Biochem 385 Exam 3

Orlistat and olestra can both lead to undigested lipids in the colon, yet they do so by contrasting mechanisms. Orlistat __________, whereas olestra __________. A. activates PPAR - gamma; inhibits pancreatic lipase B. is fat substitute that is not a substrate for pancreatic lipase; inhibits pancreatic lipase C. inhibits pancreatic lipase; activates PPAR - gamma D. inhibits pancreatic lipase; is fat substitute that is not a substrate for pancreatic lipase

D. inhibits pancreatic lipase; is fat substitute that is not a substrate for pancreatic lipase

Diseases affecting heme biosynthesis as a result of deficiencies in the heme biosynthetic pathway are called_____ A. shikimate B. porphyrias C. albinism D. alkaptonuria

B. porphyrias

What are two of the three biochemical causes of gout? A. Dietary chlorophyll from eating plants; lack of feedback inhibition in glutamine-PRPP amidotransferase. B. Deficiency in the HGPRT enzyme; super active PRPP synthetase. C. Super active PRPP synthetase; mental stress from a high pressure lifestyle. D. Too much high intensity training (HIT); deficiency in HGPRT enzyme

B. Deficiency in the HGPRT enzyme; super active PRPP synthetase.

The lack of an immune system in patients born with a defect in the enzyme adenosine deaminase results in the disease ADA-SCID, which is caused by _________ than normal activity of _________. A. higher; ribonucleotide reductase B. lower; ribonucleotide reductase C. higher; xanthine oxidase D. lower; hypoxanthine guanine phosphoribosyltransferase

B. lower; ribonucleotide reductase

In order for a cancer cell to be resistant to the drug methotrexate, a mutation in the dihydrofolate reductase enzyme must be able to _____________. A. bind to methotrexate, but not convert dihydrofolate to tetrahydrofolate B. maintain enzyme activity without being inhibited by methotrexate C. bind to methotrexate and form an inhibitory covalent intermediate D. not bind methotrexate, but still convert dUMP and dTMP

B. maintain enzyme activity without being inhibited by methotrexate

A negative nitrogen balance in a person would be an indicator of_____________. A. overall good health. B. starvation. C. accumulation of nitrogen in the body. D. a diet heavy in protein.

B. starvation.

In the production of urea, the carbon atom comes from______________. A. aspartate. B. the citrate cycle. C. water. D. carbamoyl phosphate.

B. the citrate cycle.

Albinism is caused by______________. A. overproduction of NADPH B. the enzyme tyrosinase working inefficiently C. inefficient production of dopamine D. low levels of ATP available in the cell

B. the enzyme tyrosinase working inefficiently

Five nucleotide bases are found in nucleic acids. Choose a pyrimidine/purine pair from the list below. A. thiamine/cysteine B. thymine/adenine C. adenine/uracil D. guanine/cytosine E. guanine/adenine

B. thymine/adenine

Aspartate is an _____ amino acid, so if a person had a diet that contained no asparatate then ____ A. nonessential; they would be unable to synthesize proteins B. essential; aspartate could be synthesized from other intermediates C. essential; they would be unable to synthesize proteins D. nonessential; aspartate could be synthesized from other intermediates

D. nonessential; aspartate could be synthesized from other intermediates

Metabolic homeostasis relies on maintaining___________________. A. minimal inhibition of gluconeogenesis. B. maximum ATP synthase activity. C. maximum flux through the citric acid cycle. D. optimal metabolite concentrations.

D. optimal metabolite concentrations.

When the ____________ second-order neurons are activated, appetite increases and basal metabolic rates are decreased. A. POMC B. anorexigenic C. ghrelin D. orexigenic

D. orexigenic

Insulin signaling increases the catalytic activity of ___________ in liver cells. A. phosphorylase kinase B. fructose-1,6-bisphosphatase C. glycogen phosphorylase D. phosphofructokinase-1

D. phosphofructokinase-1

Match the drug used to treat type 2 diabetes with its mechanism of action. _____ Glipizide _____ Pioglitazone _____ Glargine _____ Miglitol _____ Dulaglutide _____ Metformin 1. Stimulates insulin secretion by blocking K+ channels in beta cells. 2. Alpha-glucosidase inhibitor that delays dietary carbohydrate absorption. 3. Activates POMC gene expression in first-order neurons. 4. Directly activates insulin signaling in liver, muscle, and adipose cells. 5. Activates expression of adipocyte genes required for fatty acid uptake. 6. Stimulates the activity of AMP-activated protein kinase.

__1__ Glipizide __5__ Pioglitazone __4__ Glargine __2__ Miglitol __3__ Dulaglutide __6__ Metformin

Which metabolite listed below is considered central to human physiology based on its link to multiple biochemical pathways? A. Glucose-6-phosphate B. Glucose C. 6-phosphogluconolactone D. Fructose-6P

A. Glucose-6-phosphate

Which of the following amino acids are required in the first step of heme biosynthesis? A. Glycine B. Alanine C. Alanine D. Histidine E. Phenylalanine

A. Glycine

The enzyme _______ dephosphorylates nucleotides removing the phosphoryl group from theribose sugar, forming nucleosides. A. Phosphorylase B. Nucleoside diphosphate kinase C. Adenosine deaminase D. Nucleotidase E. Ligase

D. Nucleotidase

The thrifty genes hypothesis states that ______ A) certain genes may have been advantageous in a culture when times of famine were routine but have become detrimental in modern society where food is in abundance. B) people who eat a lot of junk food are more likely to have genes that make them better at processing unhealthy foods. C) genetic information flows only in one direction, from DNA, to RNA, to protein, or RNA directly too protein. D) people who are thrifty with their money are more likely to pass on their genes to their offspring. E) individuals with a genetic predisposition for saving money and being frugal are more likely to survive and reproduce in times of famine

A) certain genes may have been advantageous in a culture when times of famine were routine but have become detrimental in modern society where food is in abundance.

Albinism is caused by a defect in the enzyme tyrosinase (1) / phenylalanine hydroxylase (2). The symptoms of the disorder are caused by substrate accumulation (3)/ lack of product (4) and unlike phenylketonuria (5) / Lesch-Nyhan (6), albinism cannot be treated by altering the diet. The biochemical basis for albinism relates to defects in the melatonin (7) / melanin (8) metabolic pathway and is associated with an increased (9) /decreased (10) survival rate in the nature for animals with this defective enzyme. A. 1, 4, 5, 8, 10 B. 2, 4, 5, 7, 10 C. 1, 3, 5, 8, 9 D. 1, 4, 6, 7, 10 E. 2, 3, 6, 7, 9

A. 1, 4, 5, 8, 10

Phenylketonuria (1) / Albinism (2) is characterized by white skin due to a defect in the enzyme tyrosinase, which leads to a block in the pathway needed to synthesize adrenaline (3) / melanin (4). Animals with this condition have an increased risk of skin cancer (5) / mental illness (6). The genetic disease albinism (7) / phenylketonuria (8) is caused by a defect in the enzyme phenylalanine hydroxylase, which leads to the accumulation of tyrosine (9) / phenylalanine (10) derivatives that are toxic metabolites Choose the best underline word or phrase that correctly completes the sentence and record the numbers. A. 2, 4, 5, 8, 10 B. 2, 3, 5, 7, 10 C. 2, 4, 6, 8, 9 D. 1, 3, 6, 7, 9 E. 1, 4, 5, 7, 10

A. 2, 4, 5, 8, 10

Match the classes of proteins involved in ubiquitination A) E1 1. enzymes that attach ubiquitin to target proteins B) E2 2. ubiquitin ligases C) E3 3. enzymes that attach ubiquitin to E2 enzymes A. A-3; B-1; C-2 B. A-2; B-3; C-1 C. A-3; B-2; C-1 D. A-1; B-3; C-3 E. A-1; B-2; C-3

A. A-3; B-1; C-2

Explain how regulatory cross-talk mechanisms within purine biosynthetic pathways ensure that pools of ATP and GTP are balanced. A. ATP is required for the GMP synthetase reaction leading to GMP production, and GTP is required for the adenylosuccinate synthetase reaction leading to AMP production. B. The level of ATP and GTP is regulated by cross-talk through a mechanism involving the ratio of R and T conformations in the enzyme GMP synthetase. C. The level of ATP and GTP is regulated by cross-talk through a mechanism involving the ratio of R and T conformations in the enzyme adenylosuccinate synthetase. D. Cross-talk refers to the communication between IMP and hypoxanthine, both of which are required forthe synthesis of AMP and GMP. E. AMP inhibits the activity of adenylosuccinate to limit GMP synthesis and GMP inhibits IMP dehydrogenase to limit AMP synthesis.

A. ATP is required for the GMP synthetase reaction leading to GMP production, and GTP is required for the adenylosuccinate synthetase reaction leading to AMP production.

Why does a defect in the enzyme adenosine deaminase cause the human disease ADA-SCID? A. Accumulation of adenosine leads to excess dATP, which inhibits ribonucleotide reductase activity. B. Adenosine deaminase controls the activity of HGPRT, which is needed for immune system development. C. Adenosine is the precursor to allopurinol, which is required to stimulate ribonucleotide reductase. D. ADA-SCID results from insufficient PRPP needed for purine biosynthesis, which inhibits the enzyme urate oxidase.

A. Accumulation of adenosine leads to excess dATP, which inhibits ribonucleotide reductase activity.

How do you cure albinism; how do you cure gray hair? A. No treatment for albinism; gray hair can be treated with dye. B, Injections with tyrosine treat albinism; gray hair can be treated with dye. C. No treatment for albinism; gray hair can be treated with dietary tyrosine. D. Albinism can be treated with UV light; gray hair can be treated with a haircut.

A. No treatment for albinism; gray hair can be treated with dye.

Defects in nucleotide metabolism that lead to a buildup of uric acid cause the disease gout. Select the TWO true statements below regarding potential treatments for gout. A. An inhibitor of xanthine oxidase, such as allopurinol, will limit the conversion of hypoxanthine to uric acid, and could be effective in reducing uric acid levels. B. If gout is caused by increased levels of PRPP synthetase, increasing the activity of other enzymes in the uric acid production pathway could be effective in reducing uric acid levels. C. Supplying humans with the enzyme urate oxidase theoretically could be effective in reducing uric acid levels. D. If gout is caused by HGPRT deficiency, increasing the amount of guanine available would shunt more hypoxanthine to GMP production, and could be effective in reducing uric acid levels. E. If gout is caused by insensitivity of glutamine-PRPP amidotransferase to feedback inhibition, raising the levels of 5-phosphoribosylamine could be effective in reducing uric acid levels.

A. An inhibitor of xanthine oxidase, such as allopurinol, will limit the conversion of hypoxanthine to uric acid, and could be effective in reducing uric acid levels. C. Supplying humans with the enzyme urate oxidase theoretically could be effective in reducing uric acid levels.

Why is ingesting large amounts of L-arginine a viable treatment for argininosuccinase deficiency? A. Arginine is converted to ornithine, which provides urea cycle intermediates needed for nitrogen removal. B. Secreting fumarate would also work, but fumarate is an acid and it causes stomach bleeding. C. By ingesting large amounts of L-arginine, the patient is able to excrete large amounts of urea. D. The aspartate-argininosuccinate shunt requires arginine to carry the nitrogen to the urea cycle. E. Citrulline can be excreted in the urine, which provides a way to remove excess dietary nitrogen.

