Lecture 9

Question 1

What are reactants?

Answer 1

The starting molecules of a chemical reaction

Question 2

What are products?

Answer 2

The final molecules of a chemical recation

Question 3

What does the free energy charge tell us?

Answer 3

Whether or not a reaction occurred spontaneously or not

Question 4

What is a living systems free energy?

Answer 4

energy that can do work when temperature and pressure are uniform, as in a living cell

Question 5

what is delta G

Answer 5

Free-Energy Change

Question 6

What is an exergonic reaction?

Answer 6

energy released spontaneously

Question 7

What do enzymes do to metabolic recations?

Answer 7

They speed them up by lowering energy barriers

Question 8

Thermodynamics does not tell us about the ____ of a reaction.

Answer 8

speed

Question 9

What is a catalyst?

Answer 9

a chemical agent that speeds up a reaction without being consumed by the reaction

Question 10

What is an enzyme? Example?

Answer 10

a catalytic protein (occasionally RNA)

Question 11

What occurs during chemical reactions?

Answer 11

bond breaking and bond forming

Question 12

What is activation energy (Ea)?

Answer 12

The initial energy needed to start a chemical reaction

Question 13

What is the activation energy often consist of?

Answer 13

thermal energy that the reactant molecules absorb from their surroundings

Question 14

What happens at the transition state?

Answer 14

The reactants become unstable and start to go downhill

Question 15

How is the change in free energy affected by enzymes?

Answer 15

enzymes have no effect on it; they only hasten reactions that would occur eventually

Question 16

List the 3 characteristics of all enzymes.

Answer 16

-increase speed of reacton by lowering Ea
-Are not altered by reactions
-Can catalyze multiple rounds of reactions

Question 17

List the 3 characteristics specific to enzymes.

Answer 17

-Highly specific for reactants and reactions they catalyze
-Perform highly specific catalysis (few side products)
-Can be regulated

Question 18

What is a substrate?

Answer 18

The reactant that an enzyme acts on

Question 19

What is an enzyme-substrate (ES) complex?

Answer 19

when an enzyme binds to its substrate

Question 20

The reaction catalyzed by each enzyme is _______.

Answer 20

very specific.

Question 21

What is the active site?

Answer 21

The region on the enzyme where the substrate binds.

Question 22

How much enzyme do you need in a reaction and why?

Answer 22

very small amounts because they are used repeatedly (catalytic)

Question 23

Enzyme shape is not ___ .

Answer 23

static

Question 24

What are the 4 ways an active site can lower an Ea barrier?

Answer 24

-orienting substrates correctly
-straining substrate bonds
-providing a favorable microenvironment
-covalently bonding to the substrate

Question 25

What are the three ways an enzymes activity can be affected?

Answer 25

-general environmental factors, such as temperature and pH
-chemicals that specifically influence the enzyme
-substrate concentration

Question 26

What are cofactors?

Answer 26

Nonprotein enzyme helpers; may be organic or inorganic

Question 27

What is a coenzyme?

Answer 27

an organic cofactor including vitamins

Question 28

What is enzyme kinetics?

Answer 28

Measuring the rate if reactions under varying conditions

Question 29

What can enzyme kinetics tell you?

Answer 29

the catalyst mechanism, its role in metabolism, how its activity is controlled, how a drug might alter it

Question 30

What is V_max in enzyme kinetics?

Answer 30

-saturation point for a particular amount of enzyme
-maximal reaction rate when substrate is not limiting

Question 31

What is K_m in enzyme kinetics?

Answer 31

-substrate concentration at which reaction velocity is half maximal
-inversely related to enzyme affinity

Question 32

What do competitive inhibitors do?

Answer 32

bind the active site of an enzyme, competing with the substrate

Question 33

What so non-competitive inhibitors do?

Answer 33

bind to another part of the enzyme, making the active site less effective

Question 34

List some examples of inhibitors?

Answer 34

Toxins, poisons, pesticides, and antibiotics