USABO Open Exam Questions and

USABO Open Exam Questions and Answers 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?

• ACTH production would increase, CRF production would

increase

• ACTH production would increase, CRF production would

decrease

• ACTH production would decrease, CRF production would

decrease

• ACTH production would decrease, CRF production would

increase

• ACTH and CRF production would not change - Correct

Answers ✅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. 1 / 4

USABO Open Exam Questions and Answers Carbon particles were injected into the blood of mice. In which of the following places would you most likely find the particles?

• In the glomerular filtrate
• In the adipose tissue of the liver
• In monocytes of the spleen
• In plasma cells of the bone marrow
• In the loops of Henle - Correct Answers ✅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?

• Cellulose
• Fat 2 / 4

USABO Open Exam Questions and Answers

• Oil
• Protein
• Starch - Correct Answers ✅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:

• the TATA box.
• the mRNA cap.
• the terminator sequence.
• an enhancer sequence.
• the Shine-Dalgarno sequence. - Correct Answers ✅E. the

Shine-Dalgarno sequence. 3 / 4

USABO Open Exam Questions and Answers 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:

• interactions between distant amino acids of the same

polypeptide.

• interactions between close amino acids of the same

polypeptide.

• interactions between amino acids of different polypeptide

chains.

• the arrangement of the alpha helices and beta sheets in

the protein.

• binding of a coenzyme or cofactor to the protein. - Correct

Answers ✅C. interactions between amino acids of different polypeptide chains.

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