Biochem 3 exam Flashcards
1
Q
Which of the following are discrete bodies within cells?
a. nuclei c. both a and b
b. mitochondria d. neither a nor b
A
C. Both a and b
2
Q
Where are receptors found?
a. inside the cell nucleus c. inside the mitochondria
b. in the cytoplasm d. on the cell surface
A
D. On the cell surface
3
Q
Ligand is a term which can be used to describe which of the following?
a. a chemical messenger c. a receptor
b. a neuron d. none of these
A
A
4
Q
Which of the following carry messages from the receptor to the inside of the cell?
a. primary messengers c. both (a) and (b)
b. secondary messengers d. neither (a) nor (b)
A
C
5
Q
Secondary messengers perform which of the following functions?
a. transmission of a message from one cell to another
b. transmission of a message from the cell surface to its interior
c. both a and b
d. neither a nor b
A
B
6
Q
Secondary messengers perform which of the following functions?
a. amplification of a message
b. transmission of a message from the cell surface to its interior
c. both a and b
d. neither a nor b
A
C
7
Q
Which of the following functions are performed by secondary messengers?
a. amplification of a message
b. transmission of a message one cell to another
c. both a and b
d. neither a nor b
A
A
8
Q
Which of the following activates the receptor sites for acetylcholine?
a. curare c. opiates
b. nicotine d. none of these
A
B
9
Q
Which of the following blocks the receptor sites for acetylcholine?
a. curare c. opiate
b. nicotine d. none of these
A
A
10
Q
Which of the following activates the receptor sites for enkephalins?
a. curare c. nicotine
b. opiates d. none of these
A
B
11
Q
Which of the following blocks the receptor sites for enkephalins?
a. curare c. opiates
b. morphine d. none of these
A
D
12
Q
Which of the following can be the target of a neurotransmitter?
a. a muscle cell c. a neuron
b. the cell of a gland d. all of these
A
D
13
Q
Which of the following blocks a receptor and prevents its stimulation?
a. an agonist c. both a and b
b. an antagonist d. neither a nor b
A
B
14
Q
Which of the following competes with a natural messenger and stimulates a receptor?
a. an agonist c. both a and b
b. an antagonist d. neither a nor b
A
A
15
Q
Which of the following is true of a hormone?
a. It is produced at the site of its action.
b. It is produced at one location and then transported to its site of action.
c. Either a or b is true, depending on the hormone.
d. Neither a nor b is true.
A
B
16
Q
Which of the following is the long fiber-like part of a nerve cell?
a. the axon c. the synapse
b. a dendrite d. the vesicle
A
A
17
Q
Which of the following is the hair-like part of a nerve cell?
a. the axon c. the synapse
b. a dendrite d. the vesicle
A
B
18
Q
What name is used from the gap between the tip of a nerve cell and its target?
a. axon c. synapse
b. dendrite d. vesicle
A
C
19
Q
Where are neurotransmitters stored in a nerve cell?
a. the axon c. the synapse
b. a dendrite d. the vesicle
A
D
20
Q
Which of the following is used to characterize a material as either a neurotransmitter or a hormone?
a. its chemical composition c. both a and b
b. its physiological behavior d. either a or b
A
B
21
Q
Which of the following hormones is not produced in the pancreas?
a. insulin
b. glucagon
c. renin
d. None, they are all produced in the pancreas.
A
C
22
Q
Which of the following hormones is produced in the kidney?
a. insulin c. renin
b. glucagon d. vasopressin
A
C
23
Q
Which of the following is true of epinephrine?
a. It is a hormone but not a neurotransmitter.
b. It is a neurotransmitter but not a hormone.
c. It is both a hormone and a neurotransmitter.
d. It is neither a hormone nor a neurotransmitter.
A
C
24
Q
Broadly speaking, based on their chemical nature, how many different classes of chemical messengers are there?
a. 2 c. 4
b. 3 d. 5
A
D
25
Hormones can belong to which of the following classes of chemical messengers?
a. adrenergic c. steroid
b. peptidergic d. all of these
D
26
Hormones cannot belong to which of the following classes of chemical messengers?
a. adrenergic c. peptidergic
b. cholinergic d. steroid
B
27
Which of the following functions by activating an enzyme?
a. acetylcholine c. estradiol
b. epinephrine d. insulin
B
28
Which of the following functions by affecting the synthesis of proteins?
a. acetylcholine c. estradiol
b. epinephrine d. insulin
C
29
Which of the following functions by affecting the permeability of membranes?
a. acetylcholine c. estradiol
b. epinephrine d. none of these
A
30
Which of the following functions by affecting the permeability of membranes?
a. acetylcholine c. insulin
b. glucagon d. all of these
D
31
Which of the following messengers acts directly?
a. epinephrine c. vasopressin
b. estradiol d. none of these
B
32
Which of the following acts through a secondary messenger?
a. epinephrine c. luteinizing hormone
b. glucagon d. all of these
D
33
Which of the following is a secondary messenger?
a. cAMP c. vasopressin
b. estradiol d. none of these
A
34
Choline is converted to acetylcholine by which of the following reactions?
a. condensation c. oxidation
b. reduction d. substitution
A
35
How many different kinds of receptors are there for acetylcholine?
a. 1 c. 3
b. 2 d. 4
B
36
36. Which of the following is a secondary messenger associated with acetylcholine?
a. Ca2+ c. Mg2+
b. K+ d. Na+
A
37
How many different subunits are present in the nicotinic acetylcholine receptor?
a. 4 c. 6
b. 5 d. 7
B
38
Which of the following ions can pass through the open channel of the acetylcholine receptor?
a. Ca2+ c. both a and b
b. K+ d. neither a nor b
B
39
Which of the following ions can pass through the open channel of the acetylcholine receptor?
