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USABO Open Exam with correct Answers
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USABO Open Exam with correct Answers
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USABO Open Exam with correctAnswers
Assume a person is placed on cortisol medication, a glucocorticoid. How would you
expect the rates of ACTH and CRF hormone production to change in the person?
A. ACTH production would increase, CRF production would increase
B. ACTH production would increase, CRF production would decrease
C. ACTH production would decrease, CRF production would decrease
D. ACTH production would decrease, CRF production would increase
E. ACTH and CRF production would not change - Answer -D. ACTH production would
decrease, CRF production would increase
The adrenal cortex reacts to stress and responds to endocrine signals. Stressful stimuli
cause the hypothalamus to secrete a releasing hormone that stimulates the anterior
pituitary to release the tropic hormone ACTH. When ACTH reaches its target via the
bloodstream, it stimulates cells of the adrenal cortex to synthesize and secrete a family
of steroids called corticosteriods [There are two main types in humans: glucocorticoids,
such as cortisol and the mineralocorticoids, such as aldosterone]. The elevated levels of
corticosteriods in the blood suppress the secretion of ACTH. The production of ACTH
therefore decreases and CRF, corticoptropin-releasing factor/hormone, increases.
Carbon particles were injected into the blood of mice. In which of the following places
would you most likely find the particles?
A. In the glomerular filtrate
B. In the adipose tissue of the liver
C. In monocytes of the spleen
D. In plasma cells of the bone marrow
E. In the loops of Henle - Answer -C. In monocytes of the spleen
Monocytes constitute 5% of leukocytes, which are part of a phagocytic defense
(ingestion of invading organisms by white blood cells). New monocytes circulate in the
blood for only a few hours and then migrate into tissues, developing into large
macrophages. Organs of the lymphatic system that trap "foreign" molecules and
particles are the spleen, lymph nodes, adenoid, tonsil, appendix and Peyer's patch,
which is located in the small intestine.
Kidneys provide osmoregulation for the body. Consumption of which nutrient creates
the greatest need for osmoregulation?
,A. Cellulose
B. Fat
C. Oil
D. Protein
E. Starch - Answer -D. Protein
Osmoregulation is the control of water balance in organisms living in hypertonic,
hypotonic, or terrestrial environments. Osmoregulation also holds the concentration of
solutes in the blood (and indirectly, the concentration in tissues) at appropriate levels.
The kidney has two distinct regions, the outer renal cortex and the inner renal medulla,
which are packed with nephrons. Nephrons consist of the glomerulus and Bowman's
capsule. Bowman's capsule contains porous capillaries that are permeable to water and
small solutes. Proteins are large molecules, which generally do not filter. The high
concentration of proteins in the blood creates high osmotic pressure. Osmoregulation in
the kidneys maintains the body's water balance and solute concentration in the blood
During translation in prokaryotes, the ribosome binds to:
A. the TATA box.
B. the mRNA cap.
C. the terminator sequence.
D. an enhancer sequence.
E. the Shine-Dalgarno sequence. - Answer -E. the Shine-Dalgarno sequence.
Translation is the synthesis of a polypeptide, which occurs under the direction of mRNA.
In prokaryotes, the DNA is not segregated from ribosomes and the other protein-
synthesizing equipment. Transcription and translation are coupled, with ribosomes
attaching to the leading end of an mRNA molecule, at the Shine-Dalgarno sequence
while transcription is still in progress. A short stretch of nucleotides on a prokaryotic
mRNA molecule, upstream of the translational start site that serves to bind to ribosomal
RNA, bring the ribosome to the initiation codon on the mRNA.
The quaternary structure of a protein is determined by:
A. interactions between distant amino acids of the same polypeptide.
B. interactions between close amino acids of the same polypeptide.
C. interactions between amino acids of different polypeptide chains.
D. the arrangement of the alpha helices and beta sheets in the protein.
E. binding of a coenzyme or cofactor to the protein. - Answer -C. interactions between
amino acids of different polypeptide chains.
Quaternary structure is the association between two or more polypeptides that make up
a protein. Proteins that contain more than one chain of amino acids are called
oligomeric proteins, and each chain is called a protomer. These chains are held
together to form the larger protein by bonds that exist between the side groups of
different chains. As with tertiary structure, the bonds involved in holding these separate
, chains together can be van der Waals bonds, hydrogen bonds, ionic bonds or covalent
bonds.
Which of the following is not a function of the parasympathetic division of the nervous
system?
A. Constriction of the bronchi in the lungs
B. Constriction of the pupil of the eye
C. Slowing of the heart rate
D. Stimulation of the adrenal medulla
E. Stimulation of activity of the stomach and the intestines - Answer -D. Stimulation of
the adrenal medulla
Activity of the parasympathetic nerves decrease heart rate, constrict the pupils of the
eye, stimulate salivary glands, constrict bronchii in the lungs, stimulate activity of the
stomach and the intestines, stimulate activity of the pancreas, stimulate the gallbladder,
promote voiding from the bladder and erection of the genitals.
You place a growing seedling in an east-facing window. On which side of the plant will
active auxin accumulate?
A. North side
B. South side
C. East side
D. West side
E. Equally distributed on all sides of the plant - Answer -D. West side
A houseplant in a window will grow towards light. If you rotate the plant, it will soon re-
orient its growth such that the terminal portions of the branches again bend toward the
window. Auxin is a term used for a group of plant hormones that stimulate stem
elongation, root growth and cell differentiation. In angiosperms active auxins
accumulate in its shaded side and stimulate cell elongation such that the shaded side
overgrows the more brightly lighted side which results in a bending toward the light.
Which of the following is NOT a characteristic of all mammalian species?
A. Dorsal nerve cord
B. Endothermic metabolism
C. Lungs
D. Mammary glands
E. Placenta - Answer -E. Placenta
Mammalian species were first defined by their possession of mammary glands, which
produce milk. Other mammalian characteristics are the possession of hair, a four-
chamber heart, lungs, variety of teeth size and shape, and endothermic metabolism.
Some mammals however do not have placentas, such as monotremes and marsupials.
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