Enzymes Flashcards
How do enzymes accelerate reaction rates?
By decreasing the Activation Energy
Where do substrates bind to on an enzyme?
The Active Site
What is the Induced-Fit Model?
The enzyme conformation changes to accommodate the substrate
What is the substrate for the enzyme Hexokinase?
Glucose
Adds a phosphate group to make glucose-6-phosphate
What kind of bonds hold the substrate in the active site?
Non-covalent bonds (such as hydrogen bonds and ionic bonds)
What type of reaction occurs when sucrose is catalysed?
Hydrolysis
What enzyme catalyses sucrose?
Sucrase
What bond is broken by hydrolysis when catalysing sucrose?
Glycosidic Bond
What are the products when sucrose is catalysed?
Glucose and Fructose
Which two amino acids are involved in breaking the glycosidic bond between sugar D and sugar E in a Lysozome catalytic reaction?
Glutamate 35
Aspartate 52
How does Lysozome break the bond between sugar D and E?
- Sugar D is forced into a strained conformation
- Glu 35 donates a proton (H+)
- Asp 52 attacks C1 which forms a covalent bond with sugar D
- O of H20 attacks C1 which displaces Asp 52 and returns the enzyme to its original state
What is the optimal pH for the enzyme Pepsin (stomach)?
pH2
What is the optimal pH for the enzyme Trypsin (small intestine)?
pH8
How does Rifampicin inhibit enzymes?
It binds to RNA polymerase in bacteria and prevents initiation of transcription
What is a Competitive Inhibitor?
They bind to the active site of an enzyme and compete with the substrate (structurally similar to S)
What is a Noncompetitive Inhibitor?
They bind to another part of the enzyme causing the enzyme to change shape so that the substrate can’t bind to the active site
What is Feedback Inhibition?
It is the end product of a metabolic pathway.
It prevents a cell from wasting chemical resources by synthesising more product than is needed.
What is the name of the enzyme that ADDS a phosphate group?
Protein Kinase
What is the name of the enzyme that REMOVES a phosphate group?
Protein Phosphatase
What are enzymes called when stored as inactive precursors?
Proenzymes or Zymogens
How are Proenzymes activated?
By irreversible cleavage of 1 or more peptide bonds
How is Fibrinogen converted into Fibrin?
- Injury to a blood vessel produces a signal that converts Prothrombin to Thrombin.
- Thrombin converts Fibrinogen to Fibrin by cleaving off A and B ends of the polypeptide chains.
