Enzymes Flashcards
What are the two types of enzymes and what do they do?
Anabolic - Reactions which build up molecules
Catabolic - Reactions which break down molecules
How do enzymes work in terms of energy?
Enzymes create an alternate pathway for a reaction and lower the Activation energy required for a reaction to start.
What is the substance that goes into an enzyme’s active site called?
A substrate
What are the two theories of enzyme mechanism and what do they suggest?
1) Lock and key theory
This theory suggests that enzymes and substrates are specific to eachother, complementary to each other and are rigid molecules.
2) Induced fit mechanism
A modification of the lock and key theory, this suggests that the active site moulds itself around the substrate.
What are the limitations of the lock and key theory?
- Some enzymes can catalyse multiple reactions
2. Non-competitive inhibitors can change the shape of the active site, showing that it is not rigid.
How do competitive inhibitors work?
They bind to the enzyme’s active site and block the substrate from entering. They are reversible and do not change the shape of the active site. The degree of inhibition depends on the concentration relative to the concentration of substrate.
How do non-competitive inhibitors work?
They bind with the allosteric site, which is away from the active site. They cause the active site to change shape, and thus the substrate cannot fit it any more, and so reactions cannot occur. Some are reversible, whereas some are not.
What are the 4 different conditions that effect enzyme rate of reaction? And how?
- Temperature - Increases rate of reaction up to a point, but after the optimum temperature has been reached, the enzymes start to denature so rate decreases.
- Substrate concentration - Increases rate up until the point that there is so much substrate that all enzymes are filled at all times, so there cannot be any more reactions.
- pH - Changing the pH of an enzyme breaks the bonds, and so denatures it. Every enzyme has a preferred pH, depending on where they are working.
- Enzyme conc. - Increases rate of reaction as there are more enzymes for the substrates to enter, up until the point where enzyme conc = Substrate conc, and so there could not be more reactions.
What are coenzymes?
Small, non-protein molecules that bind to an enzyme at the same time as the substrate. They facilitate the reaction and make sure that reactions happen in the correct order. They are NOT CATALYSTS, as they are ALTERED and must be remade. Vitamins are a common source of coenzymes in humans.
What are cofactors?
Inorganic ions that combine with the enzyme to make formation of the enzyme-substrate complex easier. They can move and detach from the enzyme or attach to the substrate.
What are prosthetic groups?
Inorganic ions that combine with the enzyme to make formation of the enzyme-substrate complex easier. They become permanently attach to the enzyme.
What is a metabolic pathway?
A series of linked reactions whereby the product of one enzyme becomes the substrate of another enzyme. The last product in the pathway is known as the end product.
