Biomolecules Flashcards for NEET — 21 cards

First 8 of 21 Biomolecules flashcards

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1. Card 1 of 21

   What chemically distinguishes reducing sugars from non-reducing sugars? Give an example of a non-reducing disaccharide.

   Hint: Table sugar does not reduce.

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   Answer

   Reducing sugars contain a free aldehyde or ketone group (hemiacetal/hemiketal) and can reduce Tollens' or Fehling's reagents. Sucrose is a non-reducing sugar because its reducing groups are tied up in the glycosidic bond.

2. Card 2 of 21

   Name the constituent monosaccharide units and the specific glycosidic linkage present in Sucrose.

   Hint: Involves the anomeric carbons of both units.

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   Answer

   Constituents: $\alpha$-D-Glucose and $\beta$-D-Fructose. Linkage: Glycosidic bond between C1 of $\alpha$-D-glucose and C2 of $\beta$-D-fructose.

3. Card 3 of 21

   Identify the constituent monosaccharides and linkages of Maltose and Lactose.

   Hint: Malt sugar vs Milk sugar.

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   Answer

   Maltose: Two units of $\alpha$-D-glucose (C1-C4 linkage). Lactose: $\beta$-D-galactose and $\beta$-D-glucose (C1-C4 linkage).

4. Card 4 of 21

   What are anomers? Give the standard example found in carbohydrates.

   Hint: Alpha is 'down', Beta is 'up'.

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   Answer

   Anomers are a pair of cyclic diastereomers that differ in configuration ONLY at the anomeric carbon (C1 for aldoses, C2 for ketoses). Example: $\alpha$-D-glucose and $\beta$-D-glucose.

5. Card 5 of 21

   What is the main structural difference between Starch and Cellulose?

   Hint: Humans digest alpha linkages (starch) but not beta linkages (cellulose).

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   Answer

   Starch is a branched polymer of $\alpha$-D-glucose (composed of water-soluble amylose and water-insoluble amylopectin). Cellulose is a straight-chain polymer of $\beta$-D-glucose.

6. Card 6 of 21

   What type of chemical linkage joins individual nucleotides to form a long nucleic acid chain (polynucleotide)?

   Hint: Connects 3' to 5'.

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   Answer

   Phosphodiester linkage. It is formed between the 5'-OH group of the pentose sugar of one nucleotide and the 3'-OH group of the sugar of the next nucleotide.

7. Card 7 of 21

   State the complementary base pairing rule in the DNA double helix and note the number of hydrogen bonds.

   Hint: A-T has two, G-C has three.

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   Answer

   Adenine pairs with Thymine via 2 hydrogen bonds ($A=T$). Guanine pairs with Cytosine via 3 hydrogen bonds ($G\equiv C$).

8. Card 8 of 21

   Differentiate between essential and non-essential amino acids.

   Hint: Essential means 'essential to eat'.

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   Answer

   Essential: Cannot be synthesized by the human body and must be obtained through diet (e.g., Valine, Leucine). Non-essential: Can be synthesized by the body (e.g., Glycine, Alanine).