Unit 4 quiz questions

Which of the following enzyme-catalyzed reactions is the rate-limiting and regulated step in purine synthesis? Ribose 5-phosphate -> 5'-phosphoribosyl pyrophosphate 5'-phosphoribosyl amine -> 5'-phosphoribosyl glycinamide 5'-phosphoribosyl N-formylglycinamide -> 5'-phosphoribosyl N-formylglycinamidine 5'-phosphoribosyl pyrophosphate -> 5'-phosphoribosyl amine 5'-phosphoribosyl glycinamide -> 5'-phosphoribosyl N-formylglycinamide

5'-phosphoribosyl pyrophosphate -> 5'-phosphoribosyl amine

Which of the following compounds serves as the precursor molecule for de novo synthesis of purines? Ribose 5-phosphate Adenosine triphosphate 5-Phosphribosyl-1-pyrophosphate Uridine monophosphate 5-Phosphoribosylamine

5-Phosphribosyl-1-pyrophosphate

GLUT4 is an example of which of the following type of protein A class of cell surface receptors that are involved in glucose transport None of the above A class of gut proteins involved in fatty acid metabolsim A class of proteins involved in nucleotide metabolism A class proteins involved in glycogen degradation

A class of cell surface receptors that are involved in glucose transport

Which of the following statements concerning adipose tissue metabolism in the fasting state is CORRECT? Liver and muscle use released glucose as a major energy source during fasting Glycerol is converted to glycerol 3-phosphate in the liver and is used as a substrate for glycolysis Free fatty acids are transported in the circulation bound to hemoglobin Hormone-sensitive lipase is required for the synthesis of triglycerides from glycerol and free fatty acids A low insulin-to-glucagon ratio and release of epinephrine promote formation of the active phosphorylated form of hormone-sensitive lipase

A low insulin-to-glucagon ratio and release of epinephrine promote formation of the active phosphorylated form of hormone-sensitive lipase

A deficiency in which of the following compounds would result in decreased guanosine monophosphate (GMP) synthesis? Alanine ATP Asparagine Carbon monoxide (CO) GTP

ATP

Complete hydrolysis of nucleic acids will NOT yield? Ribose Guanine Adenosine Phosphate Cytosine

Adenosine

The major amino acid that is released from muscle and converted to glucose in the liver is? Alanine Valine Aspartate Glutamate Glutamine

Alanine

Which of the following is NOT an essential amino acid? Histidine Alanine Threonine Methionine Lysine

Alanine

In the liver, during fasting metabolism, ATP, acetyl-CoA, and citrate are important effectors during gluconeogenesis because? Acetyl-CoA activates pyruvate carboxylase, which converts pyruvate to oxaloacetate (OAA) for use in the gluconeogenic pathway All of the above Inhibition of pyruvate dehydrogenase by acetyl-CoA also increases shunting of pyruvate toward oxaloacetate Increased ATP concentrations inhibit glycolysis while providing energy for gluconeogenesis Citrate allosterically inhibits phosphofructokinase 1, preventing a futile cycle with fructose 1,6-bisphosphatase

All of the above

In the untreated insulin diabetic state, the absence of insulin produces which of the following metabolic abnormalities? All of the above Hypertriglyceridemia is caused by reduced lipoprotein lipase activity in adipose tissue and excessive fatty acid esterification in liver Ketoacidosis results from excessive mobilization of fatty acids from adipose tissue Muscle wasting results from excessive degradation of muscle protein Hyperglycemia is caused by increased hepatic glucose production and reduced glucose uptake by insulin-sensitive GLUT4 in adipose tissue and muscle

All of the above

In the untreated insulin-dependent diabetic state (IDDM), which of the following characteristics is CORRECT? Muscle wasting results from excessive degradation of muscle protein Hyperglycemia is caused by increased hepatic glucose production and reduced glucose uptake by insulin-sensitive GLUT4 in adipose tissue and muscle Ketoacidosis results from excessive mobilization of fatty acids from adipose tissue All of the above Hypertriglyceridemia is caused by reduced lipoprotein lipase activity in adipose tissue and excessive fatty acid esterification in liver

