Biology MCQs

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The liver makes a digestive juice called bile that helps digest fats and certain vitamins.

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The thyroid is a lipid-soluble hormone whereas amine, peptide, and protein hormones are water-soluble, ranging in size from 3 to more than 200 amino acids.

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Rhizobium leguminocerium bacteria live symbiotically in the root nodules of legumes and some non-legumes. They fix atmospheric N2 and hence increase soil fertility.

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Restriction enzymes were discovered by Smith and Nathans. Proteins produced by bacteria that cleave DNA at specific sites along the molecule are called restriction enzymes.

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Traditional biotechnology and Modern molecular biotechnology are two ideas included in the definition of biotechnology.

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The chief cells of the stomach secrete enzymes for protein breakdown (inactive pepsinogen and rennin). Hydrochloric acid activates pepsinogen into the enzyme pepsin, which then helps digestion by breaking the bonds linking amino acids, a process known as proteolysis.

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Fluorine is the element that is associated with teeth disorder because the presence of sodium fluoride in drinking water at the level of 2ppm may cause mottled enamel in teeth, skeletal fluorosis, and may be associated with cancer and other diseases. However, topically applied fluoride (toothpaste, dental rinses) has been shown to help reduce dental caries.

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Humming birds are birds that comprise the family Trochilidae. They are among the smallest of birds, most species measuring in the 7.5–13 cm (3–5 in) range. Indeed, the smallest extinct bird species is a humming bird, the 5-cm Bee Humming bird. These birds being the smallest are, capable of flying both in forward and back direction.

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A typical adult human stomach will secrete about 1.5 liters of gastric acid daily. The best-known component of gastric juice is hydrochloric acid, the secretory product of the parietal, or oxyntic cell. It is known that the capacity of the stomach to secrete HCl is almost linearly related to parietal cell numbers.

Notes:
Cecum is a pouch connected to the junction of the small and large intestines. It is a large tube-like structure in the lower abdominal cavity that receives undigested food material from the small intestine and is considered the first region of the large intestine. It is separated from the ileum (the final portion of the small intestine) by the ileocecal valve (also called Bauhin valve). The main functions of the cecum are to absorb fluids and salts that remain after completion of intestinal digestion and absorption and to mix its contents with a lubricating substance, mucus.