPT for: AMP ATP NADH Acetyl-CoA

AMP

About urea cycle, which of the following statement is INCORRECT? Each urea has two nitrogen, one from oxidative deamination of glutamate, and the other one from aspartate Urea cycle borrows oxaloacetate from TCA cycle to take over amino group from glutamate via transamination: and return fumarate to TCA cycle The urea cycle uses ornithine at early stage, and regenerate ornithine after arginine breakdown to urea and ornithine If arginine is consumed in other biological processes, ornithine will be exhausted

If arginine is consumed in other biological processes, ornithine will be exhausted

Purine and pyrimidine biosynthesis pathways could be targeted as approach to treat cancers and certain microbial pathogens such as viruses True False

True

Biosynthesis of fatty acids and cholesterol needs acetyl-CoA and NADPH as substrates. In addition to pentose phosphate pathway, which of the following is an additional source of NADPH for each biosynthesis? Malic enzyme-catalyzed oxidation of malate in the cytosol Glycolysis TCA cycle Beta-oxidation of fatty acids in mitochondria recovers NADPH from NADP+

Malic enzyme-catalyzed oxidation of malate in the cytosol

Patients with G6PD deficiency may show jaundice after ingesting certain food or drugs that triggers oxidative stress to cells. The most likely causes of jaundice in this case is the injury and breakdown of: Hepatocytes Red blood cells Adipocytes Myocytes

Red blood cells

Transamination carried out by either amidotransferases or aminotransferases is an important process in both biosynthesis of non-essential amino acids and transport of amino groups from extrahepatic tissues to hepatocytes for disposal. This process requires a cofactor derived from vitamin: B2 B5 B6 B7

If 15N-labeled glutamine is introduced into hepatocytes, which one of the following molecules is likely the last one to be labeled the tracible 15N? Glutamate Spermidine Aspartate Arginine

Spermidine

Final Practice Exam Flashcards

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