A. Arginine is converted to ornithine, which provides urea cycle intermediates needed for nitrogen removal.

How is excess intracellular ammonia removed from skeletal muscles a result of protein turnover? A. By the Glucose-Alanine Cycle, which converts pyruvate to alanine using glutamate as the nitrogen donor. B. By production of urea in the urea cycle using glutamate and glutamine as nitrogen donors. C. By the Cori Cycle, which converts glucose to pyruvate and alanine as a product of aminotransferase. D. By exporting glutamine produced by glutamine synthetase, which is converted to alanine in the liver. E. By the Glucose-Glutamine Cycle, which converts pyruvate to alanine using urea as the nitrogen donor

A. By the Glucose-Alanine Cycle, which converts pyruvate to alanine using glutamate as the nitrogen donor.

The pyrimidine thymine is only found in DNA, whereas the pyrimidine uracil is only found in RNA. What is the one BEST explanation for this observation? A. Deamination of cytosine generates uracil, which will result in a G-C to A-T mutation in DNA if uracil is allowed to persist. Evolution solved this problem by selecting for enzymes that constantly remove uracil from DNA. B. Deamination reactions cause pyrimidines to be converted to purines, which means that a G-C base pair will become an A-T base pair after two rounds of replication. Therefore thymine is in DNA and uracil is in RNA. C. Uracil base pairs with adenine and thymine base pairs with adenine, therefore if both thymine and uracil were in DNA, then there would be no difference beween an A-T base pair and an U-A base pair. D. RNA is easily hydrolyzed into single strands that break, but DNA is a double helix and it cannot break. Therefore, if thymine was incorporated into RNA and uracil was incorporated into DNA, then DNA would be hydrolyzed and genetic information would be lost.

A. Deamination of cytosine generates uracil, which will result in a G-C to A-T mutation in DNA if uracil is allowed to persist. Evolution solved this problem by selecting for enzymes that constantly remove uracil from DNA.

Which of the following is a coenzyme that is derived from ATP? A. FAD B. heme C. Fe4-S4 cluster D. coenzyme Q

A. FAD

Besides Gly, which other 2 amino acids are required for synthesizing all 5 nucleotide bases? A. Gln, Asp B. Asp, Ala C. Gln, Asn D. Asn, Val E. Gln, Glu

A. Gln, Asp

What is the function of the enzyme hypoxanthine-guanine-phosphoribosyltransferase (HGPRT) in the nucleotide salvage pathways? A. HGPRT adds hypoxanthine to PRPP to form IMP, which is converted to GMP and AMP to replenish nucleotide pools. B. HGPRT is the redox enzyme that removes the -OH group from ribonucleotides to generate deoxyribonucleotides using Fe3+ as a cofactor. C. HGPRT converts purines to pyrimidines, which saves energy by eliminating the need for de novo synthesis. D. HGPRT converts hypoxanthine to uric acid to scavage nitrogen for use in de novo nucleotide biosynthesis. E. HGPRT is responsible for dephosphorylating nucleotides to form nucleosides, which are required for the synthesis of dNTPs.

A. HGPRT adds hypoxanthine to PRPP to form IMP, which is converted to GMP and AMP to replenish nucleotide pools.

What biochemical marker differentiates insulin-sensitive and insulin-resistant muscle cells? A. High levels of tyrosine phosphorylated IRS-1 in insulin-sensitive muscle cells B. High levels of tyrosine phosphorylated IRS-1 in insulin-resistant muscle cells C. Low levels of TNF-alpha receptor activation in insulin-resistant muscle cells D. High levels of serine phosphorylated IRS-1 in insulin-sensitive muscle cells

A. High levels of tyrosine phosphorylated IRS-1 in insulin-sensitive muscle cells

Which two statements below accurately describe the roles of insulin and glucagon in maintaining metabolic homeostasis? A. Insulin stimulates glucose uptake in muscle cells B. insulin stimulates glucose release from liver cells C. glucagon stimulates glucose uptake in liver cells D.insulin inhibits glucose uptake in the brain E. glucagon increases blood glucose levels in between meals F. glucagon stimulates glucose release from muscle cells

A. Insulin stimulates glucose uptake in muscle cells E. glucagon increases blood glucose levels in between meals

Explain why glyphosate works faster in the summer after rain than after two weeks without rain. A. It works faster after it rains because the plants rapidly use up phenylalanine, which becomes limiting in the presence of glyphosate. B. It does not work faster after it rains, it actually works less well because the glyphosate is oil based. C. It works faster after it rains because the roots take up the glyphosate that is sprayed on the dirt. D. It works faster after it rains because the leaves are not wilted and the glyphosate spray sticks better.

A. It works faster after it rains because the plants rapidly use up phenylalanine, which becomes limiting in the presence of glyphosate.

What explains why a mutation the HGPRT gene that does not affect the catalytic activity of the enzyme can result in a loss-of-function mutation in patients with Lesch-Nyhan syndrome? A. Mutations outside of the enzyme active site can cause protein misfolding that lead to protein degradation. B. The HGPRT enzyme is only active when it is phosphorylated and some mutations occur at serine and threonine residues, which block phosphorylation. C. The catalytic activity of an enzyme always requires protein-protein interactions that do not occur when there are amino acid substitutions. D. Some mutations change a negative charge to a positive charge, such as aspartate to lysine, and this change in charge causes the protein to aggregate. E. Loss-of-function mutations only occur outside of the enzyme active site, whereas gain-of-function mutations always occur within the active site.

A. Mutations outside of the enzyme active site can cause protein misfolding that lead to protein degradation.

In the human disease called severe combined immunodeficiency (ADA-SCID), ribonucleotide reductase activity is __________ because of an overabundance of __________. A. inhibited; dATP B. activated; dATP C. activated; cAMP D. Inhibited; cAMP

A. inhibited; dATP

What are three mechanisms by which cancer cells become resistant to the drug methotrexate? A. Over expression of drug transporter, DHFR mutation blocking drug binding, DHFR gene amplification B. Inactivation of the cell death pathway, blocking oncogenic kinase inhibitor, DHFR gene amplification C. DHFR gene amplification, thymidylate synthase mutation, mutation in membrane receptor binding D. Deletion of all copies of DHFR gene, DHFR mutation blocking drug binding, DHFR transporter mutation E. MDR inhibition of DHFR by DPD deficiency, Raltitrexed drug amplification, DHFR gene mutation.

A. Over expression of drug transporter, DHFR mutation blocking drug binding, DHFR gene amplification

Which of the following statements is a correct comparison of patients with type 1 versus patients with type 2 diabetes? A. Patients with Type 1 diabetes are generally of normal weight whereas patients with type 2 diabetes are often obese B. Patients with Type 1 diabetes are treated with metformin whereas patients with type 2 diabetes are treated with insulin C. Patients with Type 1 diabetes are resistant to insulin whereas patients with type 2 diabetes have enhanced sensitivity to insulin D. Patients with Type 1 diabetes can only be children whereas patients with type 2 diabetes can only be adults

A. Patients with Type 1 diabetes are generally of normal weight whereas patients with type 2 diabetes are often obese

What is the biochemical basis for giving individuals with hyperammonemia phenylbutyrate? A. Phenylbutyrate treatment leads to the production of phenylacetylglutamine, which is a soluble metabolite that reduces ammonia levels by removing glutamine. B. Phenylbutyrate treatment leads to the production of argininosuccinate, which is a soluble metabolite that reduces ammonia levels by removing aspartate. C. Phenylbutyrate treatment is used to reduce hyperammonemia by stimulating the expression of genes involved in nitrogen fixation and assimilation. D. Phenylbutyrate treatment removes ammonia by forming an insoluble precipitate that is excreted in the feces, which alleviates the symptoms of hyperammonemia. E. Phenylbutyrate treatment leads to the production of phenylacetylglutamate, which is a soluble metabolite that reduces ammonia levels by removing glutamate.

A. Phenylbutyrate treatment leads to the production of phenylacetylglutamine, which is a soluble metabolite that reduces ammonia levels by removing glutamine.

Why does it make sense that tadpoles (aquatic) have low levels of the enzyme arginase, but after metamorphosis into frogs (terrestrial), their arginase levels increase? A. Tadpoles living in water can excrete ammonia directly, but once on land, they need to excrete urea. B. The volume of water in a pond is so large that tadpoles can excrete ammonia directly and not die. C. Arginase is the enzyme that converts glutamine to glutamate and therefore required for urea cycle. D. Tadpoles develop into frogs when ammonia levels in the pond gets too high and they crawl on land. E. Frogs are able to walk around and excrete urea in lots of places, but tadpoles are confined to a pond

A. Tadpoles living in water can excrete ammonia directly, but once on land, they need to excrete urea.

It has been observed that some individuals with PKU have lighter skin than other individuals with PKU. What contributing factors explain this difference in pigmentation? A. The severity of the phenylalanine hydroxylase deficiency and the amount of tyrosine in the diet of the individual. B. The severity of the phenylalanine hydroxylase deficiency and the amount of time the individual with PKU is exposed to sunlight. C. Some PKU individuals are also albinos, while other individuals consume high levels of dietary protein. D. Some PKU individuals are also albinos and this affects the amount of phenylalanine they can have in their diet. E. The amount of phenylalanine in the diet and the amount of time the individual with PKU is exposed to sunlight.

A. The severity of the phenylalanine hydroxylase deficiency and the amount of tyrosine in the diet of the individual.

What nitrogen source is used to produce carbamoyl phosphate? A. ammonia B. urea C. alanine D. glutamine

A. ammonia

Which metabolite unique to the urea cycle connects the urea cycle to the citrate cycle through the "Krebs bicycle" pathway? A. argininosuccinate B. citrulline C. malate D. aspartate

A. argininosuccinate

What are the sources for the two nitrogens in urea? A. aspartate and carbamoyl phosphate B. asparagine and glutamine C. NH4+ and carbamoyl phosphate D. glutamate and glutamine

A. aspartate and carbamoyl phosphate

The molecule below is a precursor to the formation of which of the following second messengers? A. cAMP B. NAD+ C. ADP D. cGMP F. PKA

A. cAMP

It is important for proteolytic enzymes in the lysosome are optimized to work at low ph because low pH_____ A. enhances protein denaturing B. enhances the degradation of ubiquitinated proteins C. makes it easier for ATP to be converted to ADP + PI D. deavtivates cysteine proteases

A. enhances protein denaturing

After food enters the stomach, gastrin triggers the release of __________ and secretion of __________. A. gastric juices; pepsinogen B. secreton; enteropeptidase C. chime; enteropeptidase D. gastric juices; chyme

A. gastric juices; pepsinogen

Tyr122 is important in the mechanism of the E. coli ribonucleotide reductase. The function of this amino acid in the mechanism is to ________________. A. generate the Cys439 radical species B. carry out a nucleophilic attack on the substrate C. hydrogen-bond to the phosphates of the substrate D. coordinate water in the active site

A. generate the Cys439 radical species

What is the explanation for why leptin injections cause weight loss in the strain of ob/ob mutant mice, but leptin injections has no effect in the majority of people? A. ob/ob mutant mice lack leptin, and by providing it through injection, they are able to better maintain energy balance and metabolic homeostasis. In contrast, obese humans have chronically high leptin levels and are in fact leptin-insensitive. B. Leptin injections cause weight loss in ob/ob mice because they stimulate the increased expression of leptin receptors. Obese humans, in contrast, are producing too much leptin receptor and therefore leptin injections have no effect. C. ob/ob mice do not respond to leptin injections unless insulin is also provided. Obese humans will respond the same. D. ob/ob mice are insulin sensitive but leptin insensitive, and therefore the leptin injections stimulate insuling signaling, and increases metabolism. Obese humans are also insulin sensitive, but because they have the ob gene, do not respond via insulin signaling.

