3 free questions from this chapter (the full set has 30). Marking: +4 for correct · −1 for incorrect · 0 for unattempted.
Question 1Level 3 · AdvancedSingle correct
A living tissue is ground in trichloroacetic acid and the slurry is strained through cheesecloth. Consider the following statements. (i) The filtrate obtained is called the acid-insoluble fraction. (ii) Lipids appear in the acid-insoluble fraction even though their molecular weight does not exceed 800 Da. (iii) The acid-soluble pool roughly represents the cytoplasmic composition. (iv) All four classes of organic compounds found in the acid-insoluble fraction have molecular weights of ten thousand daltons and above. (v) Compounds with molecular weight less than one thousand daltons are referred to as micromolecules or simply biomolecules. (vi) The ash left after burning a tissue sample contains inorganic elements such as calcium and magnesium. How many of the above statements are correct?
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Answer: D
Key idea: filtrate = acid-soluble, retentate = acid-insoluble; lipids are the odd class in the retentate. (i) False: the filtrate is the acid-soluble pool; the retentate is the acid-insoluble fraction. (ii) True: grinding breaks membranes into vesicles that are not water soluble, so lipids separate with the acid-insoluble pool even though their molecular weight does not exceed 800 Da. (iii) True as per NCERT. (iv) False: proteins, nucleic acids and polysaccharides are ten thousand daltons and above, but lipids are not, which is why lipids are not strictly macromolecules. (v) True. (vi) True: on burning, carbon compounds are oxidised to gaseous forms and removed, leaving ash with inorganic elements. Correct = (ii), (iii), (v), (vi) = 4. Trap: marking (iv) true because all four classes sit together in the retentate.
Exam pattern: NEET – acid-insoluble pool and why lipids are not true macromoleculesQuestion 2Level 3 · AdvancedSingle correct
NCERT compares the percentage weight of elements in the earth's crust and in the human body. From the list oxygen, sodium, calcium, sulphur, magnesium, hydrogen and silicon, how many elements have a higher percentage weight in the earth's crust than in the human body?
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Answer: D
NCERT table values (earth's crust vs human body, % weight): oxygen 46.6 vs 65.0; sodium 2.8 vs 0.2; calcium 3.6 vs 1.5; sulphur 0.03 vs 0.3; magnesium 2.1 vs 0.1; hydrogen 0.14 vs 0.5; silicon 27.7 vs negligible. Higher in crust: sodium, calcium, magnesium, silicon = 4. Higher in body: oxygen, sulphur, hydrogen (also carbon and nitrogen, not listed). Trap: oxygen is the most abundant element of the crust, so students assume it is higher there, but the body has 65.0 percent oxygen. Option A results from wrongly placing calcium (bone) in the body column; option B from adding oxygen to the crust list.
Exam pattern: NEET – NCERT table comparing elements in living and non-living matterQuestion 3Level 2 · ExamSingle correct
Match List I (amino acid) with List II (feature as described in NCERT). List I: (a) Valine (b) Glutamic acid (c) Serine (d) Tyrosine. List II: (i) Acidic amino acid (ii) Aromatic amino acid (iii) Neutral amino acid (iv) R group is a hydroxymethyl group. Choose the correct option.
Aa-i, b-iii, c-iv, d-ii
Ba-iii, b-i, c-iv, d-ii
Ca-iii, b-iv, c-i, d-ii
Da-iii, b-i, c-ii, d-iv
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Answer: B
NCERT: amino acids are substituted methanes and their properties depend on the R group. Valine is the NCERT example of a neutral amino acid (a-iii); glutamic acid of an acidic amino acid (b-i); serine has R = hydroxymethyl (c-iv), whereas glycine has R = hydrogen and alanine R = methyl; tyrosine, phenylalanine and tryptophan are aromatic (d-ii). Option D is the trap: tyrosine also carries an OH group, but on an aromatic ring, so it is classed as aromatic; the hydroxymethyl R group belongs to serine. Option A swaps acidic and neutral; option C swaps the hydroxymethyl and acidic labels.
Exam pattern: NEET – NCERT examples of acidic, basic, neutral and aromatic amino acids