Enzymes Flashcards
- What is a catabolic reaction?
A reaction which breaks larger molecules into smaller molecules.
- What is an anabolic reaction?
A reaction which forms larger molecules from smaller molecules.
- What is a catalyst?
A substance which increases the rate of reaction by providing a lower activation energy pathway without being used up itself.
- What biological polymer are enzymes made of?
Polypeptides (Globular Protein)
- What is the difference between an intracellular and extracellular enzyme?
Intracellular enzymes act within the cell, e.g digestive enzymes in the lysosomes inside cells. Some are membrane-bound like ATP synthetase.
Extracellular enzymes are secreted out of the cells onto their food and then absorbed the soluble products by saprotrophic organisms.
- Describe the lock and key theory of enzyme action.
Lock and key theory states that the enzymes active site is specific like a lock and that the substrate that fits is already complementary to that enzyme like a key.
- Describe what is meant by induced fit
The shape of the active site is not complementary to the substrate, so when it binds, the enzyme makes conformational changes to fit to produce the enzyme-substrate complex. By altering its shape, it puts strain on the substrate molecule, which distorts a particular bond on the substrate and so lowers the activation energy to break it. The active site returns to its original shape once the products are released.
- Give an example of an enzyme that works by induced fit.
Lysosomes bind to the polysaccharide coating of bacteria. By initiating the induced fit, it breaks apart the polysaccharide, ultimately killing the bacteria.
- Explain how the active site makes enzymes specific to their substrate.
Enzymes are globular proteins with specific 3D shapes. The active site is a cleft on the enzyme molecule with the specific 3D shape to which a substrate molecule fits and binds during metabolic reactions.
- What is the name of the energy lowered by enzymes that increases the rate of reactions?
Activation Energy
- Explain how increasing temperature increases the rate of reaction up to the optimum.
Rate of reaction increases because the molecules have greater KE and thus collide more frequently and more successful collisions between the active site of the enzyme and substrate to form enzyme-substrate complexes.
- What is meant by optimum?
The value of the variable where rate of reaction is at a maximum.
E.g the temperature where rate of reaction is highest
- Explain how increasing the temperature above the optimum decreases the rate of reaction.
The increased temperature causes more vibrations within the enzyme, which can distort/break the hydrogen and ionic bonds. This breaks the specific shape, and the tertiary structure has changed. This causes the enzyme’s active site to denature. As it no longer has a complementary shape, the substrate cannot successfully bind to it.
- What is meant by denaturation?
When the specific 3D shape has changed and the active site is no longer complementary. Thus no longer functionable.
- Describe the effect of small changes in pH away from the optimum.
They break a few ionic and hydrogen bonds, causing minor conformational changes. Small changes are temporary and can be reversed.
- Describe the effect of large changes in pH away from the optimum.
They break many ionic and hydrogen bonds, causing more drastic conformational changes, denaturing the enzyme. They are irreversible.
- Describe the difference between competitive and non-competitive inhibition.
Competitive inhibitors bind directly to the active site as they have a similar shape to the substrate. They block the active site from binding to the substrate by occupying it. Fewer ESCs form, so there is less/no product. ROR slows down. The effect is reversible if the substrate concentration increased.
Non-competitive inhibition binds to an allosteric site of the enzyme, which causes conformational changes to the enzyme’s 3D shape, altering the specific tertiary structure of the active site. Substrate is not complementary and cannot successfully form ESCs. Irreversible if the inhibitor bonds permanently with the enzyme.
- End-product inhibition is a type of non-competitive inhibition where the product of a metabolic pathway can bind to the active site of the first enzyme to denature it. This stops the pathway when there is a higher rate of production than they are being used (prevents energy being wasted).
- Sketch a graph to show the effects of increasing substrate concentration on: the rate of an enzyme controlled reaction; the rate of reaction affected by a competitive inhibitor; the rate of reaction affected by a non-competitive inhibitor.
the rate of an enzyme controlled reaction: normal linear then levels off at Vmax
the rate of reaction affected by a competitive inhibitor:
slower rate of reaction but still reaches Vmax
the rate of reaction affected by a non-competitive inhibitor:
slower rate of reaction and does NOT reach Vmax
- Explain the difference between the graphs for non-competitive and competitive inhibitors.
non-competitive:
- They cause some enzymes to become non-functional so the rate of reaction will neve be equal to the Vmax
competitive inhibitors
- Higher substrate concentrations increase the chance of them binding to the active site, which leaves fewer available to the inhibitor. The inhibition is reversible (can unbind), so eventually all the substrate will be used up.
10a. List advantages of using immobilised enzymes in industry.
Immobilised enzymes are bound to an inert material, over which the substance can move
- They do not contaminate the product
- More stable, so they can work in higher temperatures and more extreme pH.
- Easily recovered for reuse
- Several enzymes with different optimums can work at the same time.
e.g adsorption to alginate beads
10b. Describe a disadvantage of using immobilised enzymes in industry.
They are less accessible so typically have lower rates of reaction than free enzymes
- What are biosensors?
An instrument which contains immobilised enzymes which are used to detect specific metabolites from a mixture of substances
- What are the advantages of biosensors?
-Rapid
-Accurate
-Detects even at very low concentrations of the metabolite
-Quantitative readings
- Give an example of a biosensor.
- Blood glucose monitors
- Medical diagnosis
- Environmental monitoring
