Biochemistry Comprehensive Examination SY 2004-2005 Flashcards
Which of the following serves as the main storage form of fatty acids?
A. triacylglycerol C. phosphoglyceride
B. cholesterol ester D. glycosphingolipid
A. triacylglycerol
What will be the effect of biotin deficiency on the controlling step of lipogenesis?
A. There will be no carbon dioxide fixation because of lack of CO2.
B. Malonyl even if present will not be incorporated to acyl carrier protein.
C. Decarboxylation reaction will not take place.
D. Malonyl CoA will not be produced
D. Malonyl CoA will not be produced
Which of the following reactions in beta oxidation of fatty acids is true?
A. Activation of fatty acids takes place in the mitochondrial matrix.
B. Long-chain fatty acids penetrate the inner mitochondrial membrane
as acylcarnitine.
C. Per cycle of beta oxidation involves repetitive steps of oxidation,
hydration and reduction.
D. Beta oxidation involves successive cleavage of two carbons which is
released as propionyl CoA
B. Long-chain fatty acids penetrate the inner mitochondrial membrane
- Regulation of ketogenesis takes place in all of the following steps, EXCEPT:
A. Mobilization of free fatty acids from the adipose tissue
B. Entry of fatty acid into beta oxidation.
C. Increased in insulin/glucagon ratio.
D. Availability of oxaloacetate in the citric acid cycle.
C. Increased in insulin/glucagon ratio.
Prostaglandin, thromboxane and leukotriene cannot be formed if this essential
fatty acid is missing from the diet.
A. oleic acid C. palmitoleic acid
B. arachidonic acid D. palmitic acid
B. arachidonic acid
Which of the following lipoproteins serve as the vehicle that transports
triacylglycerols from the liver to extrahepatic tissues?
A. chylomicron C. beta lipoprotein
B. alpha lipoprotein D. prebeta lipoprotein
D. prebeta lipoprotein
Which of the following lipoproteins serve as the vehicle that transports
triacylglycerols from the liver to extrahepatic tissues?
A. chylomicron C. beta lipoprotein
B. alpha lipoprotein D. prebeta lipoprotein
D. prebeta lipoprotein
The plasma concentration of this subfraction of HDL is inversely proportional to
the incidence of coronary atherosclerosis.
A. HDL1 C. HDL 3
B. HDL2 D. HDLc
B. HDL2
Cholesterol synthesis is regulated mainly by controlling the activity of this enzyme.
A. HMG-CoA reductase C. squalene oxidocyclase
B. HMG-CoA synthase D. mevalonate kinase
A. HMG-CoA reductase
Which of the following phospholipases play a key role in producing second
messengers of hormones?
A. Phospholipase A2 C. Phospholipase C
B. Phospholipase B D. Phospholipase D
C. Phospholipase C
Which of the functional groups of amino acids determine primarily their
properties?
A. alpha-carbon atom C. alpha-carboxyl group
B. alpha-amino group D. alpha-R groups
D. alpha-R groups
. Which one of the following amino acids play a key role in enzymatic catalysis?
A. asparagine C. glutamic acid
B. histidine D. threonine
B. histidine
Reductive amination of alpha-ketoglutarate will convert it to this amino acid.
A. glutamic acid C. aspartic acid
B. glutamine D. asparagines
A. glutamic acid
Which chemical reaction interconverts pairs of alpha-amino acids and alpha-
keto acids?
A. oxidative deamination C. non-oxidative deamination
B. transamidination D. transamination
D. transamination
Which reaction of the urea cycle is impaired by a deficiency of ornithine
transcarbamylase?
A. formation of ornithine from arginine
B. formation of carbamoyl phosphate from NH4 and CO2
C. formation of citrulline from carbamoyl phosphate and ornithine
D. formation of fumarate from argininosuccinate
C. formation of citrulline from carbamoyl phosphate and ornithine
Catabolism of the carbon skeletons of all the following amino acids will form
pyruvic acid, EXCEPT:
A. glycine C. serine
B. tyrosine D. alanine
B. tyrosine
. Deficiency of which enzyme will give rise to urine which smells like maple
syrup?
