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Chemistry · Class 10 · Chapter 12: Biochemistry

8 min

Key points

Biochemistry is the branch of chemistry that deals with the chemical processes and substances in living organisms
Carbohydrates are polyhydroxy aldehydes or ketones with general formula Cn(H2O)n
Proteins are complex organic compounds made up of amino acids joined by peptide bonds
Lipids are esters of fatty acids and glycerol, insoluble in water but soluble in organic solvents
Enzymes are biological catalysts that speed up biochemical reactions without being consumed
Vitamins are organic compounds required in small amounts for normal growth and development
Nucleic acids (DNA and RNA) store and transmit genetic information in living cells
Carbohydrates provide energy (4 kcal/g), proteins build tissues, and lipids provide energy (9 kcal/g)

Definitions

Biochemistry: The branch of chemistry that deals with the chemical processes and substances that occur within living organisms
Carbohydrates: Polyhydroxy aldehydes or ketones or compounds which yield these on hydrolysis with general formula Cn(H2O)n
Proteins: Complex organic nitrogenous compounds made up of amino acids joined together by peptide bonds
Enzyme: A biological catalyst that increases the rate of biochemical reactions without itself being permanently altered
Lipids: Esters of fatty acids and alcohols which are insoluble in water but soluble in organic solvents like ether and chloroform

Worked example

Define enzymes and explain any three factors that affect enzyme activity. (6 marks)

Enzymes are biological catalysts that speed up biochemical reactions without being consumed in the process. Three factors affecting enzyme activity are: (1) Temperature - increase in temperature increases enzyme activity up to optimum level, beyond which enzymes denature. (2) pH - each enzyme works best at specific pH, deviation causes change in enzyme shape and reduces activity. (3) Enzyme concentration - higher enzyme concentration increases reaction rate until substrate becomes limiting factor.

Common mistakes

Students confuse the general formula of carbohydrates - remember it's Cn(H2O)n, not CnH2nOn
Writing 'amino acid' instead of 'amino acids' when defining proteins
Forgetting to mention 'peptide bonds' when discussing protein structure
Mixing up functions of different biomolecules - carbohydrates for energy, proteins for structure
Not writing complete definitions word-for-word as given in STBB textbook

Quick recap

Biochemistry studies biomolecules in living organisms. Four main types are carbohydrates (energy source), proteins (structural and functional), lipids (energy storage and membranes), and nucleic acids (genetic material). Enzymes are biological catalysts affected by temperature, pH and concentration. Remember exact textbook definitions and structural formulas for exam success.

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