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Example Questions
Example Question #781 : Mcat Biological Sciences
Grave's Disease is an autoimmune disorder that causes antibodies to bind onto thyroid-stimulating hormone (TSH) receptors on the thyroid. This causes the thyroid to constantly release T3 and T4. What effect would this have on TSH levels?
TSH levels would decrease, and then increase
TSH levels would increase, and then decrease
TSH levels would be decreased
TSH levels would be increased
TSH levels would not be affected
TSH levels would be decreased
Thyroid-stimulating hormone (TSH) levels would be decreased.
The thyroid hormones T3 and T4 act in a negative feedback loop to regulate thyroid activity. Release of TSH increases thyroid activity, while release of the thyroid hormones decreases thyroid activity by suppressing further release of TSH. Since the thyroid is overstimulated in Grave's Disease, excess T3 and T4 are being produced. These hormones will act on the feedback loop to suppress TSH release, lowering TSH levels in individuals with this disease. Since the antibodies bind to the TSH receptors, there are increased levels of T3 and T4 in the body, which negatively inhibit the production of TSH because the body is already flooded with the products of TSH action.
Example Question #1 : Endocrine Regulatory Mechanisms
Insulin is a peptide hormone responsible for lowering blood glucose levels. In some forms of diabetes mellitus, insulin is lacking. Why do diabetics inject insulin into their bodies rather than consuming an insulin pill?
Injecting insulin delivers it directly to the brain, while consuming a pill would require it to travel through the gastrointestinal tract first
There is no advantage to injecting insulin versus consuming an insulin pill; insulin is injected simply because that is how it is manufactured
Injecting insulin directly into the bloodstream is much safer than consuming an insulin pill
Injecting insulin allows for it to be dispensed in a slow-release fashion, while consuming an insulin pill releases the hormone rapidly
Injecting insulin delivers it directly into the bloodstream, while consuming a pill would require it to travel through the gastrointestinal tract before being utilized
Injecting insulin delivers it directly into the bloodstream, while consuming a pill would require it to travel through the gastrointestinal tract before being utilized
Injecting insulin into the body delivers it directly into the bloodstream, while consuming an insulin pill would require it to pass through the gastrointestinal tract. In the gut, the pill would be degraded first and then absorbed into the bloodstream. This entire process would result in a small amount of insulin circulating in the blood, and therefore be much less effective than an insulin injection. Additionally, injecting insulin directly allows more rapid administration of a more consistent dose.
Example Question #782 : Mcat Biological Sciences
Which hormones act as antagonists to bone growth?
Adrenalines and cortisols
Vasopressin and erythropoietin
Gonadotropins and luteins
Epinephrines and norepinephrines
Androgens and estrogens
Androgens and estrogens
Androgens and estrogens, the sex hormones, feedback to inhibit somatotropins, the growth hormones. In humans, the sex hormones are produced in puberty, disabling the growth plates and halting growth.
Example Question #143 : Endocrine System
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?
Insulin
Aldosterone
Somatostatin
Glucagon
Trypsinogen
Trypsinogen
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 #144 : Endocrine System
Which of these hormones is released by the posterior pituitary?
Thyroid-stimulating hormone
Oxytocin
Luteinizing hormone
Prolactin
Growth hormone
Oxytocin
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?
The gland cannot synthesize and secrete both types of hormones
The gland can synthesize and secrete the steroid hormones but not the peptide hormones
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 can synthesize and secrete the peptide hormones but not the steroid hormones
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 #783 : Mcat Biological Sciences
Which of the following hormones most likely affects gene expression in its target cell?
Cortisol
Glucagon
FSH
TSH
Cortisol
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 #784 : Mcat Biological Sciences
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?
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 nuclear membrane
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 plasma membrane
It is a peptide hormone and it binds to a receptor on the plasma membrane
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 #785 : Mcat Biological Sciences
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?
Both glands could be found in the pancreas
Gland A is an exocrine gland whereas gland B is an endocrine gland
Neither gland is controlled by the hypothalamus
Gland A and gland B release their respective substances into the bloodstream
Both glands could be found in the pancreas
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 #6 : 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
I only
I, II, and III
II only
I and III
I, II, and III
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.
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