Test 1

Question 1

A patient has sever weakness of a muscle group after repeatedly contracting that muscle group. After rest, the muscle reappears function normally unless repeatedly contracted again. The antibody causing this disease process would directly affect which one of the following?
A. The number of ACh vesicles
B. Voltage-gated Ca2+ channels 
C. ACh receptors in smooth muscle
D. ACh receptors in the skeletal muscle

Answer 1

Answer: D. ACh receptors in the skeletal muscle
This disease is myasthenia gravis caused by the production of an antibody directed against ACh receptors in skeletal muscles.

Question 2

In the patient described with myasthenia gravis, ACh and other similar neurotransmitters use which one of the following modes of action to transmit their signal?
A. Endocrine
B. Paracrine
C. Autocrine
D. Neuropeptide
E. Cytokine

Answer 2

Answer: B. Paracrine

Question 3

Pseudohypoparathyroidism is a heritable disease caused by target-organ unresponsiveness to parathyroid hormone (a polypeptide hormone secreted by the parathyroid gland). One of the mutations that causes this disease occurs in the gene encoding Galphas in certain cells.
The receptor for parathyroid hormone is most likely which one of the following?
A. An intracellular transcription factor
B. A cytoplasmic guanylyl cyclase
C. A receptor that must be endocytosed in clathrin-coated pits to transmit its signal
D. A heptahelical receptor
E. A tyrosin kinase receptor

Answer 3

Answer: A heptahelical receptor

Heptahelical receptors work through heterotrimeric G-proteins that have an alpha subunit.

Question 4

Pseudohypoparathyroidism is a heritable disease caused by target-organ unresponsiveness to parathyroid hormone (a polypeptide hormone secreted by the parathyroid gland). One of the mutations that causes this disease occurs in the gene encoding Galphas in certain cells.
This mutation most likely has which one of the following characteristics?
A. It is a gain of function mutation
B. It decreases the GTPase activity of the Galphas subunit.
C. It decreases synthesis of cAMP in response to parathyroid hormone
D. It decreased generation of IP3 in response to parathyroid hormone
E. It decreases synthesis of PI-3,4,5-trisP in response to parathyroid hormone

Answer 4

Answer:C. It decrease synthesis of cAMP in response to parathyroid hormone

Question 5

Techniques are now available to allow one to introduce mutations in proteins at a selected amino acid residue (site-directed mutagenesis). Which step of the signal transduction pathway would be blocked if you created a tyrosine kinase receptor in which all of the tyrosine residues normally phosphorylated on the receptor were converted to phenylalanine residues?
A. Grb2 binding to the receptor to propagate the response
B. Binding of the growth factor to the receptor
C. Induction of a conformational change in the receptor upon growth factor binding
D. Activation of the receptor’s intrinsic tyrosine kinase activity
E. Dimerization of the receptors

Answer 5

Answer: A. Grb2 binding to the receptor to propagate the response

Question 6

A patient has been diagnosed with a glucagonoma, a pancreatic tumor that independently and episodically secretes glucagon. Which of the following would be expected in this patient?
A. Low serum glucose
B. Increased glycogenolysis in the liver
C. Increased glycogenolysis in the muscle tissue
D. Increased glycogenesis in the liver
E. Increased glycogenesis in the muscle tissue

Answer 6

Answer: B. Increased glycogenolysis in the liver

Question 7

Curare has been given as a paralyzing agent in patients undergoing surgical procedures, and its mode of action is best described as inhibiting the action of which one of the following?
A. Atropine
B. Muscarinic receptors
C. Nicotinic receptors
D. The formation of ACh
E. The breakdown of ACh

Answer 7

Answer: C. Nicotinic receptors

Question 8

A patient with allergies is taking a drug that blocks the actions of leukotrienes. The leukotrienes are derived from which one of the following molecules?
A. Oleic acid
B. Linolenic acid
C. Stearic acid
D. Arachidonic acid
E. Palmitic acid

Answer 8

Answer: Arachidonic acid

Question 9

A pheochromocytoma is an adrenal tumor that episodically produces epinephrine and/or norepinephrine. Tissues that respond to these adrenal hormones must express which one of the following?
A. A tyrosine kinase receptor
B. An intracellular receptor
C. A ligand-gated receptor 
D. The Sad transcription factor
E. A heptahelical receptor

Answer 9

Answer: E A heptahelical receptor

Question 10

A patient attempted suicide by ingesting 50 aspirin tablets. This led to a fairly severe metabolic acidosis. A decrease of blood pH from 7.5 to the 6.5 would be accompanied by which one of the following changes in ion concentration?
A. A 10-fold increase in hydrogen ion concentration
B. A 10-fold increase in hydroxyl ion concentration
C. An increase in hydrogen ion concentration by a factor of 7.5/6.5
D. A decrease in hydrogen ion concentration by a factor of 6.5/7.5
E. A shift in concentration of buffer anions, with no change in hydrogen ion concentration

