Biology - Review Qns - 4.1 & 4.2 Flashcards
Inhibition
4 characteristics
Depending on bond strength:
Reversible
Irreversible
Depending on binding point:
Competitive
Non-competitive
Cofactors
Cofactors are additional components required by some enzymes to catalyse a reaction.
Can enzymes be reused?
As enzymes do not form part of the product of the reaction they catalyse, they are not used up and can be reused over and over again.
Non-competitive inhibition
The inhibitor binds to a site of the enzyme that is not the active site (an allosteric site)
Changes the shape (or conformation) of the enzyme
thereby
It affects the binding of substrate to the active site
or
It blocks the changes in shape needed for the reaction to progress once the substrate is bound.
Reversible inhibition
2 Points
The bonds formed between inhibitor and enzyme are weak and easily broken, so the inhibition is reversible.
Reversible inhibition can be partially overcome by increasing the concentration of substrate.
What major factors affect the rate of enzymatic reactions?
3 factors
Temperature
pH
Concentration
What is
A biochemical pathway
A biochemical pathway is a sequence of biochemical reactions catalysed by different enzymes, in which the product of each reaction becomes the substrate in the next reaction.
How many models are there of enzyme-substrate reaction?
Two
- The lock and key model
- The induced-fit model
Coenzymes
3 points
Coenzymes are small, non-protein organic cofactors such as vitamins, ATP, NADH and NADPH.
Coenzymes are needed for reactions in biochemical pathways, including cellular respiration and photosynthesis.
Coenzymes carry chemical groups, protons and electrons between reactions in order to transfer energy between them.
What is the active site?
The active site is a three-dimensional pocket-like part of the enzyme that is shaped to interact with its specific substrate.
Describe
Catabolic reactions
Catabolic reactions are reactions in which substrates are broken down and energy is released.
Affect on enzyme reaction of:
Temperature
High temperatures can alter an enzyme’s three-dimensional structure and change the shape of the active site. This means the enzyme cannot act as a catalyst.
This change is called denaturation.
What is
Metabolism
Metabolism is the collection of all the biochemical (or metabolic) reactions that occur in living cells.
Describe
Enzymes
Most enzymes are globular proteins that have a tertiary or quaternary structure.
Describe
Anabolic reactions
Anabolic reactions are reactions in which larger molecules are produced from smaller substrates. They require an input of energy
What is Activation Energy?
Activation energy is the amount of energy input required for a reaction to start.
Affect on enzyme reaction of:
pH
Enzymes have an optimum pH range and if the enzyme is exposed to a pH outside its tolerances, the enzyme may become denatured.
Unloaded coenzymes
Unloaded coenzymes accept a chemical group, proton or electron.
competitive inhibition
The inhibitor binds to the active site of the enzyme, blocking the substrate from binding
Describe
The induced-fit model
(of enzyme–substrate interaction)
The induced-fit model states that when a substrate binds to the active site of an enzyme, the active site can alter its shape to better ft the shape of the substrate.
Affect on enzyme reaction of:
Concentration
The concentrations of enzymes and their substrates will have an effect on the rate of a reaction, as both substrate and enzyme are required for the reaction to occur.
Loaded coenzymes
Loaded coenzymes donate a chemical group, proton or electron.
Irreversible inhibition
The bonds formed between inhibitor and enzyme are strong, so the binding is irreversible.
If the inhibition is irreversible increasing substrate concentration will have no effect.
What happens when enzymes and substrates interact?
When enzymes and substrates interact, they form an enzyme–substrate complex.
