General Science GK Questions with Answers – Page 75

A muscle contracts when calcium ions are released from the sarcoplasmic reticulum, and it relaxes when they are pumped back into it.

Tropolone is aromatic, but its seven-membered ring is made only of carbon atoms, so it is not heterocyclic. A heterocyclic compound has at least one atom other than carbon, such as oxygen, sulphur or nitrogen, inside its ring.

Breaking down carbohydrates to release energy is respiration, which happens in the cytoplasm and mitochondria, not a job of chlorophyll.

Biogas is mostly methane, with carbon dioxide as the second gas and only small amounts of nitrogen and others. Biogas forms when cattle dung, kitchen waste or crop residue is broken down by anaerobic bacteria, that is, without air, inside a digester.

Red blood cells far outnumber both platelets and white blood cells. A microlitre of healthy adult blood holds about 4.5 to 5.5 million red blood cells, about 1.5 to 4.5 lakh platelets and only about 4,000 to 11,000 white blood cells.

When the two mix, they release a rush of carbon dioxide that pushes water out onto the fire. In a soda-acid extinguisher a small bottle of dilute sulphuric acid sits inside a cylinder filled with a solution of sodium hydrogencarbonate (baking soda, NaHCO3).

Natural chlorine is a mixture of two isotopes, and their weighted average is about 35.5 u. Chlorine has two stable isotopes: chlorine-35, which makes up about 75 per cent of natural chlorine, and chlorine-37, about 25 per cent.

Guard cells are specialised epidermal cells that surround each stoma on the surface of a leaf. Each stoma is a tiny pore bordered by two guard cells, which are bean-shaped in most plants and dumb-bell shaped in grasses.

Vitamin C has no carboxyl group; its acidity comes from an enol group in its ring. Ascorbic acid, C6H8O6, is a five-membered lactone ring carrying hydroxyl groups.

Above the threshold, the kinetic energy of the ejected electrons rises as the frequency of the light rises, so the statement that it does not change is wrong.

Charge equals current multiplied by time, so Q = 1.5 A × 0.010 s = 0.015 C. Electric current is the rate at which charge flows, I = Q/t, so the charge that passes in a given time is Q = I × t. One ampere means one coulomb of…

Platelets plug a damaged vessel and start the chain that forms a clot. Platelets, or thrombocytes, are small cell fragments made from large cells called megakaryocytes in the bone marrow.

Mendel worked out the laws of inheritance by crossing garden pea plants, Pisum sativum. Gregor Johann Mendel, an Austrian monk, carried out his hybridisation experiments between 1856 and 1863 in the monastery garden at Brno and published the results in 1866.

All three statements are correct; microbes called extremophiles live in all these conditions. Hyperthermophiles, many of them archaea living near deep-sea hydrothermal vents, grow above 100 °C; Methanopyrus kandleri and 'Strain 121' grow at about 120 °C, where high pressure keeps water liquid.

All four statements are correct; mushrooms show every one of these properties. Mushrooms are the fruiting bodies of fungi.

It is caused by a virus that stays latent in the nerve cells for life, so the attacks can be controlled with medicines but the infection cannot be completely cured; hepatitis B and HIV infection fall in the same group.

Colostrum is the thin yellowish milk secreted in the first days after delivery and is rich in antibodies, especially immunoglobulin A, which pass to the baby and protect it from infection at a stage when its own immune system is immature; this protection is called passive immunity.

The amendment of 2021 kept termination up to twenty weeks on the opinion of one registered medical practitioner, allowed it between twenty and twenty-four weeks for certain categories of women such as survivors of rape or incest on the opinion of two practitioners, and removed the upper limit where a…

Saheli contains centchroman and is a non-steroidal pill taken once a week after an initial daily course, which makes it different from the combined hormonal pills that have to be taken daily and carry hormonal side effects.

Rising oestrogen from the ripening follicle triggers a sharp rise in LH from the anterior pituitary in the middle of the cycle, and this surge bursts the mature Graafian follicle and releases the ovum.