Biochemistry-Physiology 3 1987

The km value of an enzyme is numerically equal to
1. Half the maximum velocity expressed in moles/liter
2. Velocity of a reaction divided by substrate concentration
3. Substrate concentration in moles/liter necessary to achieve half the maximum velocity of a reaction
4. Maximum velocity divided by half the substrate concentration in moles necessary to achieve maximum velocity

The major driving force for formation of a lipid micelle is
1. Protein-lipid interaction
2. Hydrophobic interaction between hydrocarbon tails
3. Hydrogen bonding between water molecules of the micellar core
4. Electrostatic interaction between the micellar core and polar heads

Excluding the effect of drugs, apnea occurring after hyperventilation of an anesthetized patient results from
1. Decreased demand for oxygen 
2. Increased cerebral blood flow
3. Decreased carbon dioxide tension
4. Increased hydrogen ion concentration
5. Decreased oxygenation of carotid bodies

Within physiologic limits, activity of the respiratory center is decreased directly by
1. Decreased pH
2. Increased pH
3. Increased hemoglobin concentration
4. Increased plasma carbon dioxide partial pressure

Strong stimulation of spindles in the masseter muscle causes
1. Relaxation of the masseter muscle
2. Contraction of the masseter muscle
3. Contraction if the digastric muscle
4. No change in the mandibular position

Chondroitin sulfate occurs primarily in
1. Bile
2. Blood
3. Liver
4. Urine
5. Cartilage

Complete hydrolysis of one mole of lecithin yields
1. L-amino acids
2. D-monosaccharides
3. ohosohatidylethanolamines
4. 2 fatty acids, 1 glycerol, 1 phosphoric acid and 1 choline residue
5. 2 fatty acids, 1 glycerol, 1 phosphoric acid and 1 cholesterol molecule

Which of the following amino acids lessens the need for phenylalanine?
1. Lysine
2. Leucine
3. Glycine
4. Tyrosine 
5. Tryptophan

What is the product P in the following reaction?
a-ketoglutarate + alanine ⇌ pyruvate + P

1. Glutamate
2. Glutamine
3. Aspartate
4. Succinate
5. Pyridoxine phosphate

An action potential in a nerve fiber is related to
1. Entry of sodium ion followed by exit of potassium ion
2. Flow of electrons across the membrane following a change in membrane permeability 
3. Change orientation of molecules in the membrane giving rise to a static potential difference
4. A breakdown of metabolic products resulting in different concentrations of potassium across the membrane

Pantothenic acid is an integral part of
1. NAD
2. Cobalamin
3. Folic acid
4. Coenzyme A
5. Pyridoxine phosphate

Spatial summation results from the 
1. Convergence of several afferent impulses not heave post synaptic nerve soma
2. Repetitive firing of discharges (from the same presynaptic terminal), eventually producing an action potential
3. Exhaustion of the stores of transmitter substance at the synapse
4. Elaboration of some inhibitory substance, such as y-aminobutyric acid, at the synapse

What type of bond link amino acid residues to form proteins?
1. Amide
2. Anomeric
3. Epimeric
4. Hydrogen
5. Glycosidic

Of the following, the most immediate source of oxaloacetic acid during metabolism is
1. Glycine
2. Aspartic acid
3. Glutamic acid
4. Acetoacetic acid
5. a-ketoglutaric acid

Proteins rich in basic amino acids, such as lysine and arginine, which bind strongly to DNA are
1. Albumins
2. Keratins
3. Histones
4. y-globulins
5. Scleroproteins

ATP inhibits phosphofructokinase even though ATP is also a substrate for the enzyme. This phenomenon is an example of
1. Genetic repression
2. genetic suppression
3. Allosteric inhibition
4. Competitive inhibition
5. Noncompetititive inhibition

When are nerve fibers hypoexcitable?
1. During resting potential
2. At the firing level
3. During local depolarization
4. During negative atpfter-potential
5. During positive after potential

The spinal cord is the only structure in the central nervous system necessary for which of the following body functions?
1. Respiration 
2. Simple reflex
3. Temperature regulation
4. Coordinated muscle movement

Addition of synthetic polyuridylic acid to a cell-free system capable of protein synthesis results in greatly enhanced incorporation of phenylalanine into peptide linkages.  In this system, polyuridylic acid is performing a function normally performed by
1. DNA
2. transfer RNA
3. Ribosomal RNA
4. Messenger RNA
5. Mitochondrial RNA

Neutral fats contain mixtures of one or more fatty acids esterified with
1. Sterol
2. Glycerol
3. lecithin
4. Sphingosine
5. Alcohols of high molecular weight