A. ob/ob mutant mice lack leptin, and by providing it through injection, they are able to better maintain energy balance and metabolic homeostasis. In contrast, obese humans have chronically high leptin levels and are in fact leptin-insensitive.

Arginine, leucine, and lysine are all essential amino acids. This means that they are ____ A. only available from dietary sources B. the main intermediates to the urea cycle C. produced from other intermediates D. not needed for a body to function

A. only available from dietary sources

A person who has alkaptonuria is easily diagnosed from their black urine. What causes the black color? A. oxidation of homogentisate B. oxidation of phenylalanine C. reduction of acetoacetyl - CoA D. phenylpyruvate and phenylacetate

A. oxidation of homogentisate

What two pathways provide the ATP needed to phosphorylate creatine during muscle contraction? A. oxidative phosphorylation and glycolysis B. fatty acid oxidation and muscle contraction C. glycolysis and gluconeogenesis D. electron transport system and oxidative phosphorylation

A. oxidative phosphorylation and glycolysis

A person who has phenylketonuria will have an excess amount of ___________ in the cell. A. phenylalanine B. alanine C. tyrosine D. pyruvate

A. phenylalanine

Diseases affecting heme biosynthesis as result of deficiences in the heme biosynthetic pathway are called _____ A. porphyria B. albinism C. phenylketonuria D. alkaptonuria

A. porphyria

Nucleotide salvage pathways are favored in cells over de novo nucleotide synthesis because of __________________. A. reduced energy expenditure. B. increased half-life of mRNA. C. increased variety of nucleotides produced. D. decreased regulation of nucleotide homeostasis.

A. reduced energy expenditure.

The overall activity of ribonucleotide reductase is regulated by allosteric binding of the activator _____ and the inhibitor______ to the activity site. A. ADP; dTTP B. ATP; dATP C. dGTP; ATP D. dUDP; ADP E. UMP; dGT

B. ATP; dATP

A phosphate-group carrier called ___(1)____ is used to provide chemical energy to muscle cellsin a phosphoryl transfer reaction catalyzed by the enzyme ___(2)_____. This reaction leads to the formationof ___(3)____ from ____(4)_____. This source of chemical energy is required for muscle ____(5)_______. A. (1) creatine; (2) glycogen phosphorylase; (3) ATP; (4) ADP; (5) contraction B. (1) phosphocreatine; (2) creatine kinase; (3) ATP; (4) ADP; (5) contraction C. (1) phosphocreatine; (2) creatine kinase; (3) ADP; (4) AMP; (5) relaxation D. (1) biotin; (2) AMP kinase; (3) ATP; (4) ADP; (5) cell division E. (1) phosphate; (2) creatine kinase; (3) ADP; (4) ATP; (5) contraction

B. (1) phosphocreatine; (2) creatine kinase; (3) ATP; (4) ADP; (5) contraction

A volunteer with Flying Samaritans brings a small boy to the local physician for treatment. Based on the background information listed below, what is the most likely biochemical basis for the boy's symptoms? =========== • The boy's body is hunched over and he is barely able to walk on his own • The physician noticed his wrists and ankles were thickened and enlarged • The patient's abdomen is distended and his breastbone is protruding • The volunteer measures his height and it is at the 30th percentile for age • The villagers live in a large cave during the day to avoid the hot sun A. Homogentisate 1,2-dioxygenase deficiency B. 1, 25-hydroxyvitamin D3 deficiency C. Porphobilinogen deaminase deficiency D. Hypoxanthine-guanine phosphoribosyltransferase deficiency E. Glucose-6P dehydrogenase deficiency

B. 1, 25-hydroxyvitamin D3 deficiency

Which FIVE of the following gene variants are good candidates to function as Thrifty Genes? 1) Acetyl-CoA carboxylase with high affinity for citrate 2) Glucokinase with decreased affinity for glucose 3) Decreased catalytic activity of fatty acyl-CoA synthetase 4) Hexokinase with decreased affinity for fructose 5) Acetyl-CoA carboxylase with low affinity for palmitoyl-CoA 6) Gherlin mutant with a low affinity for the ghrelin receptor 7) Decreased catalytic activity of fatty acid synthase 8) High basal level expression of Uncoupling Protein 1 9) Low activity lipoprotein lipase on the membrane of adipocytes A. 1, 8, 2, 7, 3 B. 1, 4, 2, 5, 3 C. 6, 8, 9, 7, 3 D. 4, 7, 2, 9, 8 E. 9, 6, 8, 5, 7

B. 1, 4, 2, 5, 3

In purines, __________ nitrogen atoms and __________ carbon atoms originate from glycine. A. 1; 1 B. 1; 2 C. 2; 1 D. 0; 2

B. 1; 2

Which FIVE of the following gene variants are good candidates to function as Thrifty Genes? 1) Acetyl-CoA carboxylase with high affinity for citrate 2) Glucokinase with decreased affinity for glucose 3) Increased catalytic activity of fatty acyl-CoA synthetase 4) Fructokinase with decreased affinity for fructose 5) Acetyl-CoA carboxylase with low affinity for palmitoyl-CoA 6) Ghrelin mutant with a low affinity for the ghrelin receptor 7) Increased catalytic activity of fatty acid synthase 8) Low basal level expression of Uncoupling Protein 1 9) High activity lipoprotein lipase on the membrane of adipocytes A. 1, 4, 2, 5, 3 B. 5, 8, 9, 7, 1 C. 1, 8, 2, 7, 3 D. 4, 7, 2, 3, 8 E. 9, 3, 8, 5, 7

B. 5, 8, 9, 7, 1

An oncologist has a patient with dihydropyrimidine dehydrogenase deficiency. Which of the following is a chemotherapy agent that the doctor should be cautious about using with this patient because of serious side effects? A. 5-dihydrothymine B. 5-fluorouracil C. primaquine D. -alanine

B. 5-fluorouracil

Explain how regulatory cross-talk mechanisms within purine biosynthetic pathways ensure that pools of ATP and GTP are balanced. A. Cross-talk refers to the communication between IMP and hypoxanthine, both of which are required for the synthesis of AMP and GMP. B. ATP is required for the GMP synthetase reaction leading to GMP production, and GTP is required for the adenylosuccinate synthetase reaction leading to AMP production. C. The level of ATP and GTP is regulated by cross-talk through a mechanism involving the ratio of R and T conformations in the enzyme adenylsuccinate synthetase. D. The level of ATP and GTP is regulated by cross-talk through a mechanism involving the ratio of R and T conformations in the enzyme GMP synthetase. E. AMP inhibits the activity of adenylosuccinate to limit GMP synthesis and GMP inhibits IMP dehydrogenase to limit AMP synthesis.

B. ATP is required for the GMP synthetase reaction leading to GMP production, and GTP is required for the adenylosuccinate synthetase reaction leading to AMP production.

What is the biochemical basis for allopurinol treatment of gout? A. Allopurinol dissolves uric acid crystals in the big toe by acting as an organic solvent. B. Allopurinol inhibits xanthine oxidase, which decreases the production of uric acid. C. Allopurinol inhibits PRPP synthetase, which decreases the production of uric acid. D. Allopurinol inhibits xanthine oxidase, which increases the production of urea to prevent uric acid synthesis. E. Allopurinol has a high affinity for urate, and when excreted in urine, it reduces the symptoms of gout.

B. Allopurinol inhibits xanthine oxidase, which decreases the production of uric acid.

What is the biochemical explanation for why rapid weight loss is reported with protein-rich diets? A. Dieters usually over-estimate how much weight they actually lose on a diet and the data are likely flawed. B. Amino acid degradation results in urea production to remove excess NH4+, so mostly water weight loss. C. A protein-rich diet is a high energy regimen that leads to nervous energy and a strong desire to exercise. D. The rapid weight loss is due to ketogenesis and the "melting" of fat away from the thighs and upper body.

B. Amino acid degradation results in urea production to remove excess NH4+, so mostly water weight loss.

What is the regulatory mechanism by which arginine stimulates flux through the urea cycle? A. arginine stimulates flux through the urea cycle by inhibiting the enzyme nitrogenase B. Arginine stimulates the production of the allosteric activator N-acetylglutamate C. Arginine stimulates the activity of carbamoyl phosphate synthetase I. D. Arginine stimulates the production of N-acetylglutamate which activates arginase

B. Arginine stimulates the production of the allosteric activator N-acetylglutamate

Which of the following reactions corresponds to the net reaction of the urea cycle? A. Aspartate + HCO3- + 2 ATP + NH4+ 1 ADP + Fumarate + 3 Pi + Urea + AMP B. Aspartate + HCO3- + 3 ATP + NH4+ 2 ADP + Fumarate + PPi + Urea + 2 Pi + AMP C. Fumarate + HCO3- + 3 ATP + NH4+ Aspartate + 2 ADP + PPi + Urea + 2 Pi + ADP D. Aspartate + 2 CO2 + 3 ATP + NH4+ 2 ADP + Fumarate + PPi + Urate + 2 Pi + AMP E. Aspartate + HCO3- + 3 ATP + 2 NH4+ Urea + 4 ADP + Fumarate + PPi + 2 Pi + ATP

B. Aspartate + HCO3- + 3 ATP + NH4+ 2 ADP + Fumarate + PPi + Urea + 2 Pi + AMP

Explain why recessive X-linked mutations, such as those found in the PRPP synthetase and HGPRT genes, will only be present 50% of the time in males born to mothers who are asymptomatic carriers of the mutation. A. Because carrier females donate one chromosome to each of their offspring, of which 50% are males and 50% are females. B. Because carrier females have one normal X chromosome and one X chromosome with the mutation; males have a 50% chance of receiving the mutated X chromosome. C. Because 50% of the males who receive the mutated X chromosome from their mothers are able to repair the mutation using DNA from the Y chromosome. D. Because males have an X and Y chromosome, so only 50% of their sex-linked chromosomes carry the mutation. E. Because fathers donate a X chromosome to male offspring and a Y chromosome to female offspring, so males have a 50% probability of inheriting the mutation.

B. Because carrier females have one normal X chromosome and one X chromosome with the mutation; males have a 50% chance of receiving the mutated X chromosome.

Hemoglobin is degraded by liver enzymes everyday. What is one of the products of hemoglobin degradation and what condition does it cause when accumulated in the blood? A. Phenylalanine metabolites; Phenylketonuria B. Bilirubin; jaundice C. Homogentisate; Alkaptonuria D. biliverdin; jaundice

B. Bilirubin; jaundice

If HCO3 that is radioactively labeled with 13C is available, which carbon atom in the molecule below would ultimately be expected to be radioactive? A. D B. C C. A D. B

B. C

Which statement describes how the pyrimidine biosynthetic pathway is allosterically-regulated? A. ATP binds to the regulatory subunit which shifts ATCase to the T-state. B. CTP binds to the regulatory subunit and inhibits ATCase activity. C. CTP binds to the active site to accomplish activate catalysis. D. The binding of ATP to ATCase changes the equilibrium of the reaction. E. ATP binding increases the standard change in free energy of the reaction.

