All Free Biology MCQs with Answers
Every Biology question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
19844 questions · page 706 of 1985
7051. Which of the following hormones is least directly regulated by the anterior pituitary?
- A. Epinephrine
- B. Thyroxine
- C. Cortisone
- D. Progesterone
Explanation: Epinephrine is released from the adrenal medulla and regulated by the sympathetic system.
Correct answer: Epinephrine7052. Which of these is NOT true of steroid hormones?
- A. Their receptors are usually located inside the cell
- B. Their effects are long-lived
- C. They interfere at the level of transcription
- D. They cannot cross the cell membrane
Explanation: Because of their nonpolar nature, steroid hormones can easily cross the cell membrane. This enables the hormone to work with its receptor, commonly located inside the cell. Their effects are long-lived since they involve genetic alteration at the transcription level. This, however, also means that steroid hormones take longer than peptide hormones to produce a response.
Correct answer: They cannot cross the cell membrane7053. 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 fertilised 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 immobilised 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 colour when they are immobilised, indicating a positive test result (i.e., pregnancy). As described in the passage, the home pregnancy test _.
- A. Lacks positive and negative controls
- B. Is inaccurate because hCG can be produced normally in the non-pregnant mother
- C. Accuracy improves when administered during early morning hours
- D. Is inaccurate because hCG is sometimes not produced by the fertilized zygote
Explanation: The test, as described in the passage, simply assays for the presence of hCG in the urine. The person using the test would either obtain a positive or negative result. Whether or not this result is valid remains in question because there are no experimental controls involved. In other words, there is nothing to test whether the test reagents are faulty or the procedure was done incorrectly. A positive control would involve using a sample liquid containing hCG and testing to see whether the pregnancy test could actually detect it. If it can't, then something is wrong. A negative control might involve using a urine sample with no hCG in it and seeing if the test gives a false positive result. Such controls are not included in the test as described in the passage. The other answer choices can be eliminated. The answer: 'is only effective after at least one month of pregnancy' is wrong because the passage states that hCG levels are high enough to be detected by the time of the first missed period (anywhere from 7-14 days from the time of fertilization.)The answer: 'is inaccurate because hCG can be produced normally in the non-pregnant mother,' can be eliminated because the mother does not produce hCG. If she did, the test would be entirely useless. Only the embryo produces the hormone. The answer choice, 'is inaccurate because hCG is sometimes not produced by the fertilized zygote,' is also incorrect because the embryo must produce hCG in order to prevent menstruation and maintain the corpus luteum. If it doesn't, menstruation will occur and the embryo will be sloughed off with the uterine lining.
Correct answer: Lacks positive and negative controls7054. 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 fertilised 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 immobilised 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 colour when they are immobilised, indicating a positive test result (i.e., pregnancy).The mechanism by which hCG acts on its target cells is most similar to that of _.
- A. Progesterone
- B. Testosterone
- C. Glucagon
- D. Estradiol
Explanation: From the passage we learn that hCG is a peptide hormone. Peptide hormones act by binding to receptors on the plasma membranes of their target cells. This binding then triggers a signalling cascade which results in the transcription of specific genes. Peptide hormones can't cross the plasma membrane directly because they are not lipid soluble. Glucagon is a peptide hormone secreted by the alpha cells of the pancreas; it therefore uses a similar mechanism to that of hCG.The other answer choices can be eliminated because they are steroid hormones. These act by directly crossing the plasma membrane and binding to receptors either in the cytoplasm or in the nucleus.
Correct answer: Glucagon7055. John goes to the doctor and is told that his anterior pituitary is not functioning. Which of the following hormones is likely at lower levels than normal?
- A. Parathyroid hormone
- B. Thyroid-stimulating hormone (TSH)
- C. Melatonin
- D. Glucagon
Explanation: Of all the choices, the only one released by the anterior pituitary is TSH (thyroid-stimulating hormone). Glucagon is released from the pancreas, parathyroid hormone is released from the parathyroid glands, melatonin comes from the pineal gland, and atrial natriuretic hormone is a heart hormone.
Correct answer: Thyroid-stimulating hormone (TSH)7056. After ingesting a meal heavy in polysaccharides, an individual has their blood drawn. Levels of which hormone would you expect to be higher than normal?
- A. Insulin
- B. Oxytocin
- C. Gastrin
- D. Glucagon
Explanation: The polysaccharides from the meal will be digested down into glucose by various enzymes in the digestive tract. That glucose will be absorbed in the small intestine and travel into the bloodstream. This increase in blood glucose will cause a release of insulin to allow for tissue to take up the glucose and use it for energy. In this individual's blood, we would expect insulin to be higher than normal.
Correct answer: Insulin7057. Which steroid hormone, produced in the ovaries, is responsible for the growth of female sex organs and is responsible for causing a surge in luteinizing hormone through positive feedback?
- A. Testosterone
- B. Progesterone
- C. Estrogen
- D. Androstenedione
Explanation: Estrogen is produced by the combination of luteinizing hormone and follicle-stimulating hormone in the ovaries. Estrogen is responsible for causing the luteinizing hormone surge through positive feedback (one of the only examples of positive feedback in endocrine biology) and the growth of the female sex organs.
Correct answer: Estrogen7058. Mineralocorticoids, including aldosterone, are able to maintain blood pressure during times of stress. Which of the following is not an effect of aldosterone?
- A. Decreased blood sodium levels
- B. Decreased urine sodium content
- C. Decreased blood potassium levels
- D. Increased blood pressure
Explanation: The mineralocorticoid aldosterone is stimulated by the renin-angiotensin system of the kidney when blood volume falls. Aldosterone acts at the distal convoluted tubule of the kidney to increase sodium reabsorption, thus raising sodium levels in the blood and lowering sodium levels in the urine. Aldosterone also increases potassium excretion, thus causing low levels of potassium in the blood. The overall retention of sodium draws water from the filtrate into the blood, causing increased blood pressure by increasing blood volume.
Correct answer: Decreased blood sodium levels7059. Persons with diabetes mellitus have abnormally elevated blood glucose levels. In an attempt to rid the body of excess glucose, the kidneys filter the glucose into the urine for excretion. The amount of glucose in the urine overwhelms the kidneys, which are unable to reabsorb the glucose during concentration of the urine in the nephrons. What would be the blood volume status of a patient with uncontrolled diabetes mellitus?
- A. No conclusion can be drawn
- B. High blood volume
- C. Low blood volume
- D. Normal blood volume
Explanation: Water moves to regions where solute concentrations are high. Because the kidney is unable to reabsorb the filtrate glucose, the urine has a high osmolarity and will draw water into the collecting duct to balance solute concentrations. The water that was part of the filtered blood volume is usually reabsorbed, but instead will be excreted. This excess loss of water will lead to decreased blood volume.
Correct answer: Low blood volume7060. All of the following are matched correctly EXCEPT
- A. Nerve net-hydra
- B. Malpighian tubules-earthworms
- C. Nematocysts-hydra
- D. Contractile vacuoles-amoeba
- E. Flame cells-planaria
Explanation: Malpighian tubules: These are excretory organs found in insects that remove waste products from the hemolymph (insect blood). Earthworms don't have Malpighian tubules and use a different excretory system.
Correct answer: Malpighian tubules-earthworms