Calcium ions trigger contraction of muscles by binding to
1. Actin 
2. Myosin
3. Troponin
4. Tropomyosin

The degenerate nature of the genetic code implies 
1. A common tRNA for at least two amino acids
2. That a remarkable degree of inaccuracy occurs in transcription
3. The existence of multiple codons for each amino acid
4. The existence of multiple species of ribosomes for control of messenger translation

Vitamin A functions to
1. Prevent pellagra
2. Promote absorption of calcium
3. Promote differentiation of epithelial cells
4. Maintain the integrity of connective tissues

In which of the following conditions is oxygen partial pressure in arterial blood low?
1. Anemia
2. Polycythemia
3. Pulmonary AV shunt
4. Hipovolemia due to hemorrhage

Which of the following characterize the links between monomeric units of Nucleic acids?
1. Ionic bonds
2. Glycosidic bonds
3. Phosphidester bonds
4. Phosphotriester bonds

Purine bases taken in the human diet in the form of DNA or RNA are mostly
1. Excreted as urea
2. Excreted in the form of Uric acid
3. Reused and converted to ATP needed as a source of energy
4. Broken down to give NH3 and either Masonic acid or methylmalonic acid

Ribose phosphate needed for Nucleic acid synthesis can be derived from
1. Gluconeogenesis
2. The pentose phosphate pathway
3. The Kreb's tryicarboxylicic acid cycle
4. Decarboxylation of aromatic amino acids
5. One-carbon transfer from tetrahydrofolate derivatives

A submaximal direct stimulus to a skeletal muscle causes
1. Contraction of no fibers
2. Contraction of some fibers
3. Partial contraction of all fibers in the muscle
4. Less contraction than with a subminimal stimulus 
5. More contraction than with a maximal stimulus

A deficiency in choline in the diet may cause abnormalities in metabolism of 
1. Lipids
2. Proteins
3. Minerals 
4. Carbohydrates
5. Nucleoproteins

Destruction of the cerebellum cause lost of 
1. Memory
2. Vision
3. Hearing
4. Muscular coordination
5. Both (2) and (3) above

Which of the following lipids participates in mitochondrial electron transport
1. Ubiquinone
2. B-carotene
3. a-tocopherol
4. Sphingomyelin

Corti's organ is responsible for perception of
1. Light
2. Sound
3. Taste
4. Temperature
5. Proprioception

The annulospiral (primary) ending of the skeletal muscle spindle is stimulated when the
1. Muscle is relaxed
2. Muscle is stretched
3. Intramural fibers are relaxed
4. Gamma efferent fibers are inhibited

Functionally, visceral smooth muscle and cardiac pacemaker cells are similar in that
1. Neither contracts without neural point
2. Neither has a true "resting" membrane potential
3. Both require a precontractile stretch to initiate contraction 
4. The "resting" membrane potential of each is approximately 85 mV

Failure of the heart to show tetanus when stimulated is explained by
1. Fatigue
2. Automaticity
3. A long chronaxie
4. A long refractory period

The usual plasma concentration of glucose is 80-100 mg/dl., yet, normally glucose does not appear in the urine.  The best explanation for the fact is 
1. Glucose is freely filtered, but is removed by the collecting duct
2. Glucose is freely filtered, but is removed by reabsorption in the proximal convoluted tubule
3. Glucose is secreted by the proximal convoluted tubule and reabsorbed by the distal convoluted tubule
4. The glomerulus prevents glucose from being filtered into the nephron

Avidin influences which of the following vitamins?
1. Niacin
2. Biotin
3. Thiamine
4. Tocopherol 
5. Phylloquinone

Mobilization of blood sugar from liver glycogen occurs by way of a series of enzymatic reactions.  The last step in this sequence is catalyzed by
1. Glucokinase
2. Adenylate cyclase
3. Glucose-6- phosphatase
4. Glycogen phosphorylase
5. Phosphorylase phosphatase

Acids found in the citric acid (krebs) cycle are
1. Glutamic acid and succinct acid
2. Glucoronic acid and aspartic acid
3. Oxaloacetic acid and aspartic acid
4. Oxaloacetic acid and pyruvic acid
5. Oxaloacetic acid and a-ketoglutaric acid

Albinism is a genetic disease that results in incomplete metabolism of 
1. Alanine
2. Tyrosine
3. Cysteine
4. Histidine
5. Tryptophan

Which of the following reactions is the immediate source of energy for muscle contraction?
1. Creatinine ⇀ creatinine