B. CTP binds to the regulatory subunit and inhibits ATCase activity.

Fish food used in aquatic farming can minimally consist of just two required dietary nutrients. This is because fish excrete NH4+ directly into water and thereby avoid ammonia toxicity. Which diet below is sufficient and safe to be used as fish food in aquatic farming? Explain. Diet 1: carbohydrate + lipid Diet 2: protein + carbohydrates Diet 3: protein + lipid Diet 4: nucleic acid + lipid A. Diet 1; because it lacks protein, which can lead to ammonia toxicity; fish can use carbs for amino acids. B. Diet 3; because protein degradation yields carbohydrates; together providing proteins, carbs, and lipids. C. Diet 4; because purine degradation yields carbohydrates and fish need DNA/RNA for reproduction. D. Diet 1; because it has the carbon needed to synthesize all biomolecules; fish obtain NH4+ from water. E. Diet 2; because it lacks lipids, which are hydrophobic and will kill the fish due to formation of micelles.

B. Diet 3; because protein degradation yields carbohydrates; together providing proteins, carbs, and lipids.

What is the biochemical role of the E3 enzyme in the proteasomal degradation of proteins? A. E3 is ubiquitinated by E2, which then transfers ubiquitin to E1 B. E3 functions as a target protein binding site to facilitate ubiquitination by E2 C. E3 is a protease that cleaves the target protein before entering the proteasome D. E3 functions as a target protein binding site to facilitate phosphorylation by E2

B. E3 functions as a target protein binding site to facilitate ubiquitination by E2

Which of the five symptoms listed below are associated with undiagnosed Type 2 diabetes? A. Black urine B. Frequent urination C. Increased thirst D. Sensitivity to light E. Insomnia F. Blurred vision G. Psychotic episodes H. Slow-healing sores I. Obesity J. Loss of smell

B. Frequent urination C. Increased thirst F. Blurred vision H. Slow-healing sores I. Obesity

Glucagon-like peptide-1 (GLP-1) is a hormone peptide secreted by intestinal L cells. It is secreted in response to the nutrient detection in the small intestine. The resulting physiological response is the lowering of blood glucose levels. Which of the following is a potential mechanism for how GLP-1 causes this physiological response? A. GLP-1 decreases GLUT4 synthesis in muscle cells to decrease glucose uptake and lower blood glucose levels. B. GLP-1 stimulates insulin release by pancreatic beta cells to lower blood glucose levels. C. GLP-1 stimulates glucagon release by pancreatic alpha cells to lower blood glucose levels. D. GLP-1 increases the rate of apoptosis in pancreatic alpha cells to reduce glucagon and lower blood glucose levels.

B. GLP-1 stimulates insulin release by pancreatic beta cells to lower blood glucose levels.

Which of the following THREE statements are true regarding neuropeptides and appetite control? A. Orexigenic neurons decrease appetite. B. Ghrelin stimulates orexigenic signaling by binding to NPY/POMC neurons. C. Orexigenic neurons increase fat stores. D. Anorexigenic neurons send out signals that increase appetite. E. Anorexigenic neurons are responsible for increasing fat stores. F. Leptin and insulin in the fed state inhibit both POMC and NPY/AGRP neurons. G. Anorexigenic neurons send out signals that increase energy expenditure. H. PYY3-36 binding to NPY/AGRP neurons stimulates orexigenic signaling. I . Orexigenic neurons increase energy expenditure.

B. Ghrelin stimulates orexigenic signaling by binding to NPY/POMC neurons. C. Orexigenic neurons increase fat stores. G. Anorexigenic neurons send out signals that increase energy expenditure.

What biochemical marker differentiates insulin-sensitive and insulin-resistant muscle cells? A. High levels of serine phosphorylated IRS-1 in insulin-sensitive muscle cells. B. High levels of serine phosphorylated IRS-1 in insulin-resistant muscle cells. C. High levels phosphocreatine in insulin-resistant muscle cells. D. High levels of tyrosine phosphorylated IRS-1 in insulin-resistant muscle cells. E. Low levels of TNF-alpha receptor activation in insulin-resistant muscle cells.

B. High levels of serine phosphorylated IRS-1 in insulin-resistant muscle cells

What clinical test distinguishes between Type 1 and Type 2 diabetes? A. Drink glucose and measure blood glucose levels over time B. Inject insulin and measure blood glucose levels over time C. Drink water and measure urine production over time D. Measure levels of glycosylated hemoglobin over 3 month period

B. Inject insulin and measure blood glucose levels over time

Which of the following is the reaction for nitric oxide synthase? A. L-arginine + 1.5 NADPH + H+ + 2O2 --> citrulline + NO + 1.5 NADP+ B. L-arginine + 1.5 NADP+ + H+ + 2O2 ---> citrulline + NO + 1.5 NADPH C. L-arginine + 1.5 NADPH + H+ + 2O2 --> dopamine + NO + 1.5 NADP+ D. citrulline + NO + 1.5 NADP+ ---> L - arginine + 1.5 NADPH + H+ + 2O2

B. L-arginine + 1.5 NADP+ + H+ + 2O2 ---> citrulline + NO + 1.5 NADPH

What differentiates pyrimidine biosynthesis from purine biosynthesis? A. Undergoes less reactions than the than purine biosynthesis B. The base is built and then adds the ribose C. Generates IMP while purine biosynthesis does not. D. The base is built directly on the ribose E. The intermediate of pyrimidine biosynthesis is IMP

B. The base is built and then adds the ribose

Animals cannot synthesize tyrosine from shikimate-3P because they lack EPSP synthase. However, tyrosine is listed as a non-essential amino acid in most tables. What is the explanation? A. There are other pathways to synthesize tyrosine from shikimate-3P, so EPSP synthase is not required. B. Tyrosine can be synthesized from phenylalanine, and since phenylalanine is essential, tyrosine is not. C. Most animals do actually contain the enzyme EPSP synthase it is just not expressed all of the time. D. Tyrosine is essential until reaching puberty, and then after that, it is non-essential because of hormones. E. Tyrosine is not essential because it can be synthesized from tryptophan, and tryptophan is essential.

B. Tyrosine can be synthesized from phenylalanine, and since phenylalanine is essential, tyrosine is not.

When AMPK is bound by AMP and is phosphorylated at Thr172, ______ activity will ______ A. glycogen synthase; increase B. acetyl - CoA carboxylase; decrease C. hormone - sensitive lipase; decrease D. Phosphofructokinase - 2; decrease

B. acetyl - CoA carboxylase; decrease

What molecule signals the endothelial cell to produce NO? A. dopamine B. acetylcholine C. citrulline D. phosphate

B. acetylcholine

What molecule signals the endothelial cell to produce nitric oxide, and what is the enzymatic reaction? A. acteylcholine; citrulline + NO + 1.5 NADP+ --> L-arginine + 1.5 NADPH + H+ + 2O2 B. acetylcholine; L-arigine + 1.5 NADPH + H+ + 2O2 --> citrulline + NO + 1.5 NADP+ C. dopamine; L-arginine + 1.5 NADPH + H+ + 2O2 --> citrulline + NO + 1.5 NADP+ D. citrulline; L - arginine + 1.5 NADPH +H+ + 2O2 --> citulline + NO + 1.5 NADP+

B. acetylcholine; L-arigine + 1.5 NADPH + H+ + 2O2 --> citrulline + NO + 1.5 NADP+

Which of the following biomolecules is secreted by visceral fat? A. somatostatin B. adipokines C. glucagon D. phosphocreatine

B. adipokines

Which metabolite listed below serves as the biochemical link between the urea cycle and the citrate cycle? A. malate B. fumarate C. arginine D. ornithine

B. fumarate

Alanine, cysteine, glycine, and serine are all considered __________ amino acids. A. essential B. glucogenic C. urea D. ketogenic

B. glucogenic

Compared with a normal patient, a person with type 1 diabetes would display __________ during a glucose tolerance test. A. more rapid recovery to normal blood glucose levels after drinking the glucose solution B. higher starting blood glucose level C. more rapid rise in blood glucose levels after drinking the glucose solution D. reduction in blood glucose levels after drinking the glucose solution

B. higher starting blood glucose level

Which three processes show altered rates of metabolic flux in response to AMPK activation? A. increased fatty acid oxidation, decreased oxidative phosphorylation, increased gluconeogenesis B. increased fatty acid oxidation, increased oxidative phosphorylation, increased glycolytic flux C. decreased fatty acid oxidation, increased oxidative phosphorylation, decreased glycolytic flux D. increased fatty acid synthesis, increased glycogen synthesis, increased gluconeogenesis

B. increased fatty acid oxidation, increased oxidative phosphorylation, increased glycolytic flux

What is the effect of leptin receptor activation in NPY/AGRP first order neurons? A) Stimulation of NPY and AGRP gene expression through activation of JAK2/PI3K signaling B) Stimulation of catalytic activity of fatty acyl-CoA C) Inhibition of NPY and AGRP gene expression through activation of JAK2/PI3K signaling D) Increased fat storage E) Fully active AMPK

C) Inhibition of NPY and AGRP gene expression through activation of JAK2/PI3K signaling

Why does it makes sense that ghrelin stimulates orexigenic neurons? A. Because leptin stimulates anorexigenic neurons when you have extra fat. B. Because ghrelin is released from the brain when you exercise intensely. C. Because ghrelin is released from stomach cells when your stomach is empty. D. Because ghrelin is released from the intestines when your stomach is full of food. E. Because orexigenic neurons are the neurons that tell your brain to close your mouth.

