Enzymes🧫 Flashcards
What is metabolism?
Chemical reactions taking place in your body
What are anabolic reactions?
Building up/synthesis
What are catabolic reactions?
Breaking down
What are enzymes?
Molecules controlling reactions in your body
What level of protein structure is shown by enzymes?
Tertiary structure - globular, specific 3D shape, hydrogen bonds, ionic bonds, disulphide bonds
Properties of enzymes
- Specific - will only catalyse with a particular reaction
- Not used up in the reactions - reusable
- Combine with their substrates to form enzyme/substrate complexes - release products when finished
- Only a small amount is used
- Fast acting - high turnover number
- Affected by changes in temp or pH
- Many can only work if a cofactor is present
- Can be slower or stopped by inhibitors
What are intracellular enzymes?
Functions within the cell where it was produced
What are extracellular enzymes?
Secreted by a cell and functions outside the cell
What is the lock and key theory?
- Explains why enzymes are specific
- Enzymes have an active site made up of 3-12 amino acids - has the right structure to fit with the substrate
- The active site and substrate lock into place to form an enzyme/substrate complex
- Products are formed at active site - have different shape so are repelled - active site is freed up
What is the induced fit theory?
- Suggests active site may not exactly correspond to shape of the substrate
- Active site is more flexible - module itself round the substrate
- When it’s binds closely to the substrate the active site catalyses the reaction
- Products are repelled
- Enzyme reverts to relaxed shape
TIP
Always mention kinetic energy and more frequent successful collisions
What is activation energy?
The energy needed to start a chemical reaction
How does lowering the activation energy work?
Provides a different pathway for the reaction as the enzymes reduce the input of energy needed and allow reactions to take place at lower temperatures
What does lysozyme do?
Breaks chemical bonds in the outer wall of the bacteria - targets peptidoglycan
What is denaturing?
- When factors alter the tertiary structure of the enzymes/3D shape by breaking hydrogen bonds - includes active site
- Permanent change
What is inactivation?
Cooling the enzyme below the optimum temperature
How does temperature affect the rate of activity of enzymes?
- Increase give molecules more K.E which increases chance of successful collisions and impact - increases rate of reaction
- Only increases to an optimum temp - begins to denature - hydrogen bonds break
How does pH affect the rate of activity of enzymes?
- Small changes in pH affect ROR - these are reversible - inactivation
- Extreme changes in pH can denature an enzyme
- Free H+ and OH- ions can affect the charges of amino acid side chains of the enzyme’s active site
- Affects hydrogen bonds - alters tertiary
How can a pH buffer help the rate of activity of enzymes?
It is a chemical that maintains a constant pH by absorbing excess ions
How does enzyme concentration affect the rate of activity of enzymes?
- ROR is directly proportional to the enzyme concentration
* Increasing enzyme concentration increases rate of reaction
How does substrate concentration affect the rate of activity of enzymes?
- Increasing the substrate concentration increases ROR up to a certain point - increases frequency of successful collisions
- All the active sites become filled - working at maximum rate
What is an inhibitor?
- A substance that can slow down or stop a reaction
- Combines with the enzyme and stops it from attaching to the substrate
- Either reversible or non-reversible
What is a competitive inhibitor?
- Similar structure to substrate
- Competes with substrate for active site of enzyme
- Prevents formation of enzyme/substrate complexes - ROR decreases
- Increasing substrate concentration can reduce the effects of a competitive inhibitor
What is a non competitive inhibitor?
- Doesn’t bind to active site - attaches to another part of the enzyme
- Alters overall shape of the enzyme - including active site
- Substrate can no longer bind to active site
- Increasing substrate concentration doesn’t affect inhibition - not competing with substrate
What are immobilised enzymes?
Enzymes that are bound to inert (unreactive) or trapped in a matrix
Advantages of immobilised enzymes
- More stable at higher temps and a wider range of pHs
- Can be added or removed easily - helpful in controlling the reaction and avoids contamination, ensuring that a pure product is formed
- Easily recovered and reused in industrial processes
- A mixture of enzymes with different optimum pHs and temps can be used together
Disadvantages of immobilising enzymes
Fixing process may damage enzymes
Examples of immobilised enzymes
Biofuels, food production
What are biosensors?
Device which uses enzymes to detect the presence of chemicals
What is polymerisation?
Joining together of monomers
When is the enzyme concentration the limiting factor?
At the start of the graph
When is the substrate concentration the limiting factor?
Near the plateau when the reaction begins to slow down - most of the substrate has been converted into product - limits chance of a successful collision
Why is the use of a control important in enzyme investigations?
It shows that it is the enzymes that are causing the effect that you are measuring (dependant variable)
What is the usual control for an enzyme reaction?
- Boil and cool the enzyme solution
- This denatures the enzymes and ensures they will not catalyse any reactions
- The experiment should then be repeated using the boiled and cooled solution - if the same results are obtained, indicates another factor is influencing the results
