Exam Review: Chapter 6 - Energy, Enzymes and Biological Reactions

Entropy

the measure of molecular disorder, or randomness.
the more randomly arranged a collection of matter is, the greater the value of this value.

Free Energy

refers to the measure of a system's instability; the tendency to change to a more stable state

What is chemical energy?

Potential energy available for release in a chemical reaction

How do biologists refer to the potential energy in a chemical reaction?

Chemical energy

Electrical Energy

Energy caused by the movement of electrons.

Thermal Energy

energy contained within a system that is responsible for its temperature

Radiant Energy

the transfer of energy through electromagnetic waves; transmits energy by emitting waves that can travel through space, heating objects they come in contact with

Surroundings

everything outside of the system

1st Law of thermodynamics

law of conservation of energy, energy can be transformed from one form to another, or transferred from one place to another, but it cannot be created or destroyed

What happens when a system moves toward equilibrium

its free energy becomes progressively lower and reaches its lowest point when the system achieves equilibrium (∆G=0)

How does an exergonic (catabolic) reaction proceed?

proceeds with a net release of free energy. ∆G is negative for an exergonic reaction.

What determines the function of a protein?

the 3-d structure of a protein's conformation; each enzyme has a specific protein structure that catalyzes a specific reaction

Enzyme Denaturation

a process that occurs when an enzyme loses its shape and isn't able to bind to a substrate and catalyze a reaction

Enzyme inhibitors

nonsubstrate molecules that bind to an enzyme and decrease its activity

reversible enzyme inhibition

inactivates an enzyme through non-covalent, reversible interactions

uncompetitive inhibitor

binds to the enzyme-substrate complex, preventing release of products

Bioenergetics

focuses on how cells transform energy, often by producing, storing or consuming adenosine triphosphate (ATP)

Kinetic Energy

energy of an object in motion; energy associated with the relative motion of objects

Example of kinetic energy

a falling rock, electricity, and light
-moving objects can perform work by impairing motion to other matter

potential energy

stored energy

Examples of potential energy

a rock at the top of a hill, chemical energy, gravitational energy, and stored mechanical energy

System

the object under study

Isolated System

is unable to exchange either energy or matter with it surroundings outside
ex: in the case of approximated liquid in a thermos bottle, the liquid is unable to exchange energy or matter with the outside of the thermos

Closed System

this type of system can exchange energy (as heat or work) but not matter, with its surroundings
ex: earth is considered to be the best example of this as it on transfers energy but not matter around its atmosphere

Open Systems

energy and matter can be transferred between the system and its surroundings
ex: all livings things are considered this type of system; they absorb energy, like light or chemical energy organically, and they release heat and metabolic waste products like carbon dioxide to its surroundings

2nd Law of Thermodynamics

entropy, the total disorder (entropy) of a system and its surroundings always increases (although the total energy in the universe does not change)

The portion of a system's energy that is available to do work is called

Free Energy (G)

What does Gibbs free energy determine?

if a process can occur spontaneously or not

Define Spontaneous Reaction.

A chemical or physical reaction that will occur without an input of energy.

What determines if a reaction tends to occur spontaneously?

If the entropy of the products is greater than the entropy of the reactants.

nonspontaneous reaction

a process that, on its own, leads to a decrease in entropy ; only happens if energy is supplied

For a reaction to be spontaneous

ΔG must be negative; negative enthalpy (∆H), dominates in making a reaction spontaneous

Gibbs free energy change

∆G=∆H-T∆S

Are organisms open or closed systems?

Open systems; materials flow in and out, keeping metabolic pathways from ever reaching equilibrium, and the cell continues to do work throughout its life

how does an endergonic (anabolic) reaction act?

it absorbs free energy from its surroundings; ∆G is positive for endergonic reactions

Do reactions with a negative ∆G or a positive ∆G occur spontaneously?

reactions with a negative ∆G occur spontaneously

Energy Coupling

how the energy released by ATP hydrolysis is used to perform work inside the cell

How do cells use ATP hydrolysis to power other chemical reactions?

cells couple the exergonic reaction of ATP hydrolysis with endergonic reactions (ATP coupling)

Describe the process of energy coupling

when ATP is hydrolyzed, the terminal phosphate group is transferred to a reactant molecule involved in an endergonic reaction. (remember phosphorylation)

Phosphroylation

the addition of a phosphoryl (PO3) group to a molecule

Spontaneous Chemical Reaction

occurs without any requirement for outside energy, but it may occur so slowly that it is imperceptible

Enzymes

biological catalysts; they increase the rate of chemical reactions by lowering the energy of activation (Ea)

What is the initial investment of energy for starting a reaction
ACTIVATION ENERGY

the energy required to contort the reactant molecules so the bonds can break

Enzymes regulate reactions for what reason

because most metabolic reactions need to surpass the activation energy before proceeding

Describe the Lock-and-key model

the shape of the substrate and the conformation of the active site are complimentary to another like a key in a lock or the missing piece to a puzzle

Describe the induced fit model

the enzyme undergoes a conformational change upon binding to substrate. The shape of the active site become complementary to the shape of a substrate only after the substrate binds to the enzyme

How does pH affect enzyme activity?

each enzyme has an optimal pH where it works at peak efficiency; rate of reaction decreases on wither side of the pH optimum

why are enzymes dependent on pH?

it is due to the ionizable amino acids; the pH changes modify the conformation of the protein and denatures the enzyme

How does temperature affect enzyme activity?

as the temperature rises, the rate of chemical reactions increase
if temperatures are too high, it will inactivate the enzymes because at high temps the enzyme molecules vibrate and twist so rapidly that some of the non-covalent bonds break

what is this an example of

Normal substrate binding to enzyme active site.

what is this an example of

a competitive inhibitor binds to the active site preventing substrate binding

what is this an example of

a noncompetitive inhibitor
- binds at a site other than the active site, changing enzyme structure so that normal substrate binding cannot occur