A. branched-chain alpha keto acid dehydrogenase
B. alpha-keto acid decarboxylase
C. phenylalanine hydroxylase
D. homogentisic acid oxidase
B. alpha-keto acid decarboxylase
What is the significance of phosphorylation or dephosphorylation of serine
and threonine residues in an enzyme molecule?
A. It regulates the activity of covalently modulated enzymes.
B. Zymogens are converted to active enzymes.
C. Enzymes become more susceptible to degradation.
D. Isoenzymes are released from the cell
A. It regulates the activity of covalently modulated enzymes.
What is the principal source of methyl groups in the body?
A. carnosine C. S-adenosylmethionine
B. ergothionine D. spermidine
C. S-adenosylmethionine
All of the following amino acids are needed for the synthesis of creatine
phosphate, EXCEPT:
A. arginine C. methionine
B. glycine D. cysteine
D. cysteine
Which of the following is a ribonucleotide?
A. adenosine C. deoxycytidine
B. guanosine monophosphate D. thymidine
B. guanosine monophosphate
- Synthetic nucleotide analogs like 5-fluorouracil are used as:
A. chemotherapeutic agents C. antibiotics
B. amoebicidal agents D. antifungal
A. chemotherapeutic agents
The major determinant of the rate of de novo synthesis of purine nucleotide
is the concentration of:
A. ribose 5-phosphate C. phosphoribosylamine
B. phosphoribosyl pyrophosphate
D. inosine monophosphate
B. phosphoribosyl pyrophosphate
. Which enzyme of the de novo synthesis of pyrimidine nucleotide is controlled by allosteric regulation? A. carbamyl phosphate synthase I C. aspartate transcarbamylase B. ribonucleotide reductase D. thymidylate synthase
C. aspartate transcarbamylase
All of the following about the Watson and Crick model of DNA are true, EXCEPT:
A. The two strands of DNA are antiparallel.
B. A single turn of the DNA contains ten base pairs.
C. There are two grooves, minor and major.
D. The base pairs are tilted along the central axis in B-DNA.
D. The base pairs are tilted along the central axis in B-DNA.
Which of the following about transfer RNA is correct?
A. Double stranded C. Contains the codon
B. Has unique or peculiar bases
D. Associated with ribosomal proteins
B. Has unique or peculiar bases
What is the significance of knowing the redox potential in mammalian oxidation
systems?
A. Allows prediction of the direction of flow of electrons.
B. Measures the free energy change of the redox pair.
C. Serves as guide as to the direction of the chemical reaction.
D. Tells whether the chemical reaction will take place or not.
A. Allows prediction of the direction of flow of electrons.
. Which of these enzymes use hydrogen peroxide as electron donor and electron
acceptor?
A. peroxidase C. catalase
B. dehydrogenase D. oxygenase
C. catalase
. The potential toxicity of oxygen is due to its conversion to:
A. hydroxyl radicals C. hydrogen peroxide
B. superoxide D. monoxime
B. superoxide
. Complex IV of the respiratory chain is inhibited by all of the following,
EXCEPT:
A. hydrogen sulfide C. carbon monoxide
B. cyanide D. amobarbital
D. amobarbital
How does dinitrophenol inhibits oxidative phosphorylation?
A. Allows leakage of H+ across the inner mitochondrial membrane.
B. Inhibits ADP/ATP transporter.
C. Inhibits complex II of the ETC.
D. Blocks conduction of H+ through Fo in ATP synthase.
A. Allows leakage of H+ across the inner mitochondrial membrane.
. All of the following hormones, EXCEPT ONE, share common antigenic
determinants and growth promoting activity.
A. growth hormone C. gonadotropic hormone
B. prolactin D. placental lactogen
C. gonadotropic hormone
Which step in thyroid hormone synthesis is inhibited by potassium iodide?
