EnzymesEdexcel GCSE Biology: Flashcards
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What is an enzyme?
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- What is an enzyme?
- A biological catalyst, made of protein, that speeds up a specific reaction without being used up.
- Define 'active site'.
- The region of an enzyme with a shape complementary to its substrate, where the reaction occurs.
- Explain enzyme specificity.
- An enzyme's active site has a shape complementary to only one substrate shape, so it will only catalyse the reaction of that specific substrate.
- Explain how high temperature denatures an enzyme.
- High temperature breaks the bonds holding the enzyme's tertiary structure together; this changes the active site's shape so the substrate no longer fits.
- Explain how extreme pH denatures an enzyme.
- Extreme pH disrupts the bonds maintaining the enzyme's 3D shape, changing the active site's shape.
- What happens to enzyme activity above the optimum temperature?
- Rate falls sharply because the enzyme denatures.
- What happens to reaction rate as substrate concentration increases?
- Rate increases until all active sites are occupied, then plateaus.
- Name the core practical investigating pH and enzyme activity.
- Investigating the effect of pH on the breakdown of starch by amylase, timed using the iodine test.
- Give the equation for calculating rate from time taken.
- Rate = 1 ÷ time taken.
- Name the reagent and positive result for testing reducing sugars.
- Benedict's solution, heated; blue to green/yellow/brick-red precipitate.
- Name the reagent and positive result for testing protein.
- Biuret test; blue to purple/lilac.
- Name the test and positive result for identifying lipids.
- Sudan III or ethanol emulsion test; red stain or milky white emulsion.
- What are carbohydrates, proteins and lipids broken down into?
- Carbohydrates → simple sugars; proteins → amino acids; lipids → fatty acids and glycerol.
- Give the calorimetry equation for energy transferred to water.
- Energy (J) = mass of water (g) × temperature change (°C) × 4.2.