USABO OPEN EXAM QUESTIONS AND
ANSWERS GRADED A+ 2025/2026
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 - ANS 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
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,C. In monocytes of the spleen
D. In plasma cells of the bone marrow
E. In the loops of Henle - ANS 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 - ANS 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.
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, C. the terminator sequence.
D. an enhancer sequence.
E. the Shine-Dalgarno sequence. - ANS 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. - ANS 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
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ANSWERS GRADED A+ 2025/2026
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 - ANS 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
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
,C. In monocytes of the spleen
D. In plasma cells of the bone marrow
E. In the loops of Henle - ANS 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 - ANS 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.
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, C. the terminator sequence.
D. an enhancer sequence.
E. the Shine-Dalgarno sequence. - ANS 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. - ANS 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
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