All of the above

Which of the following compounds provide atoms of the purine ring in de novo purine nucleotide synthesis? Glutamine All of the above Glycine CO2 Aspartate

All of the above

Which of the following enzyme activities are increased in the liver in response to insulin HMG-CoA reductase Phosphofructokinase-1 Glycogen synthase Glucokinase All of the above

All of the above

Which of the following statements concerning deoxyribonucleotide synthesis is CORRECT? Ribonucleotide reductase requires thioredoxin as a cofactor Only ribonucleotide diphosphates are required for synthesis The synthesis requires the conversion of ribonucleotide diphosphates to 2'-deoxyribonucleotide diphosphates All of the above The enzyme ribonucleotide reductase is required

All of the above

Which of the following statements concerning gout is CORRECT? The distal joints such as the feet are affected first Patients develop painful inflammation of joint tissues Tissue damage is caused by deposition of Na-urate crystals All of the above Increased formation of PRPP or decreased renal clearance of urate are causes

All of the above

Which of the following statements concerning heme biosynthesis are CORRECT? All of the above The activity of ALA synthase is decreased by elevated levels of hemin, which is heme containing Fe3+ (ferric iron) The activity of ALA synthase is dependent on the presence of pyridoxal phosphate as a prosthetic group Two molecules of d-aminolevulinic acid are required to form porphobilinogen catalyzed by ALA dehydrase All the carbon and nitrogen atoms of the prophyrin molecule are provided by glycine and succinyl-CoA

All of the above

Which of the following statements concerning metabolism in the well-fed and fasting states is CORRECT? Brain utilizes glucose exclusively for fuel except during starvation, when it burns ketone bodies in order to spare blood glucose Adipose tissue responds to insulin by increasing uptake of fat and storing it; it responds to epinephrine by mobilizing fat All of the above Muscle tissue responds to insulin by synthesizing protein and glycogen; it responds to epinephrine by mobilizing its own glycogen for energy Liver tissue responds to increased insulin by storing glycogen and synthesizing fat; it responds to increased glucagon by synthesizing glucose and burning fat.

All of the above

Which of the following statements concerning muscle metabolism in the fasting state is correct? All of the above Skeletal muscle lacks G6Pase and therefore degradation of muscle glycogen cannot contribute to blood glucose formation. In the absence of insulin, an inducer of protein synthesis, there is a shift toward net degradation of muscle protein Most amino acids released from muscle protein are transported directly to the liver, where they are transaminated and converted to glucose The transport of alanine to the liver followed by its conversion to glucose that returns to muscle to form more pyruvate is called the alanine cycle

All of the above

Which of the following statements concerning purine and pyrimidine nucleotides is CORRECT? They comprise part of the structure of sever coenzymes, such as NAD+ They serve as precursors for DNA and RNA anabolism They serve as high energy substrates for many anabolic reactions They function in intracellular signaling All of the above

All of the above

Which of the following statements concerning the catabolism of heme are CORRECT? The first step in heme catabolism is catalyzed by the enzyme, heme oxygenase Heme catabolism occurs primarily in the liver and spleen (reticuloendothelial system) Biliverdin is reduced to bilirubin which is only slightly soluble in plasma and is transported to the liver by binding to albumin for further metabolism All of the above The enzyme heme oxygenase cleaves the prophyrin ring to release Fe3+ and CO

All of the above

Which of the following statements concerning the hormonal influences on metabolism is CORRECT? Glucocorticoids are steroid hormones produced by the adrenal glands to help tissues respond to long-term metabolic stress All of the above Insulin primarily dephosphorylates enzymes, whereas glucagon primarily phosphorylates them Insulin acts to reduce blood glucose (hypoglycemic effect); glucagon acts to increase blood glucose (hyperglycemic effect). Insulin and glucagon are the key hormones in the short-term regulation of blood glucose concentration under normal physiologic conditions