a. K+ c. both a and b
b. Na+ d. neither a nor b
C
40
What concentration of Ca2+ ion is required to trigger the release of acetylcholine?
a. 1 × 10−6 M c. 1 × 10−8 M
b. 1 × 10−7 M d. 1 × 10−9 M
A
41
Which of the following elements is found in all three of the nerve gases parathion, sarin and soman?
a. chlorine c. phosphorous
b. nitrogen d. sulfur
C
42
A nerve gas such as sarin does which of the following?
a. causes a decrease in acetylcholine
b. irreversibly inhibits acetylcholinesterase
c. reversibly inhibits acetylcholinesterase
d. reacts directly with acetylcholine
B
43
Which of the following is true of succinylcholine?
a. In small doses it causes muscles to relax.
b. In small doses it causes muscles to become tense.
c. It is an irreversible inhibitor.
d. None of the above is true.
A
44
Which of the following is true of nicotine?
a. It is an agonist at all doses.
b. It is an antagonist at all doses.
c. It is an agonist at low doses but an antagonist at high doses.
d. It is an agonist at high doses but an antagonist at low doses.
C
45
Botulism toxin acts by doing which of the following?
a. inhibiting the synthesis of acetylcholine
b. irreversibly inhibiting acetylcholinesterase
c. reversibly inhibiting acetylcholinesterase
d. preventing the release acetylcholine from vesicles
D
46
Which of the following is associated with botulism poisoning?
a. improper functioning of the acetylcholine receptor
b. improper release of the acetylcholine messenger
c. improper synthesis of acetylcholine
d. improper synthesis of the acetylcholine messenger
B
47
Which of the following is associated with Alzheimer's disease?
a. improper functioning of the acetylcholine receptor
b. improper release of the acetylcholine messenger
c. improper synthesis of acetylcholine
d. improper synthesis of the acetylcholine messenger
C
48
How many distinct mechanisms are there for the control of neurotransmission by acetylcholine?
a. 1 c. 3
b. 2 d. 4
B
49
Which of the following is an excitatory neurotransmitter?
a. β-alanine c. taurine
b. cysteine d. none of these
B
50
Which of the following is an inhibitory neurotransmitter?
a. aspartic acid c. taurine
b. cysteine d. none of these
C
51
Which of the following is true of the receptor site for amino acid neurotransmitters?
a. All amino acids have a common receptor site.
b. Each amino acid has its own receptor sites.
c. There are four different types of receptor sites corresponding to the four different types of side chains on the amino acids.
d. None of the above is true.
B
52
Which of the following is true of the receptor site for amino acid neurotransmitters?
a. All amino acids have a common receptor site.
b. Each amino acid has a single unique receptor site.
c. There are four different types of receptor sites corresponding to the four different types of side chains on the amino acids.
d. None of the above is true.
D
53
N-methyl-D-aspartate (NMDA) is a receptor for which of the following amino acids?
a. aspartic acid c. glutamic acid
b. asparagine d. glutamine
C
54
Which of the following is an antagonist of the N-methyl-D-aspartate (NMDA) site?
a. γ-aminobutyric acid c. taurine
b. phenylcyclidine d. none of these
B
55
Adrenergic messengers belong to which class of compounds?
a. amides c. amino acids
b. amines d. polypeptides
B
56
Which of the following in an adrenergic messenger?
a. acetylcholine c. taurine
b. dopamine d. all of these
B
57
Which of the following is an adrenergic messenger?
a. dopamine c. serotonin
b. histamine d. all of these
D
58
Which of the following is not an adrenergic messenger?
a. dopamine
b. histamine
c. serotonin
d. None of these, they are all adrenergic messengers.
D
59
Which of the following won a Nobel Prize for studies of signal transduction?
a. K. Mullis c. M. Rodbell
b. M. Nirenberg d. R. Roberts
C
60
Which of the following is associated with signal transduction?
a. amplification of a signal c. modulation of a signal
b. modification of a signal d. none of these
A
61
Adenylate cyclase produces cAMP by acting on which of the following?
a. adenosine c. AMP
b. ADP d. ATP
D
62
Which of the following is produced by the reaction of phosphodiesterase with cAMP?
a. adenosine c. AMP
b. ADP d. ATP
C
63
Which of the following is the time frame for amplification of a signal by cAMP?
a. 1 to 10 milliseconds c. 0.1 second to a few minutes
b. 10 to 100 milliseconds d. more than 5 minutes
C
64
Which of the following is true of the G-protein−adenylate cyclase cascade?
a. It is only associated with monoamine messengers.
b. It is only associated with peptidergic messengers.
c. It is associated with both monoamine and peptidergic messengers.
d. It is associated with neither monoamine nor peptidergic messengers.
C
65
Which of the following diseases is associated with the overproduction of cAMP?
a. Alzheimer's c. Parkinson's
b. cholera d. none of these
B
66
Which of the following diseases is associated with insufficient dopamine?
a. Alzheimer's c. Parkinson's
b. cholera d. none of these
C
67
The reaction which deactivates monoamines by converting them to aldehydes is which of the following?
a. condensation c. oxidation
b. hydrolysis d. reduction
C
68
Antidepressants such as Marplan do which of the following?
a. increase the activity of monoamine oxidases
b. suppress the activity of monoamine oxidases
c. suppress the G-protein−adenylate cyclase cascade
d. suppress the synthesis of monoamine messengers
C
69
Which of the following gaseous molecules functions as a secondary messenger?
a. NH3 c. NO
b. N2O d. NO2
C
70
Which small molecule is produced when histamine is synthesized from histidine?
