What traumatic event does Zitkala-Sa describe at the school?

The forcible cutting of her long hair

Why was the cutting of her hair so humiliating to Zitkala-Sa?

Among her people, shingled hair was worn by cowards and mourners

How are carbohydrates classified on hydrolysis?

As monosaccharides, oligosaccharides (mainly disaccharides) and polysaccharides.

What is a reducing sugar?

A carbohydrate that reduces Fehling's solution or Tollens' reagent because of a free aldehyde or ketone group.

The alpha and beta cyclic forms of a sugar differing only in the configuration at the anomeric carbon.

What is a peptide bond?

The amide (-CO-NH-) linkage formed between the carboxyl group of one amino acid and the amino group of another.

Distinguish between essential and non-essential amino acids.

Essential amino acids cannot be made in the body and must come from food; non-essential ones can be synthesised.

What is denaturation of a protein?

Disruption of its secondary and tertiary structure by heat or pH, destroying activity while the primary structure stays intact.

Why are enzymes called biocatalysts?

They speed up biochemical reactions, are highly specific and lower the activation energy without being consumed.

How are vitamins classified?

Into fat-soluble (A, D, E, K) and water-soluble (B group and C) vitamins.

What are the structural differences between DNA and RNA?

DNA has deoxyribose, the base thymine and a double helix; RNA has ribose, uracil and is single stranded.

State the base pairing rule in DNA.

Adenine pairs with thymine and guanine pairs with cytosine through hydrogen bonds.

Biomolecules

Class 12 Chemistry · Chemistry Part II · Chapter 5

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CBSE Class 12 · Chemistry

Unit 8 carbonyls: 8 marks, biggest unit

Marks booster + cheatsheet: key concepts in 2 lines each, common traps
7 marks in every paper: Biomolecules
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Summary

Biomolecules are the complex organic molecules that build and run living systems: carbohydrates, proteins, nucleic acids and lipids, along with vitamins and hormones. Carbohydrates are optically active polyhydroxy aldehydes or ketones, or compounds that yield these on hydrolysis; they are classed as monosaccharides (glucose, fructose), oligosaccharides such as disaccharides (sucrose, maltose, lactose) and polysaccharides (starch, cellulose, glycogen). Glucose, an aldohexose, exists in open-chain and cyclic hemiacetal (pyranose) forms whose anomers differ at the anomeric carbon. Proteins are polymers of about twenty alpha-amino acids joined by peptide bonds; ten are essential and must come from the diet. Proteins have primary, secondary (alpha-helix and beta-pleated sheet), tertiary and quaternary structures, and lose biological activity on denaturation when these higher structures are disrupted. Enzymes are highly specific protein biocatalysts that lower activation energy. Vitamins are essential dietary factors classed as fat soluble (A, D, E, K) or water soluble (B group and C), and their deficiency causes specific diseases. Nucleic acids, DNA and RNA, are polymers of nucleotides made of a base, a pentose sugar and a phosphate; DNA stores genetic information as a double helix while RNA carries out protein synthesis. Hormones act as chemical messengers regulating body functions.

Carbohydrates: classification and structureGlucose, fructose and disaccharidesProteins, amino acids and structureEnzymes and denaturationVitamins and their deficienciesNucleic acids, DNA, RNA and hormones

Key terms

Monosaccharide

A carbohydrate that cannot be hydrolysed to a simpler sugar, e.g. glucose or fructose.

Glycosidic linkage

The oxygen bridge joining two monosaccharide units, formed by loss of water.

Peptide bond

The -CO-NH- amide linkage joining amino acids in a protein chain.

Denaturation

Loss of a protein's secondary and tertiary structure and biological activity by heat or pH change.

Enzyme

A protein biocatalyst that is highly specific and lowers the activation energy of a reaction.

Nucleotide

The repeating unit of nucleic acids, made of a base, a pentose sugar and a phosphate group.

Extra questions & answers

Try one from this chapter

Carbohydrates are chemically defined as:

Flashcards & interactive practice