All of the above

Which of the following statements concerning the hormone epinephrine is CORRECT? All of the above Epinephrine receptors in muscle and adipose tissue create a wave of phosphorylation through the cell by stimulating adenylate cyclase You Answered Epinephrine together with norepinephrine act to mobilize energy for the flight-or-fight response The metabolic actions of epinephrine are most pronounced in muscle and adipose tissue Epinephrine activates glycogenolysis in muscle and the liver, and fat mobilization in adipose tissue

All of the above

Which of the following statements concerning the hormone, glucagon, are CORRECT? Glucagon is secreted from pancreatic a-cells Glucagon receptors are coupled to stimulatory G proteins The overll role of glucagon is to prevent fasting hypoglycemia The overall effect of glucagon is promote both glycogenolysis and gluconeogenesis All of the above

All of the above

Which of the following statements regarding the peptide hormone, insulin, are CORRECT? Insulin promotes the synthesis of glycogen in liver and muscle The levels of insulin hormone are primarily influenced by the blood glucose concentration The two peptide chains (A & B) in the mature insulin molecule are linked by disulfide bonds All of the above Insulin is synthesized as an inactive precursor, proinsulin

All of the above

Which of the following steps are involved in the transfer of amino acid nitrogen to the urea cycle? All of the above Transamination Formation of ammonia None of the above Formation of carbamoyl phosphate

All of the above

which of the following statements is CORRECT concerning the pathway of purine degradation? Degradation of adenine produced hypoxanthine Degradation of guanine produces xanthine Uric acid, which is not very water soluble, is excreted by the kidneys Xanthine is oxidized to uric acid by xanthine oxidase/dehydrogenase All of the above

All of the above

An increase deposition of uric acid or urate crystals in distal tissues (feet) has been identified as one of the major causes of gout. Which of the following compounds would be useful in the treatment of this disease? Dicumerol Allopurinol Adenine Oligomycin 2,4-dinitrophenol

Allopurinol

Consider the amino acids, aspartate, methionine, glutamate, leucine and isoleucine. Which of the following statements concerning these amino acids is CORRECT? Isoleucine is exclusively ketogenic Leucine is glucogenic Glutamate is degraded to pyruvate after transamination The amino acids, methionine, glutamate and leucine are essential amino acids Asparate and histidine are glucogenic

Asparate and histidine are glucogenic

Which of the following enzymes catalyzes the reversible transamination of nitrogen between aspartate and glutamate? Argininosuccinase Aspartate aminotransferase Glutamate dehydrogenase Alanine aminotransferase Arginase

Aspartate aminotransferase

The biosynthesis of the heme macrocycle occurs in which of the following subcellular compartments None of the above Cytosol Mitochondrial matrix Neither Both

Both

Maple syrup urine disease, also known as branched-chain ketonuria is due to a deficiency in which of the following enzymes? Branched-chain a-ketoacid dehydrogenase Ornithine transcarbamoylase Methylmalonyl-CoA mutase Phenylalanine hydroxylase Dihydrobiopterin reductase

Branched-chain a-ketoacid dehydrogenase

An intermediate in the biosynthesis of pyrimidines is which of the following compounds? Dihydrouracil Argininosuccinate Carbamoyl aspartate 5-Phosphoribosylamine None of the above

Carbamoyl aspartate

Which of the following is true of de novo pyrimidine synthesis but NOT of purine biosynthesis? Glutamine is a nitrogen donor The bases are synthesized while attached to ribose 5-phosphate 1-Carbon fragments are donated by folic acid derivatives Carbamoyl phosphate donates a carbamoyl group Glycine is incorporated intact

Carbamoyl phosphate donates a carbamoyl group

The rate-limiting step in pyrimidine biosynthesis is catalyzed by the enzyme? Dihydroorotase Carbamoyl phosphate synthetase Orotate phosphoribosyltransferase Dihydroorotate dehydrogenase aspartate transcarbamoylase (ATCase)