a. CO2 c. H2O
b. HCl d. NO
A
71
The anti-ulcer drug cimetidine blocks which of the following receptors?
a. only H1 c. both H1 and H2
b. only H2 d. neither H1 nor H2
B
72
Which portion of an enkephalin is believed to fit the receptor site?
a. the C-terminus c. the middle amino acid
b. the entire molecule d. the N-terminus
D
73
Neuropeptide Y does which of the following?
a. stimulate appetite c. suppress pain
b. suppress appetite d. transmit pain signals
A
74
Substance P does which of the following?
a. stimulate appetite c. suppress pain
b. suppress appetite d. transmit pain signals
D
75
How many amino acids make up substance P?
a. 5 c. 9
b. 7 d. 11
D
76
Which of the following is true of peptidergic messengers?
a. None act directly, they all require a secondary messenger.
b. They all utilize G-protein-adenylate cyclase in a second messenger system.
c. They all use derivatives of phosphatidylinositol in a second messenger system.
d. None of the above is true.
A
77
Which of the following reactions is involved in the activation of phosphatidylinositol secondary messengers?
a. dephosphorylation c. reduction
b. phosphorylation d. oxidation
B
78
Which of the following reactions is involved in the deactivation of phosphatidylinositol secondary messengers?
a. dephosphorylation c. reduction
b. phosphorylation d. oxidation
A
79
By which of the following mechanisms do steroid hormones cross plasma membranes?
a. active transport c. both a and b
b. diffusion d. neither a nor b
B
80
Which of the following is true of the receptors for steroid hormones?
a. They are hydrophilic.
b. They are proteins.
c. both a and b
d. neither a nor b
C
81
81. Which of the following is true of the receptors for steroid hormones?
a. They are hydrophobic.
b. They are proteins.
c. both a and b
d. neither a nor b
B
82
A steroid hormone might act by doing which of the following?
a. activating enzymes c. changing membrane permeability
b. affecting gene transcription d. any one of these
D
83
Which of the following types of drugs currently under study for the treatment of Alzeheimer’s disease does not involve amyloid-beta?
a. enzyme inhibitors
b. vaccines
c. antibodies
d. neuroprotective agents.
e. all involve amyloid-beta
D
84
Which of the following best describes the known biological effects of BPA (bisphenol A), an estrogen-like compound?
a. linked to early onset of puberty
b. linked to breast cancer
c. both a and b
d. neither a nor b
D
85
Which of the following is the most universal signaling agent?
a. Ca2+ c. K+
b. Na+ d. Cl–
A
86
Consider a substance which carries a message from a receptor to the inside of a cell. To which of the following classifications does this substance most likely belong?
a. secondary messenger
b. ligand
c. chemical messenger
d. Any of the above.
A
87
Which of the following distinguishes a neurotransmitter from a hormone?
a. the diversity of compounds in the classification
b. the chemical structure of the compounds
c. the source of the compound
d. the distance over which it acts
e. all of the above
D
88
1) Which of the following is NOT a function of a hormone?
a) Regulates chemical composition and volume of the internal environment
b) Regulates metabolism
c) Regulates glandular secretions
d) Produces electrolytes
e) Controls growth and development
D
89
When a hormone is present in excessive levels, the number of target-cell receptors may decrease. This is called
a) receptor recognition.
b) sensory adaptation.
c) paracrine regulation.
d) up-regulation.
e) down-regulation.
E
90
3) Which of the choices below is a type of hormone that acts on neighboring cells without entering the bloodstream?
1. Local hormone
2. Paracrine
3. Autocrine
4. Circulating hormone
a) 1 only
b) 2 only
c) 3 only
d) 4 only
e) Both 1 and 2
E
91
4) Which of the following are a group of lipid-soluble hormones derived from cholesterol?
a) Steroids
b) Thyroid hormones
c) Nitric oxide
d) Amine hormones
e) Peptide hormones
A
92
Which of the following is an eicosanoid?
1. Prostaglandin
2. Leukotriene
3. Glycoprotein
a) 1 only
b) 2 only
c) 3 only
d) Both 1and 2
e) All of these choices
D
93
6) Which of the following statements correctly compares water-soluble hormones with lipid-soluble hormones?
a) Both types of hormone are carried in the blood attached to a carrier protein.
b) Both types of hormone almost always stimulate increases in mRNA transcription.
c) Only water-soluble hormones use second messengers.
d) Only water-soluble hormones require a receptor.
e) Lipid-soluble hormones are not found in the bloodstream.
C
94
7) When one hormone opposes the action of another hormone, it is called a(n)
a) synergistic effect.
b) permissive effect.
c) antagonistic effect.
d) circulating effect.
e) local effect.
C
95
8) Which of the following is NOT a common method of stimulating hormone secretion from an endocrine cell?
a) Signals from the nervous system
b) Chemical changes in the blood
c) Mechanical stretching of the endocrine cell
d) Releasing hormones.
e) Both Signals from the nervous system and Chemical changes in the blood
C
96
9) What controls hormone release from the anterior pituitary gland?
a) Muscle contraction
b) The peripheral nervous system
c) Hormones released from the hypothalamus
d) Action potentials from the thalamus
e) Chemical changes in the cerebrospinal fluid (CSF)
C
97
10) Which of the following anterior pituitary hormones stimulates general body growth?
a) Growth hormone
b) Prolactin
c) Thyrotropin
d) Luteinizing hormone
e) Adrenocorticotropic hormone
A
98
11) Which of the following anterior pituitary hormones stimulates milk production?
a) Luteinizing hormone
b) Prolactin
c) Thyrotropin
d) Melanocyte stimulating hormone
e) Adrenocorticotropic hormone
B
99
12) Which of the following anterior pituitary hormones stimulates the adrenal cortex to secrete cortisol?
