Enzymes Flashcards
What are enzymes and their function?
Can be proteins
Biological catalysts, increase rate of chemical reaction
Specific to their action and substrate
What are the molecules that bind to enzymes called?
Substrates which binds at catalytic or active site
What is a cofactor?
Helper molecules that assist in biochemical transformation
What is an organic cofactor called? What are the two classifications?
Coenzymes (vitamin derivatives, fat or water soluble)
Prosthetic groups: permanently bound
Cosubstrates: temporarily bound
What are 4 important coenzymes? What do they contain?
ATP
NAD
FAD
Coenzyme A
Contain AMP
What is ATP made up of? What is it a building block of?
Nitrogenous base adenine
Sugar ribose
Triphosphate
Building blocks for RNA synthesis
What is GTP made of? What is it a building block of?How is it produced?
Nitrogenous base guanine
Sugar ribose
Triphosphate
Building block of RNA
Produced from GTP dephosphorylation
What is NAD made up of? What reactions is it involved in?
Adenine
Sugar ribose
Phosphate
Nicotinamide
Oxidation reduction, glycolysis, fatty acid oxidation, TCA, respiratory chain, autophagy
What is FAD made up of? What type of coenzyme is it? What reaction is it involved in?
Adenine
Sugar ribose
Phosphate
Riboflavin
Redox active coenzyme
ETC
What is coenzyme A involved in? What is it synthesized from?
Synthesis and oxidation of fatty acids
Oxidation of pyruvate in the citric acid cycle
Synthesized from Vitamin B5
Are vitamins essential or nonessential?
Essential- cannot be produced in the organism
Where can pyruvate dehydrogenase be found in mechanisms? How many coenzymes does it contain?
At the junction of glycolysis and citric acid cycle
5 coenzymes and 1 metal ion
What is an apoenzyme?
Inactive
Enzyme without cofactor (activator)
What is a holoenzyme?
Apoenzyme and coenzyme (activator)
Active
How does activation of an enzyme occur?
Substrate enters active site of enzyme
Enzyme/substrate complex forms
Substrate converted to products
Products leave the active site of the enzyme
How many classes of enzymes are there? What are the names?
7
EC1: Oxidoreductases
EC2: Transferases
EC3: Hydrolases: catalyze hydrolysis
EC4: Lyases
EC5: Isomerases
EC6: Ligases/Synthetases
EC7: Translocase
Describe EC1: oxidoreductases.
Catalyze redox reaction
Dehydrogenase oxidizes a substrate
Describe EC2: Tranferases. What is an example in the retina?
Transfer of atoms (functional group) from one molecule to another
Glutathione S-transferase (GST) regulates photoreceptor
Describe EC3: Hydrolases.
Use water to break bonds, through insertion of water
Describe EC4: Lyases.
Cleave bonds other then hydrolysis or oxidation usually by removing a group
Describe EC5: Isomerases.
Catalyze isomerization changes within a single molecule to convert from one isomer to another
Describe EC6: Ligases/Synthetases
Catalyze joining of 2 molecules (covalent bonds)
Describe EC 7: Translocases
Catalyze movement of ions or molecules across membranes
What is the difference between the lock and key model vs the induced fit model of enzyme-substrate reactions?
Lock and key the substrate already has the shape needed for the enzyme to fit.
Induced fit the substrate and active site of enzyme undergo changed to attain optimal fit.
How does the activation energy relate to the reaction rate? How can reaction rate be increased?
Higher the activation energy, the slower the reaction
By raising the temperature
What is an exergonic reaction?
Energy level of the products is less then the reactants
Energy is released
Spontaneous
What is an endergonic reaction?
Energy level of the products is greater then that of the reactants
Nonspontaneous
Energy absorbed
What is the Michaelis-Menten Equation used for?
Interprets the behaviors of enzymes
Calculates the rate of catalysis of an enzyme at a particular substrate concentration
What happens in a catalytic reaction if the concentration of substrate is increased?
Increase in substrate= increase in velocity
Up to how many substrates can an enzyme catalyze?
Two or more substrates
Is the optimal pH different for different enzymes?
Yes, every enzymes has an optimal pH at which it has maximal activity
What are inhibitors? What is an example?
Interfere with catalysts by slowing/halting enzymatic reactions
Ex: aspirin
What are the two classes of inhibitors?
Reversible (noncovalent) and irreversible (covalent)
What is competitive inhibition?
Type of reversible enzyme inactivation
Binds to substrate active site
Increase in substrate can overcome this inhibition
What is non competitive inhibition?
Type of reversible enzyme inactivation
Binds to different site to change the shape of the substrate
Increase in substrate cannot overcome this inhibition
What is an allosteric site?
The site that the enzyme binds to in non competitive inhibition that is not the active site
What is allosteric regulation?
Regulation of enzyme by binding an effector/regulator at site other than active site (noncovalent)
What is an allosteric activator?
Effectors/regulators that enhance the protein’s activity
What is an allosteric inhibitor?
Effectors/regulators that decrease the protein’s activity
What is a reversible covalent modification of an enzyme?
Between a non-protein group and an enzyme to turn it on or off.
Ex: kinase phosphorylation an inactive enzyme, phosphates reverses that
What is a proteolytic activation?
Cleavage of one or more specific peptide bonds to activate the inactive precursors proenzymes and zymogens.
No energy needed
Irreversible (only occurs once during an enzymes life)
What are zymogens? What is one example?
Enzymes, hormones or active proteins synthesized as inactive precursors
Ex: Prothrombin
