Other Hormone Physiology - MCAT Biological and Biochemical Foundations of Living Systems

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.

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

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.

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.

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.

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.

Answering this question simply requires picking the answer choice that doesn't have anything in common with the others. Conditions in which specific antibodies are produced which might be tested for using the same technique are described in the passage. After all, antibodies are proteins, and monoclonal antibodies can be made to detect them. HIV infection can be detected by assaying for the antibodies against HIV.Arthritis can be detected by looking for antibodies against "self" proteins. Strep throat can be detected by directly assaying for the presence of bacterial proteins. The same technique which was used to detect hCG can be used in these instances. Tryptophan blood levels, however, cannot be determined using the same methodology. For one thing, tryptophan (an amino acid) does not elicit antibody production. Secondly, the actual levels of substances in the blood can't be detected by the type of test described in the passage. This test yields either a "present" or "not-present" result

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

Answering this question simply requires picking the answer choice that doesn't have anything in common with the others. Conditions in which specific antibodies are produced which might be tested for using the same technique are described in the passage. After all, antibodies are proteins, and monoclonal antibodies can be made to detect them. HIV infection can be detected by assaying for the antibodies against HIV.Arthritis can be detected by looking for antibodies against "self" proteins. Strep throat can be detected by directly assaying for the presence of bacterial proteins. The same technique which was used to detect hCG can be used in these instances. Tryptophan blood levels, however, cannot be determined using the same methodology. For one thing, tryptophan (an amino acid) does not elicit antibody production. Secondly, the actual levels of substances in the blood can't be detected by the type of test described in the passage. This test yields either a "present" or "not-present" result

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.