a) Leutinizing hormone
b) Prolactin
c) Insulin-like growth factors
d) Melanocyte-stimulating hormone
e) Adrenocorticotropic hormone
E
100
Which of the following anterior pituitary hormones stimulates the gonads to secrete progesterone and/or testosterone?
a) Luteinizing hormone
b) TSH
c) Corticotropin
d) Melanocyte-stimulating hormone
e) Growth hormone
A
101
14) Which type of anterior pituitary cell secretes human growth hormone?
a) Thyrotrophs
b) Gonadotrophs
c) Somatotrophs
d) Lactotrophs
e) Corticotrophs
C
102
15) Which of the following pairs of hormones are secreted by the posterior pituitary gland?
a) Prolactin and growth hormone
b) Melatonin-stimulating hormone and oxytocin
c) Oxytocin and antidiuretic hormone
d) Follicle-stimulating hormone and thyroid-stimulating hormone
e) Prolactin and ACTH
C
103
16) The amount of ADH that is secreted by the posterior pituitary glands varies with
a) blood osmotic pressure.
b) blood calcium levels.
c) blood oxygen levels.
d) blood glucose levels.
e) All of these choices.
A
104
Which of the following hormones opposes the action of parathyroid hormone?
a) Thyroid-stimulating hormone
b) Testosterone
c) Insulin
d) Calcitonin
e) Calcitriol
D
105
18) Which of the following statements does NOT describe a step in the synthesis and secretion of T3 and T4?
a) Iodide trapping
b) Oxidation of iodide
c) Coupling of T1 and T2
d) Synthesis of calcitonin
e) Iodination of tyrosine
D
106
Parathyroid hormone is the major regulator of the plasma concentration of which of the following ions?
a) Calcium
b) Sodium
c) Potassium
d) Chloride
e) Manganese
A
107
Which of the following conditions would result from hyposecretion of aldosterone?
a) Decreased heart rate
b) Decreased airway dilation
c) Dehydration
d) Decreased oxygen delivery to the brain
e) Metabolic acidosis
C
108
Which of the following is NOT a common effect of glucocorticoid stimulation?
a) Protein and fat breakdown
b) Glucose formation
c) Depression of immune responses
d) Reduction of inflammation
e) Increased production of all types of blood cells
E
109
Which blood glucose-lowering hormone is produced by the pancreatic islet cells?
a) Insulin
b) Glucagon
c) Somatostatin
d) Thyroid hormones
e) Calcitonin
A
110
Which of the following hormones promotes increases in the basal metabolic rate (BMR)?
a) Insulin
b) Adrenocorticotropic hormone
c) Glucagon
d) Thyroid hormone
e) Calcitonin
D
111
Which of the following hormones are released in response to decreases in blood glucose concentration?
a) Insulin
b) Luteinizing hormone
c) Glucagon
d) Parathyroid hormone
e) Calcitonin
C
112
Which of the following hormones play key regulatory roles in the body’s long-term response to stress?
a) Insulin, Glucagon, Thyroid hormone
b) hGH, Insulin, Aldosterone
c) Cortisol, hGH, Thyroid hormone
d) Parathyroid hormone, Cortisol, hGH
e) Calcitonin, Thyroid hormone, Insulin
C
113
Which of the following is NOT a common response of the body to long-term stress?
a) Increased lipolysis
b) Increased glycogenesis
c) Increased gluconeogenesis
d) Increased digestive activities
e) Increased breakdown of proteins
D
114
Which of the following is NOT an endocrine gland aging effect?
a) Rise in the blood levels of PTH
b) Less cortisol and aldosterone production
c) Decreased levels of gonadotropins
d) Decreased levels of calcitriol and calcitonin
e) Increase in thymus size
E
115
Which of the following is an incorrect pairing of a body system and an endocrine contribution to that system?
a) Thyroid hormones promote normal development and growth of the skeleton.
b) Erythropoietin regulates the amount of oxygen carried in blood by adjusting the number of red blood cells.
c) Leptin enhances appetite.
d) Glucocorticoids depress inflammation and immune responses.
e) Epinephrine depresses the activity of the digestive system.
C
116
Hypothyroidism during adulthood can produce which of the following disorders?
a) Acromegaly
b) Graves’ Disease
c) Hypoglycemia
d) Cushing’s syndrome
e) Myxedema
E
117
The following is a possible progression of which of the following disorders: Inadequate dietary iodine intake → low level of thyroid hormone in blood → increased TSH secretion → thyroid gland enlargement.
a) Acromegaly
b) Tetany
c) Goiter
d) Cushing’s syndrome
e) Addison’s disease
C
118
Which of the following is an abnormal condition of excess androgen secretion, observed primarily in women, that is characterized by the presence of excessive body and facial hair in a male pattern?
a) Acromegaly
b) Tetany
c) Hirsutism
d) Gynecomastia
e) Myxedema
C
119
A condition characterized by excessive development of mammary glands in a male is called
a) acromegaly.
b) pheochromocytoma.
c) hirsutism.
d) gynecomastia.
e) myxedema.
D
120
All prostaglandins are derived from a 20-carbon precursor molecule called
a) thromboxane.
b) intrinsic factor.
c) thymopoietin.
d) arachidonic acid.
e) cholesterol.
D
121
Human chorionic gonadotropin (hCG) is produced by the
a) placenta.
b) ovaries.
c) testes.
d) pituitary gland.
e) hypothalamus.
A
122
Leptin is a hormone produced by the
a) placenta.
b) ovaries.
c) testes.
d) pituitary gland.
e) adipose tissue.