Carbamoyl phosphate synthetase

Which of the following enzymes is controlled in the short term regulation of the urea cycle by the allosteric effector, N-acetylglutamate? Carbamoyl phosphate synthetase I (CPS I) Argininosuccinic acid synthetase Argininosuccinase Ornithine transcarbamoylase Arginase

Carbamoyl phosphate synthetase I (CPS I)

Which of the following statements concerning amino acid metabolism is CORRECT All essential amino acids are glycogenic In the presence of adequate dietary sources of tyrosine, phenylalanine is not an essential amino acid An increase in gluconeogenesis from amino acids results in a decrease in urea formation Cysteine is an essential amino acid in individuals consuming a diet devoid of methionine Ornithine and citrulline are found in tissue proteins

Cysteine is an essential amino acid in individuals consuming a diet devoid of methionine

De novo purine biosynthesis occurs in which of the following sub-cellular compartments? Mitochondrial matrix Cytosol Lysosomes Nucleus Mitochondrial inner membrane

Cytosol

De novo pyrimidine biosynthesis occurs in which of the following sub-cellular compartments? Mitochondrial matrix Cytosol Lysosomes Nucleus Mitochondrial inner membrane

Cytosol

The polypeptide hormone insulin acts by promoting which of the following post-translational modifications of enzymes? Dephosphorylation Myristilation Phosphorylation Glycosylation Acetylation

Dephosphorylation

In the brain, which of the following compounds CANNOT be used for energy? Glucose Free fatty acids Ketone bodies None of the above Glycogen

Free fatty acids

The enzyme, isocitrate dehydrogenase is required for the synthesis from glucose of which of the following amino acids? Glutamate Alanine Serine Cysteine Aspartate

Glutamate

A compound that is required for BOTH purine and pyrimidine ribonucleotide biosynthesis is? Asparagine Formate Fumarate Glutamine ribose 1-phosphate

Glutamine

Which of the following is a common intermediate in the synthesis of arginine, serine and aspartate from glucose? Ornithine Oxaloacetate Glyceraldehyde 3-phosphate a-Ketoglutarate Pyruvate

Glyceraldehyde 3-phosphate

The compound that supplies only one carbon for the biosynthesis of each purine ring is? Formate HCO3- (CO2) Glycine Glutamine Aspartate

HCO3- (CO2)

In the well-fed state, which of the following hormone ratios promotes energy storage in muscle? Muscle does not use hormones High glucagon/insulin ratio High insulin/glucagon ratio Neither Both

High insulin/glucagon ratio

The metabolic effects of epinephrine are most pronounced in muscle and adipose tissue. Which of the following enzyme activities are increased in adipose tissue? Glycogen phosphorylase Pyruvate kinase Glycogen synthase Phosphofructokinase-1 Hormone-sensitive lipase

Hormone-sensitive lipase

Lesch-Nyhan syndrome is a lethal disease caused by a deficiency of which of the following enzymes? Xanthine oxidase (XO) Adenine phosphoribosyltransferase (APRT) Hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) Xanthine dehydrogenase (XDH) Ribose phosphate kinase (RPK)

Hypoxanthine-guanine phosphoribosyltransferase (HGPRTase)

Which of the following compounds serves as an intermediate in the synthesis of AMP and GMP? Uracil diphosphate Carbamoyl phosphate Hypoxanthine Inosine monophosphate Orotate

Inosine monophosphate

Which of the following intermediates in the biosynthesis of purines is the first to possess and intact ring? Ribose 5-phosphate (R5P) 5-Phosphoribosylamine (5PRA) Adenosine monophosphate (AMP) Guanosine monophosphate (GMP) Inosine monophosphate (IMP)

Inosine monophosphate (IMP)

The catabolism of hemoglobin Is the sole source of bilirubin Involves the oxidative cleavage of the porphyrin ring Results in the formation of protoporphyrinogen Occurs in red blood cells Results in the liberation of carbon dioxide