Answer 10

Answer: A. A 10-fold increase in hydrogen ion concentration

Question 11

A medical student is attempting to understand the buffering system of the human body and has set up the following experiment in the lab to help with his understanding. Consider a biochemical reaction that is taking place in a 0.1 M buffer. The initial pH is 7.4, and the pKa of the buffer is 7.2. If in a final reaction volume of 1.0mL, 10µmol if protons are generated, what would be the final pH of the solution?
A. 7.59
B. 7.25
C. 7.22
D. 7.20
E. 7.15

Answer 11

Answer: 7.22

Question 12

A patient with an enteropathy produced large amounts of ammonia from bacterial overgrowth in the intestine. The NH3 was absorbed through the intestine into the portal vein and entered the circulation. Which of the following is a likely consequence of his NH3 absorption?
A. A decrease of blood pH
B. Conversion of NH3 to ammonium ion in the blood
C. A decreased concentration of bicarbonate in the blood
D. Kussmaul respiration
E. Increased expiration of CO2.

Answer 12

Answer: B. Conversion of NH3 to ammonium ion in the blood

Question 13

Which of the following physiologic/pathologic conditions is most likely to result in an alkalosis, provided the body could not fully compensate?
A. Production of lactic acid
B. Production of ketone bodies by a patient with diabetes mellitus
C. Repeated vomiting of stomach contents, including HCl
D. Diarrhea with loss of the bicarbonate anions secreted in to the intestine
E. An infection resulting in a fever and hypercatabolism

Answer 13

Answer: C. Repeated vomiting of stomach contents, including HCl

Question 14

Laboratory tests on the urine of a patient identified the presence of methylmalonate (-OOC-Ch(CH3)-COO-). Methylmalonate is best described as which one of the following?
A. A strong acid
B. The conjugate base of a weak acid
C. It is 100% dissociated at its pKa
D. it is 50% dissociated at the pH of the blood
E. It is a major intracellular buffer

Answer 14

Answer: B The conjugate base of a weak acid

Question 15

A patient with influenza has a fever of 101.8 orally. The excess heat is dissipated throughout the body via a substance that can be best described by which one of the following?
A. It is a dipolar molecule
B. It is composed mostly of amino acids
C. It is a weak acid
D. It is a weak base
E. It is composed mostly of carbohydrates

Answer 15

Answer: A. It is a dipolar molecule

Question 16

A patient with hypertension is being treated with hydrochlorothiazide, a diuretic medication that can cause some dehydration and major intracellular electrolyte imbalance. Which one of the following electrolytes might be in imbalance under these conditions?
A. Na+
B. K+
C. Cl-
D. HCO3-
E. H2O

Answer 16

Answer: K+

Question 17

A patient with panic attacks and hyperventilation is in a respiratory alkalosis. The excess hydroxide ions were able to overcome which one of the following buffers, which has the greatest buffering capacity in and near to normal blood pH.
A. carbonic acid
B. Dihydrogen phosphate
C. Ammonium ion
D. Acetoacetic acid
E. Ascetic acid

Answer 17

Answer: B. Dihydrogen phosphate

Question 18

A patient is in early DKA. Which one of the following would this patient be expected to exhibit upon examination?
A. Excess fluid in the tissues of the lower extremity
B. Increased respiratory rate
C. Low blood glucose
D. Decreased respiratory rate
E. Decreased urine output as an attempt to preserve water

Answer 18

Answer: B Increased respiratory rate

Question 19

A patient with severe anemia has a a decreased capacity to use the bicarbonate buffer system to help maintain blood pH in the normal range. Which one of the following statements best describes the reason for this decreased capacity?
A. The total amount of carbonic anhydrase in blood plasma is decreased in anemia.
B. The total amount of carbonic anhydrase in blood plasma is increased in anemia
C. The total amount of carbonic anhydrase in red blood cells is decreased in anemia
D. The total amount of carbonic anhydrase in red blood cells in increase in anemia
E. The total amount of carbonic anhydrase in interstitial fluid is decreased
F. The total amount of carbonic anhydrase in interstitial fluid is increased

Answer 19

Answer: C. The total amount of carbonic anhydrase in red blood cells is decreased in anemia

Question 20

A component of a lipid panel for a patient is triglyceride, which is best described by which one of the following?
A. Contains a steroid nucleus
B. Three fatty acids esterified to sphingosine
C. Two fatty acids esterified to a carbohydrate
D. Two fatty acids and a phosphate esterified to a sphingosine
E Two Fatty acids and a phosphate esterified to a carbohydrate

Answer 20

Answer: Three fatty acids to a carbohydrate

Question 21

A patient was admitted to the hospital emergency department in a coma. Laboratory tests found high levels of the compound shown below in her blood. On the basis of its structure, identify the compound as which one of the following?
A. Methanol
B. Ethanol
C. Ethylene glycol
D. beta-hydroxybutyrate
E. gamma-hydroxybutyrate

Answer 21

Answer: gamma-hydroxybutyrate

Question 22

A patient was diagnosed with a deficiency of the lysosomal enzyme alpha-glycoside. The name of the deficient enzyme suggests that it hydrolyzes a glycosidic bond, which is best described as a bond formed via which one of the following?
A. Through multiple hydrogen bonds between two suga molecules
B. Between the anomeric carbon of a sugar and an O-H of another molecule
C. Between two anomeric carbons in polysaccharides
D. Internal bond formation between the anomeric carbon of a monosaccharide and its own fifth carbon hydroxyl group
E. Between the carbon containing the aldol or kept group and the alpha carbon of the sugar

