Photosynthesis that converts light energy into chemical energy by the plants, involves the use of green pigments of leaves called chlorophyll. The only structure in a leaf that hosts chlorophyll is:
- A.Nucleus
- B.Ribosome
- C.Chloroplast
- D.Chromosome
Correct answer
Explanation
The correct answer is C, Chloroplast. Chlorophyll is held in the chloroplasts, the green plastids of leaf cells where photosynthesis takes place.
A chloroplast is a double-membrane organelle. Inside it, stacks of flattened sacs called thylakoids form grana, and the chlorophyll on the thylakoid membranes absorbs mainly red and blue light; green light is reflected, which is why leaves look green. The light reactions in the thylakoids split water and release oxygen, and the dark reactions in the fluid stroma fix carbon dioxide into glucose. Chloroplasts, like mitochondria, contain their own DNA and ribosomes and are thought to have descended from free-living bacteria.
A is wrong: the nucleus holds the cell's genetic material and controls its activities.
B is wrong: ribosomes are the sites of protein synthesis.
D is wrong: chromosomes are threads of DNA and protein that carry genes.
Exam tip: photosynthesis equation 6CO2 + 6H2O → C6H12O6 + 6O2; oxygen released comes from water; chloroplasts and mitochondria are semi-autonomous organelles.
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
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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
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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.
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