Involves the oxidative cleavage of the porphyrin ring

Which of the following statements about bilirubin is TRUE? It is produced by the enzyme heme oxygenase in the liver It is produced by oxidation of heme with loss of carbon monoxide (CO) It contains iron in the Fe2+ state It is excreted mainly in the urine It is made more soluble in the liver by the attachment of residues of glucose

It is produced by oxidation of heme with loss of carbon monoxide (CO)

In Maple syrup urine disease, which of the following amino acid is not properly catabolized? Methionine Phenylalanine Glutamine Histidine Leucine

Leucine

Insulin exhibits its most pronounced effects on regulating metabolism in which of the following organs? Kidney Spleen Heart Liver Brain

Liver

The metabolic effects of glucagon are most pronounced in which of the following organs? Liver Heart Kidney Pancreas Brain

Liver

In humans, the rate-limiting step for urea synthesis is regulated by which of the following? Aspartate. Oxaloacetate Citrulline N-acetyl glutamate Fumarate

N-acetyl glutamate

Which of the following coenzymes is required to recycle oxidized thioredoxin back to its reduced form for use by the enzyme ribonucleotide reductase? ATP NADPH NAD+ NADP+ NADH

NADPH

Which of the following statements concerning purine salvage are CORRECT? Refers to increased intestinal absorption of purines Results in increased uric acid excetion Leads to increased de novo purine synthesis None of the above Involves the formation of purine nucleotides by the transfer of phosphate from ATP to purine nucleosides

None of the above

Tryptophan, can be made in the tissues from which of the following? Any other amino acid Thiamin None of the responses Niacin Riboflavin.

None of the responses

In pyrimidine nucleotide biosynthesis? Mitochondrial carbamoyl phosphate synthetase is utilized One of the pyrimidine ring carbons is derived from CO2 Free ammonia is a substrate for carbamoyl phosphate synthetase Dihydroorotate dehydrogenase is the rate-limiting enzyme CMP is the precursor of the other pyrimidine nucleotides

One of the pyrimidine ring carbons is derived from CO2

In the urea cycle? Ornithine directly reacts with carbamoyl phosphate to form citrulline N-acetylglutamate is a positive allosteric effector of ornithine transcarbamoylase The a-amino group of arginine forms one of the nitrogens of urea Ornithine reacts with aspartate to generate argininosuccinate Carbamoyl phosphate is derived directly from glutamine and CO2

Ornithine directly reacts with carbamoyl phosphate to form citrulline

The hormone glucagon acts by promoting which of the following post-translational modifications of enzymes? Phosphorylation Myristilation Glycosylation Acetylation Dephosphorylation

Phosphorylation

The Lesch-Nyhan syndrome is caused by a deficiency of an enzyme in which of the following pathways? None of the above Pyrimidine anabolism Purine anabolism Purine salvage Purine catabolism

Purine salvage

Which of the following is a metabolic pathway common to bacteria and humans? Cell-wall mucopeptide synthesis Fermentation to ethyl alcohol Purine synthesis Nitrogen fixation Noncyclic photophosphorylation

Purine synthesis

Each of the following enzymes is involved in the synthesis of serine from glucose EXCEPT? Glyceraldehyde 3-phosphate dehydrogenase Pyruvate kinase Phosphoserine phosphatase Phosphofructokinase Aldolase

Pyruvate kinase

Which of the following are properties of the amino acid glutamine (Gln, Q)? Is an intermediate in the urea cycle Is formed by transamination of oxaloacetate Releases two moles of ammonia when converted to one mole of a-ketoglutarate Contains two amino agroups Possesses and ionizable side chain

Releases two moles of ammonia when converted to one mole of a-ketoglutarate

Purine and pyrimidine biosynthesis begins which which of the following compounds? Ribulose 5-phosphate (Rbl5P) Guanosine monophosphate (GMP) Ribose 5-phosphate (R5P) 5-Phosphoribosyl 1-pyrophosphate (PRPP) Adenosine monophosphate (AMP)

Ribose 5-phosphate (R5P)

