Enzyme definition
Enzymes are proteins that act as biological catalysts (made by living organisms) to speed up the rate of a chemical reaction without being changed or used up in the reaction
Why are enzymes necessary?
To maintain reaction speeds of all metabolic reactions at a rate to sustain life
Why are enzymes specific to one particular substrate?
Because the shape of the enzyme’s active site only fits one specific substrate.
What is the enzyme-substrate complex?
A temporary structure formed when a substrate binds to an enzyme’s active site.
Describe the process of enzyme action.
1) Enzymes and substrates randomly move in solution.
2) When a substrate with a complementary shape collides with the enzyme’s active site, they form an enzyme-substrate complex.
3) The enzyme catalyses the reaction, converting the substrate into product(s).
4) The products are released, and the enzyme remains unchanged, ready to catalyse another reaction.
What are enzymes made of?
Enzymes are proteins made from amino acids, held in shape by bonds.
Why is enzyme shape important?
The specific shape of the active site ensures the substrate fits and the reaction can occur.
What is the optimum temperature for enzymes in the human body?
37°C.
What happens to enzyme activity as temperature increases toward the optimum?
Enzyme activity increases due to more kinetic energy and more frequent collisions with substrates.
What happens if temperature goes beyond the optimum?
The bonds holding the enzyme’s shape break, causing it to lose its shape — this is called denaturation.
What is denaturation?
A permanent change in the enzyme’s shape, especially the active site, so the substrate no longer fits.
Can denaturation be reversed?
No, denaturation is irreversible — the enzyme cannot regain its shape or function.
What happens to enzyme activity at low temperatures?
Enzymes work more slowly due to reduced kinetic energy, but they are not denatured.
What is amylase?
Enzyme that digests starch -> maltose
What is maltose made from
Glucose + Glucose
What is used to test for starch?
Iodine
Apparatus used in “Investigating Temperature & Enzyme Activity” practical
Spotting tile
Measuring cylinder
Test tube
Syringe
Pipette
Stopwatch
Water
Thermometer
Water bath
Iodine solution
Starch solution
Amylase solution
Method for “Investigating Temperature & Enzyme Activity” practical
Add 5cm³ starch solution to test tube, heat to target temp.
Add iodine drops to spotting tile.
Add 2cm³ amylase to starch, mix, start timer.
Every minute transfer drop to iodine well
Repeat until iodine stays yellow-brown.
Record time when starch fully digested (iodine doesn’t change colour)
Repeat at same temp 2 more times.
Test other temps (e.g. 30–60°C).
What does the “Investigating Temperature & Enzyme Activity” practical show?
Optimum temp etc…
Give limitations and improvements for amylase temperature experiment
Limitation: temp may not stay constant using Bunsen burner.
Improvement: use water bath and let solutions reach temp before mixing.
Limitation: judging iodine colour by eye is subjective.
Improvement: use colorimeter for accurate, objective results.
What is a coloromiter?
Device that measures colour intensity by detecting how much light passes through a solution
What is the optimum pH for most enzymes?
7
Why might the enzymes produced in the stomach have low optimum pH?
Acid conditions.
Pepsin
Where might you find enzymes with high optimum pH?
Alkaline conditions like the duodenum.
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Movement of substances into and out of cells17
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Respiration19
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Gas exchange - humans31
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Transport22
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Coordination and response80
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Excretion - humans28
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Food tests12
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Characteristics of Living Organisms28
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Levels of Organisation5
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Cell Structure39
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Structure of biological molecules27
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Enzymes28
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Nutrition146
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Gas exchange - Plants22
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Transport systems - plants21
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Reproduction145
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The organism in the environment35
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Feeding relationships17
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Cycles within ecosystem11
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Human influences on environment21
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Food production74
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Key Hormones28