A. iodide trapping C. iodination of tyrosine
B. thyroglobulin hydrolysis D. coupling of iodotyrosyls
B. thyroglobulin hydrolysis
. All of the following are biologic effects of parathyroid hormone, EXCEPT:
A. Reduces the renal excretion of calcium.
B. Increases rate of dissolution of bones.
C. Promotes the synthesis of 1,25-dihydroxycholecalciferol
D. Mobilizes the calcium stored in the endoplasmic reticulum.
D. Mobilizes the calcium stored in the endoplasmic reticulum.
The activity of which of the following enzymes is decreased by insulin?
A. glycogen synthase C. phosphofructokinase
B. triacylglycerol lipase D. HMG-CoA reductase
B. triacylglycerol lipase
Which enzyme is induced by a low insulin/glucagon ratio?A. glucokinase C. glucose 6-phosphatase
B. acetyl CoA carboxylase D. pyruvate kinase
C. glucose 6-phosphatase
In the induced fit model:
A. the enzyme changes shape on binding to the substrate
B. the correct substrate fits into the active site of the enzyme
C. substrates bind to the enzyme in a large number of different ways, only one of which is correct
D. enzyme specificity uses complimentarity between enzyme active site & substrate
A. the enzyme changes shape on binding to the substrate
Is the highest energy arrangement of atoms during a chemical reaction:
A. activation energy C. free energy
B. transition state D. standard free energy
B. transition state
Is the measurement of the rate under conditions in which there is no
significant change in substrate concentration:
A. Km C. initial velocity (v)
B. Vmax D. Kcat
C. initial velocity (v)
This class of enzymes catalyzes reactions which add H2O, ammonia, or
CO2 across double bonds or remove them to produce double bonds:
A. Ligases C. hydrolases
B. Lyases D. lipases
B. Lyases
Are gene products that catalyze identical reactions:
A. Apoenzyme C. isozymes
B. Holoenzymes D. prosthetic groups
C. isozymes
Are sugars which are mirror images of one another and are designated as
D & L forms:
A. Enantiomers C. epimers
B. Tautomers D. diastereoisomers
A. Enantiomers
Are multiple forms of sugars that have orientations about one carbon atom:
A. Enantiomers C. tautomers
B. Epimers D. stereoisomers
D. stereoisomers
the sugar units of lactose are:
A. Gal & Glc C. Gal & Fru
B. Glc & Glc D. Glc & Fru
A. Gal & Glc
. Which mucopolysaccharide acts a natural anti-coagulant
A. Chitin C. Heparin
B. hyaluronic acid D. Dextran
C. Heparin
Which reaction(s) in glycolysis is/are phosphorylation reactions?
A. glucose to G6P C. phosphoenol to pyruvate
B. G6P to F6P D. fructose 1,6 biphosphate to GAP
A. glucose to G6P
Hexokinase:
A. has high Km C. is found in liver
B. strong affinity for glucose D. is a regulatory enzyme in glycolysis
D. is a regulatory enzyme in glycolysis
Which enzyme catalyzes the only oxidative phosphorylation in glycolysis? A. Hexokinase B. Glucokinase C. PFKI D. pyruvate kinase
C. PFKI
The rate-limiting step in glycolysis is catalyzed by:
A. Hexokinase C. PFK1
B. Glucokinase D. pyruvate kinase
C. PFK1
Is the enzyme which catalyzes a substrate level phosphorylation step in
A. Hexokinase C. pyruvate kinase
B. PFK 1 D. G3PDH
D. G3PDH
How many moles of ATP are produced in one turn of the Kreb’s cycle
starting from the PDH complex?
