Enzymes - Spec

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What are enzymes?
They are globular proteins, with a specific tertiary structure, which catalyse metabolic reactions in living things.
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Where in cells can enzymes work?
They can be intracellular or extracellular.
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Describe the mechanism of action of enzyme molecules, with reference to specificity.
The active site of an enzyme is a specific shape, depending on the reaction that it catalyses, meaning that other molecules won't fit into the active site.
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Describe the mechanism of action of enzyme molecules, with reference to their active site.
The area on an enzyme which the substrate binds to.
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Describe the mechanism of action of enzyme molecules, with reference to the lock & key hypothesis.
The theory of enzyme action in which the enzymes active site is complementary to the substrate molecule, like a lock & key.
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Describe the mechanism of action of enzyme molecules, with reference to the induced fit hypothesis.
The theory of enzyme action in which the enzyme molecule changes shape to fit the substrate molecule more closely as it binds to it.
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Describe the mechanism of action of enzyme molecules, with reference to enzyme-substrate complex.
The intermediary formed when a substrate molecule binds to an enzyme molecule.
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Describe the mechanism of action of enzyme molecules, with reference to the enzyme-product complex.
The intermediate structure in which product molecules are bound to an enzyme molecule, lowering activation energy.
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What is the result of enzymes being able to reduce activation energies.
Reactions can proceed at much lower temperatures.
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Describe & Explain the effects of pH.
Low pH = lots of H+. Either extreme of H+ ion conc. interfere with H & ionic bonds holding T. structure together. If pH change affects charge on amino acid at active site, properties change & sub wont bind. High pH = -COOH dissociates& becomes charge
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Describe & Explain the effects of temperature.
Up to optimum point, > temp >rate of reaction due to collisions with required activation energy. Heat -> vibration (more kinetic energy) & puts strain on H bonds. Enzymes have large no. bonds. As temp > further, more bonds break & t structure changes
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What is denaturation?
When the tertiary structure of the enzyme unravels & the enzyme stops working as substrate can't fit disintegrated active site.(may be due to pH or temp).
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Describe & Explain the effects of enzyme concentration.
As enzyme concentration increases, rate of reaction increases as there are more active sites available, until the substrate concentration becomes a limiting factor & the rate of reaction stops increasing
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Describe & Explain the effects of substrate concentration.
As the substrate concentration rises, the rate of reaction rises because there's more substrate mol. to react & there are free active sites. At higher conc, all of the active sites become filled (enzyme is saturated) so rate of reaction remains same.
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Explain the effects of competitive inhibitors on the rate of enzyme-controlled reactions with reference to both reversible & non-reversible inhibitors.
Similar shape to substrate, so occupy AS forming enzyme inhibitor complexes. Level of inhibition depends on conc. of inhibitor & substrate. > of substrate = < in level of inhibition. Most competitive I's don't bind permanently(they leave again).
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If you increase the number of substrate molecules, the level of inhibition decreases. Why is this?
Because a substrate molecule is more likely to collide with the active site, over the inhibitor molecule.
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Why are the competitive inhibitors actions considered reversible?
Because they bind & then leave. The removal of the inhibitor from the reaction mixture leaves the enzyme unaffected.
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Explain the effects of non-competitive inhibitors on the rate of enzyme-controlled reactions with reference to both reversible & non-reversible inhibitors.
Attach to enzyme in place away form AS. Attachment distorts t structure & shape of AS changes. Substrate no longer fits & reaction rate <. Level of inhibition depends on no. inhibitor mol present. Most bind permanently & inhibition is irreversible.
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Why does the level of inhibition depend on no. inhibitor mol present?
Because if there are enough inhibitor molecules to bind to all of enzyme, enzyme controlled reaction will stop.
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Explain the importance of cofactors in enzyme controlled reactions.
Cofactors are Ions that increase the rate of enzyme-controlled reactions. They bind to the enzyme & allows enzyme substrate complexes to form easily.
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Explain the importance of coenzymes in enzyme controlled reactions.
Small, organic, non-protein mol & bind for short period to AS. Take part in reaction & are changed. Recycled back. Role: carry chem groups between enzymes so link. Used when reaction needs to occur in sequence. Some permanent& contribute to shape.
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What is meant when it says coenzymes are 'recycled'?
They come back again & take part in the reaction again.
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Metabolic poisons may be enzyme inhibitors. Describe the action of one named poison (lactic acid).
Potassium Cyanide acts as non-compet. inhibitor of enzyme cytochrome oxidase, (involved in oxidation of ATP). When this is inhibited, aerobic respir. can't occur so organism respir. aerobically which leads to build up of lactic acid, toxic to cells.
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Fill in the gap: Some _____ drugs work by ______ the activity of enzymes.
1. Medical. 2. inhibiting.
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Card 2

Front

Where in cells can enzymes work?

Back

They can be intracellular or extracellular.

Card 3

Front

Describe the mechanism of action of enzyme molecules, with reference to specificity.

Back

Preview of the front of card 3

Card 4

Front

Describe the mechanism of action of enzyme molecules, with reference to their active site.

Back

Preview of the front of card 4

Card 5

Front

Describe the mechanism of action of enzyme molecules, with reference to the lock & key hypothesis.

Back

Preview of the front of card 5
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