IGCSE Biology: Enzymes | Questions by Topic

Past paper questions, key definitions, and mark schemes — all files verified from our archive.

• Enzymes are biological catalysts that speed up reactions
• Active site: specific shape that substrate fits into
• Lock and Key model: substrate fits exactly into active site
• Denaturation: enzyme loses shape at high temperature or extreme pH
• Optimum temperature for most enzymes: ~37°C (human)
• Optimum pH varies per enzyme (e.g. pepsin = pH 2, trypsin = pH 8)

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