Metabolism

The total of all reactions in a cell

Components of Metabolism

• Catabolism

• Breakdown of large molecules into smaller ones

• Energy is released

Components of Metabolism

• Anabolism

• Building of large molecules from smaller ones

• Energy is required

Energy Basics

• Two types—kinetic & potential

• Many forms—chemical, electromagnetic, mechanical, heat, nuclear

• Energy can be transformed from one type to another

1st Law of Thermodynamics

• Energy can be neither created nor destroyed but it can change forms

• Energy is conserved in a reaction

2nd Law of Thermodynamics

• Every energy transfer or transformation makes the universe more disordered.

• Entropy—The measure of the amount of disorder or randomness

Which has more entropy???

• A cluttered closet or a well-organized closet?

• An ice cube or a glass or water?

• A gallon of gasoline or the carbon dioxide and water vapor that escape the exhaust pipe?

There is an unstoppable trend toward randomization in nature

• Heat is a very disorganized form of energy and is the fate of all energy transformations.

• The quantity of energy in the universe is constant, but its quality is not.

Reactions that occur spontaneously

• Increase the stability of the system

• Increase the entropy (randomness or disorder) of the system

Spontaneous reactions

• Release energy that can perform work

• This energy is known as free energy

• It is represented by the letter G

Free energy is

• A measure of a system’s instability

• Systems that change to a more stable state have high free energy, low entropy or both.

The ATP molecule

• ATP is the energy currency for cellular work.

• Cells do the following kinds of work:

• Mechanical work

• Transport work

• Chemical work

The ATP molecule

• Is highly organized (low entropy)

• Very unstable (negative phosphates in close proximity)

• Therefore, has a very high free energy

• ΔG = -7.3 kcal/mol for hydrolysis of ATP

Free Energy and Equilibrium

• Equilibrium is point of maximum stability• At equilibrium ΔG = 0, there is no

change in the system• At equilibrium, cells are dead!• Cells must remain at disequilibrium

to continue to work

Exergonic reactions

• Release free energy

• ΔG is negative

• Occur spontaneously

• Can do work

• Respiration is an example

• ΔG for respiration = -686 kcal/mol

Endergonic Reactions

• Absorbs free energy

• ΔG is positive

• Do not occur spontaneously

• Photosynthesis is an example

• ΔG for photosynthesis is 686 kcal/mol

Analyze the ATP Cycle in terms of anabolism, catabolism,

endergoonic, exergonic, and free energy

How does ATP work?