MCAT Biology : Other Hormone Physiology

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

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Example Question #1 : Other Hormone Physiology

The pancreas is one of the few organs with both exocrine and endocrine functions. Exocrine glands can release a variety of substances via ducts, while endocrine glands release hormones directly into the bloodstream without the use of ducts. Which of these choices is a pancreatic exocrine secretion?

Possible Answers:

Somatostatin

Insulin

Glucagon

Trypsinogen

Aldosterone

Correct answer:

Trypsinogen

Explanation:

There are several pancreatic exocrine secretions, most of which are released into the duodenum of the small intestine. Trypsinogen, which is later cleaved into its active form of trypsin, is one of these. Insulin, glucagon, and somatostatin are endocrine secretions. Aldosterone is not released by the pancreas at all, but is instead secreted by the adrenal cortex.

Example Question #145 : Endocrine System

Which of these hormones is released by the posterior pituitary?

Possible Answers:

Thyroid-stimulating hormone

Prolactin

Oxytocin

Luteinizing hormone

Growth hormone

Correct answer:

Oxytocin

Explanation:

The posterior pituitary only releases two hormones: oxytocin and ADH (antidiuretic hormone). The rest of the hormones are released by the anterior pituitary.

Example Question #2 : Other Hormone Physiology

A gland that secretes both peptide and steroid hormones suddenly starts to malfunction. After analysis it is determined that the gland has dysfunctional free floating ribosomes and smooth endoplasmic reticulum. The rest of the cell machinery is working fine. Which of the following can you conclude about the gland?

Possible Answers:

The gland can still synthesize and secrete both types of hormones

The gland can synthesize and secrete the peptide hormones but not the steroid hormones

The gland cannot synthesize and secrete both types of hormones

The gland can synthesize and secrete the steroid hormones but not the peptide hormones

Correct answer:

The gland can synthesize and secrete the peptide hormones but not the steroid hormones

Explanation:

To answer this question you need to know the organelles within a cell that are involved in secreting peptide and steroid hormones. Peptide hormones are polar molecules made up of proteins. Since they are proteins, peptide hormones are synthesized on ribosomes. There are two kinds of ribosomes: free floating ribosomes and ribosomes on rough endoplasmic reticulum (RER). The free floating ribosomes exist in the cytoplasm and, therefore, create cytoplasmic proteins (proteins that are retained inside the cell’s cytoplasm). Ribosomes on RER, on the other hand, are involved in synthesizing proteins that will be exported out of the cell through exocytosis. Since they are secreted out into the blood, hormones are synthesized on RER ribosomes. The question doesn’t mention anything about the RER ribosomes; therefore, peptide synthesis should be normal.

Steroid hormones are nonpolar molecules that are synthesized in the smooth endoplasmic reticulum. Recall that smooth endoplasmic reticulum plays a major role in synthesis of lipids (particularly cholesterol), a major component of steroid hormones. Therefore, a dysfunctional smooth endoplasmic reticulum will halt steroid hormone production.

Example Question #2 : Other Hormone Physiology

Which of the following hormones most likely affects gene expression in its target cell?

Possible Answers:

Glucagon

TSH

Cortisol

FSH

Correct answer:

Cortisol

Explanation:

Gene expression involves DNA replication, transcription, and translation. Regulation of these processes occur in the nucleus via regulation of essential factors. These factors are regulated by hormones that bind to receptors on the nuclear membrane (which is located inside the cell). Recall that only nonpolar molecules can traverse the nonpolar interior of the plasma membrane; therefore, only nonpolar hormones can enter the cell and bind to receptors on the nuclear membrane. Hormones are classified as peptide or steroid hormones. Peptide hormones  are polar because they contain several protein subunits whereas steroid hormones are nonpolar because they are mostly made up of cholesterol and other types of steroids. Of the given hormones, only cortisol is classified as a steroid hormone; therefore, cortisol most likely has its receptor on the nuclear membrane and functions to regulate gene expression. 