E
123
The anterior pituitary develops from which of the following germ layers during embryonic development?
a) Mesoderm
b) Endoderm
c) Ectoderm
d) A combination of two of the layers
e) None of the answer selections are correct
C
124
The thyroid gland develops from which of the following germ layers during embryonic development?
a) Mesoderm
b) Endoderm
c) Ectoderm
d) A combination of two of the layers
e) None of the answer selections are correct
B
125
The adrenal medulla develops from which of the following germ layers during embryonic development?
a) Mesoderm
b) Endoderm
c) Ectoderm
d) A combination of two of the layers
e) None of the answer selections are correct
C
126
Endocrine tissues that secrete steroid hormones are derived from
a) mesoderm.
b) endoderm.
c) ectoderm.
d) a combination of two or more layers.
e) none of the layers that are listed.
A
127
Which of the following glands is NOT an endocrine gland?
a) pituitary gland
b) thyroid gland
c) adrenal gland
d) sebaceous gland
e) pineal gland
D
128
Which of the following is NOT a common characteristic of an exocrine gland?
a) Initially secretes its products into a duct.
b) Secretes materials onto outer surface of the body.
c) Secretes materials into the lumen of hollow organs.
d) Its secretory products are carried in body fluids to distant target cells.
e) All the answer selections describe characteristics of exocrine glands.
D
129
Since insulin released from the pancreas is carried in the bloodstream to distant target cells, like muscle cells, it is considered to be a(n)
a) local hormone.
b) circulating hormone.
c) paracrine.
d) autocrine.
e) neurotransmitter.
B
130
Which of the following is an example of a hormone that is secreted from an endocrine gland in response to a chemical change in the blood?
a) Parathyroid hormone release from the parathyroid gland.
b) Insulin release from the pancreas.
c) Glucagon release from the pancreas.
d) ADH release from the posterior pituitary gland.
e) All the answer selections are correct.
E
131
All the following hormones are produced and secreted by the ovaries EXCEPT
a) estradiol.
b) estrone.
c) progesterone.
d) inhibin.
e) follicle-stimulating hormone.
E
132
Which of the following is a protein hormone produced by the testes that inhibits secretion of follicle-stimulating hormone by the anterior pituitary gland?
a) chorionic gonadotropin
b) testosterone
c) estradiol
d) inhibin
e) relaxin
D
133
```
Identify the metabolite that does NOT serve as a precursor of a dietarily essential amino acid:
A. Alpha-ketoglutarate
B. 3-phosphoglycerate
C. Glutamate
D. Aspartate
E. Histamine
```
E
134
```
. Select the CORRECT answer:
The first reaction in the degradation of most of the protein amino acids involves the participation of....
A. NAD+
B. Thiamine pyrophosphate (TPP)
C. Pyridoxal phosphate
D. FAD
E. NAD+ and TPP
```
C
135
```
. Identify the amino acid that is the major contributor to the transport of nitrogen destined for excretion as urea:
A. Alanine
B. Glutamine
C. Glycine
D. Lysine
E. Ornithine
```
B
136
. For metabolic disorders of the urea cycle, which statement is NOT CORRECT:
A. Ammonia intoxication is most severe when the metabolic block in the urea cycle occurs prior to the reaction catalyzed by argininosuccinate synthase
B. Clinical symptoms include mental retardation and the avoidance of protein-rich foods
C. Clinical signs can include acidosis
D. Aspartate provides the second nitrogen of argininosuccinate
E. Dietary management focuses on a low-protein diet ingested as frequent small meals
C
137
Select one of the following statements that is NOT CORRECT:
A. One metabolic function of glutamine is to sequester nitrogen in a nontoxic form
B. Liver glutamate dehydrogenase is allosterically inhibited by ATP and activated by ADP.
C. Urea is formed both from absorbed ammonia produced by enteric bacteria and from ammonia generated by tissue metabolic activity.
D. The concerted action of glutamate dehydrogenase and glutamate aminotransferase may be termed transdeamination
E. Fumarate generated during biosynthesis of argininosuccinate ultimately forms oxaloacetate in reactions in mitochondria catalyzed successively by fumarase and malate dehydrogenase
E
138
Select one of the following statements that is NOT CORRECT:
A. Threonine provides the thioethanol moiety for biosynthesis of coenzyme A
B. Histamine arises by decarboxylation of histidine
C. Ornithine serves as a precursor of both spermine and spermidine
D. Serotonin and melatonin are metabolites of tryptophan
E. Glycine, arginine, and methionine each contribute atoms for biosynthesis of creatinine
A
139
Select one of the following statements that is NOT CORRECT:
A. Excreted creatinine is a function of muscle mass, and can be used to determine whether a patient has provided a complete 24-hour urine specimen
B. Many drugs and drug catabolites are excreted in urine as glycine conjugates.
C. The major nonprotein metabolic fate of methionine is conversion to S-adenosylmethionine.
D. The concentration of histamine in brain hypothalamus exhibits a circadian rhythm
E. Decarboxylation of glutamine forms the inhibitory neurotransmitter GABA
E
140
```
Which of the following is NOT a hemoprotein?
