Chapter 6: Energy and Metabolism

What is metabolism

The sum of all chemical reactions in a living organism that maintain life

Types of Metabolsim:

1. Catabolism

   1. Anabolism

What is metabolism

The sum of all chemical reactions in a living organism that maintain life

Types of Metabolsim:

1. Catabolism

   1. Anabolism

Catabolism

breakdown of molecules to release energy

anabolism

synthesis of complex molecules using energy

Metabolic Pathway Oveview

Begins with: A substrate (reactant)

Ends with: A final product

Steps: Series of enzyme-catalzyed reactions

Example: glycolysis (breakdown of glucose into pyruvate)

Catabolic Pathways

Characteristics: Exergonic (energy releasing), Produces ATP

example: cellular respiration (glucose to ATP) & Lipid breakdown (fat → fatty acids)

Anabolic pathways

build complex molecules from simpler ones, requiring energy

Characteristics: Endergonic (energy-consuming)

Uses ATP

example: protein synthesis (amino acids to proteins)

photosynthesis

Energy

the ability to do work

sources; sunlight, food, ATP

potential energy

stored energy due to position

kinetic energy

energy in motion

Gibbs Free energy

measures the energy available to do work

Negative delta G (exergonic reaction)

• spontaneous

  • Example: cellular respiration

Positive delta G (Endergonic Reaction)

• Requires energy input

• Example photosynthesis

Activation energy

the energy required to start a reaction

• Ensure reaction occurs at controlled rates

  • Enzymes lower activation energy to speed up reactions

open system

exchanges energy/matter with surroundings

closed systems

no exchange with surroundings

living organisms:

open systems

1st law of therm

energy cannot be created or destroyed

2nd law of thermodynamics

energy transfer increases entropy (disorder)

entropy

measure of disorder

increase entropy: heat transfer, phase changes, mixing substances, chemical reactions

ATP

energy currency of cells

Structure: adenine + ribose + 3 phosphate groups

ATP Cycle: Hydrolysis: ATP → ADP + Pi (releases energy) Phosphorylation: ADP + Pi → ATP (stores energy)

Enzymes

biological catalysts that speed up reactions

enzymatic reaction

1. Substrate binds to enzyme

2. enzyme-substrate complex forms

3. Reaction occurs

4. Products are released

Factors affecting enzyme activity

Temperature too high → denaturation

pH: extreme pH → loss of function

competitive inhibitors

bind to active site, blocking substrate

non-competitive inhibitors

bind elsewhere, altering enzyme shape

allosteric regulators

bind to enzyme at a site other than active site

feedback inhibitation

end products inhibits enzyme to regulate pathway

cooperativity

binding of one substrade enhances enzyme activity