Friday February 26, 1999
Announcements:

Lecture notes:

Points to ponder: Why do we need oxygen?
Why do we exhale CO₂?
Why are aerobic organisms more successful than anaerobic organisms?

Energy is needed to create and sustain life.

Metabolism is the controlled capacity to acquire and use energy.

Living organisms: 1. Acquire energy from photosynthesis (autotrophs) or by heterotropic means.
2. Transform energy into a form they can use for energy.
3. Use this energy to do "work"

There are two basic types of metabolic reactions:

Those that "take" energy are endergonic.

Those that "release" energy are exergonic.

The energy got exergonic reactions is used to fuel endergonic reactions.

All organisms use organic compounds in the same way to make energy.

All organisms use ATP as an energy carrier.

There are 3 stages in energy transfer in aerobic cells.

1. Glycolysis
2. Krebs Cycle
3. Electron transport

There are 2 stages in energy transfer in anaerobic cells (or in aerobic cells in the absence of CO₂)

1. Glycoysis
2. Fermentation

1^st stage in the energy releasing pathway.

It occurs in the cytoplasm of the cell.

It occurs in both aerobic and anaerobic organisms.

Pyruvate can follow 3 different pathways:

1. Alcoholic fermentation
2. Lactate fermentation
3. Aerobic respiration.

The pathway used in determined by the type of organism and by the amount of oxygen available.

Fermentations

No oxygen is used. The product of fermentation accepts the electrons released during glycolysis. THE REASON THAT THESE ELECTRONS HAVE TO BE "DEALT WITH" IS THAT THERE IS ONLY A LIMITED AMOUNT OF THE ELECTRON CARRYING MOLECULES (NAD+) THEY HAVE TO BE RECYCLED FOR GLYCOLYSIS TO CONTINUE.