Answer 22

Answer: Between the anomeric carbon of a sugar and an O-H of another molecule

Question 23

In the congenital disease galactosemia, high concentrations of galactose and galactitol accumulate in the blood. On the basis of their names, you would expect which one of the following statements to be correct?
A. Galactitol is an aldehyde formed from the keto sugar galactose
B. Galactitol is the oxidized form of galactose
C. Galactitol is the sugar alcohol of galactose
D. Both galactose and galactitol are sugars
E. Both galactose and galactitol would give a positive reducing sugar test

Answer 23

Answer: C. Galactitol is the sugar alcohol of galactose

Question 24

A patient was diagnosed with one of the types of sphingolipidoses, which are congenital diseases involving the inability to degrade sphingolipids. All sphingolipids have in common which one of the following?
A. A glycerol backbone
B. Ceramide
C. Phosphoylcholine
D. N-Acetylneuraminic acid (NANA)
E. A steroid ring structure to which sphingosine is attached

Answer 24

Answer: B. Ceramide

Question 25

In DKA, a metabolic acidosis results from increased hepatic production of ketone bodies. Which one of the following terms best describes all three of these ketone bodies?
A. butyl structure
B. Aromatic structure
C. Alipathic structure
D. Hydroxyl-containing structure
E. Amine-containing structure

Answer 25

Answer: C. Alipathic structure

Question 26

Omega-3 fatty acids are found in oily fish and are considered beneficial for heart health. A food containing which one of the following would fall into this category/
A. Cis ∆9,12,15 C18:3
B. Cis ∆9,12 C18:2
C. Cis ∆6,9,12 C18:3
D. Cis ∆9,12,15 C20:3
E. Cis ∆6,9 C16:2

Answer 26

Answer: A Cis ∆9,12,15 C18:3

Question 27

A patient ha had viral gastroenteritis for 3 days and has been unable to keep any oral intake down, such that the patient is now dehydrated. In the emergency department, he is given 2 L of IV D5 0.9% NaCl solution. Which of the following best describes this IV solution?
A. Hypotonic
B. Hypertonic
C. It contains D-glucose
D. It contains L-glucose
E. It contains D-galactose

Answer 27

Answer: C. It contains D-glucose

Question 28

A patient with hyperlipidemia has been counseled reduce the saturated fats in his diet, so he has replaced butter with a butter substitute that he knows is made from a polyunsaturated oil. The manufacturer of this butter substitute has partially hydrogenated this product. Which of the following is the best description of why this product was partially hydrogenated?
A. The trans-fatty acids produced by commercial hydrogenation are very healthy in humans
B. Hydrogenation reduces the double bonds, creating a more saturated product, which is more marketable
C. Hydrogenation makes the product less expensive to produce
D. Hydrogenation reduces the cholesterol content of the oil
E. Hydrogenation increases the cholesterol content of the oil

Answer 28

Answer: B. Hydrogenation reduces the doubles bonds, creating a more saturated product, which is more marketable

Question 29

A researcher is trying to design an antibiotic to kill bacteria but not harm any human cells.Which one of the following theoretically could be used for this purpose?
A. A medication that inhibits reactions using only D-amino acids
B. A medication that inhibits reactions using only L-amino acids
C. A medication that inhibits reactions using only amino acids containing a beta-amino group
D. A medication that inhibits reactions using only amino acids containing gamma amino group
E. A medication that only inhibits reactions using only aromatic amino acids

Answer 29

Answer: A. A medication that inhibits reactions using only D-amino acids

Question 30

Sickle cell anemia is caused by a single nucleotide change in DNA that leads to the substitution of one amino acid in the beta chain. This one change in the primary sequence leads to the ability of the deoxygenated form of HbS to form polymers. As the polymers grow in size, the shape of the red blood cell is altered to accommodate the chains of hemoglobin. Which one of the following primarily dictates the polymerization of deoxygenated HbS?
A. The peptide backbone
B. Ionic reactions
C. Hydrophobic interactions
D. Hydrogen bonds
E. Peptide bonds

Answer 30

Answer: C. Hydrophobic interactions

Question 31

One of the main sources of nonvolatile acid in the body is sulfuric acid generated from the sulfur-containing compounds in ingested food or from the metabolism of the sulfur-containing amino acids. Which of the following amino acids would lead to sulfuric acid formation?
A. Cysteine and isoleucine
B. Cysteine and alanine
C. Cysteine and methionine
D. Methionine and isoleucine
E. isoleucine and alanine

