Enzyme Action and Inhibition Flashcards
How does and an enzyme lower the activation energy?
An enzyme binds to a substrate and stresses some of its chemical bonds, or binds to two substrates and forces them close together
What effect does a lower activation energy have on reaction speed?
Reactions are more likely to happen so the reaction rate speeds up.
What type of reaction are enzymes involved in which join molecules together?
Synthesis anabolic (usually condensation)
What type of reaction are enzymes involved in which break molecules apart?
Degradation, catabolic (usually hydrolysis)
What does the amino acid sequence of an enzyme affect?
The shape of the active site
Which amino acids are in the active site.
Why are enzymes specific to one substrate or a group of very similar substrate
Because of their highly defined structure
What is the enzyme which is specific to glucose?
Glucokinase
What does the enzyme hexokinase work on?
Glucose and some other six-carbon sugars
What is the effect of the active site having amino acids?
The amino acids have an affinity for areas on the substrate molecule.
How do the substrate and the enzyme bind?
By forming hydrogen and ionic bonds
What is the effect of the arrival of the substrate bonding to the active site?
Brings about a conformational change in the enzyme.
How can an enzyme showing an induced fit lower the activation energy?
The reaction becomes more likely as the substrate is under tension.
What are the 4 types of enzyme you are expected to know?
Proteases (pepsin + trypsin + bromelain)
Nucleases (EcoRI)
ATPases (sodium potassium pump)
Kinases (Adds a phosphate to inactivate glycogen synthesis)
What is the action of proteases?
Hydrolysis of peptide bonds to break down proteins
What is the action of nucleases?
Hydrolysis of phosphodiester bonds to break down nucleic acids
What is the function of ATPases?
Hydrolysis of phosphoester bonds in ATP to form ADP and phosphate
What is the function of kinases?
Condensation reaction to add a phosphate group to another molecule.
How can you find the activity of an enzyme?
Using a constant concentration of enzyme and then measuring the initial rate of reaction at different substrate concentrations.
What are the two ways an inhibitor can reduce reaction rate
- They can resemble the substrate
- They alter the enzymes shape so that it becomes inactive.
What is a competitive inhibitor
Similar to the substrate in size, shape and charge pattern
How is vMax reached in the presence of a competitive inhibitor?
Increasing the substrate concentration will eventually dilute the competitive inhibitor so much that all the enzyme molecules bind to the genuine substrate.
Where do non-competitive inhibitors bind to?
Another part of the enzyme away from the active site.
What do mercury and lead bind to?
The -SH groups of cysteines in the protein
What is the result of a non-competitive inhibitor?
The active site no longer fits the substrate.
Why is Vmax reduced with a non-competitive inhibitor?
A proportion of the enzymes are inactive.
