Enzymes Flashcards
(32 cards)
What are enzymes?
Enzymes are globular proteins that act as catalysts.
What do catalysts do?
Catalysts alter the rate of a chemical reaction without undergoing permanent changes themselves.
What are some advantages of using catalysts?
- Can be reused repeatedly, and are therefore effective in small amounts.
- Speed up chemical reactions.
What is the activation energy?
Minimum amount of energy needed to activate the reaction.
How do enzymes affect activation energy ( and therefore temperature too )?
Enzymes lower the activation energy, allowing reactions to take place at a lower temperature than normal.
What is the difference between intracellular and extracellular?
- Intracellular - Inside Cells.
* Extracellular - Outside cells.
What is the functional region of the enzyme?
The Active Site.
What determines the shape of the enzyme?
The sequence of amino acids in the primary structure.
What is the substrate?
Molecule on which the enzyme acts.
How are enzyme-substrate complexes formed?
• When a substrate fits into an enzyme’s active site, it forms an enzyme substrate complex.
How does the enzyme lower the activation energy required?
- if two substrate molecules need to be joined, being attached to the enzyme holds them close together, reducing repulsion between the molecules allowing for easier bonding.
- If the enzyme is catalysing a breakdown reaction, fitting in to the active site, puts a strain on bonds in the substrate.
How do enzymes allow molecules to be more easily joined?
if two substrate molecules need to be joined, being attached to the enzyme holds them close together, reducing repulsion between the molecules allowing for easier bonding.
How do enzymes allow molecules to be more easily split?
If the enzyme is catalysing a breakdown reaction, fitting in to the active site, puts a strain on bonds in the substrate, allowing for the molecule to more easily be split with less energy.
What is the induced fit model?
- Active site forms as the enzyme and substrate interact.
- The substrate results in a change of proximity of the enzyme, and leads to a change in the enzyme that forms the functional active site.
Why can enzymes only catalyse one reaction?
- Only one complementary substrate will fit the active site.
- Each different enzyme has a different tertiary structure, and therefore a differently shaped active site.
- if the substrate shape doesn’t match the active site, an enzyme substrate complex won’t be formed, and therefore a reaction will not place.
What determines the shape of the active site?
The active site’s shape is determined by the enzyme’s tertiary structure, which is determined by the enzymes primary structure.
What bond maintains the enzyme’s shape?
Hydrogen Bonds.
What is required for an enzyme to carry out its function?
- Come into physical contact with its substrate.
* Have an active site which fits the substrate.
How does temperature affect an enzyme activity?
- A rise in temperature increases the kinetic energy of molecules.
- Increase in kinetic energy results in molecules moving around quicker, which increases the amount of collisions, more substrates and enzymes will come together in a given time.
- The enzyme substrate complexes will have a higher energy and a more frequent collision rate, which increases the number of successful collisions, increasing the rate of reaction
- Eventually the temperature rises too high, and it causes the bonds in the enzyme molecule to break ( hydrogen bonds for example ), resulting in the enzyme and it’s active site changing shape, meaning the substrate can no longer bind to the active site, resulting in less enzyme substrate complexes forming, reducing the rate of reaction, the enzyme is now denatured.
What is meant by an enzyme being denatured?
Where the enzyme ceases to function as a catalyst, denaturation is a permanent change.
How does pH affect enzyme activity?
- Change in pH alters the charge son the amino acids that make up the active site of the enzyme.
- Change in charges means the substrate can no longer become attached to the active site, and so the enzyme substrate complex cannot be formed.
What is the optimum pH value?
pH at which the enzyme fastest at.
How does enzyme concentration affect rate of reaction/
- Once the enzyme has acted on its substrate, it is is able to act on another one of its substrate molecules, enzymes are not used up in a reaction.
- The more enzyme molecules there are in a solution, the more likely a substrate molecule is to collide with one and form an enzyme substrate.
- Increase in enzyme concentration leads to an increase in rate of reaction.
How does enzyme concentration affect rate of reaction if the substrate is limited?
- If the enzyme concentration is increased, excess substrate can be acted upon.
- If the substrate is the limiting factor, there will not be sufficient supply to all enzyme active sites after a certain point, therefore any increase in enzyme concentration beyond this point, ,will not have any affect on the rate of reaction.
- The rate of reaction will eventually stabilise at a constant amount, because the available substrate is already being used by the existing enzsyme molecules.