Answer 31

Answer: C. Cysteine and methionine

Question 32

Dianna A.’s different preparations of insulin contain some insulin complexed with protamine that is absorbed slowly after injection. Protamine is a protein preparation from rainbow trout sperm containing arginine-rich peptides that bind insulin. Which one of the following provides the best explanation for complex formation between protamine and insulin?
A. Arginine is a basic amino acid that binds negatively charged amino acid side chains in insulin
B. Arginine is a basic amino acid that binds to the alpha-carboxylic acid groups at the N-terminals of insulin chains
C. Arginine is a larger, bulky hydrophobic amino acid that complexes with leucine and phenylalanine in insulin
D. Arginine forms disulfide bonds with the cysteine residues that hold the A and the B chains together
E. Arginine has a side chain that forms peptide bonds with the carboxyl terminals of the insulin chains

Answer 32

Answer: A. Arginine is a basic amino acid that binds negatively charged amino acid side chains in insulin

Question 33

Phosphorylation of proteins is an important component of signal transduction. Protein kinases phosphorylate proteins only at certain hydroxyl groups on amino acid side chains. Which of the following groups of amino acids contain side-chain hydroxyl groups and could be a potential substrate for a protein kinase?
A. Aspartate, glutamate, and serine
B. Serine, Threonine, and tyrosine
C. Threonine, phenylalanine, and arginine
D. Lysine, Arginine, and proline
E. Alanine, asparagine and serine

Answer 33

Answer: B. Serine, threonine, and tyrosine

Question 34

A protein's activity is altered when a particular serine side chain is phosphorylated. Which of the following amino acid substitutions at this position could lead to a permanent alteration in normal enzyme activity?
A. S--> E
B. S-->T
C. S-->Y
D. S-->K
E. S-->L

Answer 34

Answer: A. S–>E

Question 35

Proteins, which are composed of amino acids, help transport lipids in the blood stream. These proteins need to be able to cluster with other non polar molecules and exclude water. Which of the following would best describe the side chains of these amino acids in the lipid transport proteins?
A. A more positive hydropathic index
B. A more negative hydropathic inex
C. A neutral hydropathic index
D. A pKa of the primary carboxylic acid group of approximately 2
E. A pKa of the alpha amino group of approximately 9.5

Answer 35

Answer: A. A more positive hydropathic index

Question 36

A patient with high cholesterol begins taking a statin medication and develops myalgias (muscle soreness and aches). The physician orders CK (creatine kinase) levels to check for muscle damage, a known side effect of statins. Lab results show a higher than normal level of CK-MM. Which of the following best describes CK-MM?
A. Heterodimer
B. Isozyme
C. Produced by the brain
D. Produced by the heart
E. Produced by the liver

Answer 36

Answer: Isozyme

Question 37

All of the amino acids that are used to synthesize human proteins have which one of the following in common?
A. An aromatic group
B. A hydroxyl group
C. An asymmetric carbon in the D-configuration
D. An asymmetric carbon in the L-configuration
E. An asymmetric beta carbon

Answer 37

Answer: D. An asymmetric carbon in the L-configuration

Question 38

A patient with recurrent kidney stones is found to have an inherited amino acid substitution in a transport protein that reabsorbs certain amino acids from the glomerular filtrate so they are not lost in the urine. Which of the following amino acid groups are not reabsorbed from theglomerular filtrate in this disease process?
A. Cysteine, methionine, and arginine
B. Cysteine, methionine, and lysine
C. Cysteine, arginine, and lysine
D. Methionine, arginine, and histidine
E. Methionine, arginine, and histidine

Answer 38

Answer: C. Cysteine, arginine, and lysine

Question 39

A patient with recurrent kidney stones is found to have an inherited amino acid substitution in a transport protein that reabsorbs certain amino acids from the glomerular filtrate so they are not lost in the urine.Which one of the following amino acids is most responsible for this patient's recurrent kidney stones?
A. Cysteine
B. Methionine
C. Arginine
D. Lysine
E. Histidine

Answer 39

Answer: A. Cysteine

Question 40

One theory of amyloid fibril formation is that sections of alpha helical structure are converted to beta sheets. Such regions of the amyloid proteins would most likely lack which one of the following amino acids?
A. Cysteine
B. Methionine
C. Proline
D. Leucine
E. Isoleucine

Answer 40

Answer: C. Proline

Question 41

In order for lipid-based hormones such as testosterone or estrogen to be transported in the blood stream, they are bound to and transported by water-soluble proteins. in order to be water-soluble, the transporting protein contains which one of the following amino acids on its surface in contact with aqueous blood?
A. Valine
B. Arginine
C. Leucine
D. Isoleucine
E. Phenylalanine

Answer 41

Answer: B. Arginine

Question 42

A patient has wheezing and shortness of breath, which are his typical asthma symptoms, so he takes a rescue inhalant which is beta2 adrenergic receptor agonist. The active ingredient of the inhalant relaxes the smooth muscle of the bronchi and allows him to breathe more normally. The receptor to which the agonist binds can be best described by which one of the following?
A. A globular protein
B. A transmembrane protein
C. A protein containing a nucleotide binding fold
D. Sn exclusively beta-pleated sheet protein
E. A protein containing an actin fold

Answer 42

Answer: A transmembrane protein

Question 43

Autopsies of patient with Alzheimers disease show protein aggreagates called neurofibrillary tangles and neuritic plaques in various regions of the brain. These plaques exhibit the characteristic staining of amyloid. Which of the following structural features is the most likely characteristic of at least one protein in these plaques?
A. A high content of beta pleated sheet structure
B. A high content of alpha helical structure
C. A high content of random coils
D. Disulfide bond cross-links between polypeptide chains
E. A low-energy native conformation

Answer 43

Answer: A high content of beta pleated sheet structure

Question 44

While studying a novel pathway in a remote species of bacteria, you discover a new globular protein that phosphorylates a substrate, using ATP as the phosphate donor. This protein is most likely contains which one of the following structures?
A. An actin fold
B. an immuniglobulin fold
C. a nucleotide binding fold
D. A global fold
E. A beta barrel.

