Unit 1 - Metabolic Pathways Key Area 5 Flashcards
Key Area 6
What is Metabolism
Metabolism can be defined as all the chemical reactions that occur within the human body.
What does Metabolic Pathways involve
Metabolic pathways involve the building up and breaking down of molecules.
Are metabolic pathways reversible
Metabolic pathways can have reversible/irreversible steps, and alternative routes.
How are metabolic reactions controlled
Metabolic pathways are controlled by the
presence or absence of particular enzymes
and the regulation of the rate of reaction of
key enzymes.
What are the 2 types of reactions within metabolic pathways
Anabolic
Catabolic
What is Anabolic
Anabolic reactions build up large molecules from small
molecules and require energy
e.g. building up of amino acids to form proteins
What is catabolic
Catabolic reactions break down large molecules into
smaller molecules and release energy.
e.g. breaking down of glucose in glycolysis
What is activation energy
Activation energy is the energy required to break chemical bonds in a reaction. It is the energy that is needed to allow the reaction to take place.
What are metabolic pathways
Metabolic pathways are integrated and
controlled pathways of enzyme-catalysed
reactions within a cell.
What is meant by the term affinity
The substrates show affinity (chemical attraction) for the active site.
After the reaction, the products have a low affinity for the active site and are released, leaving the enzyme free to repeat this process with new substrates
How do reactants turn into products
Chemical bonds are broken when the reactants have gained enough energy to make them unstable, this is where they turn into products.
How do enzymes speed up reactions
Enzymes speed up a chemical reaction by lowering the activation energy required for the reaction to take place.
Describe Induced Fit
The active site of an enzyme is not a rigid structure. It is flexible and dynamic.
When a molecule of a substrate enters the active site, the shape of the enzyme’s active site change slightly, making the active site fit very closely round the substrate molecule – this is called induced fit
Induced fit ensures that the active site comes into very close contact with the molecules of substrate and increases the chance of the reaction taking place
What do enzymes need to function efficiently
To function efficiently, an enzyme requires a suitable:
- Temperature
- pH
- Substrate concentration
- Product Concentration
What are the effects of substrate and product
concentration on the direction and rate of
enzyme reactions
Some metabolic reactions are reversible and
the presence of a substrate or the removal of
a product will drive a sequence of reactions
in a particular direction.
Explain the relationship between the rate of reaction and the substrate concentration in terms of the enzymes active site
1) At low substrate concentrations the reaction rate is slow because not all of the active sites are occupied by a substrate.
2) When the substrate concentration is increased the rate of the reaction increases as more active sites become occupied by a substrate.
3) At high substrate concentrations the reaction rate does not increase as there are no more active sites for the substrate to bind to.
What is an inhibitor
An inhibitor is a substance that decreases the rate of an enzyme controlled reaction.
What are the 3 types of inhibitors
There are three kinds of inhibition
- Competitive Inhibition
- Non competitive Inhibition
- Feedback Inhibition
What is a competitive inhibitor
Competitive Inhibitor = competes with the substrate for the active site of an enzyme
Describe how does a competitive inhibitor work
is it reversible
2 mark question usually
It has a similar molecular structure to the substrate, therefore can bind to the active site and block the substrate form binding, so the rate of the reaction decreases.
Competitive Inhibition can be reversed by increasing the substrate concentration. The substrate will eventually outnumber the competitive inhibitor.
What is a non competitive inhibitor and how does it work
Does not have a similar molecular structure to the substrate and does not combine directly with the active site.
Attaches to a different area of the enzyme called a non-active (allosteric) site and changes the shape of the active site. This means that the substrate molecule no longer fits therefore preventing it from binding.
Non-competitive inhibition cannot be reversed by increasing substrate concentration
When does feedback inhibition occur
Feedback inhibition occurs when the end-
product in the metabolic pathway reaches a
critical concentration
Describe how a feedback inhibitor works
The end product binds to an enzyme that catalyses a reaction early in the pathway.
This binding blocks the pathway and prevents further synthesis of the product.
Feedback inhibition prevents waste of resources