A. Myoglobin
B. Cytochrome c
C. Catalase
D. Cytochrome P450
E. Albumin
```
E
141
```
A 30-year old man presented at a clinic with a history of intermittent abdominal pain and episodes of confusion and psychiatric problems. Laboratory tests revealed increases of urinary Gamma-aminolevulinate and porphobilinogen. Mutational analysis revealed a mutation in the gene for uroporphyrinogen I synthase. The probable diagnosis was:
A. Acute intermitten porphyria
B. X-linked sideroblastic anemia
C. Congenital erythropoietic porphyria
D. Porphyria cutanea tarda
E. Variegate porphyria
```
A
142
Select one of the following statements that is NOT CORRECT:
A. Bilirubin is a cyclic tetrapyrrole
B. Albumin-bound bilirubin is transported to the liver
C. High levels of bilirubin can cause damage to the brains of newborn infants.
D. Bilirubin contains methyl and vinyl groups
E. Bilirubin does not contain iron
A
143
```
A 62-year old female presented at a clinic with intense jaundice, steadily increasing over the preceding 3 months. She gave a history of severe upper abdominal pain, radiating to the back, and has lost considerable weight. She had noted that her stools had been very pale for some time. Lab tests revealed a very high level of direct bilirubin, and also elevated urinary bilirubin. The plasma level of alanine aminotransferase (ALT) was only slightly elevated, whereas the level of alkaline phosphatase was markedly elevated. Abdominal ultrasonography revealed no evidence of gallstones. Of the following, which is most likely the diagnosis?
A. Gilbert Syndrome
B. Hemolytic anemia
C. Type I Crigler-Najjar syndrome
D. Carcinoma of the pancreas
E. Infectious hepatitis
```
D
144
Which one of the following statements about beta-gamma methylene and beta-gamma imino derivatives of purine and pyrimidine triphosphates is CORRECT?
A. They are potential anticancer drugs
B. They are precursors of B vitamins.
C. They readily undergo hydrolytic removal of the terminal phosphate.
D. They can be used to implicate involvement of nucleotide triphosphates by effects other than phosphoryl transfer.
E. They serve as polynucleotide precursors.
D
145
Which one of the following statements about nucleotide structures is NOT CORRECT?
A. Nucleotides are polyfunctional acids.
B. Caffeine and theobromine differ structurally solely with respect to the number of methyl groups attached to their ring nitrogens.
C. The atoms of the purine ring portion of pyrimidines are numbered in the same direction as those of a pyrimidine
D. NAD+, FMN, “active methionine” and coenzyme A all are derivatives of ribonucleotides
E. 3’,5’-cyclic AMP and GMP (cAMP and cGMP) serve as second messengers in human biochemistry
D
146
Which of the following statements about purine nucleotide metabolism is NOT CORRECT?
A. An early step in purine biosynthesis is the formation of PRPP
B. Inosine monophosphate (IMP) is a precursor of both AMP and GMP
C. Orotic acid is an intermediate in pyrimidine nucleotide biosynthesis
D. Humans catabolize uridine and pseudouridine by analogous reactions
E. Ribonucleotide reductase converts nucleoside diphosphates to the corresponding deoxyribonucleoside diphosphates.
E
147
Which of the following statements is NOT CORRECT?
A. Metabolic disorders are only infrequently associated with defects in the catabolism of purines
B. Immune dysfunction are associated both with a defective adenosine deaminase and with a defective purine nucleoside phosphorylase
C. The Lesch-Nyhan syndrome reflects a defect in hypoxanthine-guanine phosphoribosyl transferase
D. Xanthine lithiasis can be due to a severe defect in xanthine oxidase
E. Hyperuricemia can result from conditions such as cancer characterized by enhanced by tissue turnover.
A
148
Which of the following components are found in DNA?
A. A phosphate group, adenine, and ribose
B. A phosphate group, guanine, and deoxyribose
C. Cytosine and ribose
D. Thymine and deoxyribose
E. A phosphate group and adenine
B
149
The backbone of a DNA molecule consists of which of the following?
A. Alternating sugars and nitrogenous bases
B. Nitrogenous bases alone
C. Phosphate groups alone
D. Alternating phosphate and sugar groups
E. Five carbon sugars alone
B
150
```
The interconnecting bonds that connect the nucleotides of RNA and DNA are termed:
A. N-glycosidic bonds
B. 3’,5’ phosphodiester bonds
C. Phosphomonoesters
D. -2’ phosphodiester linkages
E. peptide nucleic bonds
```
B
151
```
Which component of the DNA duplex causes the molecule to have a net negative charge at physiological pH?
A. Deoxyribose
B. Ribose
C. Phosphate groups
D. Chlorine ion
E. Adenine
```
C
152
```
Name the mechanism through which RNAs are synthesized from DNA
A. Replicational duplication
B. Translation
C. Translesion repair
D. Transesterification
E. Transcription
```
E
153
```
Name the enzyme that synthesizes RNA from a double stranded DNA template.
A. RNA-dependent RNA polymerase
B. DNA-dependent RNA convertase
C. RNA-dependent replicase
D. DNA-dependent RNA polymerase
E. Reverse transcriptase
```
D
154
```
What is the name of the unusual repeated stretch of DNA localized at the tips of all eukaryotic chromosomes?
A. Kinetochore
B. Telomere
C. Centriole
D. Chromomere
E. Micromere
```
B
155
```
Given that DNA polymerases are unable to synthesize DNA without a primer, what molecule serves as the primer for these enzymes during DNA replication?
A. Five carbon sugars
B. Deoxyribose alone
C. A short RNA molecule
D. Proteins with free hydroxyl groups
E. Phosphomonoester
```
C
156
```
The discontinuous DNA replication that occurs during replication is catalyzed via the production of small DNA segments termed
A. Okazaki fragments
B. Toshihiro pieces
C. Onishi oligonucleotides
D. Crick strands
E. Watson fragments
```
A
157
```
What molecule or force supplies the energy that drives the relief of mechanical strain by DNA gyrase?
