C1.1 Flashcards
What is an enzyme?
An enzyme is a globular protein which acts as a biological catalyst by speeding up the rate of reaction.
What is the induced fit model?
Where an enzyme and active site (sometimes substrate) change shape slightly as the substrate molecule enters the enzyme.
This ensures ideal binding arrangement and these changes in shapes are known as conformational changes.
Also maximises the ability of the enzyme to catalyse the reaction.
Differences between lock and key model and induced fit model?
- in lock and key substrate fits exactly while in induced fit it’s not exact
- active site changes in induced fit
- In induced fit it’s the change in substrate which reduces activation energy
- induced fit explains competitive inhibition while lock and key doesn’t
ESC (Enzyme substrate complex) formation
Both substrate and enzyme are in continual motion in a dissolved state
Reaction only occurs when a substrate comes in contact with the complimentary active site of an enzyme
Chances are random but will increase in certain conditions like a higher temperature
Anabolism
Synthesis of complex molecules from simpler molecules
Example: protein synthesis
Catabolism
Break down of complex molecules into simpler molecules by hydrolysis
Example: Digestion of food
What is a competitive inhibitor and what is an example?
Definition - a substance that slows down the rate of an enzyme controlled reaction by preventing binding of the substrate to the active site of an enzyme.
Scenarios:
Low substrate concentration:
Competitive inhibitor binds to active site preventing substrate entry
High substrate concentration:
Substrate more likely to come into contact with an enzymes active site OR the substrate molecules displace the competitive inhibitor.
Example:
Statins
Enzyme function - enzyme HMG-COA reductase normally catalyses one reaction in the metabolic pathway used to form cholesterol in the liver.
How: statins bind to active site of the enzyme HMG-COA reductase
Effect: Can be used to control cholesterol levels
What is a non-competitive inhibitor and what is an example?
What are they? They slow down the enzymes reaction but they don’t bind to the active site, they bind to the allosteric site, preventing substrates from binding
Unlike competitive inhibition this one is actually permanent
Example: potassium cyanide
Enzyme function: cytochrome oxidase assists in the reduction of molecular oxygen to water and translocation of protons from the internal mitochondrial matrix to the inter membrane space.
How: cyanide attaches to the cytochrome oxidase changing the shape of its active site meaning no cellular respiration because it has blocked the reduction of oxygen to water.
What is end product inhibition?
- form of negative feedback by which metabolic pathways can be controlled
- final product in a series of reactions inhibits an enzyme from an earlier steps in the sequence.
- product binds to an allosteric site and temporarily inactivates the enzyme (non-competitive)
- as the enzyme can no longer function, the reaction sequence is halted and the rate of product formation is decreased
What is ATP
ATP - Adenosine TriPhosohate
Role: removing a phosphate releases 30.5 KJ of energy. This is a hydrolysis reaction and is catalysed by enzymes called ATPases
When a phosphate is released it becomes ADP adenosine diphosphate.
Importance - it’s used in:
Locomotion
Movement
Active transport
Growth and repair
Biosynthesis of macromolecules
Aerobic vs anerobic respiration
Aerobic respiration occurs with oxygen and releases more energy but more slowly.
Anaerobic respiration occurs without oxygen and releases less energy but more quickly.