2. ATP ⇀ ADP + inorganic phosphate

3. Creatinine phosphate + ADP ⇀ ATP + creatine

4. Creatine phosphate ⇀ Creatine + inorganic phosphate

Decreased blood colloidal osmotic pressure causes fluid to shift from
1. Interstitial space to blood
2. Blood to interstitial space
3. Intracellular space to interstitial space
4. Extracellular space to intracellular space
5. None of the above

The most abundant form of iron in human blood plasma is found 
1. As free Fe++
2. As free Fe +++
3. As ferritin
4. Associated with transferrin
5. Associated with ceruloplasmin

Hydroxylation at the 1 position of 25 hydroxycholecalciferol occurs primarily in the
1. Skin
2. Liver
3. Kidney
4. Intestinal mucosa

Carbonic anhydrase in erythrocytes increases
1. Rate of dissociation of H2CO3
2. Rate of formation of oxyhemoglobin
3. Permeability of erythrocytes to HCO3
4. Formation of carbamino compounds with hemoglobin

Which of the following is present in plasma but absent in serum?
1. Albumin
2. Globulin
3. Lecithin
4. Fibrinogen
5. Prothrombin

Which of the following hormones are produced by the neurohypophysis and affect contraction of smooth muscle?
1. Vasopressin (ADH) and oxytocin
2. Thyrotropin and intermedin
3. Adenotropic and somatotropin
4. Aldosterone and luteinizing hormone

During extended, strenuous exercise, the energy require for contracting skeletal muscle is supplied largely from
1. Oxidation of fatty acids and acetoacetate
2. Oxidative decarboxylation of pyruvic acid to acetyl coenzyme A
3.  Oxidation of acetyl coenzyme A in the tryicarboxylic acid cycle
4. Anaerobic transformation of glucose from glycogen to lactic acid

Dental plaque arises primarily as a result of enzymatic reactions using which of the following?
1. Sucrose and lipid
2. Sucrose and saliva
3. Glucose and saliva
4. Glucose and protein

Compared with systemic circulation under normal conditions, pulmonary circulation is characterized by low pressure and
1. Low flow and low resistance
2. Equal flow and low resistance
3. Low flow and equal resistance 
4. Equal flow and equal resistance
5. High flow and equal resistance

Sounds heard during systole in the antecubital space are produced by 
1. Closure of AV valves
2. Closure of the aortic valve
3. Turbulent blood flow through the artery
4. Laminar blood flow through the occluded artery

The PR interval in an electrocardiogram is an index of the 
1. Length of auricular filling
2. Period of isometric relaxation
3. Length of auricular contraction
4. Conduction time between atria and ventricles
5. Period of maximal ejection of ventricular systole

The high ratio of postganglionic to preganglionic fibers in the sympathetic system has The physiologic result that
1. Convergence of stimuli occurs
2. Synaptic transmission is low, leading to a delay in response
3. Stimulation of the sympathetic nervous system leads to widespread effects
4. Stimulation of the sympathetic nervous systems leads to very localized, discrete effects
5. The presuynaptic stimulus must have a greater amplitude than when the number of preganglionic and postganglionic fibers is equal

Cell bodies of sympathetic preganglionic neurons are located in
1. dorsal root ganglia
2. Sympathetic chain ganglia
3. The brain stem and the spinal cord
4. Thoracic and lumbar segments of the spinal cord 
5. None of the above

Which of the following causes some degree of temporary alkalosis?
1. Hyperventilation 
2. High fluid intake
3. Excessive smoking
4. Severe muscular effort
5. Ingestion of ammonium chloride

The pathway of extramitochondrial synthesis of even-numbered fatty acids differs from that of the catabolism of fatty acids in that
1. Malonyl CoA is an intermediate in synthesis
2. Acyl carrier protein is needed in catabolism
3. No flavoprotein enzymes are required for catabolism
4. Propionyl CoA may serve as an intermediate in synthesis

Tropic hormone releasing factors produced in the hypothalamus are transported into the anterior pituitary through
1. Nerve impulses
2. The ultrashort feedback mechanism
3. The peripheral circulatory system
4. The microcirculatory portal system
5. Long nerve fibers or ducts that also transport neurophysins

Glomerular filtration rate may be determined by clearance of
1. Urea
2. Water
3. Inulin
4. Glucose
5. Para-aminohippuric acid and (PHA)

Secretin functions in digestion of proteins by increasing
1. Flow of bile
2. Secretion of pepsin
3. Flow of pancreatic juice
4. Secretion of carboxypeptidase