Answer 44

Answer: An actin fold

Question 45

Beta2 adrenergic agonists used as treatments for acute asthma attacks were formulated to have a higher affinity for the beta2 adrenergic receptor than epinephrine. Which one of the following would be true of the beta 2 agonist sd compared to epinephrine?
A. The Ka of the agonist is higher than that of adrenaline
B. The Ka of the agonist is lower than that of adrenaline
C. The Ka of the agonist is the same as adrenlina
D. The Kd of the agonist is higher than that of adrenaline
E. The Kd of the agonist is equal to adrenaline

Answer 45

Answer: A. The Ka of the agonist is higher than that of adrenaline

Question 46

A patient is exposed to hepatitis A and as a preventative measure is given hepatitis A immune glubulin to prevent the patient from contracting the disease. The vaccine is an IgG immunoglobulin specific for coat proteins of the hepatitis A virus. The target of the immunoglobulin binds to which of the following locations in the immunoglobulin?
A. A site consisting of the constant regions of the heavy chains
B. A site consisting of the constant regions of the light chains
C. A site consisting of the variable regions of the light chains
D. A site consisting of the variable regions of the heavy chains
E. A site consisting of variable regions of both the light and heavy chains

Answer 46

Answer: E. A site consisting of variable regions of both the light and heavy chains

Question 47

Each IgG molecule contains two light and two heavy chains, which can be separated by the loss of which one of the following types of interactions?
A. Hydrogen bonds
B. Disulfide bonds
C. Ionic bonds
D. Van der Waals interactions
E. The hydrophobic effect

Answer 47

Answer: B. Disulfide bonds

Question 48

A patient with type 1 diabetes was able to lower her HbA1c value from 8.2% to 5/9%. This occurred because of a reduction of which one of the following processes>
A. Enzymatic oxidation
B. Nonenzymatic oxidation
C. Enzymatic glycosylation
D. Nonenzymatic glycosylation
E. Enzymatic reduction
F. Nonenzymatic reduction

Answer 48

Answer: D. Nonenzymatic glycosylation

Question 49

In amyloidosis, alpha helices may form alternative beta sheets of amyloid fibers. The alpha helices in these proteins can be characterized by which one of the following?
A. They all have the same primary structure
B. They are formed principally by hydrogen bonds between a carbonyl oxygen atom in one peptide bond and the amide hydrogen from a different peptide bond
C. They are formed principally by hydrogen bonds between a carbonyl atom in one peptide bond and the amide hydrogen atoms on the side chain of another amino acid
D. They are formed by hydrogen bonding between two adjacent amino acids in the primary sequence
E. They require a high content of proline and glycine

Answer 49

Answer: B. They are formed principally by hydrogen bonds between a carbonyl oxygen atom in one peptide bond and the amide hydrogen from a different peptide bond.

Question 50

A patient is born with a congenital mutation in an enzyme that severely affected its ability to bind an activation-transfer coenzyme. As a consequence, which one of the following is most likely to occur?
A. The enzyme will be unable to bind the substrate of the reaction
B. The enzyme will be unable to form the transition-state complex
C. The enzyme will normally use a different activation-transfer coenzyme
D. The enzyme will normally substitute the functional group of an active-site amino acid residue for the coenzyme
E. The reaction may be carried out by the free coenzyme, provided the diet carries an adequate amount of its vitamin precursor.

Answer 50

Answer: B. The enzyme will be unable to form the transition-state complex

Question 51

An individual had a congenital mutation in glucokinase in which a proline was substituted for a leucine on a surface helix far from the active site but within the hinge region of the actin fold. This mutation would be expected to have which one of the following effects?
A. It would have no effect on the rate of the reaction because it is not in the active site
B. It would have no effect on the rate of the reaction because proline and leucine are both non polar amino acids
C. It would have no effect on the number of substrate molecules reaching the transition state
D. It would probably affect the binding of ATP or a subsequent step in the reaction process
E. It would probably cause the reaction to proceed through an alternate mechanism

Answer 51

Answer: D. It would probably affect the binding of ATP or a subsequent step in the reaction sequence.

