Enzymes. Flashcards
Inhibitor definition.
- Binds to the enzyme.
- Stops it from catalysing the reaction.
Competitive inhibitors.
- Similar shape to substrate.
- Complementary to active site.
- Forms enzyme-inhibitor complex.
- Competes with the substrate in order to bind to active site.
- Reduces rate of reaction.
- Reversible: increased sub conc overtakes.
Non-competitive inhibitors.
- Binds to allosteric site.
- Forms enzyme-inhibitor complex.
- Causes shape of active site to change.
- Becomes not complementary to substrate.
- Decreases reaction rate.
- Can be reversible/irreversible.
Functions of an enzyme.
- Catalyses reactions.
- Speeds up reaction rate by lowering activation energy of a reaction.
- Affects digestive and metabolic reactions.
Lock and key model.
- Perfect fit.
- Enzyme makes temporary bonds to substrate.
- Highly specific, unique shape of active site.
- Enzymes can only catalyse one type of reaction.
- Active site complementary to substrate.
DIAGRAM. - Form enzyme-substrate complex.
- Products released.
- Unchanged and reusable enzyme.
Activation energy definition.
The minimum energy required for molecules to react, breaking existing bonds and forming new ones.
How do enzymes lower activation energy(and increase rate of reaction)?
1) Substrate enters active site of enzyme.
2) Shape of molecule alters.
3) So reactions can occur at a lower temperature than without the enzyme.
Induced fit model.
- Flexible enzyme, not rigid.
- Initially, shape of active site not complementary to substrate.
- Active site shape alters to bind to substrate.
- Becomes complementary.
- Can bind at any angle.
- Products released.
- Enzyme unchanged and reusable.
- Enzyme still specific at start and active site and substrate become complementary.
Enzyme properties.
- Globular proteins.
- Soluble.
- Not durable (low).
- Non-repetitive.
- Speed up metabolic reactions.
Metabolic reaction definition.
Involves the making of large molecule or the breaking down/degrading of large molecule.
Anabolic reactions.
- Making large molecules.
E.g.
Formation of triglyceride, phospholipid.
Catabolic reactions.
- Degrading/breaking down large molecules into their separate components.
E.g.
Opposite of formation in anabolic.
Intracellular enzymes.
Works inside a cell.
Extracellular enzymes.
Works outside a cell.
Affect of temperature on rate of reaction.
-Higher temp=more kinetic energy=more enzyme-substrate collisions with enough energy= more complexes formed=higher rate.
-Above 40C, molecules have more energy.
Rate decreases because increasing vibration breaks hydrogen bonds .
Changes shape of active site=not complementary=cannot bind with substrate.
Lowe temps don’t change shape, just decrease activity.
Effect of pH on ROR.
-Optimum pH where ROR is highest.
-Only extreme pH denatures.
-Small pH chnages around optimum=small reversible changes in structure/activity.
Explanation of pH effect.
-Low pH, H+ ions attracted to negative charges and neutralise them.
-High pH, OH- ions neutralise positive charges .
-Disrupts ionic and H bonds that maintain active site shape.
Effect of substrate concentration on ROR.
ROR increases as substrate conc increases.
-low conc=few sub molecules to collide w enzymes.
-Higher conc=more active sites full.
-Saturated=all active sites full=plateau.
-Plateau=not limiting factor=not controlling rate.
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Effect of enzyme concentration on ROR.
-High enzyme conc=more active sites available=higher ROR.
-Enzymes can be reused so smaller conc needed to catalyse more reactions.
-Plateau=not limiting factor.
Turn over rate meaning.
Number of substrate molecules that one enzyme molecule can turn into products in a given time.
Buffers.
-Maintain a specific pH.
-Contain acid and conjugate base.
-Any added OH- or H+ ions added are neutralised by these components.
-Allows metabolic processes to occur optimally.
Immobilised enzymes definition.
-Fixed, bonded or trapped on an inert matrix.
Advantages of immobilised enzymes.
-Increased temp and pH stability over wider range.
-Products are not contaminated w enzyme.
-Enzymes easily recovered for reuse.
Immobilised enzymes uses.
-Lactose free milk.
-Biosensors.
-High fructose corn syrup manfacturing.