Note that most steroid hormones only bind to receptors on the nuclear membrane and initiate a response to regulate processes involved in gene expression, particularly transcription. This is why many steroid hormones are considered transcription factors. 

Example Question #3 : Other Hormone Physiology

A researcher is analyzing the effects of a specific hormone. He observes that the hormone causes a signaling cascade in the cell that involves a second messenger molecule called cAMP. What can the researcher conclude about this hormone?

Possible Answers:

It is a peptide hormone and it binds to a receptor on the plasma membrane

It is a steroid hormone and it binds to a receptor on the nuclear membrane

It is a peptide hormone and it binds to a receptor on the nuclear membrane

It is a steroid hormone and it binds to a receptor on the plasma membrane

Correct answer:

It is a peptide hormone and it binds to a receptor on the plasma membrane

Explanation:

cAMP, or cyclic adenosine monophosphate, is a key signaling molecule found within cells. Upon activation, cAMP initiates many pathways within a cell that have various functions. Activation of cAMP typically involves an extracellular molecule that binds to and activates a membrane bound receptor. Since it activates cAMP, the hormone mentioned in this question must bind to a receptor on the plasma membrane. Recall that peptide hormones are polar molecules that cannot enter the cell; therefore, peptide hormones bind to receptors on the plasma membrane and activate subsequent pathways such as cAMP. 

Steroid hormones are nonpolar and can traverse through the nonpolar core of phospholipid bilayer (plasma membrane) and bind to receptors on the nucleus or in cytoplasm.

Example Question #4 : Other Hormone Physiology

Consider two glands: gland A and gland B. Gland A releases insulin whereas gland B releases digestive zymogens. What can you conclude about these two glands? 

Possible Answers:

Gland A and gland B release their respective substances into the bloodstream

Gland A is an exocrine gland whereas gland B is an endocrine gland

Both glands could be found in the pancreas

Neither gland is controlled by the hypothalamus

Correct answer:

Both glands could be found in the pancreas

Explanation:

Recall that pancreas is an organ that has both endocrine and exocrine functions. The endocrine cells are found in specialized regions of pancreas called Islets of Langerhans and function to secrete insulin and glucagon. Insulin, a hormone involved in the uptake of glucose from blood, is synthesized and secreted in the beta cells whereas glucagon, a hormone involved in the release of glucose into blood, is synthesized and secreted in the alpha cells of Islets of Langerhans.

The exocrine portion of pancreas is involved in the release of several digestive zymogens into the small intestine. The pancreas connects directly to the duodenum of the small intestine and releases digestive zymogens such as tryspinogen, chymotrypsinogen, and pancreatic amylase. Remember that zymogens are inactive forms of enzymes; upon entering the small intestine these zymogens are cleaved by proteases and converted to their active forms.

Example Question #5 : Other Hormone Physiology

Which of the following is true regarding a peptide hormone and a steroid hormone?

I. Peptide hormones are polar and steroid hormones are nonpolar

II. Peptide hormones can travel freely through blood, but steroid hormones cannot

III. The components that make up peptide hormones are created during translation

Possible Answers:

II only

I only

I, II, and III

I and III

Correct answer:

I, II, and III

Explanation:

There are two main types of hormones: peptide hormones and steroid hormones. Peptide hormones, as the name suggests, are made up of protein subunits (polypeptide chains); therefore, peptide hormones are made from monomeric amino acids. Recall that amino acids contain polar groups such as carboxylic acids and amines. This means that peptide hormones are polar molecules. Steroid hormones are made up of steroid molecules. Recall that steroids are lipid molecules; therefore, steroid hormones are nonpolar. Statement I is true.

Hormones are part of the endocrine system and act on cells that are far away from the glands that released them. Glands release hormones into the bloodstream, which allows them to travel throughout the body (via blood) to the target cell. Since peptide hormones are polar, they can dissolve in the fluid of the blood (water); however, steroid hormones require an amphipathic (both polar and nonpolar regions) protein transporter that can dissolve in the blood. The steroid hormones attach to the nonpolar region of the protein whereas the polar region dissolves in the blood. Peptide hormones can travel freely through the blood, but stroid hormones cannot. Statement II is true.