C. Because ghrelin is released from stomach cells when your stomach is empty.

_____________ _______________ contains two subunits, R1 and R2, that function as a tetrameric complex (R12R22). The catalytic mechanism in _________ is unusual in that it depends on formation of a(n) ____________ to catalyze the reaction and requires contributions from a __________ iron center that is coordinated by an __________ ___________. A) Ribonucleotide synthase, S. pyogenes, free radical, mononuclear, oxide ion B) Ribonucleotide reductase, E. coli, antioxidant, dinuclear, oxide anion C) Ribonucleotide reductase, E. coli, free radical, dinuclear, oxide ion D) Ribonucleotide phosphorylase, S. pyogenes, antioxidant, oxide anion E) Ribonucleotide synthetase, E. coli, free radical, dinuclear oxide ion

C) Ribonucleotide reductase, E. coli, free radical, dinuclear, oxide ion

Fill in the missing amino acids using the single letter code for each. A. 1: V, 2:C, 3:P, 4:M B. 1: I, 2:P, 3:C, 4:V C. 1: L, 2:C, 3:P, 4:V D. 1: K, 2:S, 3:R, 4:F

C. 1: L, 2:C, 3:P, 4:V

All _____ amino acids are derived from just ______ metabolic intermediates, which are found in three metabolic pathways; _________, _________, and _______. A. 20, 7, glycolysis, fatty acid synthesis, citrate cycle B. 15, 5, glycolysis, pentose phosphate, citrate cycle C. 20, 7, glycolysis, pentose phosphate, citrate cycle D. 20, 9, glycolysis, pentose phosphate, urea cycle

C. 20, 7, glycolysis, pentose phosphate, citrate cycle

What are the three target enzymes involved in the allosteric regulation of pyrimidine biosynthesis? A. ATCase, CAD, UMP synthase B. CTP synthetase, UMP kinase, Dihydroorotase C. CAD, UMP synthase, CTP synthetase D. 5'-Nucleotidase, CAD, UMP synthase E. UMP kinase, ATCase, 5'-Nucleotidase

C. CAD, UMP synthase, CTP synthetase

Put the following steps in the correct order describing target protein polyubiquitination. Once you have numbered the steps, record your answer from top to bottom (a -> g) and choose A, B, C, D, or E. a. Step ___ E2 ubiquitinates a target protein Lys residue within the E2-ubiquitin-E3-target protein complex. b. Step ___ Ubiquitin is covalently attached to a cysteine residue in the E1 active site at position Gly76. c. Step ___ The polyubiquitinated target protein dissociates from the E2-E3 complex and is then degraded. d. Step ___ E1 associates with E2 and transfers ubiquitin to a cysteine residue in the enzyme active site. e. Step ___ A specific target protein binds to a specific E2-ubiquitin-E3 complex to initiate ubiquitination. f. Step ___ Three more ubiquitin moieties are attached to the target protein through a Gly76-Lys48 linkage. g. Step ___ E2-ubiquitin binds to an E3 enzyme to form a complex consisting of E2-ubiquitin-E3. A. 4, 2, 7, 1, 5, 6, 3 B. 5, 1, 6, 2, 3, 7, 4 C. 5, 1, 7, 2, 4, 6, 3 D. 5, 1, 7, 3, 4, 6, 2 E. 4, 1, 6, 2, 5, 7, 3

C. 5, 1, 7, 2, 4, 6, 3

Which statement below describes the structural basis for allosteric control by AMP and ATP of AMP-activated protein kinase (AMPK) catalytic activity ? A. AMP binding to AMPK breaks the formation of a salt bridge between R299-gamma and E364-alpha, which stimulates AMPK catalytic activity in the alpha subunit; ATP binding to AMPK facilitates formation of this salt bridge. B. AMP binding to AMPK facilitates formation of a salt bridge between R299-alpha and E364-gamma, which stimulates AMPK catalytic activity in the gamma subunit; ATP binding to AMPK does not form this salt bridge. C. AMP binding to AMPK facilitates formation of a salt bridge between R299-gamma and E364-alpha, which stimulates AMPK catalytic activity in the alpha subunit; ATP binding to AMPK does not form this salt bridge. D. AMP binding to AMPK facilitates formation of a salt bridge between R299-gamma and E364-alpha, which inhibits AMPK catalytic activity in the alpha subunit; ATP binding to AMPK does not form this salt bridge. E. AMP binding to AMPK facilitates formation of a covalent bond between R299-gamma and E364-alpha, which stimulates AMPK catalytic activity in the alpha subunit; ATP binding to AMPK does not form this salt bridge.

C. AMP binding to AMPK facilitates formation of a salt bridge between R299-gamma and E364-alpha, which stimulates AMPK catalytic activity in the alpha subunit; ATP binding to AMPK does not form this salt bridge.

What explains why protein-rich diets are associated with rapid weight loss in the first week? A. A protein-rich diet is a high energy regimen that leads to nervous energy and a strong desire to exercise. B. The rapid weight loss is due to ketogenesis and the "melting" of fat away from the thighs and upper body. C. Amino acid degradation results in urea production to remove excess NH 4+ , so mostly water weight loss. D. Dieters usually over-estimate how much weight they actually lose on a diet and the data are likely flawed. E. Glycogen is degraded quickly resulting in an increase in water retention, which is then excreted quickly.

C. Amino acid degradation results in urea production to remove excess NH 4+ , so mostly water weight loss.

How does metabolic flux change during starvation? A. An increase of fatty acid mobilization, glycolysis, ketogenesis, and uric acid production. B. An increase of fatty acid mobilization, glycolysis, uric acid production, and protein degradation. C. An increase of fatty acid mobilization, gluconeogenesis, ketogenesis, and protein degradation. D. A decrease of fatty acid mobilization, gluconeogenesis, and protein synthesis. E. There is very little change in metabolic flux as a result of starvation.

C. An increase of fatty acid mobilization, gluconeogenesis, ketogenesis, and protein degradation.

Explain how a deficiency in the enzyme dihydropyrimidine dehydrogenase (DPD) could lead to severe side effects in cancer treatments using 5-fluorouracil (5-FU) as a chemotherapeutic agent. A. 5-FU is an activator of DPD, and DPD is an activator of cancer cell death, so DPD deficiency is toxic. B. DPD converts 5-FU to fluorodihydrouracil, which is needed to kill cancer cells, so without it, too toxic. C. DPD degrades 5-FU so high doses need to be given, if DPD is deficient, then high 5-FU doses are toxic. D. Toxicity occurs when the 5-FU is converted to methotrexate by a DPD deficiency, leading to cell death E. DPD deficiency leads to 5-FU accumulation, which is then converted to a toxic form of tetrahydrofolate.

C. DPD degrades 5-FU so high doses need to be given, if DPD is deficient, then high 5-FU doses are toxic.

Explain how a deficiency in the enzyme dihydropyrimidine dehydrogenase (DPD) could lead to severe side effects in cancer treatments using 5-fluorouracil (5-FU) as a chemotherapeutic agent. A. Toxicity occurs when the 5-FU is converted to methotrexate by a DPD deficiency, leading to cell death B. DPD converts 5-FU to fluorodihydrouracil, which is needed to kill cancer cells, so without it, too toxic. C. DPD degrades 5-FU so high doses need to be given, if DPD is deficient, then high 5-FU doses are toxic. D. 5-FU is an activator of DPD, and DPD is an activator of cancer cell death, so DPD deficiency is toxic.

C. DPD degrades 5-FU so high doses need to be given, if DPD is deficient, then high 5-FU doses are toxic.

Which of the following is the net reaction of the urea cycle? A. Urea + Fumerate + 2 ADP + 2Pi + AMP + PPi NH+ + HCO3- + aspartate + 3ATP B. NH+ + HCO3 + aspartate + 2 ADP + 2Pi + AMP + PPi urea + fumerate + 3ATP C. NH+ + HCO3 + aspartate + 3ATP urea + fumerate + 2 ADP + 2Pi + AMP + PPi D. NH+ + HCO3 + fumerate + 3ATP urea + aspartate + 2 ADP + 2Pi + AMP + PPi

C. NH+ + HCO3 + aspartate + 3ATP urea + fumerate + 2 ADP + 2Pi + AMP + PPi

The conversion of ribose-1-phosphate to guanosine-5'-triphosphate via the salvage pathway would require the activity of several enzymes. Choose the answer that lists them in the order that they would act in this pathway. A. PRPP synthetase; phosphopentomutrase; kinase; kinase; phosphoribosyl transferase B. PRPP synthetase; phosphoribosyl transferase; phophopentomutase; kinase; kinase C. phosphopentomutase, PRPP synthetase; phosphoribosyl transferase D. phosphopentomutase; phosphoribosyl transferase; kinase; PRPP synthetase

C. phosphopentomutase, PRPP synthetase; phosphoribosyl transferase

Based on what is known about neuronal control of energy metabolism in humans, why is it so hard to lose weight by dieting? Choose the three correct answers. A. PYY3-36 is released when you have no food in your stomach and it inhibits the signal to the brain to eat more; metabolize less. Dieters are often so hungry that they eat so fast that the PYY3-36 inhibitory signal fails. B. Ghrelin levels decrease when your stomach is empty, which is one of the objectives of dieting, yet ghrelin signals to the brain to eat more; metabolize less. The net result is you always feel hungry and eventually give in. C. Food can be addictive to some people, much like narcotics. Therefore, the reward they get from binge eating leads to food cravings during diet-induced "withdrawal." D. Leptin levels decrease when fat deposits decrease, which in turn, decreases the signal to eat less; metabolize more. The net result is that you eat more; metabolize less because your body thinks you are starving. E. Insulin levels decrease when blood sugar decrease, which is one of the objectives of dieting, therefore it decreases the signal to eat less; metabolize more. The net result is that you eat more; metabolize less because your body thinks you are starving for sugar.

C. Food can be addictive to some people, much like narcotics. Therefore, the reward they get from binge eating leads to food cravings during diet-induced "withdrawal." D. Leptin levels decrease when fat deposits decrease, which in turn, decreases the signal to eat less; metabolize more. The net result is that you eat more; metabolize less because your body thinks you are starving. E. Insulin levels decrease when blood sugar decrease, which is one of the objectives of dieting, therefore it decreases the signal to eat less; metabolize more. The net result is that you eat more; metabolize less because your body thinks you are starving for sugar.

AMP-dependent protein kinase (AMPK) is activated by low energy charge in the cell, which is the result of direct AMP binding to the gamma subunit and phosphorylation of Thr172. Name TWO enzymes that are inhibited by AMPK activation and thereby lead to increased ATP synthesis and a higher energy charge? A. PGC1-alpha and cAMP response element binding protein B. Phosphofructokinase-2 and glycogen synthase C. Glycogen synthase and acetyl-CoA carboxylase D. Hormone-sensitive lipase and phosphofructokinase-2 E. Acetyl-CoA carboxylase and phosphofructokinase-2

C. Glycogen synthase and acetyl-CoA carboxylase

What is the biochemical mechanism of Viagra? A. It upregulates acetylcholine receptors on the endothelial cell membrane. B. It allosterically activates endothelial nitric oxide synthase, leading to increased production of nitric oxide. C. It prevents degradation of cGMP, thereby maintaining high levels of cGMP in smooth muscle cells. D. It increases cardiac output, resulting in greater blood flow. E. It transports nitric oxide from the endothelium to the smooth muscle

C. It prevents degradation of cGMP, thereby maintaining high levels of cGMP in smooth muscle cells

What is the biochemical basis for phenylketonuria and what is the treatment? A. PKU is caused by a defect in the enzyme phenylalanine hydroxylase, which leads to accumulation of toxic phenylalanine metabolites; PKU treatment is to remove phenylalanine metabolites using dialysis. B. PKU is caused by a defect in the enzyme phenylalanine hydroxylase, which limits phenylalanine needed for protein synthesis; PKU treatment is to add phenylalanine to the diet. C. PKU is caused by a defect in the enzyme phenylalanine hydroxylase, which leads to accumulation of toxic phenylalanine metabolites; PKU treatment is to limit phenylalanine in the diet. D. PKU is caused by a defect in the enzyme tyrosinase, which leads to accumulation of toxic tyrosine metabolites; PKU treatment is to limit tyrosine in the diet. E. PKU is caused by a defect in the dopamine producing cells, resulting in lower levels of dopamine and the onset of neurological symptoms; PKU treatment is to add dopamine to the diet.

C. PKU is caused by a defect in the enzyme phenylalanine hydroxylase, which leads to accumulation of toxic phenylalanine metabolites; PKU treatment is to limit phenylalanine in the diet.

