Metabolism

Metabolism

The totality of an organism’s chemical reactions; all anabolic and catabolic rxns in the body

Metabolic Pathway

Begins with a specific molecule and ends with a different product; each step is catalyzed by a specific enzyme

Catabolic Pathway

Release energy by breaking big molecules down to small molecules

Anabolic Pathway

Consume energy by building big molecules from smaller molecules

Forms of Energy

• Kinetic Energy

• Heat/Thermal Energy

• Potential Energy

• Chemical Energy

First Law of Thermodynamics

Energy can not be created or destroyed; conservation of energy

Second Law of Thermodynamics

Every energy transfer or transformation increases the disorder (entropy) of the universe (High Entropy = High Disorder)

Spontaneous Reaction

• During a spontaneous change, free energy decreases and the stability of a system increases

Biological Order and Disorder

Entropy may decrease in an organism, but the universe’s total entropy increases

Free Energy (ΔG)

Free energy that can do work

Gibb’s Free Energy

• -ΔG = Shift Towards Reactants

• +ΔG = Shift Towards Products

Exergonic Reaction

Release of Energy; Spontaneous

Endergonic Reaction

Absorbs Free Energy; Nonspontaneous

Energy Coupling

The use of exergonic processes to drive endergonic ones

ATP (Adenosine Triphosphate)

• The bonds between the phosphate groups of ATP’s tail can be broken via hydrolysis

• Energy is released when the terminal phosphate bond is broken

• Release of energy comes from the change to a state of lower free energy

Phosphorylated Intermediate

The molecule that receives the phosphate from ATP

Enzyme

A catalytic protein (speeds up a rxn without being consumed)

Activation Energy (Ea)

The initial energy needed to start a chemical reaction; Often supplied in the form of thermal energy that the reactants absorb from their surroundings

Enzyme Activity is Affected By

• Temperature (98.6°F (37°C)

• pH (Physiological pH = 7.4)

• Inhibitors

Cofactors

Inorganic Nonprotein enzyme helpers (Ex: Metals like Mg2+)

Coenzymes

Organic Cofactors (Ex: Vitamins)

Allosteric Regulation

Activators stabilize the active form of an enzyme

Inhibitors stabilize the inactive form of the enzyme

Cooperativity can amplify enzyme activity

Feedback Inhibition

The end product of a metabolic pathway shuts down the pathway

Enzymes for cellular respiration are located in the

Mitochondria