Which one of the following acids is produced in human stomach?
- A.Formic acid
- B.Sulphuric acid
- C.Nitric acid
- D.Hydrochloric acid
Correct answer
Explanation
The correct answer is D, Hydrochloric acid. The parietal (oxyntic) cells in the lining of the stomach secrete hydrochloric acid into the gastric juice.
Hydrochloric acid makes the stomach strongly acidic, with a pH of roughly 1.5 to 3.5. This acid medium kills most bacteria that enter with food and converts the inactive enzyme pepsinogen into pepsin, which starts the digestion of proteins. The stomach wall protects itself with a layer of mucus. When too much acid is produced, it causes acidity and heartburn, which is treated with antacids, mild bases such as magnesium hydroxide (milk of magnesia).
A is wrong: formic acid (methanoic acid) is found in the sting of ants and bees, not in the stomach.
B is wrong: sulphuric acid is a strong industrial acid used in car batteries and fertilisers; the body does not make it.
C is wrong: nitric acid is used to make fertilisers and explosives; it is not produced in the human body.
Exam tip: stomach = HCl (parietal cells), ant sting = formic acid, curd = lactic acid, vinegar = acetic acid.
Practice Questions
View allSyngamy results in formation of
- A.haploid zygote
- B.diploid zygote
- C.non-motile male gametes
- D.motile male gametes
Show answer
Syngamy is the fusion of a male and a female gamete, and since each gamete is haploid, their union gives a diploid zygote.
Read the full explanation →Human insulin molecule is composed of one α-chain having 21 amino acids and one β-chain having 30 amino acids. How many functional insulin genes occur in adult humans?
- A.One
- B.Two
- C.Three
- D.Four
Show answer
Humans have a single functional insulin gene, INS, on the short arm of chromosome 11, and both chains of insulin come from it.
Read the full explanation →Which one of the following is the value of one nanometer?
- A.10⁻⁷ cm
- B.10⁻⁶ cm
- C.10⁻⁴ cm
- D.10⁻³ cm
Show answer
One nanometre is 10⁻⁹ metre, and since one metre is 100 (10²) centimetres, it equals 10⁻⁷ centimetre. The prefix nano means one billionth.
Read the full explanation →Which of the following is the general formula for saturated hydrocarbons?
- A.CₙH₂ₙ₊₂
- B.CₙH₂ₙ₋₂
- C.CₙH₂ₙ₊₁
- D.CₙH₂ₙ₋₁
Show answer
Saturated open-chain hydrocarbons are the alkanes, and every alkane fits the formula CₙH₂ₙ₊₂. In a saturated hydrocarbon every carbon atom is joined to others only by single bonds, so each carbon holds the largest possible number of hydrogen atoms.
Read the full explanation →Which one of the following is not an epidemic disease?
- A.Cholera
- B.Malaria
- C.Smallpox
- D.Elephantiasis
Show answer
Elephantiasis, or lymphatic filariasis, is an endemic disease: it stays steadily present in certain regions and develops slowly over years, rather than breaking out suddenly in a large number of people.
Read the full explanation →