All Free Biology MCQs with Answers

1551. MSH is produced from___________?

• A. Anterior pituitary
• B. Median pituitary
• C. Posterior pituitary
• D. None of these

Explanation: Melanocyte-stimulating hormone is produced mainly by the pars intermedia, or intermediate lobe, of the pituitary gland. In this question, median pituitary refers to this intermediate region. The likely alternative is anterior pituitary because many major hormones come from it, but MSH is associated with the intermediate lobe.

1552. Grave's disease is produced due to____________?

• A. Undersecretion of thyroxin
• B. Overproduction of thyroxin
• C. Undersecretion of corticosteroids
• D. Overproduction of corticosteroids

Explanation: Graves' disease is an autoimmune condition in which antibodies stimulate thyroid-stimulating hormone receptors, causing excessive thyroid hormone secretion. This produces hyperthyroidism, often with an enlarged thyroid and increased metabolic rate. The likely alternative is undersecretion of thyroxin, which describes hypothyroidism rather than Graves' disease.

1553. Secretin is a hormone produced by___________?

• A. Stomach
• B. Liver
• C. Pancreas
• D. Duodenum

Explanation: Secretin is released by S cells in the duodenal lining when acidic chyme enters from the stomach. It stimulates pancreatic bicarbonate secretion, helping neutralize the acid in the small intestine. The likely alternative is the pancreas because the pancreas responds to secretin, but it does not produce this hormone.

1554. All of the following are similarities between nervous and endocrine system except:_____________?

• A. Produce chemical messengers
• B. Release chemical messengers in extracellular space
• C. Homestatic in function
• D. Having slow but prolonged effects

Explanation: Both nervous and endocrine systems coordinate body functions using chemical messengers released into extracellular spaces and help maintain homeostasis. Nervous responses are usually rapid and short-lived, whereas endocrine responses are generally slower and more prolonged. The likely alternative is b, but both systems do release their messengers into extracellular fluid before they reach target cells.

1555. Which of the following is used in brewing industry to promote malting_______________?

• A. Gibberellins
• B. Cytokinins
• C. Auxins
• D. Abscisic Acid

Explanation: Gibberellins stimulate the production of hydrolytic enzymes, such as amylase, in germinating barley seeds. These enzymes digest stored food and support rapid growth during malting, which is important in brewing. The likely alternative is cytokinins because they promote cell division, but they do not have the main malting effect associated with gibberellins.

1556. The only promoter of leaf senescence in the following plant hormones is________________?

• A. Gibberellins
• B. Cytokinins
• C. Auxins
• D. Abscisic Acid

Explanation: Abscisic acid promotes leaf senescence and helps the plant enter stress-related resting states, while cytokinins generally delay senescence by maintaining chlorophyll and cellular activity. Auxins and gibberellins also have other growth effects rather than being the standard hormone identified as promoting senescence. The likely alternative is cytokinins because they strongly affect leaves, but their usual effect is to delay, not promote, senescence.

1557. Abscisic acid promotes flowering in short day plants and inhibits in long day plants, which of the following is antagonistic to abscisic acid in terms of flowering______________?

• A. Gibberellins
• B. Cytokinins
• C. Auxins
• D. Ethene.

Explanation: Gibberellins can promote flowering in many long-day plants and therefore oppose abscisic acid, which generally suppresses growth and flowering under these conditions. Cytokinins may also influence flowering, so students often choose them, but the standard antagonistic hormone pair tested here is abscisic acid and gibberellins.

1558. Which of the following is antagonist to Auxin in terms of promotion of stem growth______________?

• A. Gibberellins
• B. Cytokinins
• C. Abscisic Acid
• D. none of these.

Explanation: Abscisic acid inhibits cell growth and promotes dormancy, whereas auxin promotes cell elongation and stem growth, so they act antagonistically in this context. Gibberellins also promote stem elongation, which may lead students to choose them, but they are not the intended antagonist of auxin here.

1559. Gibberellins may be substituted for ___________ light, therefore promote flowering in long day plants?

• A. White
• B. Red
• C. Blue
• D. Green

Explanation: In some long-day plants, gibberellin treatment can replace the flowering effect normally produced by a red-light-dependent long-day response, allowing flowering without the required photoperiod. Blue light is a likely alternative because it also affects photoreceptors, but the standard answer in this plant-physiology statement is red light.

1560. Chemically auxins are____________?

• A. Indole propionic acid.
• B. Indole carboxylic acid.
• C. Indole acetaldehyde
• D. Indole acetic acid.Scheduling Virtual Doctor Consultations

Explanation: The principal natural auxin is indole-3-acetic acid, commonly written as indole acetic acid or IAA. Indole propionic acid is chemically similar in name, so students may select it, but it is not the usual primary auxin identified in basic biology.