UNIT 3: METABOLIC PATHWAYS

Catabolic

release of energy by the breakdown of complex to simpler compounds

Anabolic

consumes energy to build complicated molecules from simpler ones

Free Energy

the energy available to do work

Exergonic Reaction

energy is released, occurring spontaneously

Endergonic Reaction

requires energy to proceed, absorbing free energy

Chemical Potential Energy

type of potential energy that molecules possess as a result of the arrangement of atoms in those molecules

1st Law of Thermodynamics

energy cannot be created nor destroyed; can only be transferred or transformed

2nd Law of Thermodynamics:

every energy transfer increases the entropy of the universe

Entropy

a measure of disorder and randomness

Coupled Reactions

exergonic reactions power endergonic reactions

Enzyme

a protein acting as a biological catalyst

Substrate

the reactant an enzyme acts upon, binding to the active site

Activation Energy

free energy input required to convert reactants into products

What do enzymes do to the activation energy?

lowered by enzymes to speed up reactions

Induced Fit

the substrate binds to the enzyme's active site, causing it to change shape and improve its ability to catalyze the reaction (enzyme substrate-complex)

Properties of enzymes

specific for particular reactions, in which the substrate must have a complementary shape and charge to its enzyme for it to react

Can enzymes be reused?

recyclable; unaffected by reactions they catalyze (can act up on a substrate at a time)

Activators

Increases enzyme activity, bounding to other nonprotein helper molecules

Coenzymes

organic molecules (vitamins that bind loosely to active site)

Cofactors (Inorganic Molecules)

metals such as iron (Fe2+) and magnesium (Mg2+)

Allosteric Regulation

regulatory molecule binds to enzyme someplace besides active site

Allosteric Activator

stabilizes the shape of the active sites and changes shape of the altered active site to enable substrate binding

Allosteric Inhibitor

stabilizes the inactive form and alters active site, preventing the substrate to bind to the enzyme

Inhibitors

decreases enzyme activity

Competitive Inhibitors

compete and bind to active site; can be overcome with high substrate levels

Noncompetitive (Allosteric) Inhibitors

bind elsewhere, altering enzyme shape and reducing function; cannot be overcome by increased substrate

Feedback Inhibition

regulatory process where the end product of a metabolic pathway inhibits an earlier enzyme, halting production

How does feedback inhibition create efficiency?

enables cell to avoid wasting energy and resources when demand is met

Denaturation

disrupts stability of the protein and its active site under extreme conditions

How does hydrogen bonds break?

hydrogen bonds that holds protein in secondary and tertiary breaks and unfolds

What happens to denatured proteins?

they lose their functional shape and activity, becoming inactive and unable to perform their biological role

Temperature in Enzyme

temperatures outside its optimal range can change enzyme structure, altering its efficiency

What happens if you increase the temperature for an enzyme

increasing the temperature increases collisions and reaction rate due to increased kinetic energy (movement) of enzymes and substrates

How does pH affect enzymes?

pH change affects enzyme structure due to the change in number of H+ in solution

How do pH lead to denaturaiton

disrupts H-bonds involved in maintaining a protein’s secondary/tertiary folding

Factors Affecting Enzymes: Substrate and Enzyme Concentration

reaction rate increases with enzyme or substrate concentration until saturation point is reached