A. 8 C. 10
B. 15 D. 12
B. 15
. The reaction in the Kreb’s cycle that produces ATP via substrate level
A. succinyl CoA synthase C. alpha KG dehydrogenase
B. citrate synthase D. isocitrate dehydrogenase
A. succinyl CoA synthase
. Is the enzyme ion the Kreb’s that catalyzes the condensation reaction:
A. citrate synthase C. fumarase
B. aconitase D. malate dehydrogenase
C. fumarase
Is the net number of ATP when glucose is completely oxidized via glycerol
phosphate shuttle:
A. 15 C. 36
B. 30 D. 38
D. 38
The first law of thermodynamics state that:
A. energy is neither created or destroyed
B. in any physical or chemical change, the total amount of the energy in the universe increases
C. all physical or chemical changes tend to proceed into a randomized form called entropy
D. the degree of disorder remains constant
A. energy is neither created or destroyed
. If the reaction is at equilibrium, free energy change is:
A. equal to one C. greater than one
B. less than one D. equal to zero
D. equal to zero
. Which of these hormones increase the synthesis and amount of the
regulatory enzymes in glycolysis thus increasing rate?
A. Cortisol C. Glucagon
B. Epinephrine D. Insulin
D. Insulin
Is the glycolytic intermediate which acts as a branch point for glycogen
metabolism and the PPP?
A. Glc-1-P C. Fruc-6-P
B. Glc-6P D. Fruc-1,6BP
B. Glc-6P
The pentose phosphate pathway is located mainly in the:
A. Brain C. liver
B. skeletal muscle D. kidneys
C. liver
The reactions in the irreversible oxidative phase of the PPP are:
A. oxidation-hydrolysis-oxidative decarboxylation
B. oxidative decarboxylation-oxidation-hydrolysis
C. oxidation-hydration-oxidation
D. oxidation-transketolation-oxidation
A. oxidation-hydrolysis-oxidative decarboxylation
. Which of these gluconeogenic enzymes is found in the mitochondria?
C. Fructose-1,6 biphospahte
B. PEPCK D. Glc 6 phosphatase
A. pyruvate carboxylase
Which of the following enzymes bypasses the irreversible pyruvate kinase
reaction?
A. pyruvate carboxylase C. Fructose-1,6 biphospahte
B. PEPCK D. Glc 6 phosphatase
B. PEPCK
. Which of these enzymes is unique to the liver?
A. glycogen synthase C. pyruvate dehydrogenase
B. Glc 6 phosphatase D. PEPCK
B. Glc 6 phosphatase
which of the following statement is NOT true regarding glycogen?
A. excess dietary glucose is stored as glycogen
B. glycogen is an excellent storage material that provides energy
C. between meals, glycogen stores increase as glucose is released to help maintain glucose concentration in blood.
D. Overnight glycogen stores are mobilized to help maintain blood glucose concentration
C. between meals, glycogen stores increase as glucose is released to help maintain glucose concentration in blood.
. Which of these enzymes is NOT part of glycogenolysis?
A. glycogen phosphorylase C. glucantransferase
B. amylo-alpha-1,6-glucosidase D. amylo 1,4->1,6 transglycosylase
D. amylo 1,4->1,6 transglycosylase
Deficiency of this vitamins is associated with Wernicke’s encephalopathy:
A. Thiamine C. Niacin
B. Riboflavin D. Folic acid
A. Thiamine
The Triad of diarrhea, dermatitis & dementia are symptoms of deficiency of
which vitamins:
A. Thiamin C. Cobalamin
B. Riboflavin D. Niacin
D. Niacin
This essential amino acid is a known precursor of niacin:
A. Tryptophan C. Valine
B. Leuvine D. Isoleucine
A. Tryptophan
Deficiency of this vitamins may result from prolonged intake of isoniazid:
A. Niacin C. Pyridoxine
B. Folic acid D. Thiamine
C. Pyridoxine
The Absorption of this vitamins requires an intrinsic factor secreted by the
parietal cells:
A. Folic acid C. Niacin
B. Cobalamine D. Ascorbic acid
B. Cobalamine
. The main intracellular cation is:
A. Na+ C. H+
B. K+ D. Ca++
B. K+
The hormone which stimulate H2O resorption from the collecting tubules thus
promoting excretion of a concentrated urine is:
A. Vasopressin C. Renin
B. Aldosterone D. Angiotensin II
A. Vasopressin
The main regulatory mechanism for Na++ excretion is;
A. secretion of vasopressin
B. secretion of aldosterone
C. renin-angiotensin aldosterone loop
D. secretion of atrial natriuretic peptides
C. renin-angiotensin aldosterone loop
Which statement is NOT true regarding sodium?
