________ is secreted by the pineal gland.
- A.Melatonin
- B.Progesterone
- C.Epinephrine
- D.Insulin
Correct answer
Explanation
The correct answer is A, Melatonin. The pineal gland, a small pine-cone-shaped gland deep in the brain, secretes melatonin. Melatonin controls the body's day-night rhythm, called the circadian rhythm, and helps regulate sleep. The gland releases more melatonin in darkness and less in bright light, which is why bright screens late at night can disturb sleep. Melatonin also plays a part in the timing of puberty and in seasonal changes in some animals. The French philosopher Descartes once called the pineal gland 'the seat of the soul'. B is wrong because progesterone is made mainly by the ovaries (the corpus luteum) and helps prepare for and maintain pregnancy. C is wrong because epinephrine, or adrenaline, is released by the adrenal medulla and prepares the body for 'fight or flight'. D is wrong because insulin is made by the beta cells of the islets of Langerhans in the pancreas and lowers blood sugar. Exam tip: pineal gland, melatonin, sleep; pancreas, insulin; adrenal medulla, adrenaline.
Practice Questions
View allThe fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
Read the full explanation →Which one of the following statements is correct?
- A.Urea is produced in liver.
- B.Urea is produced in blood.
- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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Liver cells turn the toxic ammonia released from the breakdown of amino acids into urea through the ornithine cycle, also called the urea cycle.
Read the full explanation →Which one of the following is the correct sequence of passage of light in a compound microscope?
- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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Light passes through the condenser to the specimen, is picked up by the objective lens, travels up the body tube and reaches the eye through the eyepiece.
Read the full explanation →Which one of the following statements regarding haemoglobin is correct?
- A.Haemoglobin present in RBC can carry only oxygen but not carbon dioxide.
- B.Haemoglobin of RBC can carry both oxygen and carbon dioxide.
- C.Haemoglobin of RBC can carry only carbon dioxide.
- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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It binds oxygen at its iron-containing haem groups and carries some carbon dioxide on its protein chains. Each haemoglobin molecule has four polypeptide chains and four haem groups, and each haem iron can hold one oxygen molecule, forming oxyhaemoglobin in the lungs.
Read the full explanation →Which one of the following statements regarding histone proteins is correct?
- A.Histones are proteins that are present in mitochondrial membrane.
- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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They are the proteins around which DNA winds to form chromatin in the nucleus of eukaryotic cells. Histones are small basic proteins, rich in the positively charged amino acids lysine and arginine, which attract the negatively charged phosphate groups of DNA.
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