The carbons of cysteine are derived from which of the following compounds? Methionine Glycine Leucine Serine Threonine

Serine

All of the following statements concerning the degradation of amino acids are true EXCEPT? The carbons of glutamine enter the citric acid cycle as oxaloacetate Phenylalanine leads to the production of fumarate and acetoacetyl-CoA via tyrosine and homogentisic acid Asparagine and aspartic acid lead to the production of oxaloacetate Arginine, proline, histidine and glutamine all lead to the production of a-ketoglutarate via glutamate Valine, isoleucine and methionine all lead to the production of succinyl-CoA vis propionyl-CoA and methylmalonyl-CoA

The carbons of glutamine enter the citric acid cycle as oxaloacetate

Which of the following statements is CORRECT concerning the reaction that generates 5-phosphoribosylamine from 5-phosphoribosyl-1-phosphate (PRPP)? 5-Phosphoribosyl-1-phosphate (PRPP) is a negative inhibitor of the enzyme glutamine:phosphoribosyl pyrophosphate amidotransferase Inosine monophosphate (IMP) is a positive feedback regulator of the reaction Glutamate is converted to glutamine Adenosine monophosphate (AMP) is a positive feedback regulator of the reaction The overall reaction involves the hydrolysis of the liberated pyrophosphate to phosphate making the reaction irreversible

The overall reaction involves the hydrolysis of the liberated pyrophosphate to phosphate making the reaction irreversible

The "committed" step in purine biosynthesis is? Ring closure of formamidoimidazole-carboxamide ribotide to form inosinic acid Ring closure of allantoin to reform uric acid The synthesis of phosphoribosyl pyrophosphate The synthesis of phosphoribosylamine The formation of azaserine, which interferes with glutamine reactions

The synthesis of phosphoribosylamine

Phenylketonuria, alcaptonuria and albinism are caused by deficiences in enzymes involved in the metabolism of which of the following amino acids? Histidine Tyrosine Valine Lysine Tryptophan

Tyrosine

Which of the following amino acids is synthesized from an essential amino acid? Alanine Proline Tyrosine Glutamate Aspartate

Tyrosine

A normal adult is placed on a diet deficient only in phenylalanine. Which of the following statements is CORRECT? Phenylalanine is formed from alanine and benzoic acid, and therefore no metabolic changes are observed An increase in dietary intake of both vitamin B12 and biotin is required to remain in nitrogen balance Synthesis of proteins by the liver continues normally Tyrosine becomes an essential amino acid Tyrosine in the diet is used to compensate for the missing phenylalanine

Tyrosine becomes an essential amino acid

Infants with low levels of glucuronyltransferase exhibit jaundice because? Unconjugated bilirubin is less water-soluble than conjugated bilirubin Reduction of urobilinogen produces insoluble stercobilin Unconjugated bilirubin is produced from conjugated bilirubin by hydrolytic enzymes Biliverdin is more water-soluble than bilirubin Oxidation of urobilinogen produces soluble urobilin

Unconjugated bilirubin is less water-soluble than conjugated bilirubin

In urea cycle, arginine is converted to ornithine by the enzyme arginase releasing? Histidine Lysine Carbonic acid Urea Creatinine

Urea

In man, the chief catabolic product of purines is? Ammonia Allantoin Uric acid Hypoxanthine Urea

Uric acid

Glycine is an important precursor in the pathway for the biosynthesis of each of the following EXCEPT? Heme Valine Guanine All of the above Creatine

Valine

In the degradative pathway of purine metabolism, the catabolism of AMP and GMP are united at the formation of which of the following compounds?, Guanine Hypoxanthine Inosine Xanthine Uric acid

Xanthine

The rate-limiting and regulated step in heme biosynthesis is catalyzed by which of the following enzymes? d-Aminolevulinic acid dehydrase Urophophyrinogen III cosynthase d-Aminolevulinic acid synthetase Ferrochelatase Urophophyrinogen I synthase

d-Aminolevulinic acid synthetase