Biology Questions and Answers

Answer: D

The diseases related to coronaviruses are All of the above.

Coronaviruses are a family of RNA viruses. Three of them have caused serious human outbreaks: SARS (Severe Acute Respiratory Syndrome), caused by SARS-CoV in 2002-03; MERS (Middle East Respiratory Syndrome), caused by MERS-CoV from 2012; and COVID-19, caused by SARS-CoV-2 from 2019.

Since all three are coronavirus diseases, choosing any single one leaves the others out.

Answer: B

Trisomy of chromosome 21 causes Down Syndrome.

A person with Down syndrome has three copies of chromosome 21 instead of two (47 chromosomes in all), usually because the chromosomes failed to separate during egg or sperm formation. It causes intellectual disability, characteristic facial features and a higher risk of heart defects.

Turner syndrome is a missing X chromosome (45,X), Klinefelter syndrome is an extra X in a male (47,XXY), and 'super female' (triple X) is 47,XXX. All three involve sex chromosomes, not chromosome 21.

Answer: A

Lathyrism is caused by Khesari dal.

Khesari dal (grass pea, Lathyrus sativus) contains a neurotoxin, beta-ODAP. Eating it as a staple over a long period, usually in times of drought when other pulses are scarce, causes lathyrism: a crippling paralysis of the lower limbs.

Chana (Bengal gram) and moong (green gram) do not contain this toxin, so 'None of the above' is also wrong. The disease is named after the plant's genus, Lathyrus.

Answer: D

Scurvy is caused by deficiency of Vitamin 'C'.

Vitamin C (ascorbic acid) is needed to make collagen. Without it, connective tissue weakens, causing bleeding and swollen gums, easy bruising and slow healing of wounds; citrus fruits and amla prevent it.

Deficiency of vitamin A causes night blindness, of vitamin B12 pernicious anaemia, and of vitamin D rickets in children. Those are the diseases linked with the other options.

Answer: B

The gland is the Pancreas.

The pancreas is a mixed gland. Its exocrine part secretes pancreatic juice, containing digestive enzymes such as amylase, trypsin and lipase, into the duodenum. Its endocrine part, the islets of Langerhans, secretes the hormones insulin and glucagon into the blood.

The liver secretes bile, which emulsifies fats but contains no digestive enzymes. Salivary glands secrete the enzyme amylase but no hormones. The pituitary secretes hormones only.

Answer: D

Litmus is obtained from Lichen.

Litmus is a mixture of dyes extracted from certain lichens, chiefly species of Roccella and Lecanora. It is red in acidic solution and blue in basic solution, and paper soaked in it is the familiar acid-base indicator.

A lichen is a symbiotic partnership of a fungus with an alga or cyanobacterium, which is why 'a fungus' and 'alga' are tempting partial answers; but the dye is taken from the lichen as a whole, not from either partner grown on its own. Bacteria are not a source of litmus.

Answer: D

The conversion is prevented by Heparin.

Heparin is a natural anticoagulant produced by mast cells and found on the lining of blood vessels. It acts with antithrombin to block thrombin and the factors that form it, so prothrombin is not converted into thrombin and blood does not clot inside an undamaged vessel.

The other options are part of clotting, not its prevention. Fibrinogen is the soluble protein that thrombin turns into fibrin threads, calcium ions are needed at several steps of the clotting cascade, and the clotting factors drive the cascade forward. (Factor VI is in fact no longer recognised as a separate factor.)

Answer: D

Mesothelioma is caused by asbestos, so the answer is Only 3.

Mesothelioma is a cancer of the mesothelium, the thin lining of the lungs (pleura), abdomen (peritoneum) and heart. Nearly all cases follow exposure to asbestos fibres, which lodge in the lining when inhaled or swallowed and cause the disease decades later; that is why asbestos mining and asbestos-cement work are regulated.

Cadmium is linked to kidney damage and itai-itai disease, arsenic to skin lesions and skin, lung and bladder cancers, and lead to nerve and brain damage. None of them is the recognised cause of mesothelioma.

Answer: C

Pairs 1 and 4 are correct, so the answer is 1 and 4 only.

Diphtheria is caused by a bacterium, Corynebacterium diphtheriae, and kala-azar (visceral leishmaniasis) by a protozoan, Leishmania donovani, spread by sandflies.

Measles is caused by a virus, not a fungus, and cholera by a bacterium, Vibrio cholerae, not a virus. So any option containing pair 2 or pair 3 is wrong.

Answer: A

Only one statement is correct, so the answer is Only one.

Statement 2 is correct: each enzyme works best at a particular optimum temperature and pH, and its activity falls away on either side.

The other three are wrong. Enzymes speed reactions by lowering the activation energy, not raising it. Their activity can be changed by other compounds: inhibitors reduce it and activators or cofactors are needed by many enzymes. And enzymes are not consumed, so a very small amount relative to the substrate is enough; they are not used in excess.