Biology 101 Chapter 5
The Working Cell
Metabolism: The ability of living systems to acquire and use energy for growth and repair.
Energy: The capacity to do work.
1) Kinetic Energy = energy actually performing work.
Ex. heat, light, momentum
2) Potential Energy = stored energy.
Ex. gravity, chemical
Two Laws Govern Energy Reactions
· Life depends on energy; it can be changed from one form to another
1) The First Law of Thermodynamics (Law of Conservation)
2) The Second Law of Thermodynamics (Law of Entropy)
Entropy: the measure of the amount of disorder in a system.
Chemical reactions either store or release energy.
Reactions may be:
Activation Energy: The energy needed to kick-start a chemical reaction. All reactions have activation energy.
Enzymes: Are organic catalysts that speed up chemical reactions.
Properties of Enzymes: The Basic Rules
1. Enzymes only speed up reactions, they cannot make a reaction occur if it would not occur on own.
2. Enzymes are not consumed, used up, destroyed, altered, or harmed in anyway by the reaction. They are recycled.
3. Enzymes are very selective about their substrate. One to one rule.
4. Enzymes will work both the forward and reverse reactions of a particular type of reaction.
· Enzymes are organic, they are made of proteins.
· They speed up reactions by lowering the activation energy.
· Enzymes are embedded in the cell's membranes.
· They perform many of the body's functions.
Factors That Affect the Enzyme
3. Salt concentration
5. Substrate concentration
6. Enzyme concentration
8. Inherent enzyme function
Enzyme Control and Inhibition
Role of negative feedback
Substrate = that which an enzyme acts upon
Active Site = the working point or region of an enzyme
Reactants = starting materials
Products = ending materials
reactants intermediates products
Metabolic Reaction vs. Metabolic Pathway
Chloroplasts and Mitochondria
· Make energy available for work
· Photosynthesis and Cellular Respiration are circular processes
Photosynthesis: 6 CO2 + 6 H2O → 1 C6H12O6 + 6 O2
Respiration: 1 C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
ATP and Its Role in Energy Reactions
· Energy currency of cell
· Recycled process
· Redox reactions
o Something reduced = gained electrons
o Something oxidized = lost electrons
· Oxidation-Reduction reactions always coupled