Chapter 4 Enzymes & Bio Reactions Flashcards
Define enzyme
Biological catalysts that speed up the rates of reaction without being used up in the reaction.
What are enzymes made up of?
globular protein molecules.
Define metabolism
All the chemical reactions which take place in the cells of living organisms to maintain life.
Define catabolism
Reactions which break down large complex molecules into smaller, simpler molecules
What is activation energy?
The minimum quantity of energy which the reactants must possess, for a reaction to occur.
What do enzymes do to catalyse reactions?
Enzymes lower the activation energy, this means that the reaction does not need as much energy so the reaction will happen more easily.
What are extracellular enzymes?
Enzymes that work outside the cell. E.g- Amylase
What are intracellular enzymes?
Enzymes that work inside cells. E.g- DNA polymerase
What is the ‘lock & key’ mechanism?
Enzymes work under the enzyme specificity principle which is where an enzyme is specific for its substrate : The unique shape of the active site means that an enzyme can only catalyse one type of reaction.
What is the ‘induced fit’ mechanism?
The enzyme shape alters slightly to accommodate the substrate
How does temperature affect enzyme activity?
As temp increases, enzyme molecules and substrates gain more kinetic energy and move around faster. This increases the chance of collisions and forming enzyme-substrate complexes. However, as temp increases further, the enzymes vibrate more violently which can break the hydrogen bonds that hold the globular shape of the protein. If the bonds break, the shape of the active site changes and the enzyme denatures.
How does enzyme concentration affect rate of reaction?
The more molecules there are, the greater the chance of a substrate molecule meeting it and forming an enzyme-substrate complex, increasing the rate of reaction. However, it will come to a point where it doesn’t matter how many enzyme molecules you add, if there isn’t any more substrates to bind with.
How does substrate concentration affect the rate of reaction?
As you increases substrate concentration, the rate of reaction will increase until the point when all the enzyme molecules are in Constant use (enzyme saturation)
How does pH affect enzyme activity?
The tertiary structure of an enzyme is held in place by hydrogen bonds. Changes in pH alter the hydrogen bonds and so alter the shape of the active site. As the pH increases, the enzyme denatures.
How do competitive inhibitors affect enzyme activity?
Competitive inhibitors are molecules that have a very similar shape to the substrate, so they compete with the substrate for the active site. If they can get to the active site first, then the substrate cannot fit and no reaction will occur.