The air remaining in the alveoli at the end of a forced maximal expiration is the
1. Tidal volume
2. Vital capacity
3. Residual volume
4. Expiratory reserve volume
5. Inspiratory reserve volume

Normal hemoglobin in concentration is about 15 gm/dl. blood and normal arterial oxygen content is about 20 ml. O2/dl. blood.  an anemic individual breathing room air with a hemoglobin concentration of 10 gm./dl. Blood is expected to have
1. Normal arterial oxygen tension and normal arterial oxygen content
2. Reduced arterial oxygen tension and normal arterial oxygen content
3. Normal arterial oxygen tension and reduced arterial oxygen content
4. Reduced  arterial oxygen tension and reduced arterial oxygen content

The hemoglobin dissociation curve is shifted to the right by
1. A decrease in temperature
2. An increase in arterial PCO2
3. An increase in arterial hydrogen ion concentration
4. Both (1) and (3) above
5. Both (2) and (3) above

Prolonged medication with cortisol produces atrophy of the adrenal cortex through
1. Inhibition of ACTH production 
2. inhibition of aldosterone secretion
3. direct action of the synthesis of C21
4. None of the above

Countercurrent multiplier activity of the kidney is dependent upon the
1. Presence of ADH
2. Reabsorption of water from collecting ducts 
3. Intensity of vasoconstriction of efferent arterioles
4. Active reabsorption of water in the ascending limb of the loop of Henle 
5. Active reabsorption of sodium ions in the ascending limb of the loop of Henle

In the absence of compensatory changes, a drop in blood pressure results from
1.Vasoconstriction
2. Increased hematocrit
3. Increased stroke volume 
4. Increased cardiac output
5. Decreased venous return

The chemical mediator at the neuroeffector junction in sweat glands is 
1. Atropin
2. Serotonine
3. Epinephrine
4. Acetylcholine
5. Norepinephrine

Hypothyroidism in an adult results in
1. Myxedema
2. Thyrotoxicosis
3. Osteitis fibrosa cystica
4. Increased basal metabolic rate

Carbon dioxide or bicarbonate is required in the biosynthesis of fatty acids because
1. The bicarbonate/carbonic acid buffer system is very efficient at the pH optimum of this sensitive enzyme system
2. Bicarbonate is a positive effector for this system and favorably alters the conformation of it's enzyme 
3. Carbon dioxide is incorporated into acetyl coenzyme A forming malonyl coenzyme A, an intermediate in the synthetic process
4. Carbon dioxide is incorporated into carabamyl phosphate, a reactive intermediate in the synthetic process 
5. Carbon dioxide provides an anaerobic environment that prevents oxidation of the sulfhydryl groups in the reactive sites of the enzyme system

Which of the following hormones facilitates reabsorption of sodium in renal tubules?
1. Insulin
2. Cortisone
3. Vasopressin
4. Aldosterone
5. Parathyroid hormone

Which of the following is a principal action of insulin?
1. To mobilize lipid deposits
2. To enhance cell permeability to glucose
3. To decrease cell permeability to glucose
4. To conserve glucose by breaking down amino acids

Which of the following occurs in a normal menstrual cycle?
1. Ovulation generally occurs 10 days from the beginning of the cycle
2. The ovum generally disintegrates or becomes nonviable if it is not fertilized within four days
3. The blood concentration of estradiol increases as the corpus luteum develops
4. The blood level of follicle stimulating hormone increases and the level of lute ionizing hormone decreases at the time of ovulation

The nitrogenous product that is secreted in high amounts after prolonged acidosis is
1. Urea
2. Ammonia
3. Glutamine
4. Creatinine
5. Aspartic acid

Epinephrine is most closely related in structure to
1. Niacin
2. Glucose
3. Glycerol
4. Tyrosine
5. Methionine

Development of ovarian follicles to the point of ovulation is stimulated primarily by
1. Estrone 
2. Progesterone
3. Luteinizing hormone
4. Follicle stimulating hormone
5. Chronic gonadotropin hormone

Neutralization of acids by saliva results mainly from which of the following salivary contents?
1. Mucin
2. Ammonia
3. Carbonate
4. Bicarbonate
5. Amino acids

The mechanism of systemic fluoride action in reducing dental decay is most likely the result of
1. An increase in hardness of the tooth
2. An inhibition of proteolytic enzymes
3. Deposition of CaF2 in areas of enamel
4. An increase in carbohydrate metabolism in the oral cavity as a result of enzyme inhibition
5. A reduction in rate of solubilization of enamel as fluoride content of the tissue increases

