Lecture 14: Introduction to Enzymes

Question 1

what are enzymes?

Answer 1

biological catalysts; capable of speeding up reaction rates without being permanently altered themselves

Question 2

most enzymes are ___ (what type of biomolecule)

Answer 2

proteins

Question 3

the rate of reaction depends on what 2 factors?

Answer 3

1. concentrations of reactants/products

2. activation energy of reaction

Question 4

in most biological reactions, the concentrations are ___ and the activation energies are ___

Answer 4

low; high

Question 5

without catalysts, what would be the fate of biological reactions?

Answer 5

occur too slow to maintain life

Question 6

enzymes accelerate ___ while not changing ___ of the reaction

Answer 6

arrival to equilibrium; thermodynamic favourability

Question 7

what are the 6 classes of enzymes?

Answer 7

1. transferase
2. hydrolase
3. oxidoreductase
4. ligase
5. lyase
6. isomerase

Question 8

give an example of oxidoreductase

Answer 8

alcohol dehydrogenase

Question 9

function of oxidoreductase enzymes

Answer 9

catalyse oxidation-reduction reactions

Question 10

oxidoreductase enzymes result in 1-2 ___ reactions that involve changes in __/___ atoms

Answer 10

electron transfer; H or O

Question 11

ethanol is oxidized to ___

Answer 11

acetaldehyde

Question 12

give an example of transferase

Answer 12

glucose kinase

Question 13

function of transferase enzymes

Answer 13

catalyse transfer of functional groups from one molecule to another

Question 14

what functional groups can be transferred by transferase?

Answer 14

amino, acyl, methyl, carbonyl, carboxyls, phosphoryl

Question 15

example of hydrolase

Answer 15

protease

Question 16

what is the function of hydrolase?

Answer 16

catalyze cleavage of molecule by adding water (hydrolysis)

Question 17

what bonds are typically acted upon by hydrolase?

Answer 17

C-O, C-N and O-P

Question 18

example of lyase

Answer 18

pyruvate decarboxylase

Question 19

function of lyase enzymes

Answer 19

catalyze reactions in which CO2, H2O, NH3 are removed to form a double bond, or are added to a double bond

Question 20

example of isomerase

Answer 20

alanine racemase

Question 21

function of isomerase enzymes

Answer 21

catalyze intramolecular rearrangement (moving functional groups within the molecule

Question 22

example of ligase

Answer 22

pyruvate carboxylase

Question 23

function of ligase enzymes

Answer 23

catalyze reactions in which 2 molecules are joined at the expense of an ATP molecule (or similar molecule)

Question 24

how are most enzymes named?

Answer 24

by their substrates/reactions and the suffix “ase”

Question 25

what is Gibb’s Free energy?

Answer 25

energy available to do work

Question 26

enthalpy change represents__

Answer 26

the amount of heat produced/absorbed in a reaction

Question 27

entropy change represents ___

Answer 27

change in system order

Question 28

gibb’s free energy is independent of ___

Answer 28

the path of transmission

Question 29

does gibb’s free energy provide information on reaction rate?

Answer 29

no

Question 30

when delta G is negative, the reaction will occur___

Answer 30

spontaneously (no energy input needed)

Question 31

when delta G is positive, the reaction will occur___

Answer 31

non-spontaneously (needs energy input)

Question 32

when delta G = 0, the reaction is __

Answer 32

at equilibrium

Question 33

T/F enzymes alter reaction equilibria

Answer 33

false

Question 34

the ___ determines the equilibrium of reaction (how much product is made)

Answer 34

free energy difference between reactants and products

Question 35

enzymes determine what about reaction equilibrium?

Answer 35

how fast equilibrium is reached

Question 36

enzymes increase reaction rates by decreasing __

Answer 36

activation energy

Question 37

what is a transitionstate?

Answer 37

a fleeting molecular structure intermediate to reactant and product; least stable and highest energy

Question 38

how do enzymes lower activation energy?

Answer 38

by altering reaction pathway to form a more stable transition state

Question 39

the difference in energy between the substrate and transition state is the ___

Answer 39

activation energy