A. Most of the sodium consumed is absorbed from the gut
B. The only additional route for Na+ loss than the kidneys is from the skin in sweat.
C. The volume of the ICF is regulated by regulating Na+ content
D. Low-pressure stretch receptors is the central veins and atria regulate renal handling of Na+.
C. The volume of the ICF is regulated by regulating Na+ content
Which is NOT true regarding potassium?
A. Is chief intracellular cation.
B. Plays a role in acid base balance.
C. Secretion is influenced by aldosterone.
D. Respiratory acidosis greatly influences its secretion.
D. Respiratory acidosis greatly influences its secretion.
Which hormone is classified as a protein or polypeptide hormone?
A. thyroxine C. cortisol
B. estrogen D. aldosterone
A. thyroxine
. Which hormone is NOT secreted by the anterior pituitary?
A. FSH C. Growth hormone
B. Prolactin D. Oxytocin
D. Oxytocin
Which hormone stimulates sperm development in the male?
A. FSH C. Prolactin
B. GH D. TSH
A. FSH
Which hormone inhibits the production of ACTH, TSH, & GH by the pituitary?
A. insulin C. somatostatin
B. vasopressin D. prolactin
C. somatostatin
Which of the following is true regarding IDDM? A. caused by insulin resistance C. autoimmune in nature B. adult onset diabetes D. patients are usually obese
C. autoimmune in nature
Which phase of thyroid hormone is controlled by THS?
A. organification of iodide C. iodine uptake
B. synthesis of thyroglobulin D. iodination of tyrosine
C. iodine uptake
One of the following drugs inhibit the conversion ofTt4 to T3
A. propanolol C. L-thyroxine
B. methyldopa D. noradrenaline
A. propanolol
Most of the enzymes in the synthesis of cortisol is found in the
A. SER C. cytosol
B. RER D. mitochondrion
A. SER
Which of the following is the urinary metabolite of glucocorticoids?
A. Cortisone C. tetrahydrocortisol
B. Cortolone D. tetrahydrocortisone
B. Cortolone
The major androgen in females is:
A. DHEA C. androstenedrone
B. testosterone D. dehydrotestostrone
C. androstenedrone
The precursor of cathecholamines is:
A trypthophan C. threonine
B. tyrosine D. glutamine
B. tyrosine
. The rate limiting step in the conversion of cholesterol to pregnenolone is/are: A. cholesterol side chain cleavage B. dehydroepiadrosterone pathway C. alpha-ring reduction D. progesterone pathway
A. cholesterol side chain cleavage
The condition which results from the lack of testosterone synthesis A. hypogonadism B. testicular feminization syndrome C. virilization D. masculinization
A. hypogonadism
The primary estrogen hormone of ovarian origin:
A. 17B-estradiol C. estriol
B. estrone D. androstenedrone
A. 17B-estradiol
The major hormone of the luteal cycle
A. estrogen C. 17-B Estradiol
B. progesterone D. leuteinizing hormone
B. progesterone
. The major health problem in older individuals due to lower than normal
estrone Loads:
A. osteoporis C. atrophy of secondary sex tissues
B. post-menopausal syndrome D. hypertension
A. osteoporis
Most of the plasma proteins are synthesized in the
A. adipose tissue C. kidneys
B. liver D. brain
B. liver
This alpha-globulin acts as a transport protein for any free hemoglobin that
escapes into plasma.
A. VLDL C. haptoglobulin
B. HDL D. LDL
C. haptoglobulin
Which immunoglobulin is the first antibody to be produced in the primary
response and is the only Ig made by the fetus?
A. G C. A
B. M D. D
B. M
