Enzymes Flashcards
What are enzymes?
Biological catalysts which are globular proteins, that can be used to break down or built up substrates.
Describe the relationship between the enzyme and the substrate
They have a complimentary active site, which creates a enzyme-substrate complex.
What are anabolic reactions?
Building up reaction (synthesis)
What is a catabolic reaction?
Breaking down reaction (digestion)
How do enzymes speed up reactions?
It lowers the activation energy
What factors affect the rate of reaction?
- Concentration of enzymes
- Temperature
- pH
When do catalysts work best?
In a high concentration at optimum temperature and at optimum pH.
What different types of enzymes are there?
Give examples
- Extracellular enzymes
(lipase, carbohydrase, protease, amylase, maltase) - Intracellular enzymes
(catalase)
Where are enzymes found?
Mouth
Pancreas
Stomach
Salivary glands
What is the function of enzymes?
Digestion and synthesis
Where can enzymes be found?
Mouth, small intestines, stomach
Where are enzymes produced?
Salivary glands, pancreas
How do enzymes catalyse reactions?
Lower the activation energy
What are inhibitors?
Molecules that prevent enzymes from carrying out their normal function
Describe competitive inhibition
- Molecules that have a similar shape to the substrate of an enzyme can fit into the active site.
- This blocks the substrate from entering the active site, preventing the enzymes from catalysing the reaction.
- The enzyme can’t carry out its function and is ‘inhibited’
- By reducing the number of available active sites, the reaction is slowed.
What are the three types of enzyme inhibitors?
- Competitive inhibition
- Non-competitive inhibition
- End-product inhibition
What is the effect of a competitive inhibitor on rate of reaction?
It slows the rate of reaction, however it doesn’t change the v-max of the enzyme
What are examples of competitive inhibitors?
- Statins are competitive inhibitors of an enzyme used in the synthesis of cholesterol
- Aspirin irreversibly inhibits the active site of COX enzymes, preventing the synthesis of prostaglandin particles and thromboxane, the chemicals responsible for producing pain and fever.
What is a non-competitive inhibitor?
The inhibitor binds to the enzyme at a location other than the active site.
- This alternative site is called an “allosteric site”
- The binding of the inhibitor causes the tertiary structure of the enzyme to change, meaning the active site changes shape.
- The active site is no longer a complimentary shape to the substrate so it is unable to bind to the enzyme.
- The enzyme can’t carry out its function and it is said to be inhibited.
Does a non-competitive inhibitor compete for an active site?
No, it binds to an allosteric site
What is the effect of a non-competitive inhibitor on the rate of reaction?
Increasing the concentration of enzyme or substrate will not overcome the effect of a non-competitive inhibitor.
Are non-competitive inhibitors permanently bound?
No, some may be irreversible
However, Proton pump inhibitors (PPIs) are used to treat long-term indigestion. They irreversibly block an enzyme system responsible for secreting hydrogen ions into the stomach.
What is end-product inhibition?
It is a term used for enzyme inhibition that occurs when the product of a reaction acts as an inhibitor to the enzyme that produces it. This acts as a negative-feedback control mechanism for the reaction.
What is end-product inhibition an example of?
Non-competitive reversible inhibition
