Enzymes

Question 1

What are enzymes and their function?

Answer 1

Can be proteins
Biological catalysts, increase rate of chemical reaction
Specific to their action and substrate

Question 2

What are the molecules that bind to enzymes called?

Answer 2

Substrates which binds at catalytic or active site

Question 3

What is a cofactor?

Answer 3

Helper molecules that assist in biochemical transformation

Question 4

What is an organic cofactor called? What are the two classifications?

Answer 4

Coenzymes (vitamin derivatives, fat or water soluble)
Prosthetic groups: permanently bound
Cosubstrates: temporarily bound

Question 5

What are 4 important coenzymes? What do they contain?

Answer 5

ATP
NAD
FAD
Coenzyme A
Contain AMP

Question 6

What is ATP made up of? What is it a building block of?

Answer 6

Nitrogenous base adenine
Sugar ribose
Triphosphate
Building blocks for RNA synthesis

Question 7

What is GTP made of? What is it a building block of?How is it produced?

Answer 7

Nitrogenous base guanine
Sugar ribose
Triphosphate
Building block of RNA
Produced from GTP dephosphorylation

Question 8

What is NAD made up of? What reactions is it involved in?

Answer 8

Adenine
Sugar ribose
Phosphate
Nicotinamide
Oxidation reduction, glycolysis, fatty acid oxidation, TCA, respiratory chain, autophagy

Question 9

What is FAD made up of? What type of coenzyme is it? What reaction is it involved in?

Answer 9

Adenine
Sugar ribose
Phosphate
Riboflavin
Redox active coenzyme
ETC

Question 10

What is coenzyme A involved in? What is it synthesized from?

Answer 10

Synthesis and oxidation of fatty acids
Oxidation of pyruvate in the citric acid cycle
Synthesized from Vitamin B5

Question 11

Are vitamins essential or nonessential?

Answer 11

Essential- cannot be produced in the organism

Question 12

Where can pyruvate dehydrogenase be found in mechanisms? How many coenzymes does it contain?

Answer 12

At the junction of glycolysis and citric acid cycle
5 coenzymes and 1 metal ion

Question 13

What is an apoenzyme?

Answer 13

Inactive
Enzyme without cofactor (activator)

Question 14

What is a holoenzyme?

Answer 14

Apoenzyme and coenzyme (activator)
Active

Question 15

How does activation of an enzyme occur?

Answer 15

Substrate enters active site of enzyme
Enzyme/substrate complex forms
Substrate converted to products
Products leave the active site of the enzyme

Question 16

How many classes of enzymes are there? What are the names?

Answer 16

7

EC1: Oxidoreductases
EC2: Transferases
EC3: Hydrolases: catalyze hydrolysis
EC4: Lyases
EC5: Isomerases
EC6: Ligases/Synthetases
EC7: Translocase

Question 17

Describe EC1: oxidoreductases.

Answer 17

Catalyze redox reaction
Dehydrogenase oxidizes a substrate

Question 18

Describe EC2: Tranferases. What is an example in the retina?

Answer 18

Transfer of atoms (functional group) from one molecule to another
Glutathione S-transferase (GST) regulates photoreceptor

Question 19

Describe EC3: Hydrolases.

Answer 19

Use water to break bonds, through insertion of water

Question 20

Describe EC4: Lyases.

Answer 20

Cleave bonds other then hydrolysis or oxidation usually by removing a group

Question 21

Describe EC5: Isomerases.

Answer 21

Catalyze isomerization changes within a single molecule to convert from one isomer to another

Question 22

Describe EC6: Ligases/Synthetases

Answer 22

Catalyze joining of 2 molecules (covalent bonds)

Question 23

Describe EC 7: Translocases

Answer 23

Catalyze movement of ions or molecules across membranes

Question 24

What is the difference between the lock and key model vs the induced fit model of enzyme-substrate reactions?

Answer 24

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.

Question 25

How does the activation energy relate to the reaction rate? How can reaction rate be increased?

Answer 25

Higher the activation energy, the slower the reaction By raising the temperature

Question 26

What is an exergonic reaction?

Answer 26

Energy level of the products is less then the reactants Energy is released Spontaneous

Question 27

What is an endergonic reaction?

Answer 27

Energy level of the products is greater then that of the reactants Nonspontaneous Energy absorbed

Question 28

What is the Michaelis-Menten Equation used for?

Answer 28

Interprets the behaviors of enzymes Calculates the rate of catalysis of an enzyme at a particular substrate concentration

Question 29

What happens in a catalytic reaction if the concentration of substrate is increased?

Answer 29

Increase in substrate= increase in velocity

Question 30

Up to how many substrates can an enzyme catalyze?

Answer 30

Two or more substrates

Question 31

Is the optimal pH different for different enzymes?

Answer 31

Yes, every enzymes has an optimal pH at which it has maximal activity

Question 32

What are inhibitors? What is an example?

Answer 32

Interfere with catalysts by slowing/halting enzymatic reactions Ex: aspirin

Question 33

What are the two classes of inhibitors?

Answer 33

Reversible (noncovalent) and irreversible (covalent)

Question 34

What is competitive inhibition?

Answer 34

Type of reversible enzyme inactivation Binds to substrate active site Increase in substrate can overcome this inhibition

Question 35

What is non competitive inhibition?

Answer 35

Type of reversible enzyme inactivation Binds to different site to change the shape of the substrate Increase in substrate cannot overcome this inhibition

Question 36

What is an allosteric site?

Answer 36

The site that the enzyme binds to in non competitive inhibition that is not the active site

Question 37

What is allosteric regulation?

Answer 37

Regulation of enzyme by binding an effector/regulator at site other than active site (noncovalent)

Question 38

What is an allosteric activator?

Answer 38

Effectors/regulators that enhance the protein's activity

Question 39

What is an allosteric inhibitor?

Answer 39

Effectors/regulators that decrease the protein's activity

Question 40

What is a reversible covalent modification of an enzyme?

Answer 40

Between a non-protein group and an enzyme to turn it on or off. Ex: kinase phosphorylation an inactive enzyme, phosphates reverses that

Question 41

What is a proteolytic activation?

Answer 41

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)

Question 42

What are zymogens? What is one example?

Answer 42

Enzymes, hormones or active proteins synthesized as inactive precursors Ex: Prothrombin