Biology · Molecular Basis of Inheritance · NEET
Both are pentose (5-carbon) sugars. Look only at the 2' carbon (the second carbon). In RIBOSE that carbon has an –OH (hydroxyl) group. In DEOXYRIBOSE that same carbon has only an –H (hydrogen). So deoxyribose has ONE less oxygen atom than ribose. Everything else about the two sugars is the same. That one atom is the whole answer NEET wants.
DNA has DEOXYRIBOSE. RNA has RIBOSE. Easy trick: DNA starts with D, Deoxyribose starts with D. RNA has Ribose (both have the R sound). NCERT states it plainly: a nucleotide has 'a pentose sugar (ribose in case of RNA, and deoxyribose for DNA)'.
'Deoxy' means 'without oxygen' (de = remove, oxy = oxygen). Ribose has an oxygen (as part of the –OH) at the 2' carbon. Deoxyribose is missing that one oxygen at the 2' carbon, so it is 'de-oxygenated ribose'. That is why the full name is 2'-deoxyribose — the '2' tells you WHICH carbon lost the oxygen.
The carbons of the sugar ring are numbered 1', 2', 3', 4', 5' with a prime mark ('). The prime just separates sugar carbons from the base carbons. The 2' carbon is the second one. This is the exact carbon where ribose and deoxyribose differ, so NEET writes the DNA sugar as '2'-deoxyribose'.
Neither. Arabinose is a trap answer NEET uses. The only two sugars in nucleic acids are ribose (RNA) and deoxyribose (DNA). If you see 'arabinose' in an option, it is wrong. The 2016 NEET question used arabinose exactly to catch students who did not read carefully.
Yes. Because deoxyribose is missing the 2'–OH group, DNA is chemically more stable and less reactive than RNA. The extra –OH in ribose makes RNA easier to break down (hydrolyse). This is one reason DNA, not RNA, is the long-term store of genetic information.
The correct statement regarding RNA and DNA, respectively is:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Ribose has one extra oxygen atom (as part of the –OH at the 2' carbon), so ribose has slightly more mass. But both are still 5-carbon pentose sugars with the same ring shape.
No. There are three differences: (1) sugar — deoxyribose in DNA, ribose in RNA; (2) one base — DNA uses thymine, RNA uses uracil; (3) DNA is usually double-stranded, RNA is usually single-stranded. The sugar is the difference this page focuses on.
DNA = Deoxyribose (both start with D). RNA = Ribose (both have the R sound). And 'deoxy' = missing oxygen, so DNA's sugar is the 'oxygen-poor' one.
It is a one-mark, high-frequency fact that separates careful students from guessers. Knowing the 2' carbon –OH vs –H point, and spotting the 'arabinose' trap, guarantees the mark.
