enzymes Flashcards
week 8 validation
Define
Metabolism
All the chemical reactions that take place in cells.
Define
Catabolism
Reactions in which large molecules are broken down into smaller ones. These reactions release energy.
Example: digestion
Anabolism
Process in which small molecules are built up into larger ones. These reactions require energy.
Example: protein synthesis.
Define
Enzyme
A biological catalyst that speeds up chemical reactions by lowering the activation energy. It is not consumed or altered in the reaction.
** What do catalysts do?
Lower the activation energy while not being consumed in the reaction.
Define
Substrate
The molecule on which an enzyme acts.
Define
Active site
The part of the enzyme molecule that combines with the substrate.
Define
Enzyme-substrate complex
A temporary molecule formed when the substrate binds to the enzyme.
Explain
Lock and key model
The shape of the enzyme (key) is always complementary to the shape of the substrate (lock). Therefore, they will fit exactly together to form the enzyme-substrate complex.
Explain
Induced-fit model
When the enzyme and substrate join, they form weak bonds that cause the shape of the enzyme to change, creating complementary shapes.
7 factors affecting enzyme activity.
- Temperature
- pH
- Enzyme concentration
- Substrate concentration
- Product concentration
- Cofactors
- Enzyme inhibitors
How does temperature affect the rate of enzyme activity?
- As the temperature increases, the enzymes and substrates move faster (higher kinetic energy) so the active sites and substrates collide more often, speeding up the rate of activity.
- (Problem) However, continually raising the temperature causes hydrogen bonds in the enzyme’s active site to break, causing it to change shape (denature), so the substrate(s) can no longer bind to them. this results in a decline in the rate of activity.
Define
pH
A measure of the concentration of hydrogen ions in a substance. (Stands for potential of hydrogen)
How does pH affect the rate of enzyme activity?
- Enzymes work at specific pH.
- e.g., pepsin works in acidic conditions.
- Changing pH alters the enzyme’s shape, affecting rate of activity.
How does enzyme concentration affect the rate of enzyme activity?
- As enzyme concentration increases, there are more active sites available for substrates to bind to.
- Unless the substrate increases, the product(s) produced remains the same (conservation of mass).
How does substrate concentration affect the rate of enzyme activity?
- As the substrate concentration increases, so does the rate of activity until all the active sites are occupied.
- We are limited by the available active sites, so rate no longer increases. this is called the turnover number.
How does product concentration affect the rate of enzyme activity?
The products must be continually removed otherwise the rate of reaction will slow because it becomes more difficult for the substrate molecules to make contact with the enzyme molecules (because products are in the way).
Define
Cofactor
Ions or non-protein molecules that catalyse a reaction by changing the shape of the active site so that the enzyme can combine with the substrate. Without a cofactor, the enzyme is intact but cannot function.
Define
Coenzymes
Cofactors that are non-protein organic molecules. Many vitamins function as coenzymes.
Define
Enzyme inhibitors
Substances that slow or even stop the enzyme’s activity.
- May be used by cells to control reactions so that the products are produced in specific amounts.
- Many drugs are enzyme inhibitors.
- E.g., penicillin inhibits an enzyme in bacteria that is involved in construction of the cell wall.
