Chapter 8: An Introduction To Metabolism

Question 1

Thermodynamics

Answer 1

The study of energy transformation that occur in a collection of matter

Question 2

First law of thermodynamics

Answer 2

The principle of conservation of energy’s; energy can be transferred and transformed but it cannot be created or destroyed.

Question 3

Second law of thermodynamics

Answer 3

The principal stating that every energy transfer or transformation increases the entropy of the universe. Usable forms of energy are at least partly converted to heat.

Question 4

Spontaneous process

Answer 4

A process that occurs without an overall input of energy; a process that is energetically favorable.

Question 5

Metabolism

Answer 5

The totality of an organism’s chemical reactions, consisting of catabolic and anabolic pathways, which manage the material and energy resources of the organism.

Question 6

Catabolic pathways

Answer 6

A metabolic pathway that releases energy by breaking down complex molecules into simpler molecules

Question 7

Anabolic Pathways

Answer 7

A metabolic pathway that consumes energy to synthesize a complex molecule from simpler molecules

Question 8

Free energy change

Answer 8

The portion of a biological system’s energy that can perform work when temperature and pressure are uniform throughout the system.

DeltaG = Gfinal -G initial

Can be thought of as a measure of a system’s instability, or its tendency to change to a more stable state.
- systems with more free energy are less stable and more likely to change.

Question 9

Equilibrium

Answer 9

State of maximum stability. Reverse reaction rate and forwards reaction rate are the same so there is no net change

• free energy increases when the reaction is pushed away from equilibrium
• changes away from equilibrium are never spontaneous

Question 10

Exergonic reaction

Answer 10

A spontaneous chemical reaction in which there is a net release of free energy

Delta G is negative

Question 11

Endergonic Reaction

Answer 11

A non spontaneous chemical reaction in which free energy is absorbed from the surroundings
- Delta G is positive

Question 12

Energy Coupling

Answer 12

The use of energy released from an exergonic reaction to drive an endergonic reaction

Question 13

Phosphorylation

Answer 13

The transfer of a phosphate group from ATP to some other molecule, such as the reactant

Question 14

Phosphorylated intermediate

Answer 14

A molecule, often a reactant, with a phosphate group covalently bound to it, making it more reactive than the unphosphorylated molecule

Question 15

Enzyme

Answer 15

A macromolecule, often a protein, serving as a catalyst

Question 16

Catalyst

Answer 16

A chemical event that selectively increases the rate of reaction without being consumed by the reaction

Question 17

Activation energy

Answer 17

The amount of energy that reactants must absorb before a chemical reaction will start; also called free energy of activation

Question 18

Transition state

Answer 18

When molecules in a reaction have absorbed enough energy for the bonds to break and the reactants are in an unstable condition

Question 19

Catalysis

Answer 19

A process by which a catalyst selectively increases the rate of reaction without being consumed by the reaction. This is done through the enzyme lowering the energy of activation barrier

Question 20

Substrate

Answer 20

The reactant on which an enzyme works

Question 21

Enzyme-substrate complex

Answer 21

A temporary complex formed when an enzyme binds to its substrate molecule

Question 22

Active site

Answer 22

The specific region of an enzyme that binds to the substrate and formed the pocket in which catalysis occurs

Question 23

Induced fit

Answer 23

Caused by the entry of the substrate, the change in shape of the active site of an enzyme so that it binds more snugly to the substrate

Question 24

Specificity of Enzymes

Answer 24

Due to the complementary fit between the shape of its active site and the shape of the substrate

Question 25

Cofactor

Answer 25

Any non protein molecule or ion that is required for the proper functioning of an enzyme. Cofactors can permanently bound to the active site or may bind loosely and reversible, along with the substrate, during catalysis.

Question 26

Coenzyme

Answer 26

An organic molecule serving as a cofactors. Most vitamins function as coenzymes in metabolic reactions

Question 27

Competitive Inhibitors

Answer 27

A substance that reduces the activity of an enzyme by entering the active site in place of the substrate, whose structure it mimics

Question 28

Non competitive inhibitor

Answer 28

A substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing the enzyme’s shape so that the active site no longer effectively catalyzes the conversion of substrate to product

Question 29

Allosteric Regulation

Answer 29

The binding of a regulatory molecule to a protein at one site that affects the function of a protein at a different site

Question 30

Activator

Answer 30

A regulatory molecule that, which it binds to a regulatory site, stabilizes the shape that has functional active sites

Question 31

Inhibitor

Answer 31

A regulatory Molecule that, when it binds to a regulatory site, stabilizes the inactive form of the enzyme

Question 32

Cooperativity

Answer 32

A kind of allosteric regulation whereby a shape change in one subunit of a protein caused by substrate binding is transmitted to all other subunits, facilitating the binding of additional substrate molecules to those subunits

Question 33

Feedback Inhibition

Answer 33

A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway