Chapter 4: The Energy of Life
Chapter 4 Learning Objectives
• Examine the laws of thermodynamics.
• Examine the signiûcance of chemical bond energy and entropy.
• Examine endergonic and exergonic reactions.
• Examine the role played by enzymes in reactions.
• Examine the factors that aect the activity of enzymes.
• Examine endergonic and exergonic reactions using diagrams.
• Examine the unique characteristics of dierent types of cofactors using examples.
• Examine the factors that aect the rate of diusion.
• Examine the dierent mechanisms of transporting material across cell membranes.
• Dierentiate between endocytosis and exocytosis
4.1 All Cells Capture and Use Energy
A. Energy Allows Cells to Do Life’s Work
Energy – The capacity to do work
Deûne the following:
Potential energy: is stored energy available to do work. (Examples: Chemical energy
(stored in bonds, Concentration gradient across a membrane)
Kinetic energy: is the energy of motion; any moving object possesses this form of
energy. (Examples: Light, Sound waves, and moving objects)
Kilocalories: each of which equals 1000 calories. (In nutrition, 1 food Calorie—with a
capital C—is actually a kilocalorie.)
Other forms of energy: heat, light, sound, radioactivity, electricity
B. The Laws of Thermodynamics Describe Energy Transfer
What is the first law of thermodynamics? The ûrst law of thermodynamics is the law of
energy conservation. It states that energy cannot be created or destroyed, although energy
can be converted to other forms. This means that the total amount of energy in the universe
does not change.
What is the second law of thermodynamics? states that all energy transformations are
inecient because every reaction loses some energy to the surroundings as heat
, What is entropy? Entropy is a measure of this randomness. In general, the more disordered
a system is, the higher its entropy
4.2 Networks of Chemical Reactions Sustain Life
A. Chemical Reactions Absorb or Release Energy
Metabolism: encompasses all of these chemical reactions in cells, including those that build
new molecules and those that break down existing ones.
Reactants – starting substances in a chemical reaction
Products – ending substances in a chemical reaction
Activation energy – the minimum energy required to start a reaction
For the following types of reactions, be able to graph and recognize reactants, products,
activation energy, and change in free energy.
Endergonic reactions: reactants have less Exergonic reactions: reactants have
free energy than the products more free energy than the products
B. Linked Oxidation and Reduction Reactions Form Electron Transport Chains
Redox Reactions: Oxidation-reduction reactions (<redox=) are simply electron transfer
between molecules.
What happens to the molecule that is reduced?
Chapter 4 Learning Objectives
• Examine the laws of thermodynamics.
• Examine the signiûcance of chemical bond energy and entropy.
• Examine endergonic and exergonic reactions.
• Examine the role played by enzymes in reactions.
• Examine the factors that aect the activity of enzymes.
• Examine endergonic and exergonic reactions using diagrams.
• Examine the unique characteristics of dierent types of cofactors using examples.
• Examine the factors that aect the rate of diusion.
• Examine the dierent mechanisms of transporting material across cell membranes.
• Dierentiate between endocytosis and exocytosis
4.1 All Cells Capture and Use Energy
A. Energy Allows Cells to Do Life’s Work
Energy – The capacity to do work
Deûne the following:
Potential energy: is stored energy available to do work. (Examples: Chemical energy
(stored in bonds, Concentration gradient across a membrane)
Kinetic energy: is the energy of motion; any moving object possesses this form of
energy. (Examples: Light, Sound waves, and moving objects)
Kilocalories: each of which equals 1000 calories. (In nutrition, 1 food Calorie—with a
capital C—is actually a kilocalorie.)
Other forms of energy: heat, light, sound, radioactivity, electricity
B. The Laws of Thermodynamics Describe Energy Transfer
What is the first law of thermodynamics? The ûrst law of thermodynamics is the law of
energy conservation. It states that energy cannot be created or destroyed, although energy
can be converted to other forms. This means that the total amount of energy in the universe
does not change.
What is the second law of thermodynamics? states that all energy transformations are
inecient because every reaction loses some energy to the surroundings as heat
, What is entropy? Entropy is a measure of this randomness. In general, the more disordered
a system is, the higher its entropy
4.2 Networks of Chemical Reactions Sustain Life
A. Chemical Reactions Absorb or Release Energy
Metabolism: encompasses all of these chemical reactions in cells, including those that build
new molecules and those that break down existing ones.
Reactants – starting substances in a chemical reaction
Products – ending substances in a chemical reaction
Activation energy – the minimum energy required to start a reaction
For the following types of reactions, be able to graph and recognize reactants, products,
activation energy, and change in free energy.
Endergonic reactions: reactants have less Exergonic reactions: reactants have
free energy than the products more free energy than the products
B. Linked Oxidation and Reduction Reactions Form Electron Transport Chains
Redox Reactions: Oxidation-reduction reactions (<redox=) are simply electron transfer
between molecules.
What happens to the molecule that is reduced?