A. Pyrimidine to purine conversion
B. Hydrolysis of GTP
C. Hydrolysis of ATP
D. Glycolysis
E. A proton gradient molecule or force
```
C
158
Eukaryotic RNA polymerases all have a requirement for a large variety of accessory proteins to enable them to bind promoters and form physiologically relevant transcription complexes; these proteins are termed:
A. Basal or general transcription factors
B. Activators
C. Accessory factors
D. Elongation factors
E. Facilitator polypeptides
A
159
```
The DNA segment from which the primary transcript is copied or transcribed is called:
A. Coding strand
B. Initiator methionine domain
C. Translation unit
D. Transcriptome
E. Initial codon
```
A
160
```
Modifications to the nucleotides of the pre-tRNAs, pre-rRNAs, and pre-mRNAs occur:
A. Postprandially
B. Postmitotically
C. Pretranscriptionally
D. Posttranscriptionally
E. Prematurely
```
D
161
```
RNA polymerase II promoters are located on which side of the transcription unit?
A. Internal
B. 3' downstream
C. Nearest the C-terminus
D. Nearest the N-terminus
E. 5’ upstream
```
E
162
```
The bond connecting the initiation nucleotide of the mRNA with the 5-G Cap structure is a 3:
A. 3’-5’ phosphodiester bridge
B. 5’-5’ triphosphate bridge
C. 3’-3’ triphosphate bridge
D. 3’-5’ triphosphate bridge
E. 5’-3’ triphosphate bridge
```
B
163
What sequence feature of mature mRNAs listed below is thought to protect mRNAs from degradation?
A. Special posttranslational modifications
B. 3’PolyC tail
C. 5-G Cap
D. Introns
E. Lariat structures
C
164
What could be consequences of inaccurate mRNA splicing be for the RNA?
A. A single base error at a splice junction will cause a large deletion
B. A single base error at a splice junction will cause a large insertion
C. A single base error at a splice junction will cause a large inversion
D. C and E.
E. A single base error at a splice junction will change the reading frame and result in mRNA mistranslation.
E
165
```
What is the macromolecular complex that associates with introns during mRNA splicing?
A. Splicer
B. Dicer
C. Nuclear body
D. Spliceosome
E. Slicer
```
D
166
. What reaction does reverse transcriptase catalyze?
A. Translation of RNA to DNA
B. Transcription of DNA to RNA
C. Conversion of ribonucleotides into deoxyribonucleotides
D. Transcription of RNA to DNA
E. Conversion of a ribonucleotide to deoxynucleotides in the DNA double helix
D
167
```
If a tRNA has the sequence 5’-CAU-3’, what codon would it recognize?
A. 3’-UAC-5’
B. 3'-AUG-5'
C. 5'-ATG-3’
D. 5’-AUC-3’
E. 5’-AUG-3’
```
E
168
```
What is on the 3’ end of all functional, mature tRNAs?
A. The cloverleaf shop
B. The anticodon
C. The sequence CCA
D. The codon
```
C
169
```
Most aminoacyl-tRNA synthetases possess an activity that is shared with DNA polymerases. This activity is a ___________ function.
A. Proofreading
B. Hydrogenase
C. Proteolytic
D. Helicase
E. Endonucleolytic
```
A
170
```
The three distinct phases of protein synthesis, in the CORRECT order are:
A. Initiation, termination, elongation
B. Termination, initiation, elongation
C. Initiation, elongation, termination
D. Elongation, initiation, termination
E. Elongation, termination, initiation
```
C
171
```
Which amino acid is the initiating amino acid for essentially all proteins?
A. Cysteine
B. Threonine
C. Tryptophan
D. Methionine
E. Glutamic acid
```
D
172
```
The initiatior tRNA is placed within the active 80S complex at which of the three canonical ribosomal “sites” during protein synthesis?
A. E site
B. I site
C. P site
D. A site
E. Releasing factor binding site
```
C
173
```
Name the enzyme that forms the peptide bond during protein synthesis and define its chemical composition.
A. Pepsynthase, protein
B. Peptidyl transferase, RNA
C. Peptidase, glycolipid
D. Peptidyl transferase, protein
E. GTPase, glycopeptide
```
B
174
```
Mutations in the middle of an open reading frame that create a stop codon are termed:
A. Frameshift mutation
B. Missense mutation
C. No-nonsense mutation
D. Point mutation
E. Nonsense mutation
```
E
175
```
What is the directionality of polypeptide synthesis?
A. C terminal to N terminal direction
B. N terminal to 3’direction
C. N terminal to C terminal direction
D. 3’-5’ direction
E. 5’-3’ direction
```
C
176
```
Which of the following cis-acting elements typically resides adjacent to or overlaps with many prokaryotic promoters?
A. Regulatory gene
B. Structural gene(s)
C. Repressor
D. Operator
E. Terminator
```
D
177
```
What is the term applied to a segment of a bacterial chromosome where genes for the enzymes of a particular metabolic pathway are clustered and subject to coordinate control?
A. Operon
B. Operator
C. Promoter
D. Terminal Controller
E. Origin
```
A
178
```
What is the term applied to the complete collection of proteins present in a particular cell type?
A. Genome
B. Peptide collection
C. Transcriptome
D. Translatome
E. Proteome
```
E
179
Which types of molecules interact with eukaryotic mRNA gene core promoter sites to facilitate the association of RNA polymerase II?
A. Termination factors
B. Sequence-specific transcription factors (transactivators)
C. Elongation factors
D. GTPases
E. General, or basal transcription factors
E
180
```
Transcription factors bound at enhancers stimulate the initation of transcription at the cis-linked core promoter through the action of intermediaries termed
A. Coactivators
B. Cotranscription proteins
C. Corepressors
D. Receptors
E. Coordinators
```
A
181
```
What reactions among transcription proteins greatly expand the diversity of regulatory factors that can be generated from a small number of polypeptides?