The most abundant nonphospholipid component of the cell membrane is
1. Cholesterol
2. Deoxycholate
3. Prostaglandin
4. Macroglobulin
5. Triacykglyceride

After functioning in the small intestines, the largest portion of bile salts are
1. Excreted in the feces
2. Reabsorbed into the central lacteal
3. Destroyed by bacteria in the large intestines
4. Reabsorbed into the portal circulation and reused
5. removed from the circulation by the kidneys and excreted in the urine

What thermodynamic parameter is a measure of randomness or disorder in a system?
1. Entropy
2. Enthalpy
3. Free energy 
4. Potential energy

Which if the following solutions has an osmotic pressure different from all the others?
1. 1 M glucose
2. 1 M sodium chloride
3. 1 M potassium nitrate
4. 1 N lithium iodide
5. 1 N hydrochloride acid

the function of rhythmic segmentation is chiefly that of
1. Macerating food
2. Mixing food with digestive secretions
3. Increasing the surface available for absorption
4. Transporting material down the gastrointestinal tract

Which if the following describes the movement of glycine molecules in an electric field, at a pH of 6.06 (the isoelectric pH for glycine)?
1. Glycine molecules will not move 
2. All molecules will move to the anode
3. All molecules will move to the cathode
4. Half the molecules will move to the anode and half to the cathode
5. None of the above

The arrangement of sugars into D- and L- configurations is based upon their resemblance to D- and L-
1. Glycine
2. Glucose
3. Fructose
4. Glyceraldehyde
5. None of the above

Which of the following proteins contain trace elements essential for their biologic action?
a) Trypsin
b) myoglobin
c) thyroglobulin
d) salivary amylase
e) carbonic anhydrase

Hydrolysis of sucrose by the enzyme Sucrase yields
a) galactose
b) glucose
c) fructose
d) maltose

Normal production of sound enamel and dentin requires adequate amounts of which of the following vitamins?
a) A
b) B12
c) C
d) D
e) E

The amino acid composition of mammalian collagen type I is characterized by the presence of 
a) cytsteine
b) Hydroxyproline and hydroxylysine
c) no sulfur containing amino acids
d) glycine, as nearly one third the total number of amino acid residues
e) a high content of aromatic amino acids

In general, molecules that can penetrate a biological membrane with relative ease are
a) highly charged
b) non polar in nature
c) small in size (below 7.5 A in diameter)

in an experimental animal, the heart rate can ve accelerated by
a) sectioning vagus nerve
b) stimulating vagus nerves
c) section ing sympathetic nerves
d) stimulating sympathetic nerves

Which of the following occur when active transport is involved in the movement of a solute across a biological membrane?
a) expenditure of metabolic energy
b) a gain in free energy by the system
c) a unidirectional movement of the solute
d) movement of the solute against a concentration gradient

Which of the following are examples of local (electronic or subtreshold) potentials?
a) inhibitory post synaptic potentials
b) excitatory post synaptic potentials
c) generator potentials in pacinian corpuscles
d) end plate potentials at the neuromuscular junction
e) all for the above

Hydrolysis of Nucleic acids is likely to yield all of the following EXCEPT
1. Ribise
2. Adenine
3. Deoxyribose
4. Acetic acid
5. Bicarbonate

Which of the following is NOT a primary (major) electrolyte of saliva?
1. Sodium
2. Calcium
3. Fluoride
4. Potassium
5. Bicarbonate

Excessive use of fats by the body as a source of energy during starvation or disturbances in carbohydrate metabolism may lead to any of the following conditions EXCEPT
1. ketosis
2. Acidosis
3. Ketonuira
4. Alkalosis

Which if the following enzymes does NOT function in association with a membrane?
1. Permease
2. Na+/K+ ATPase
3. Adenylate cyclase
4. Phosphofructokinase
5. Coenzyme Q reductase

A substance that is actively secreted by the kidney is helpful in measurement of all of the following EXCEPT
1. Renal blood flow
2. Renal plasma flow
3. Tubular maximum
4. Filtration fraction
5. glomerular filtration rate

Coupled respiration requires all of the following EXCEPT 
1. ADP
2. Oxygen
3. Carbon dioxide
4. An election donor
5. Inorganic phosphate

Each of the following is a function of the liver EXCEPT
1. Bile formation
2. Urea elimination
3. Steroid conjugation
4. Carbohydrate storage
5. Prothrombin synthesis

Gastrointestinal hormones act on each of the following organs EXCEPT the
1. Stomach
2. Pancreas
3. Duodenum
4. Gallbladder
5. Urinary bladder