Bio midterm (Chapter 3)

•The capacity to do Work

energy

Energy of motion

kinetic energy

Stored energy

potential energy

Forms of energy

•Electrical, thermal, mechanical, chemical

•Study of energy and its transformations within a system

Thermodynamics

•exchanges energy but NOT matter with surroundings

Closed system

exchanges energy and matter with surroundings

Open system

exchanges NO energy and NO matter with surroundings

Isolated System

Energy can be transformed but not

created or destroyed

Total amount of energy in a system and its surroundings remains

constant

Total disorder of a system and its surroundings always

increases

Entropy is a measure of

disorder, randomness

Chemical or physical reactions which occur without an input of energy from the surroundings

Spontaneous Reaction

•What contributes to making a reaction spontaneous?

1.Change in enthalpy of system

2.Change in entropy

Reactions tend to be spontaneous if products have

less potential energy than reactants

Potential energy in a system

enthalpy (H)

Reactions that absorb energy

Endothermic reactions

Reactions that release energy

Exothermic reactions

What kind of reaction is this? CH4 + 2O2 -> CO2 + 2H2O

Exothermic

Spontaneous

Melting of ice requires energy meaning its

endothermic

Energy content of water is _________ than that of ice

greater

Reactions tend to be spontaneous when products are

less ordered than reactants

More random motion in water therefore water is

less ordered than ice

Portion of system's energy available to do work

Gibbs Free Energy

Δ (delta)

change

ΔG

change in free energy (Gibbs Free Energy)

ΔH

change in enthalpy

T

absolute temperature (in kelvin)

ΔS

change in entropy

Change in free energy is calculated using the change in:

1.Enthalpy

2.Entropy

Negative ΔG =

Spontaneous Reactions

Release of free energy can be used to perform

work

maximum stability

Equilibrium

Equilibrium point is reached when reactants are converted to products and products are converted back to reactants at

equal rates

Living systems are

open

ΔG of life always

negative

Organisms reach equilibrium, ΔG = 0, only when they

die

Life is highly ordered, which suggests that it goes _____ second law of thermodynamics

against

Living things bring in energy and matter to generate order out of

disorder

Organisms also release heat and byproducts to

increase disorder of surroundings

Exergonic reaction where ΔG is negative because products contain ____ free energy than reactants

less

Endergonic reaction where ΔG is positive because products contain ____ free energy than reactants

more

•Series of sequential reactions in which products of one reaction are used immediately as reactants for the next reaction in the series

Metabolic pathway

Energy is released by breakdown of complex molecules to simpler compounds

Catabolic pathway:

Energy is consumed to build complicated molecules from simpler ones

Anabolic pathway:

Catabolism is when energy-rich molecules are taken and converted to

energy poor molecules

Anabolism is taking precursor molecules and converting to

cell macromolecules

ATP

adenosine triphosphate

ATP hydrolysis releases _________ that can be used as a source of energy for the cell

free energy

most energy from ATP is stored

in the phosphates, negatives and negative's want to part so lots of energy stored in trying to keep them together

Hydrolysis of ATP is an exergonic reaction that can be coupled to make otherwise _________reactions proceed _______

endergonic, spontaneously

Coupling reactions require

enzymes

ATP used in coupling reactions is

replenished

Reactions replenishing ATP link ATP synthesis to

•catabolic reactions

continued breakdown and re-synthesis of ATP

ATP cycle

The activation energy represents a

kinetic barrier

Enzymes accelerate reactions by reducing the

activation energy

Enzymes combine with reactants and are released

unchanged

Enzymes reduce the activation energy by inducing

the transition state

A reaction that is spontaneous is ______ to the speed of the reaction

unrelated

Enzymes are a special group of proteins that can alter the

speed of a reaction

Initial input of energy to start a reaction, even if it is spontaneous

Activation Energy

Molecules that gain necessary activation energy occupy the

transition state

•Enzymes decrease ______ required for a chemical reaction to proceed

activation energy

What's wrong with using heat to speed up reactions?

Hard to regulate rxs if using heat, can break downs and denature proteins

•Chemical agent that speeds up the rate of reaction without itself taking part in the reaction

Catalyst

(can be regulated) are biological catalysts

Enzymes

Enzymes do not supply

Free energy

when using enzymes, delta G is

unchanged

Active site of enzyme combines briefly with reactants (substrates)

specific interaction

enzymes have an

induced fit model

Inorganic ions or organic nonprotein groups necessary for catalysis to occur

•Enzyme cofactors

•Metallic ions (Fe, Cu, Zn)

Cofactors:

Organic cofactors (vitamins)

Coenzymes

During catalysis, the substrate and active site form an

•intermediate transition state

•intermediate transition state

1.Bringing substrates into close proximity

2.Expose reactants to charged environments

3.Change the shape of the substrate

Conditions and Factors That Affect Enzyme Activity

enzyme and substrate concentration,

temperature, and pH

Allosteric control

enzyme inhibitors

In presence of excess substrate, rate of catalysis is proportional to

•amount of enzyme

-Reaction rate slows

-Enzymes and substrates collide infrequently

•Low substrate concentrations

-Enzymes become saturated with reactants

-Rate of reaction levels off

•High substrate concentrations

•Enzyme inhibitors are nonsubstrate molecules that can ___ to an enzyme and _____ its activity

bind, decrease

1.Inhibitor competes with normal substrate for active site

Competitive inhibition

Inhibitor does not compete with normal substrate for active site

Noncompetitive inhibition

Ex. Irreversible Competitive Inhibitor

Penicillin - antibiotic

Inhibits transpeptidase enzyme

Inhibits synthesis of peptidoglycan, part of bacterial cell wall

Therefore bacterial cell cannot survive

Why does penicillin not affect us?

our cells dont have cell walls

•two metabolic pathways run simultaneously in opposite directions

A futile cycle

A futile cycle result

•NO overall effect (waste of energy)

Enzyme activity is often regulated to meet the needs for reaction

products

occurs with reversible binding of a regulatory molecule to the allosteric site

Allosteric regulation

enzyme binds substrate strongly

High-affinity state (active form)

enzyme binds substrate weakly or not at all

Low-affinity state (inactive form)

Not on active site

noncompetitive

Feedback Inhibition

•Product of enzyme-catalyzed pathway acts as a regulator of the reaction

•Helps conserve cellular resources

•Typically, each enzyme has an optimal:

1.Temperature

2.pH

At temperature and pH values above and below optimum,

•reaction rates fall off

Most enzymes have a pH optimum near pH of cellular contents, about

7

Enzymes secreted from cells may have pH optima farther from

neutrality

•Changes in pH affect the ______ in the amino acids of the enzyme

charged groups

As temperature rises, the rate of reactions

increases

1.High temperatures effect proteins, including enzymes, by ___ them, and ___ the rate of reactions

denaturing, reducing