A mutation in ____________ would decrease the synthesis of both AMP and GMP. A. GMP synthase B. IMP dehydrogenase C. PRPP synthetase D. adenylosuccinate synthetase

C. PRPP synthetase

Compare the function of pepsin with that of secretin. A. Pepsin cleaves trypsin, whereas secretin activates proteolytic zymogens. B. Pepsin denatures proteins, whereas secretin cleaves polypeptide bonds. C. Pepsin cleaves polypeptides, whereas secretin neutralizes pH back to 7. D. Pepsin activates trypsinogen, whereas secretin neutralizes pH back to 7.

C. Pepsin cleaves polypeptides, whereas secretin neutralizes pH back to 7.

Undiagnosed phenylketonuria (PKU) can lead to severe neuronal damage and mental incapacity, which is avoidable if the disease is diagnosed at birth. In contrast, albinism is easly diagnosed at birth, but there is no treatment, which leads to an increased risk of skin cancer in these patients. Choose three statements that explain the reasons for these differences. A. It is easy to treat PKU because phenylalanine can be metabolized by other pathways to avoid neuronal damage, whereas albinos would need to eat excess tyrosine to produce pigments and not too many foods contain tyrosine. B. PKU individuals can avoid the damaging effects of pyruvate metabolites by limiting the amount of Splenda in their food. In contrast, albinos cannot avoid sun exposure and eventually die of malignant melanoma. C. Phenylalanine is found in many types of food, including aspartame, and therefore by avoiding foods with high amounts of phenylalanine, the build-up pyruvate metabolites can be controlled. In contrast, skin pigments must be made from tyrosine and there is no way to do this if tyrosine metabolism is compromised. D. PKU is the result of substrate accumulation, which can be avoided using a restricted diet. However, albinism is due to a missing product, which cannot be replaced through injections or dietary regimens. E. Defects in the enzyme tyrosinase occur in every cell of the body and there is no way to replace this enzyme without embryonic human gene therapy. In contrast, defects in the enzyme phenylalanine hydroxylase can be ameliorated by restricting certain amino acids in the diet. F. Albinism is not a disease it is a lifestyle choice, whereas PKU is recessive disease that protects people from skin cancer. G. Phenylketonuria is caused by insufficient tyrosine, which is why PKU individuals have light skin at birth. In contrast, albinism is cause by too many white pigments that accumulate when the enzyme tyrosinase is mutated.

C. Phenylalanine is found in many types of food, including aspartame, and therefore by avoiding foods with high amounts of phenylalanine, the build-up pyruvate metabolites can be controlled. In contrast, skin pigments must be made from tyrosine and there is no way to do this if tyrosine metabolism is compromised. D. PKU is the result of substrate accumulation, which can be avoided using a restricted diet. However, albinism is due to a missing product, which cannot be replaced through injections or dietary regimens. E. Defects in the enzyme tyrosinase occur in every cell of the body and there is no way to replace this enzyme without embryonic human gene therapy. In contrast, defects in the enzyme phenylalanine hydroxylase can be ameliorated by restricting certain amino acids in the diet.

Explain why cells with defects in thymidine kinase grow in media containing high amounts of 5-bromodeoxyuridine [BrdU], whereas cells with normal thymidine kinase will die when exposed to BrdU? A. Thymidine kinase is required for the thymidylate synthase reaction to work. B. When thymidine kinase is not present, protein phosphatase dephosphorylates BrdU preventing its incorporation into RNA C. When thymidine kinase is lacking, BrdU does not become phosphorylated and hence cannot be incorporated into DNA. D. Without thymidine kinase, the BrdU is phosphorylated by Dihydrofolate Reductase and inactivated.

C. When thymidine kinase is lacking, BrdU does not become phosphorylated and hence cannot be incorporated into DNA.

The twenty amino acids needed for protein synthesis can be categorized in animals as essential or nonessential with regard to dietary sources. Answer the three questions below. a) What is a characteristic of the biosynthetic pathways needed to generate essential amino acids? b) Why is arginine an essential amino acid even though it is generated by arginase in the urea cycle? c) Why is tyrosine a nonessential amino acid in animals since they don't have the shikimate pathway? A. a) metabolic pathways that synthesize essential amino acids require NADPH; nonessential amino acid pathways require NADH; b) arginase does not generate enough arginine in the urea cycle to support protein synthesis; c) tyrosine is generated from phenylalanine, which is an essential amino acid B. a) metabolic pathways that synthesize essential amino acids require many enzymes; b) even though arginine is synthesized in animals by de novo pathways it is consumed by the urea cycle; c) tyrosine is generated from phenylalanine, which is an essential amino acid in animals C. a) metabolic pathways to synthesize essential amino acids require many enzymes; b) arginase does not generate enough arginine in the urea cycle to support protein synthesis; c) tyrosine is generated from phenylalanine, which is an essential amino acid in animals D. a) metabolic pathways to synthesize essential amino acids require many enzymes b) arginase does not generate enough arginine in the urea cycle to support protein synthesis c) tyrosine is synthesized de novo by the same enzymes that synthesize alanine and pyruvate E. a) metabolic pathways to synthesize essential amino acids require very few enzymes b) arginase generates enough arginine for protein synthesis, however it is degraded by glyphosate c) tyrosine is generated from tryptophan, which is an essential amino acid in animals

C. a) metabolic pathways to synthesize essential amino acids require many enzymes; b) arginase does not generate enough arginine in the urea cycle to support protein synthesis; c) tyrosine is generated from phenylalanine, which is an essential amino acid in animals

Angina patients sometimes carry nitroglycerine pills with them____ A. as a source of ammonia for muscle relaxation B. to inhibit cGMP phosphodiesterase C. as a rapid source of NO for blood vessel dilation D. to increase heart rate during a heart attack E. to inhibit acetylcholine release from neurons

C. as a rapid source of NO for blood vessel dilation

Angina patients sometimes carry nitroglycerine pills with them___________ A. to inhibit cGMP phosphodiesterase B. to inhibit acetylcholine release from neurons C. as a rapid source of NO for blood vessel dilation D. as a source of ammonia for muscle relaxation E. to increase heart rate during a heart attack.

C. as a rapid source of NO for blood vessel dilation

Thrifty genes are __________ during times of starvation and __________ when physical activity is low. A. beneficial; beneficial B. detrimental; beneficial C. beneficial; detrimental D. detrimental; detrimental

C. beneficial; detrimental

15N-labeled aspartate is provided to bacteria during the biosynthesis of pyrimidine trinucleotides. The radiolabeled nitrogen would ultimately be found in____________. A. CTP but not UTP. B. UTP but not CTP. C. both UTP and CTP. D. neither UTP or CTP.

C. both UTP and CTP.

Partial inhibition of lipoprotein lipase would______________. A. prevent neurons in the brain from using free fatty acids as an energy source. B. increase rates of glycogen breakdown in heart muscle cells. C. decrease the level of ketone bodies in the blood. D. decrease liver lactate dehydrogenase activity.

C. decrease the level of ketone bodies in the blood

What is the mechanism by which glyphosate, the active ingredient in Roundup, kills plants? A. glyphosate is an allosteric activator to plant EPSP synthase B. glyphosate binds to tyrosine and prevents incorporation into proteins C. glyphosate is a competitive inhibitor of plant EPSP synthase D. glyphosate inhibits the production of aspartate, alanine, and glycine

C. glyphosate is a competitive inhibitor of plant EPSP synthase

Ketogenesis stimulated during starvation because it leads to______________. A. increased protein synthesis and increased glycolysis. B. decreased fatty acid oxidation and increased acetyl-CoA oxidation. C. increased gluconeogenesis and increased fatty acid oxidation. D. increased liver glycolysis and increased adipocyte fatty acid synthesis. E. increased acetyl-CoA oxidation and increased fatty acid synthesis.

C. increased gluconeogenesis and increased fatty acid oxidation.

Dihydropyrimidine dehydrogenase deficiencies can lead to toxic side effects from high doses of 5-fluorouracil because 5-fluorouracil __________ dihydropyrimidine dehydrogenase A. is activated by B. is inhibited by C. is degraded by D. denatured by

C. is degraded by

The disease ADA-SCID is due to __________ than normal activity of the enzyme __________. A. higher; adenosine deaminase B. higher; xanthine oxidase C. lower; ribonucleotide reductase D. lower; HGPRT

C. lower; ribonucleotide reductase

A compound is added to a cell and dihydrofolate reductase activity is reduced. If this compound is __________, it can be predicted that a similar result would be seen if __________ were added instead. A. aminopterin; raltitrexed B. aminopterin; fluorodeoxyuridine--monophosphate C. methotrexate; aminopterin D. methotrexate; raltitrexed

C. methotrexate; aminopterin

Nitrogen in biological compounds ultimately comes from ___________. A. hemoglobin B. ammonia C. nitrogen gas D. nucleotides E. nitrate

C. nitrogen gas

The conversion of ribose-1-phosphate to ATP via the salvage pathway would require the activity of several enzymes. Choose the answer that lists them in the order that they would act in this pathway. A. phosphopentomutase; phosphoriboxyl transferase; kinase; PRPP synthetase; kinase B. PRPP synthetase; phosphoriboxyl transferase; phosphopentomutase; kinase; kinase C. phosphopentomutase; PRPP synthetase; phosphoriboxyl transferase; kinase; kinase D. PRPP synthetase; phosphopentomutase; kinase; kinase; phosphoriboxyl transferase

C. phosphopentomutase; PRPP synthetase; phosphoriboxyl transferase; kinase; kinase

Insulin signaling in liver cells activates the enzyme __________, which in turn activates the enzyme __________. A. protein phosphatase 2A; glycogen synthase B. protein phosphatase 1; phosphorylase kinase C. protein phosphatase 2A; acetyl-CoA carboxylase D. protein phosphatase 1; glycogen phosphorylase

C. protein phosphatase 2A; acetyl-CoA carboxylase

Binding of ATP to the ______ subunit shifts ATCase to the ______ state, whereas ______ binding to the regulatory subunit stabilizes the ______ state. A. regulatory; T; CTP; R B. catalytic; R; GTP; T C. regulatory; R; CTP; T D. catalytic; R; CTP; T

C. regulatory; R; CTP; T

In what four biochemical processes can you find the nucleotide base adenine? A. gene mutations, signal transduction, acid-base catalysis, energy conversion B. coenzyme function, signal transduction, energy conversion, passive transport C. signal transduction, coenzyme function, energy conversion, genetic information D. energy conversion, genetic information, ubiquitination, coenzyme function

C. signal transduction, coenzyme function, energy conversion, genetic information

What are three mechanisms by which cancer cells become resistant to the drug methotrexate? A. 1) DHFR gene amplification, 2) thymidylate synthase mutation, 3) mutation in membrane receptor binding B. 1) MDR inhibition of DHFR by DPD deficiency, 2) Raltitrexed drug amplification, 3) DHFR gene mutation. C. 1) Deletion of all copies of DHFR gene, 2) DHFR mutation blocking drug binding, 3) DHFR transporter mutation D. 1) Overexpression of drug transporter, 2) DHFR mutation blocking drug binding, 3) DHFR gene amplification