Question 52

Lysozyme is an important component of the human innate immune system. Lysozyme is an enzyme that cleaves glycosidic linkages in bacterial cell walls. The pH optimum of the purified enzyme is 5.2. There are two acidic residues at the active site of lysozyme that are required for enzyme activity. The pKa of E35 is 5.9, whereas the pKa of D52 is 4.5. What are the primary ionization states of these two residues at the pH optimum of this enzyme?
A. E35 is protonated; D52 is ionized
B. E35 is protonated; D52 is protonated
C. E35 is ionized; D52 is protonated
D. E25 is ionized; D52 is ionized
E. This cannot be determined from the information provided

Answer 52

Answer: A. E35 is protonated; D52 is ionized

Question 53

UDP-glucose is a key intermediate in carbohydrate metabolism and serves as a precursor for glycogen synthesis and glycosylation of lipids and proteins. The type of reaction shown fits into which one of the following classifications?
A. Group transfer
B. Isomerization
C. Carbon-Carbon bond breaking
D. Carbon-carbon bond formation
E. Oxidation-reduction

Answer 53

Answer: A. Group transfer

Question 54

UDP-glucose is a key intermediate in carbohydrate metabolism and serves as a precursor for glycogen synthesis and glycosylation of lipids and proteins.
The type of enzyme that catalyzes this reaction is which one of the following?
A. Kinase
B. Dehydrogenase
C. Glycoslytransferase
D. Transaminase
E. Isomerase

Answer 54

Answer: C. Glycosyltransferase

Question 55

A patient has accidentally ingested the insecticide malathion, leading to symptoms of an overstimulated autonomic nervous system. Which one of the following best describes malathion in this context?
A. Enzyme
B. Coenzyme
C. Inhibitor
D. Cofactor
E. Coactivator

Answer 55

Answer: C. Inhibitor

Question 56

Penicillin is an antibiotic used to treat certain infections. It is a transition-state analog and suicide inhibitor. The use penicillin affect which one on the following in susceptible targets?
A. Viral cell wall
B. Bacterial cell wall
C. Viral nucleus
D. bacterial nucleus
E. Protozoan nucleus

Answer 56

Answer: B. Bacterial cell wall

Question 57

Vitamins can act as coenzymes that participate in catalysis by providing functional groups. Therefore, vitamin deficiencies reflect the loss of specific enzyme activities that depend on those coenzymes. Coenzymes are best described by which one of the following?
A. In humans, they are always synthesized from vitamin
B. They are proteins
C. They participate in only one reaction, like enzymes
D. They are complex, nonprotein organic molecules
E. They are all carbohydrates

Answer 57

Answer:D. They are complex, nonorganic molecules

Question 58

Many chronic alcohols develop thiamin deficiency because of a poor diet and an inability to absorb thiamin from the intestine in the presence of ethanol. Which one of the following cofactors, synthesized from a vitamin, or a vitamin itself, exhibits a mechanism of action similar to thiamin?
A. NAD+
B. FAD
C. Ascorbic Acid
D. gamma-tocopherol
E. CoA

Answer 58

Answer: E. CoA

Question 59

Many chronic alcohols develop thiamin deficiency because of a poor diet and an inability to absorb thiamin from the intestine in the presence of ethanol. Which one of the following vitamins is the precursor for CoA?
A. Pantothenate
B. Niacin
C. Pyridoxine
D. Folate
E. Biotin

Answer 59

Answer: A. Pantothenate

Question 60

Salivary amylase is an enzyme that digests dietary starch. Assume that salivary amylase follows Michaelis-Menten kinetics. Which one of the following best describes a characteristic feature of salivary amylase?
A. The enzyme velocity is at one-halfthe maximal rate when 100% of the enzyme molecules contain bound substrate
B. The enzyme velocity is at one-half the maximal rate when 50% of the enzyme molecules contain bound substrate
C. The enzyme velocity is at its maximal rate when 50% of the enzyme molecules contain bound substrate
D. The enzyme velocity is at its maximal rate when all of the substrate molecules contain bound substrate.
E. The velocity of the reaction is independent of the concentration enzyme

Answer 60

Answer: B. The enzyme velocity is at one-half the maximal rate when 50% of the enzyme molecules contain bound substrate.

Question 61

The pancreatic glucokinase of a patient with MODY had a mutation replacing a leucine with a proline. The result was the the Km for glucose was decreased from a normal value of 6mM to a value of 2.2mM, and the Vmax was changed from 93U/mg protein to 0.2U/mg protein. Which one of the following best describes the patient’s glucokinase compared with the normal enzyme?
A. The patient’s enzyme requires a lower concentration of glucose to reach 1/2Vmax
B. The patient’s enzyme is faster than the normal enzyme at concentrations of glucose <2.2mM
C. The patient’s enzyme is faster than the normal enzyme at concentrations of glucose >2.2mM
D. A near-saturating glucose concentration, the patient would need 90 to 100 times more enzymes than normal rates of glucose phosphorlyation
E. As blood glucose levels increase after a meal from a fasting value of 5 to 10mM, the rate of the patient’s enzyme will increase more than the rate of the normal enzyme

Answer 61

Answer: A. The patient’s enzyme requires a lower concentration os glucose to reach 1/2Vmax

