What is the difference between competitive and non-competitive inhibition?

Competitive inhibition: The inhibitor molecule structurally resembles the substrate and competes for the active site. Can be overcome by increasing substrate concentration. Km increases, Vmax unchanged. Non-competitive inhibition: Inhibitor binds to allosteric site (not active site), changing the enzyme's shape so it can't bind substrate properly. Cannot be overcome by more substrate. Vmax decreases, Km unchanged.

What happens to enzyme activity at very high temperatures?

Enzyme activity increases with temperature up to the optimum (usually 37–40°C for human enzymes). Above the optimum, the hydrogen bonds and other weak bonds holding the protein in its 3D shape break — this is denaturation. The active site changes shape and can no longer bind substrate, so enzyme activity drops to zero. Denaturation is usually irreversible.

Ribozymes are RNA molecules with catalytic activity — they act as enzymes without being proteins. Discovered by Thomas Cech and Sidney Altman (Nobel Prize 1989). Examples: RNA components of ribosomes that catalyse peptide bond formation; self-splicing introns. Their discovery supports the 'RNA World' hypothesis for the origin of life.

Proteins, Enzymes and their Properties

Biomolecules • Class 11 Biology • NCERT • CBSE

Proteins are polymers of amino acids linked by peptide bonds. Enzymes are biological catalysts (mostly proteins) that speed up reactions without being consumed. Enzymes work by lowering activation energy. Lock-and-key and Induced-fit models explain enzyme-substrate specificity.

Frequently Asked Questions

What is the difference between competitive and non-competitive inhibition?: Competitive inhibition: The inhibitor molecule structurally resembles the substrate and competes for the active site. Can be overcome by increasing substrate concentration. Km increases, Vmax unchanged. Non-competitive inhibition: Inhibitor binds to allosteric site (not active site), changing the enzyme's shape so it can't bind substrate properly. Cannot be overcome by more substrate. Vmax decreases, Km unchanged.
What happens to enzyme activity at very high temperatures?: Enzyme activity increases with temperature up to the optimum (usually 37–40°C for human enzymes). Above the optimum, the hydrogen bonds and other weak bonds holding the protein in its 3D shape break — this is denaturation. The active site changes shape and can no longer bind substrate, so enzyme activity drops to zero. Denaturation is usually irreversible.
What are ribozymes?: Ribozymes are RNA molecules with catalytic activity — they act as enzymes without being proteins. Discovered by Thomas Cech and Sidney Altman (Nobel Prize 1989). Examples: RNA components of ribosomes that catalyse peptide bond formation; self-splicing introns. Their discovery supports the 'RNA World' hypothesis for the origin of life.

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