USABO OPEN EXAM LATEST 2024/2025 WITH ACTUAL
QUESTIONS AND CORRECT VERIFIED (DETAILED)
ANSWERS/ALREADY GRADED A+
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
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
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.
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