Question 62

Methanol (CH3OH) is converted by ADHs to formaldehyde (CH2O) a compound that is highly toxic to humans. Patients who have ingested toxic levels of methanol are sometimes treated with ethanol (CH3Ch2OH) to inhibit methanol oxidation by ADH. Which one of the statements provides the best rationale for this treatment?
A, Ethanol is structural analog of methanol and might therefore be an effective noncompetitive inhibitor
B. Ethanol is a structural analog of methanol that can be expected to compete with methanol for its binding site on the enzyme
C. Ethanol can be converted to alter the Vmax of ADH for the oxidation of methanol to formaldehyde
D. Ethanol is an effective inhibitor of methanol oxidation regardless of the concentration of methanol
E. Ethanol can be expected to inhibit the enzyme by binding to the formaldehyde-binding site o the enzyme, even though it cannot bind at the substrate-binding site for methanol

Answer 62

Answer: B. Ethanol is a structural analog of methanol that can be expected to compete with methanol for its binding site on the enzyme

Question 63

A runner's muscles use glucose as a source of energy. Muscle contains glycogen stores that are degraded into glucose-1-phosphate via glycogen phosphorylase, which is an allosteric enzyme. Assume that an allosteric enzyme has the following kinetic properties: a Vmax of 25U/mg and a Km of 1.0 mM. These kinetic parameters were then measured in the presence of an allosteric activator. Which one of the following would best describe the findings of that experiment.
A. A Vmax of 25U/mg and a Km of 0.2mM
B. A Vmax of 15U/mg and a Km of 2.0mM
C. A Vmax of 25U/mg and a Km of 2.0mM
D. A Vmax of 50U/mg and a Km of 5.0mM
E. A Vmax of 50U/mg and a Km of 10.0mM

Answer 63

Answer: A. A Vmax of 25U/mg and a Km of 0.2mM

Question 64

A rate-limiting enzyme catalyzes the first step in the conversion of a toxic metabolite to urinary excretion product. Which of the following mechanisms for regulating this enzyme would provide the most protection to the body?
A. The product of the pathway should be an allosteric inhibitor of the rate-limiting enzyme
B. The product of the pathway should act through gene transcription to decrease synthesis of the enzyme
C. The toxin should act through gene transcription to increase synthesis of the enzyme
D. The enzyme should have a high Km value for the toxin
E. The toxin allosterically activates the last enzyme in the pathway

Answer 64

Answer: C. The toxin should act through gene transcription to increase synthesis of the enzyme

Question 65

I thyroid hormone production, thyrotropin-releasing hormone (TRH) from the hypothalamus stimulate thyroid-stimulation releasing hormone (TSH) from the anterior pituitary, which stimulates the thyroid to produce thyroid hormones (T3 and T4). Normal or high levels of thyroid hormone then suppress release of TRH. The regulation of this pathway is best described by which of the following>
A. Complementary regulation
B. Feedback regulation
C. Compartmentation
D. Feed-forward regulation
E. Negative Regulation

Answer 65

Answer: B Feedback regulation

Question 66

A patient with alcoholic liver disease has profound mental status changes caused by a buildup of ammonia(NH4+) and is suffering from hepatic encephalopathy. The conversion of NH4+ to urea is an example of which one of the following types of pathway regulation?
A. Complementary
B. Feedback
C. Compartmentation
D. Feed-forward
E. Negative

Answer 66

Answer: Feed-forward

Question 67

Pathway regulation can occur via the expression of tissue specific isozymes. Glucose metabolism differs in red blood cells and liver in that red blood cells need to metabolize glucose, whereas the liver prefers to store either glucokinase or hexokinase, which are isozymes. Which one of the following best describes these different isozymes and their Km for glucose?
A. The Km of hexokinase I is higher than the Km of glucokinase
B. The Km of hexokinase I is lower than the Km of glucokinase
C. The Km of hexokinase I is the same of Km of glucokinase
D. Hexokinase I is found in liver
E. GLucokinase is found in the red blood cells

Answer 67

Answer: The Km of hexokinase I is lower than the Km of glucokinase

Question 68

An antibiotic is developed that is a close structural analog of a substrate of an enzyme that participates in cell wall synthesis in bacteria. This binding of the antibiotic reduces overall enzyme activity, but such activity can be restored if more substrate is added. The binding go the antibiotic to the enzyme is not via a covalent bind, nor does the enzyme alter the structure of the antibiotic. Which one of the following would best describe this antibiotic?
A. It is a suicide inhibitor
B. It is an irreversible inhibitor
C. It is a competitive inhibitor 
D. It is a noncompetitive inhibitor
E. It is an uncompetitive inhibitor

Answer 68

Answer: C. It is a competitive inhibitor

Question 69

Which of the following is true of a competitive inhibitor?
A. It increases the apparent Km of the enzyme
B. It decreases the apparent Km of the enzyme
C. It has no effect on the apparent Km of the enzyme
D. It increases the Vmax of the enzyme
E. It decreased the Vmax of the enzyme?