Peptide hormones are polypeptide chains (proteins) that are made up of amino acids. Recall that translation is the cellular process that synthesizes polypeptide chains by joining amino acids; therefore, peptide hormones are created during translation. Statement III is true.

Example Question #6 : Other Hormone Physiology

What is the primary function of prolactin?

Possible Answers:

To cause contractions during labor

To stimulate ovulation

To stimulate milk production

To regulate the acid-base balance in the body

To regulate metabolism

Correct answer:

To stimulate milk production

Explanation:

Prolactin is responsible for causing milk production in women.

Luteinizing hormone stimulates ovulation; the LH surge is caused by a positive feedback mechanism in which estrogen elicits the release of luteinizing hormone. The thyroid hormones generally regulate metabolism, and are themselves regulated by thyroid-stimulating hormone. Antidiuretic hormone and aldosterone indirectly regulate the acid-base balance of the body by adjusting reabsorption rates in the excretory system. The presence of these hormomes leads to water retention, which will dilute the blood. Oxytocin stimulates contractions during labor.

Example Question #8 : Other Hormone Physiology

Vasopressin is an alternate name for which hormone?

Possible Answers:

Luteinizing hormone

Antidiuretic hormone

Prolactin

Thyroid-stimulating hormone

Aldosterone

Correct answer:

Antidiuretic hormone

Explanation:

Antiduretic hormone (ADH) is alternatively known as vasopressin. It is secreted from the posterior pituitary gland and acts on the collecting ducts of the kidney to facilitate the reabsorption of water. Thus, ADH reduces the volume of urine formed, and increases blood volume.

Example Question #9 : Other Hormone Physiology

There are a large variety of over-the-counter pregnancy tests, although all of them share a set of common principles.

These home pregnancy tests are immunoassays which detect the presence of the peptide hormone human chorionic gonadotropin (hCG). hCG is produced by the fertilized ovum and released into the mother's bloodstream, preventing the degradation of the corpus luteum and thereby preventing menstruation. By the time of the mother's first missed period, hCG levels in the urine are high enough to detect.

The home pregnancy test generally involves dipping a stick containing immobilized hCG monoclonal antibodies into a urine sample. If hCG is present in the urine, it will bind to the monoclonal antibodies on the dipstick. The dipstick is then placed in a solution containing a second monoclonal antibody which recognizes the bound hCG antibody complex on the surface of the dipstick. This second antibody is conjugated to colloidal gold particles which change color when they are immobilized, indicating a positive test result (i.e., pregnancy).

Which of the following can be concluded from information given in the passage?

Possible Answers:

hCG does not enter the mother's bloodstream

hCG is also secreted by the mother

antibodies must be bound to the hCG peptide hormone in the bloodstream before entering the urine in order for a positive test result to become registered

The actions of progesterone are counteracted by hCG

The tubules of the kidney do not reabsorb all the hCG filtered in the glomerulus

Correct answer:

The tubules of the kidney do not reabsorb all the hCG filtered in the glomerulus

Explanation:

In the passage it is stated that hCG is detected in the urine. In order to get there, the hormone must be filtered from the blood into the kidney tubules (via the glomerulus). The tubules must then not reabsorb all of it back into the blood; instead, the hCG must be allowed to leave in the urine. The other answer choices can be eliminated after consideration. The answer choice, 'hCG is also secreted by the mother', is wrong because hCG is only secreted by the fertilized embryo; if it was also secreted by the mother, the pregnancy test would not be effective because hCG could be detected in non-pregnant mothers.

In either case, the passage does not imply that the mother makes hCG. Answer choice, 'hCG does not enter the mother's bloodstream', can be eliminated because the passage directly states that hCG is released into the mother's bloodstream. The answer choice, 'The actions of progesterone are counteracted by hCG', is wrong because hCG works to maintain the corpus luteum, which secretes progesterone. If anything, hCG works to maintain the production and function of progesterone, not counteract it. 

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