D. 1) Overexpression of drug transporter, 2) DHFR mutation blocking drug binding, 3) DHFR gene amplification

Put the following steps in the correct order for the ribonucleotide reductase reaction. Once you have numbered the steps, record your answer from top to bottom (a à e) and choose A, B, C, D, or E. a. Step ___ The hydroxyl group on C-2' of the ribose ring gains a proton from C225 residue. b. Step ___ A thiyl free radical removes a hydrogen atom from the C-3' position of the ribose ring. c. Step ___ Deoxynucleoside diphosphate is released and a disulfide bond is reduced by thioredoxin. d. Step ___ A free radical at Y122 abstracts a hydrogen atom from C439 to form a cysteine thiyl radical. e. Step ___ Cation on C-2' is reduced by C462 creating the deoxynucleotide A. 2, 3, 5, 1, 4 B. 3, 2, 4, 1, 5 C. 3, 1, 5, 2, 4 D. 3, 2, 5, 1, 4 E. 2, 3, 4, 1, 5

D. 3, 2, 5, 1, 4

What THREE biochemical mechanisms determine glucose-6P flux through metabolic pathways? 1. Ratio of NADPH to NAD+ in the cell under conditions of oxidative stress 2. Configuration of C-C bonds in glucose-6P (cis or trans) 3. Levels of acetyl-CoA in liver cells before breakfast 4. Bioavailability of glucose-6P (concentration) when used as a substrate 5. Activity level of enzymes (allosteric control) for which glucose-6P is a substrate 6. Bioavailability of enzymes (cell localization) for which glucose-6P is a substrate 7. Level of DNA and RNA synthesis under low atmospheric pressure A. 2, 4, 6 B. 1, 3, 5 C. 1, 2, 3 D. 4, 5, 6 E. 1, 3, 7

D. 4, 5, 6

Why does it make sense that leptin and insulin both lead to stimulation of anorexigenic neurons? A. Leptin stimulates the orexigenic neurons, and insulin stimulates the anorexigenic neurons. This combined signalling leads to increase energy expenditure and decreased appetite. B. Both leptin and insulin lead to stimulation of orexigenic neurons, such that appetite increases and metabolic rate decreases. C. Leptin signals low fat storage, whereas insulin signals that blood glucose levels are high. In both cases, energy balance will be obtained with decreased appetite and increased energy expenditure. D. Both leptin and insulin lead to stimulation of anorexigenic neurons, such that appetite decreases and basal metabolic rate increases.

D. Both leptin and insulin lead to stimulation of anorexigenic neurons, such that appetite decreases and basal metabolic rate increases.

What enzyme is present in genetically-modified organism (GMO)crops called Round-Up-Ready? A. Shikimate-3-phosphatase B. CP4 ESPS synthetase C. Glyphosatase D. CP4 EPSP synthase E. Chorismate synthase

D. CP4 EPSP synthase

Which of the three proteins in the ubiquination pathway is the most responsible for recognizing the ubiquinated target protein? A.E2 B.E1 C. all three of the proteins recognize the target protein D. E3

D. E3

Which digestive protease is responsible for initiating the proteolytic cascade in the small intestine? A. trypsinogen B. proelastase C. trypsin D. Enteropeptidase

D. Enteropeptidase

The conversion of hypoxanthine to IMP is catalyzed by __________, which is deficient in __________. A. adenosine deaminase; ADA-SCID B. xanthine oxidase; Lesch-Nyhan syndrome C. purine nucleoside phosphorylase; ADA-SCID D. HGPRT; Lesch-Nyhan syndrome

D. HGPRT; Lesch-Nyhan syndrome

The conversion of hypoxanthine to IMP is catalyzed by __________, which is deficient in __________. A. purine nucleoside phosphorylase; ADA-SCID B. xanthine oxidase; Lesch-Nyhan syndrome C. adenosine deaminase; ADA-SCID D. HGPRT; Lesch-Nyhan syndrome

D. HGPRT; Lesch-Nyhan syndrome

Normal blood glucose concentration is considered to be 4.5 mM. Changes in blood glucose can lead to changes such that the level of insulin is greater than the level of glucagon (insulin>glucagon) or the level of insulin is less than that of glucagon (insulin<glucagon). Which statement correctly describes the ratio of insulin to glucagon release by the pancreas and how this ratio is affected by changes in serum glucose? A. Insulin is only released when blood glucose is less than 4.5 mM, whereas glucagon is only released if this concentration increases above 4.5 mM. Insulin and glucagon are not present at the same time. B. Insulin and glucagon are released continuously at different levels; insulin>glucagon when glucose in the blood is below 4.5 mM, whereas insulin<glucagon if this concentration increases above 4.5 mM. C. Insulin is released from the pancreas only when blood glucose levels exceed 4.5 mM, whereas glucagon is released only when blood glucose levels are below 4.5 mM; they are never released at the same time. D. Insulin and glucagon are secreted continuously at different levels; insulin>glucagon when glucose in the blood exceeds 4.5 mM, whereas insulin<glucagon if this concentration drops below 4.5 mM. E. Insulin is released when blood glucose levels fall below 4.5 mM and glucagon is release when blood glucose levels fall below 4.5 mM. These two hormones are always present in the blood at high levels

D. Insulin and glucagon are secreted continuously at different levels; insulin>glucagon when glucose in the blood exceeds 4.5 mM, whereas insulin<glucagon if this concentration drops below 4.5 mM.

What two problems have been identified as a result of overuse of glyphosate in agriculture? A. Cows and goats develop skin rashes and fish often have mutations in their fins and gills. B. Round-Up Ready soybeans and carrots grow slower and Round-Up Ready corn grows faster. C. Processed foods made from RoundUp-Ready crops turn yellow quickly and milk tastes like metal. D. Native plants become glyphosate-resistance and increased human health problems, including cancer. E. Bacteria become resistant to glyphosate causing microbiome mutations and plants grow too fast

D. Native plants become glyphosate-resistance and increased human health problems, including cancer.

Why don't brain and muscle respond to glucagon that is released from the pancreas in response to low blood glucose levels? A. There are no glucagon membrane transporters in these cell types. B. The glucagon intracellular signaling cascade is tissue specific. C. The insulin receptors in these cell types inhibit glucagon receptor signaling. D. Skeletal muscle and brain cells do not contain glucagon receptors.

D. Skeletal muscle and brain cells do not contain glucagon receptors.

Why does it make sense that tadpoles (which live in water) have low levels of the enzyme arginase, but after metamorphosis into frogs (which live on land), their arginase levels increase? A. Tadpoles develop into frogs when ammonia levels in the pond gets too high and they crawl on land. B. Arginase is the enzyme that converts glutamine to glutamate and therefore required for urea cycle. C. The volume of water in a pond is so large that tadpoles can excrete ammonia directly and not die. D. Tadpoles living in water can excrete ammonia directly, but once on land, they need to excrete urea.

D. Tadpoles living in water can excrete ammonia directly, but once on land, they need to excrete urea.

What explains why the DHFR mutant L22R has a decreased affinity for the drug methotrexate (MTX)? A. The negative charge on Arg blocks MTX binding to the active site. B. Leu in the active site is hydrophilic and H-bonds with MTX; Arg is hydrophobic. C. Leu forms a salt bridge with MTX and Arg forms a covalent bond. D. The positive charge on Arg blocks MTX binding to the active site.

D. The positive charge on Arg blocks MTX binding to the active site.

Thrifty genes are ___ during times of starvation and ___ when physical activity is low A. detrimental; beneficial B. detrimental; detrimental C. beneficial; beneficial D. beneficial; detrimental

D. beneficial; detrimental

In the duodenum, enteropeptidase.... A. neutralizes the pH of the duodenum B. generates peptides and amino acids C. cleaves chymotrypsinogen to form chymotrypsin D. cleaves trypsinogen to form trypsin

D. cleaves trypsinogen to form trypsin

The shikimate pathway involves the ________________. A. condensation of oxaloacetate and shikimate. B. synthesis of essential amino acids from pyruvate. C. synthesis of essential amino acids from oxaloacetate. D. condensation of phosphoenolpyruvate and erythrose-4-phosphate.

D. condensation of phosphoenolpyruvate and erythrose-4-phosphate.

Which enzyme activity would be directly inhibited by the addition of methotrexate? A. thymidine kinase B. serine hydroxymethyltransferase C. thymidylate synthase D. dihydrofolate reductase

D. dihydrofolate reductase

If the genomes of 100 different species were analyzed, gene sequences for which enzyme required for deoxyribonucleotide biosynthesis would most likely to be found in all of them? A. glutaredoxin B. thioredoxin C. glutathione reductase D. ribonucleotide reductase

D. ribonucleotide reductase

Regulation of protein ubiquitination is most often mediated by modification of_____________. A. E1 ubiquitin ligase complex. B. the E2-ubiquitin-E3 complex. C. target proteins and E1 ligases. D. target proteins and E3 ligases. E. E1 and E2 ligases.

D. target proteins and E3 ligases.

What would happen if purified leptin were injected daily into the db/db (diabetes) mouse compared to a littermate (db/db) mouse that did not get leptin injections? A. the mouse without leptin will be fatter than the mouse with leptin B. the mouse with leptin will be thinner than the mouse without leptin C. the mouse with leptin will be fatter than the mouse without leptin D. the mouse with leptin will be as fat as the mouse without leptin

D. the mouse with leptin will be as fat as the mouse without leptin

Fluorodeoxyuridine--monophosphate is an inhibitor of the enzyme____________. A. dihydrofolate reductase B. serine hydroxymethyltransferase C. ribonucleotide reductase D. thymidylate synthase E. thymidine kinase

D. thymidylate synthase

What is the relative activity of AMP-bound AMPK in the absence and presence of Thr172 phosphorylation? A) AMP-bound AMPK activity is lower in the presence of Thr172 phosphorylation B) Thr172 phosphorylation has nothing to do with AMP-bound AMPK C) AMP-bound AMPK activity is highest when Thr172 is unphosphorylated D) The presence of Thr172 phosphorylation only affects AMP-bound AMPK activity in certain contexts. E) AMP-bound AMPK activity is higher in the presence of Thr172 phosphorylation.

E) AMP-bound AMPK activity is higher in the presence of Thr172 phosphorylation.