Answer 69

Answer: A. It increases the apparent Km of the enzyme

Question 70

Bacteria contain a cell wall and a plasma membrane. Antibiotics targeting the cell wall do not affect human cells because the humans cells do not express a cell wall. However, antibiotics cannot target plasma membranes because both bacteria and humans express such membranes. Which one of the following is a characteristic of the eukaryotic plasma membrane?
A. It is composed principally of triacylglycerols and cholesterols
B. It contains principally non polar lipids
C. It contains phospholipids with their acyl groups extending into the cytosol
D. It contains more phosphatidylserine in the inner than the outer leaflet
E. It contains oligosaccharides sandwiched between the inner and outer leaflets

Answer 70

Answer: D. It contains more phosphatidylserine in the inner than the outer leaflets

Question 71

A marathon runner releases epinephrine before a race, which binds to a receptor with seven transmembrane domains. Such transmembrane proteins can be best described as which of the following?
A. They can usually be dissociated from membranes without disrupting the lipid bilayer
B. They are classified as peripheral membrane proteins
C. They contain hydrophobic amino acid residues at their carboxyl terminus
D. They contain hydrophilic amino acid residues extending into the lipid bilayer
E. They contain membrane-spanning regions that are aloha helices

Answer 71

Answer: They contain membrane-spanning regions that are alpha helices

Question 72

A patient had a sudden heart attack caused by inadequate blood flow through the vessels of the heart. As a consequence, there was an inadequate supply of oxygen to generate ATP in his cardiomycocytes. The compartment of the cardiomycocyte most directly involved in ATP generation is which one of the following?
A. Mitochondrion
B. Peroxisome
C. Lysosome
D. Nucleus
E. Golgi

Answer 72

Answer: A. mitochondrion

Question 73

One manner in which type 2 diabetes occurs is via a reduction in the release of insulin from the pancreas. The release of insulin from the beta cells of the pancreas requires Ca2+ influx through a channel that is activated by change in the membrane potential across the plasma membrane. The movement of calcium across the membrane is an example of which one of the following?
A. Voltage-Gated channel
B. Passive diffusion
C. active transport
D. Ligand-gated channel
E. Phosphorylation-gated channel

Answer 73

Answer: A. Voltage-Gated Channel

Question 74

Lysosomes function to help fight infection and to degrade unwanted metabolites in the cell. ATP is required for the appropriate functioning of the lysosome because of which one of the following?
A. Maintaining an acidic environment in the lysosome
B. Maintaining a basic environment in the lysosome
C. Regulation of enzyme activity
D. Activation of lysosomal zymogens
E. As a cofactor for lysosomal hydrolases

Answer 74

Answer: A. Maintaining an acidic environment in the lysosome

Question 75

Mature red blood cells are different from most other cells in the human body in that they do not contain a nucleus and must use anaerobic metabolism instead of aerobic metabolism. Anaerobic metabolism is required for these cells because of which one of the following?
A. Oxygen cannot enter Red blood cells
B. The red blood cells lack a plasma membrane
C. The red blood cells lack mitochondria
D. The red blood cells lack enzymes for glucose metabolism
E. Oxygen cannot bind to any proteins in the red blood cell

Answer 75

Answer: C. The red blood cells lack mitochondria

Question 76

Normal or physiologic serum sodium levels are around 140mEq/l, where as potassium levels are 32.5 to 5.0mEq/l. Intracellular concentrations are reversed with a high K+ level and much lower Na+ level. This ion imbalance is accomplished by the nA+, K+,ATPase, which is a protein that can be best described by which one of the following?
A. It catalyzes simple diffusion
B. It catalyzes primary active transport
C. It exchanged 2 Na+ ions for 3 K+ ions.
D. It catalyzes the transport of glucose down its concentration gradient
E. it catalyzes the efflux of urea from the cell.

Answer 76

Answer: B It catalyzes primary active transport

Question 77

A sweat chloride test is ordered on a patient with suspected cystic fibrosis. The defective protein in this patient, if the sweat test is positive, is best described by which one of the following?
A. It is a chloride channel that uses energy for diffusion
B. It is a voltage-gated chloride channel
C. It is a ligand gated chloride channel
D. It is an active transport system for sodium
E. It is a passive diffusion system for sodium that does not require energy

Answer 77

Answer: C. It is a ligand gated chloride channel

Question 78

An inherited mutation in the dystrophin gene is responsible for Duchenne muscular dystrophy. Which of the following statements accurately describe a property of dystrophin?
A. It is a spectral-like lipid
B. It is part of the inner membrane or cortical skeleton
C. It is a spectrin-like carbohydrate
D. It is a transmembrane proteins
E. It functions as a hormone or neurotransmitter finder

Answer 78

Answer: B. It is part of the inner membrane or cortical skeleton

Question 79

A patient has peripheral vascular disease, an atherosclerotic narrowing of arteries and arterioles. One type of medication to treat this condition alters the fluidity of the red blood cells so it can bend past these obstructions and deliver oxygen to the tissues past the obstruction. Theoretically, which one of the following diets would work in the same way?
A. High in saturated fats
B. Low in saturated fats
C. High in unsaturated fats
D. Low in unsaturated fats
E. Diet devoid of all fats

Answer 79

Answer: C. High in unsaturated fats.