Lecture 10 + 11 : Enzymes Speeding up Chemical Reactions

Question 1

Metabolism

Answer 1

the totality of an organism’s chemical reactions

Question 2

what does a metabolic pathway start and end with?

Answer 2

with a specific molecule and ends with a product

Question 3

how do catabolic pathways release energy?

Answer 3

by breaking down complex molecules into simpler compounds

Question 4

what is an example of a catabolic pathway?

Answer 4

Cellular respiration, the breakdown of glucose in the presence of oxygen

Question 5

why do anabolic pathways consume energy?

Answer 5

to build complex molecules from simpler ones

Question 6

what is an example of an anabolic pathway?

Answer 6

The synthesis of protein from amino acids is an example of anabolism

Question 7

energy

Answer 7

capacity to cause change

Question 8

kinetic energy

Answer 8

motion energy

Question 9

heat (thermal energy)

Answer 9

kinetic energy associated with random movement of atoms or molecules

Question 10

potential energy

Answer 10

energy that matter possesses because of its location or structure

Question 11

Chemical energy

Answer 11

potential energy available for release in a chemical reaction

Question 12

free energy

Answer 12

a portion of the system’s energy that can do work when temperature and pressure are uniform, as in a living cell

Question 13

Free energy equation

Answer 13

∆G = G final state - G initial state
∆G = ∆H -T∆S

Question 14

how do you know if a certain process is spontaneous or not?

Answer 14

-∆G

Question 15

how do spontaneous processes occur?

Answer 15

without energy input; they can happen quickly or slowly

Question 16

exergonic reaction

Answer 16

proceeds with a net release of free energy and is spontaneous

Question 17

endergonic reaction

Answer 17

absorbs free energy from its surroundings and is nonspontaneous

Question 18

what are the three types of cellular work that are nonspontaneous/endergonic

Answer 18

mechanical, transport, and chemical

Question 19

energy coupling

Answer 19

the use of an exergonic process to drive an endergonic one (Overall, the coupled reactions are exergonic)

Question 20

what is the most common example of energy coupling?

Answer 20

ATP hydrolysis

Question 21

ATP’s structure is made up of?

Answer 21

ribose (a sugar), adenosine (a nitrogenous base), and three phosphate groups

Question 22

How does the hydrolysis of ATP make a coupled endergonic reaction possible?

Answer 22

• hydrolysis breaks the bonds between the phosphate groups
• Energy is released from ATP when the terminal phosphate bond is broken
• release of energy comes from the chemical change to a state of lower free energy, not from the phosphate bonds themselves

Question 23

how is ATP regenerated?

Answer 23

• regenerated by addition of a phosphate group to adenosine diphosphate (ADP)
• The energy to phosphorylate ADP comes from catabolic reactions in the cell

Question 24

what can thermodynamics predict?

Answer 24

predicts if a reaction can occur spontaneously without input of outside energy (negative ΔG) or not

Question 25

catalyst

Answer 25

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

Question 26

enzyme

Answer 26

catalytic protein

Question 27

activation energy (free energy of activation)

Answer 27

initial energy needed to start a chemical reaction

Question 28

How do enzymes lower activation energy?

Answer 28

• increasing concentrations of substrates at active site of enzyme
• do not affect the change in free energy (∆G); instead, hasten reactions that would occur eventually

Question 29

substrate

Answer 29

The reactant that an enzyme acts on

Question 30

what is an enzyme substrate complex?

Answer 30

the location where the enzyme binds to the substrate

Question 31

active site

Answer 31

the region on the enzyme where the substrate binds

Question 32

how can the active site lower an activation energy barrier?

Answer 32

-Orienting substrates correctly
- Straining substrate bonds
- Providing a favorable microenvironment
- Covalently bonding to the substrate

Question 33

what can an enzymes active site be affected by?

Answer 33

• General environmental factors, such as temperature and pH
• Chemicals that specifically influence the enzyme

Question 34

cofactors

Answer 34

nonprotein enzyme helpers (vitamins or minerals)

Question 35

examples of cofactors

Answer 35

• Cofactors may be inorganic (such as a metal in ionic form) or organic

Question 36

what is an organic cofactor called?

Answer 36

-coenzyme (loosely bound)
- prosthetic group (tightly bound to an enzyme)
- coenzymes include vitamins

Question 37

competitive inhibitors

Answer 37

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

Question 38

Noncompetitive inhibitors

Answer 38

bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective

Question 39

how is enzyme activity regulated?

Answer 39

by switching on or offthe genes that encode specific enzymes or by regulating the activity of enzymes

Question 40

How does allosteric regulation work?

Answer 40

• Regulatory molecules bind to enzymes somewhere other than the active site to turn them on or off
• when a regulatory molecule binds to a protein at one site and affects the protein’s function at another site
• most enzymes with this regulation are made from polypeptide subunits

Question 41

feedback inhibition

Answer 41

• the end product of a metabolic pathway shuts down the pathway
• Feedback inhibition prevents a cell from wasting chemical resources by synthesizing more product than is needed