A. Recombination
B. Homodimerization
C. Heterozygosity
D. Heterodimerization
E. Trimerization
```
D
182
```
The gene region containing the TATA box and extending to the transcription start site (TSS) is often termed the ___________
A. Polymerase home
B. Initiator
C. Start selector
D. Core promoter
E. Operator
```
D
183
Which of the following possible mechanisms for how enhancers can stimulate transcription from great distances are currently thought to be CORRECT?
A. Enhancers can reversibly excise the intervening DNA between enhancers and promoters
B. RNA Polymerase II binds avidly to enhancer sequences.
C. Enhancers unwind DNA
D. Enhancers can search through DNA and bind directly to the associated core promoter
E. Enhancers and core promoters are brought into close proximity through DNA loop formation mediated by DNA binding proteins.
E
184
```
Which of the following histone amino acids are typically acetylated?
A. Lysine
B. Arginine
C. Asparagine
D. Histidine
E. Leucine
```
A
185
Which sequences extend between the 5’methylguanosine cap present on eukaryotic mRNAs to the AUG initiation codon?
```
A. Stop codon
B. Last exon
C. Last intron
D. 3’UTR
E. 5’UTR
```
E
186
Which of the following features of eukaryotic mRNA contribute importantly to message half-life?
```
A. 5’UTR sequences
B. The promoter
C. The operator
D. 3’UTR and Poly A tail
E. The first intron
```
D
187
Regarding membrane lipids, select the one FALSE answer:
A. The major phospholipid by mass in human membranes is generally phosphatidylcholine
B. Glycolipids are located on the inner and outer leaflets of the plasma membrane
C. Phosphatidic acid is a precursor of phosphatidylserine, but not of sphingomyelin
D. Phosphatidylcholine and phosphatidylethanolamine are located primarily on the outer leaflet of the plasma membrane
E. The flip-flop of phospholipids in membranes is very slow
A
188
Regarding membrane transport, select the one FALSE statement:
A. Potassium has a lower charge density than sodium and tends to move more quickly through membranes than does sodium
B. The flow of ions through ion channels is an example of passive transport.
C. Facilitated diffusion requires a protein transporter.
D. Inhibition of the Na+ K+-ATPase will inhibit sodium dependent uptake of glucose in intestinal cells
E. Insulin, by recruiting glucose transporters to the plasma membrane, increases uptake of glucose in fat cells but not in muscle
E
189
Regarding the Na+K+-ATPase, select the one FALSE answer:
A. Its action maintains the high intracellular concentration of sodium compared with potassium
B. It can use as much as 30% of the total ATP expenditure of a cell.
C. It is inhibited by digitals, a drug that is useful in certain cardiac conditions
D. It is localized in the plasma membrane of cells
E. Phosphorylation is involved in its mechanism of action, leading to its classification as a P-type ATP-driven active transporter
A
190
What molecules enable cells to respond to a specific extracellular signaling molecule?
A. Specific receptor carbohydrates localized to the inner plasma membrane surface
B. Plasma lipid bilayer
C. Ion channels
D. Receptors that specifically recognize and bind that particular messenger molecule
E. Intact nuclear membranes
D
191
Indicate the term generally applied to the extracellular messenger molecules that bind to transmembrane receptor proteins:
```
A. Competitive inhibitor
B. Ligand
C. Scatchard curve
D. Substrate
E. Key
```
B
192
The subunits of hetertrimeric G proteins are called the _____, ______, and ______ subunits.
```
A. α, β, and χ
B. α, β, and δ
C. α, γ, and δ
D.α, β, and γ
E. γ, δ, and η
```
D
193
Of the receptors listed below, which can conduct a flow of ions across the plasma membrane when bound to their cognate ligand?
```
A. Receptor tyrosine kinases (RTKs)
B. G protein-coupled receptors (GPCRs)
C. G protein coupled receptors
D. Steroid hormone receptors
E. Ligand-gated channels
```
E
194
Which of the following is NOT a natural ligand that binds to G protein-coupled receptors?
```
A. Hormones
B. Steroid hormones
C. Chemoattractants
D. Opium derivatives
E. Neurotransmitters
```
B
195
Which heterotrimeric G proteins couple receptors to adenyl cyclase via the activation of GTP bound G-alpha subunits?
```
A. Gs family
B. Gq family
C. Gi family
D. G12/13 family
E. Gx family
```
A
196
What must happen in order to prevent overstimulation by a hormone?
A. Hormones must be degraded
B. G proteins must be recycled and then degraded
C. Receptors must be blocked from continuing to activate G proteins
D. Receptors must dimerize
C
197
Which of the following hormones termed the “flight or fight” hormone is secreted by the adrenal medulla?
```
A. Epinephrine
B. Oxytocin
C. Insulin
D. Glucagon
E. Somatostatin
```
A
198
Which hormone is secreted by alpha-cells in the pancreas in response to low blood glucose levels?
```
A. Insulin
B. Glucagon
C. Estradiol
D. Epinephrine
E. Somatostatin
```
B
199
In liver cells the expression of genes encoding gluconeogenic enzymes such as phosphoenolpyruvate carboxykinase is induced in response to which of the following molecules?
```
A. cGMP
B. Insulin
C. ATP
D. cAMP
E. Cholesterol
```
D
200
What happens to protein kinase A (PKA) following the binding of cAMP?
A. The regulatory subunits of PKA dissociate, thereby activating the catalytic subunits
B. PKA catalytic subunits bind to two regulatory subunits, thereby activating the catalytic subunits
C. The inhibitory regulatory subunits dissociate from the catalytic subunits, completely inactivating the enzyme
D. The stimulatory regulatory subunits dissociate from the catalytic subunits, inhibiting the enzyme
E. Phosphodiesterase binds to the catalytic subunits, which results in enzyme inactivation.
A
