An Introduction to Metabolism

Question 1

Metabolic Pathway

Answer 1

a series of defined steps (which are each catalyzed by a certain enzyme) which alters a specific molecule, resulting in a certain product

Question 2

Catabolic Pathway

Answer 2

a metabolic pathway which releases energy via breakdown of complex compounds (ie: cellular respiration)

Question 3

Anabolic Pathway

Answer 3

a metabolic pathway which consumes energy to build complex compounds (also called biosynthesis pathway)

Question 4

Kinetic Energy

Answer 4

relative motion of objects

Question 5

Thermal Energy

Answer 5

kinetic energy associated with random movement of atoms or molecules (such transfer from one object to other is called heat)

Question 6

Potential Energy

Answer 6

An object is not moving and possesses energy due to its location or structure

Question 7

Chemical Energy

Answer 7

the potential energy available for release in a chemical reaction (catabolic pathways harvest chemical energy)

Question 8

First Law of Thermodynamics (the principle of conservation of energy)

Answer 8

Energy can be transferred and transformed, but it cannot be created or destroyed

Question 9

Second Law of Thermodynamics

Answer 9

Every energy transfer or transformation increases the entropy of the universe

Question 10

Free Energy

Answer 10

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

Question 11

The Gibbs Free Energy Equation

Answer 11

Free Energy (Delta G) = The Change in Total Energy (Delta H) - Temperature in Kelvin * The Change in the Systems Enthalpy (Delta S)

Question 12

Spontaneous Reaction

Answer 12

Unstable Systems like cells always become more stable (which explains diffusion and other phenomena), but never reach maximum stability, or equilibrium (such a stable state would mean work could not be performed, rendering the cell dead)

Question 13

Exergonic Reaction

Answer 13

Energy outward (is a spontaneous reaction that does not require energy, Delta G is negative)

Question 14

Endergonic Reaction

Answer 14

Energy Inward (is not spontaneous, energy required, Delta G is positive)

Question 15

Chemical Work

Answer 15

The pushing of endergonic reactions that would not occur spontaneously (like the synthesis of polymers from monomers)

Question 16

Transport Work

Answer 16

The pumping of substances across membranes against the direction of spontaneous movement (the concentration gradient)

Question 17

Mechanical Work

Answer 17

the beating of cilia, the contraction of muscle cells, etc.

Question 18

ATP Hydrolysis (Exergonic Reaction)

Answer 18

The bonds between the phosphate groups are broken through a dehydration reaction, ADP (Adenosine Diphosphate) is released

Question 19

Energy Coupling

Answer 19

The use of an exergonic process to drive an endergonic process (cellular respiration drives many other chemical reactions)

Question 20

Regeneration of ATP

Answer 20

ATP can be synthesized by adding a phosphate group to ADP, and uses the energy of catabolic processes to do so

Question 21

Enzyme

Answer 21

a macromolecule that is a catalyst which speeds up a reaction without being consumed by the reaction

Question 22

Activation Energy

Answer 22

the initial investment of energy required to start a reaction (which is absorbed by the molecules whose bonds are to be broken)

Question 23

Transition State

Answer 23

The stage at which molecules have absorbed enough energy for their bonds to break

Question 24

How Enzymes Speed Up Reactions

Answer 24

Enzymes lower the activation energy of the reaction (make molecules reach the transition state faster)

Question 25

Substrate

Answer 25

the reactant an enzyme acts on and binds to; forms a enzyme-substrate complex, converts substrate to products of the reaction (or vice versa)

Question 26

Active Site

Answer 26

The restricted region of the enzyme which binds to the substrate; held in place by weak interactions like hydrogen and ionic bonds

Question 27

Cofactors

Answer 27

nonprotein helpers that help carry out catalytic activity (nonorganic like zinc, copper, and iron) or organic (coenzyme)

Question 28

Competitive inhibitors

Answer 28

inhibit activity of enzyme by binding to active site so substrate cannot bind to enzyme

Question 29

Non-Competitive Inhibitors

Answer 29

inhibit activity of enzyme by binding to enzyme away from active site (does not prevent substrate from binding) and limits active site efficiency

Question 30

Allosteric Regulation

Answer 30

a protein’s function is affected by the binding of a regulatory molecule; most enzymes have multiple subunits, each with a polypeptide chain and active site, that oscillates between an active and inactive form

Question 31

Activator

Answer 31

molecule that stabilizes active enzyme that has functional active sites

Question 32

Inhibitor

Answer 32

molecules that stabilizes inactive enzyme

Question 33

Cooperativity

Answer 33

a type of allosteric regulation where a substrate binds to one of multiple active sites, which amplifies the response of other subunits of the enzyme to substrates

Question 34

Feedback Inhibition

Answer 34

type of metabolic control where a metabolic pathway is halted because of the inhibitory binding of its end product to an enzyme in the earlier stages of the pathway