Unit 1 (K6) - Metabolic pathways Flashcards
What are metabolic pathways?
Chains of integrated and controlled enzyme-catalysed reactions within a cell.
What are ANABOLIC reactions?
Anabolic reactions are biosynthetic, meaning they build up more complex molecules from simpler ones and require the input of energy.
What are CATABOLIC reactions?
Catabolic reactions breakdown (degrade) complex molecules, providing building blocks for other reactions and releasing energy.
Are the steps in a metabolic pathway reversible?
Some are reversible and irreversible.
How are metabolic pathways controlled?
By the presence and absence of some enzymes and by the regulation rate of reaction of other key enzymes.
What is the activation energy of a reaction?
The energy needed to allow a reaction to occur.
How to enzymes speed up reactions?
They lower the activation energy so more molecules have greater than the activation energy and the reaction takes place faster.
What is the role of the active site?
The enzymes active site is specific to its substrate. The shape of the substrate molecule(s) is complimentary to the enzymes active site which they show high affinity (chemical attraction).
Describe the induced fit and affinity process
- The active site is not a rigid structure - it is flexible and dynamic. Induced fit occurs when the active site changes shape to better fit the substrate after the substrate binds.
- Induced fit ensures that the active site comes very close contact with the molecules of the substrate and increases the chance of the reaction taking place.
- The substrate molecule(s) have a high affinity for the active site and the subsequent products have a low affinity allowing them to leave the active site.
What are the factors affecting Enzyme controlled reactions?
- At low concentrations of the substrate, the reaction rate is low since there are too few substrate molecules present to make maximum use of all the active sites on the enzyme molecules.
- An increase in substrate concentrations results in an increase in reaction rate since more and more active sites become involves.
What is an enzyme inhibitor?
A substance which slows down or stops the activity of an enzyme.
What is competitive inhibition of an enzyme?
The inhibitor attaches to the active site and blocks the substrate from binding. Competitive inhibition can be reversed by increasing substrate concentration.
What is non-competitive inhibition of an enzyme?
An inhibitor binds to an enzyme away from the active site (allosteric site) which changes the shape of the enzymes active site and prevents the substrate from binding. Increasing the concentration of the substrate will not increase the rate of reaction.
What is feedback inhibition?
This is when the end product in the metabolic pathway reaches a critical condition. The end products inhibits an earlier enzyme in the pathway and so blocking the pathway and preventing further synthesis of the end product.
