Metabolism- The process of converting food into energy



Energy- The ability to do work
Kinetic Energy- The energy of motion
Potential Energy- The type of energy that matter possesses because of its location or structure.

Cellular respiration and other catabolic pathways unleash energy stored in SUGAR and other complex molecules.
The chemical energy stored on the organic molecules were derived from LIGHT ENERGY, mostly by plants during photosynthesis.

Catobolic Pathways release energy by breaking down complex molecules into simple compounds

THERMODYNAMICS The study of energy transformation.

First Law of Thermodynamics- Energy can be transferred and transformed, but never created nor destroyed.

Second Law of Thermodynamics- Every energy transformation must make the universe more disordered.
  • The most disordered type of energy is HEAT

Entropy- a quanity used as a measure of disorder or randomness.
*The most random state of energy is HEAT

  • Exergonic reactions proceeds with a net release of free energy.
  • Endergonic reations absorbs free energy from its surroundings.

All cells do THREE main types of work:
    1. Mechanical Work- beating of cilia, contraction of muscle cells and movement of chromosomes.
    2. Transport Work- pumping of substances across the membranes.
    3. Chemical Work- driving endergonic reactions.

ATP- Adenosine TriPhosphate- type of nucleotide consisting of the notrogenous base adenine, the sugar ribose, and a chain of 3 phosphate groups.
  • Bonds between the phosphate groups can by broken apart by Hydrolysis.
  • ATP is a renewable resource that is always regenerated by the addition of a phosphate group to ADP/
  • The renewal comes from catabolic reactions occuring in the cell.

Enzymes accelerate the process of breaking down foods into energy.


  • Catalists speed up the rate of a chemical reaction without being consumed by the reaction.
  • An enzyme is a catabolic protien.
  • Enzymes regulate the movement of molecules thoughout the metabolic pathways.
Chemical reactions involve bond breaking and bond forming.
Activation Energy- Amount of energy needed to push the reactants through an energy barrier.
Substrate- a reactant which binds to an enzyme.

A single enzyme molecule can catalyze thousands or more reactions per second.
Enzymes catalyze reactions in the direction of equillibrium.

3-D structures of enzymes depend on the environment. The reaction rate is greatly influenced by the changes in the shape.
  • Temperature has the greatest impact on reaction rate.
  • As the temperature increases, collisions between substrates and active sites occur more frequently as molecules move faster.

pH also influences shape and reaction rate.
The optimal pH falls between 6-8 for most enzymes, but digestive enzymes are designed to work best a pH 2, and those located in the intestines work best at pH 8.