Which FOUR of the following gene variants are good candidates to function as Thrifty Genes? 1) Acetyl-CoA carboxylase with high affinity for citrate 2) Glucokinase with decreased affinity for glucose 3) Decreased catalytic activity of fatty acyl-CoA synthetase 4) Hexokinase with decreased affinity for fructose 5) Acetyl-CoA carboxylase with low affinity for palmitoyl-CoA 6) Gherlin mutant with a low affinity for the ghrelin receptor 7) Decreased catalytic activity of fatty acid synthase 8) High basal level expression of Uncoupling Protein 1 9) Low activity lipoprotein lipase on the membrane of adipocytes A. 4, 7, 2, 8 B. 6, 8, 9, 7 C. 6, 8, 5, 7 D. 8, 2, 7, 3 E. 1, 4, 5, 3

E. 1, 4, 5, 3

How does a defect in adenosine deaminase (ADA) cause the immune disease ADA-SCID? A. Cells are no longer able to control the level of dNTPs because of the ADA defect, so immune cells die. B. ADA deficiency causes a buildup of 2'-deoxyribose-5P, which can be toxic at high levels to immune cells. C. ADA-SCID is caused by mutations in the R1 subunit of ribonuclease reductase disrupting thiyl formation. D. ADA deficiency blocks the production of ribose-5P, so without ribose-5P, immune cells cannot divide. E. ADA defect increases dATP, which inhibits ribonucleotide reductase and decreases immune cell division

E. ADA defect increases dATP, which inhibits ribonucleotide reductase and decreases immune cell division

Which statement below describes the structural basis for allosteric control of the catalytic activity of the regulatory enzyme AMP-activated protein kinase (AMPK) by the metabolites AMP and ATP? A. AMP binding to AMPK facilitates formation of a salt bridge between R299-a and E364-g, which stimulates AMPK catalytic activity in the g subunit; ATP binding to doesn't form a salt bridge. B. AMP binding to AMPK facilitates formation of a covalent bond between R299-g and E364-a, which stimulates AMPK catalytic activity in the a subunit; ATP binding to AMPK does not form this salt bridge. C. AMP binding to AMPK facilitates formation of a salt bridge between R299-g and E364-a, which inhibitsAMPK catalytic activity in the a subunit; ATP binding to AMPK does not form this salt bridge. D. AMP binding to AMPK breaks the formation of a salt bridge between R299-g and E364-a, which stimulates AMPK catalytic activity in the a subunit; ATP binding facilitates formation of this salt bridge. E. AMP binding to AMPK facilitates formation of a salt bridge between R299- g and E364- a, which stimulates AMPK catalytic activity in the alpha subunit; ATP binding does not form this salt bridge

E. AMP binding to AMPK facilitates formation of a salt bridge between R299- g and E364- a, which stimulates AMPK catalytic activity in the alpha subunit; ATP binding does not form this salt bridge

Regulation of aspartate transcarbamoylase (ATCase) by nucleotides controls flux through the pyrimidine biosynthetic pathway in bacteria. Choose the two true statements below that describe this regulation A. aspartate is an allosteric inhibitor of ATCase activity B. ATP is an allosteric inhibitor of ATCase activity C. Aspartate is an allosteric activator of ATCase activity D. CTP is an allosteric activator of ATCase activity E. ATP is an allosteric activator of ATCase activity F. CTP is an allosteric inhibitor of ATCase activity

E. ATP is an allosteric activator of ATCase activity F. CTP is an allosteric inhibitor of ATCase activity

What makes the ribonucleotide reductase reaction mechanism so unusual compared to other enzyme-mediated mechanisms? A. It generates ribonucleotides from deoxyribonucleotides. B. It involves the formation of covalent intermediate C. It involves the amino acids tyrosine and threonine. D. There is a disulfide bond formed on thioredoxin. E. It is dependent on the formation of a free radical

E. It is dependent on the formation of a free radical

People with argininosuccinase deficiency have decreased ability to convert argininosuccinateinto arginine in the urea cycle. Why is supplementing with L-arginine the best treatment for this disorder? A. Urea is produced from arginine, allowing for excretion of nitrogenous waste obtained from L-arginine. B. L-arginine activates argininosuccinase, thereby increasing production of arginine endogenously. C. L-arginine activates the Krebs Bicycle, thereby increase nitrogen flux through the citrate cycle. D. L-arginine is a transcription factor that upregulates gene expression of the arginosuccinase enzyme E. Ornithine is produced from arginine, allowing for nitrogen to be excreted in the form of argininosuccinate.

E. Ornithine is produced from arginine, allowing for nitrogen to be excreted in the form of argininosuccinate.

5. Ribose sugar in ribonucleosides and deoxyribonucleosides is derived from which pathway? A. Glycogen synthesis B. Krebs bicycle C. Fatty acid synthesis D. Ketogenesis E. Pentose Phosphate

E. Pentose Phosphate

How do GLP-1 agonists result in a) increased insulin-sensitivity and b) weight loss? A. a) by decreasing glucagon secretion; b) by increasing secretion of alpha-MSH from POMC neurons. B. a) by increasing insulin receptor expression; b) by increasing secretion of AGRP from POMC neurons. C. a) by increasing flux through gluconeogenesis; b) by decreasing secretion of NPY from POMC neurons. D. a) by increasing glucagon secretion; b) by increasing rates of gastric clearing and food absorption. E. a) by increasing insulin secretion; b) by increasing secretion of alpha-MSH from POMC neurons.

E. a) by increasing insulin secretion; b) by increasing secretion of alpha-MSH from POMC neurons.

The twenty amino acids needed for protein synthesis can be categorized in animals as essential or nonessential with regard to dietary sources. a) What is a characteristic of the biosynthetic pathways needed to generate essential amino acids? b) Why is arginine an essential amino acid even though it is generated by arginase in the urea cycle? c) Why is tyrosine a nonessential amino acid in animals even though they do not contain shikimate pathway enzymes? Choose: Option 1: a) metabolic pathways to synthesize essential amino acids require many enzymes b) arginase does not generate enough arginine in the urea cycle to support protein synthesis c) tyrosine is synthesized de novo by the same enzymes that synthesize alanine and pyruvate Option 2: a) metabolic pathways to synthesize essential amino acids require NADPH; pathways for nonessential amino acid pathways require NADH b) arginase does not generate enough arginine in the urea cycle to support protein synthesis c) tyrosine is generated from phenylalanine, which is an essential amino acid in animals Option 3: a) metabolic pathways to synthesize essential amino acids require many enzymes b) arginase does not generate enough arginine in the urea cycle to support protein synthesis c) tyrosine is generated from phenylalanine, which is an essential amino acid in animals Option 4: a) metabolic pathways to synthesize essential amino acids require many enzymes b) even though arginine is synthesized in animals by de novo pathways it is consumed by the urea cycle c) tyrosine is generated from phenylalanine, which is an essential amino acid in animals Option 5: a) metabolic pathways to synthesize essential amino acids require very few enzymes b) arginase generates enough arginine for protein synthesis, however it is degraded by glyphosate c) tyrosine is generated from tryptophan, which is an essential amino acid in animals

Option 3: a) metabolic pathways to synthesize essential amino acids require many enzymes b) arginase does not generate enough arginine in the urea cycle to support protein synthesis c) tyrosine is generated from phenylalanine, which is an essential amino acid in animals

Treatment of type 2 diabetics with GLP-1 agonists have been associated with weight loss and decreased A1C values, which reflect the percent of glycosylated hemoglobin in blood. A1C values are directly correlated to serum glucose levels over a 3-month period. Put the following steps in the correct order to explain how dulaglutide (Trulicity) injections result in weight loss and decreased A1C values by suppressing appetite and increasing energy expenditure. _____GLP-1 receptor signaling activates POMC gene expression. ______Patient loses weight and has decreased blood glucose levels. ______ Trulicity binds to the GLP-1 receptor on POMC neurons. ____Reduced percentage of glycosylated hemoglobin is reflected in a lower A1C value. _____ Alpha-MSH is secreted from POMC neurons. _____POMC protein is processed to generate alpha-MSH hormone. _____Activation of MC4 receptors on anorexigenic neurons. _____Neuronal signaling by anorexigenic neurons suppresses appetite and increases energy expenditure.

__2__GLP-1 receptor signaling activates POMC gene expression. __7__Patient loses weight and has decreased blood glucose levels. __1__Trulicity binds to the GLP-1 receptor on POMC neurons. __8__Reduced percentage of glycosylated hemoglobin is reflected in a lower A1C value. __4__Alpha-MSH is secreted from POMC neurons. __3__POMC protein is processed to generate alpha-MSH hormone. __5__Activation of MC4 receptors on anorexigenic neurons. __6__Neuronal signaling by anorexigenic neurons suppresses appetite and increases energy expenditure.

Put the following steps in the correct order describing the excretion of nitrogen derived from amino acid degradation in the form of urea. _____Carbamoyl phosphate is combined with ornithine to form citrulline. _____Citrulline is exported from the mitochondrial matrix to the cytosol. _____Glutamate dehydrogenase and glutaminase generate NH4+_ _____Carbamoyl phosphate synthetase 1 generates carbamoyl phosphate. _____Argininosuccinase generates fumarate and arginine from argininosuccinate. _____Urea excretion removes nitrogen derived from glutamate, glutamine, and aspartate. _____Urea is formed following the hydrolytic cleavage of arginine by arginase _____Citrulline + aspartate combine to form argininosuccinate using ATP.

__3__Carbamoyl phosphate is combined with ornithine to form citrulline. __4__Citrulline is exported from the mitochondrial matrix to the cytosol. __1__Glutamate dehydrogenase and glutaminase generate NH4+ _2__Carbamoyl phosphate synthetase 1 generates carbamoyl phosphate. __6__Argininosuccinase generates fumarate and arginine from argininosuccinate. __8__Urea excretion removes nitrogen derived from glutamate, glutamine, and aspartate. __7__Urea is formed following the hydrolytic cleavage of arginine by arginase __5__Citrulline + aspartate combine to form argininosuccinate using ATP.

Match the metabolic disease with the correct biochemical mechanism. _____ Phenylketonuria _____ Alkaptonuria _____ Parkinson's disease _____ Albinism 1. Reduced levels of product 2. Increased levels of product 3. Reduced levels of substrate 4. Increased levels of substrate

__4__ Phenylketonuria __4__ Alkaptonuria __1__ Parkinson's disease __1__ Albinism

Put the following steps in the correct order for the ribonucleotide reductase reaction mechanism. Step 1 of the six step reaction mechanism is shown above to help you get started. _____Cation on C-2' is reduced by C462 creating the deoxynucleotide and the radical at C-3' is reduced by C439 _____A thiyl free radical removes a hydrogen atom from the C-3' position of the ribose ring to generate a radical _____The hydroxyl group on C-2' of the ribose ring gains a proton from the C225 residue of the enzyme _____A free radical at Y122 abstracts a hydrogen atom from C439 to form a cysteine thiyl radical _____A water molecule is removed in the reaction leaving behind a cation on C-2' that is stabilized by the radical on C-3' _____Deoxynucleoside diphosphate is released from the enzyme and C225-C462 disulfide bond is reduced by thioredoxin

__5__Cation on C-2' is reduced by C462 creating the deoxynucleotide and the radical at C-3' is reduced by C439 __2__A thiyl free radical removes a hydrogen atom from the C-3' position of the ribose ring to generate a radical __3__The hydroxyl group on C-2' of the ribose ring gains a proton from the C225 residue of the enzyme __1__A free radical at Y122 abstracts a hydrogen atom from C439 to form a cysteine thiyl radical __4__A water molecule is removed in the reaction leaving behind a cation on C-2' that is stabilized by the radical on C-3' __6__Deoxynucleoside diphosphate is released from the enzyme and C225-C462 disulfide bond is reduced by thioredoxin

Glucose-6P is a central metabolite in human physiology and functions as a substrate or product in at least six metabolic pathways. What biochemical mechanisms determine glucose-6P flux through these pathways? Choose the THREE BEST answers below. a) Allosteric control. b) Substrate availability. c) Standard change in free energy. d) Actual change in free energy. e) Enzyme levels. f) Proton Motive Force (PMF). g) Equilibrium constant. h) Standard reduction potential.

a) Allosteric control. b) Substrate availability. d) Actual change in free energy.