Exam 4: Quiz Questions

Which of the following enzyme-catalyzed reactions is the rate-limiting and regulated step in purine synthesis?

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

GLUT4 is an example of which of the following type of protein

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?

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?

ATP

Complete hydrolysis of nucleic acids will NOT yield?

Adenosine

The major amino acid that is released from muscle and converted to glucose in the liver is?

Alanine

Which of the following is NOT an essential amino acid?

Alanine

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 -Epinephrine activates glycogenolysis in muscle and the liver, and fat mobilization in adipose tissue -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

Which of the following compounds provide atoms of the purine ring in de novo purine nucleotide synthesis?

All of the above -Glycine -Aspartate -CO2 -Glutamine

Which of the following statements concerning the catabolism of heme are CORRECT?

All of the above -Heme catabolism occurs primarily in the liver and spleen (reticuloendothelial system) -The enzyme heme oxygenase cleaves the prophyrin ring to release Fe3+ and CO -The first step in heme catabolism is catalyzed by the enzyme, heme oxygenase -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

Which of the following statements concerning metabolism in the well-fed and fasting states is CORRECT?

All of the above -Liver tissue responds to increased insulin by storing glycogen and synthesizing fat; it responds to increased glucagon by synthesizing glucose and burning fat. -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 -Muscle tissue responds to insulin by synthesizing protein and glycogen; it responds to epinephrine by mobilizing its own glycogen for energy

In the untreated insulin diabetic state, the absence of insulin produces which of the following metabolic abnormalities?

All of the above -Muscle wasting results from excessive degradation of muscle protein -Ketoacidosis results from excessive mobilization of fatty acids from adipose tissue -Hyperglycemia is caused by increased hepatic glucose production and reduced glucose uptake by insulin-sensitive GLUT4 in adipose tissue and muscle -Hypertriglyceridemia is caused by reduced lipoprotein lipase activity in adipose tissue and excessive fatty acid esterification in liver

Which of the following statements regarding the peptide hormone, insulin, are CORRECT?

All of the above -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 -Insulin promotes the synthesis of glycogen in liver and muscle -Insulin is synthesized as an inactive precursor, proinsulin

In the liver, during fasting metabolism, ATP, acetyl-CoA, and citrate are important effectors during gluconeogenesis because?

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

which of the following statements is CORRECT concerning the pathway of purine degradation?

All of the above -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

Which of the following steps are involved in the transfer of amino acid nitrogen to the urea cycle?

All of the above -Formation of carbamoyl phosphate -Formation of ammonia -Transamination

Which of the following enzyme activities are increased in the liver in response to insulin

All of the above -HMG-CoA reductase -Glucokinase -Glycogen synthase -Phosphofructokinase-1

In the untreated insulin-dependent diabetic state (IDDM), which of the following characteristics is CORRECT?

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

Which of the following statements concerning the hormonal influences on metabolism is CORRECT?

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

Which of the following statements concerning muscle metabolism in the fasting state is correct?

All of the above -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 -In the absence of insulin, an inducer of protein synthesis, there is a shift toward net degradation of muscle protein -Skeletal muscle lacks G6Pase and therefore degradation of muscle glycogen cannot contribute to blood glucose formation.

Which of the following statements concerning gout is CORRECT?

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

Which of the following statements concerning the hormone, glucagon, are CORRECT?

All of the above -The overall role of glucagon is to prevent fasting hypoglycemia -The overall effect of glucagon is promote both glycogenolysis and gluconeogenesis -Glucagon receptors are coupled to stimulatory G proteins -Glucagon is secreted from pancreatic a-cells

Which of the following statements concerning heme biosynthesis are CORRECT?

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

Consider the amino acids, aspartate, methionine, glutamate, leucine and isoleucine. Which of the following statements concerning these amino acids is CORRECT?

Asparate and histidine are glucogenic

The biosynthesis of the heme macrocycle occurs in which of the following subcellular compartments

Both -Cytosol -Mitochondrial matrix

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

An intermediate in the biosynthesis of pyrimidines is which of the following compounds?

Carbamoyl aspartate

Which of the following is true of de novo pyrimidine synthesis but NOT of purine biosynthesis?

Carbamoyl phosphate donates a carbamoyl group

The rate-limiting step in pyrimidine biosynthesis is catalyzed by the enzyme?

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)

Which of the following statements concerning amino acid metabolism is CORRECT

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?

Cytosol

De novo pyrimidine biosynthesis occurs in which of the following sub-cellular compartments?

Cytosol

The polypeptide hormone insulin acts by promoting which of the following post-translational modifications of enzymes?

Dephosphorylation

In the brain, which of the following compounds CANNOT be used for energy?

Free fatty acids

Which of the following is a common intermediate in the synthesis of arginine, serine and aspartate from glucose?

Glyceraldehyde 3-phosphate

The compound that supplies only one carbon for the biosynthesis of each purine ring is?

HCO3- (CO2)

In the well-fed state, which of the following hormone ratios promotes energy storage in muscle?

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?

Hormone-sensitive lipase

Which of the following compounds serves as an intermediate in the synthesis of AMP and GMP?

Inosine monophosphate

Which of the following intermediates in the biosynthesis of purines is the first to possess and intact ring?

Inosine monophosphate (IMP)

The catabolism of hemoglobin

Involves the oxidative cleavage of the porphyrin ring

Which of the following statements about bilirubin is TRUE?

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?

Leucine

Insulin exhibits its most pronounced effects on regulating metabolism in which of the following organs?

Liver

The metabolic effects of glucagon are most pronounced in which of the following organs?

Liver

In humans, the rate-limiting step for urea synthesis is regulated by which of the following?

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?

NADPH

The essential amino acid, tryptophan, can be made in the tissues from which of the following?

Niacin

Which of the following statements concerning purine salvage are CORRECT?

None of the above -Results in increased uric acid excretion -Leads to increased de novo purine synthesis -Involves the formation of purine nucleotides by the transfer of phosphate from ATP to purine nucleosides -Refers to increased intestinal absorption of purines

In pyrimidine nucleotide biosynthesis?

One of the pyrimidine ring carbons is derived from CO2

In the urea cycle?

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

The Lesch-Nyhan syndrome is caused by a deficiency of an enzyme in which of the following pathways?

Purine salvage

Which of the following are properties of the amino acid glutamine (Gln, Q)?

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

Purine and pyrimidine biosynthesis begins which which of the following compounds?

Ribose 5-phosphate (R5P)

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

Which of the following statements is CORRECT concerning the reaction that generates 5-phosphoribosylamine from 5-phosphoribosyl-1-phosphate (PRPP)?

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

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

Tyrosine

Which of the following amino acids is synthesized from an essential amino acid?

Tyrosine

A normal adult is placed on a diet deficient only in phenylalanine. Which of the following statements is CORRECT?

Tyrosine becomes an essential amino acid

Infants with low levels of glucuronyltransferase exhibit jaundice because?

Unconjugated bilirubin is less water-soluble than conjugated bilirubin

In urea cycle, arginine is converted to ornithine by the enzyme arginase releasing?

Urea

Glycine is an important precursor in the pathway for the biosynthesis of each of the following EXCEPT?

Valine

The rate-limiting and regulated step in heme biosynthesis is catalyzed by which of the following enzymes?

d-Aminolevulinic acid synthetase