1. Chapter 9.1
Chemical Pathways

2. Chemical Energy and Food
Food is the source of raw materials for cells. It is also a source of energy.
A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius.
Calorie – used on food labels – is a kilocalorie (1000 calories).
1 gram of glucose releases 3811 calories of energy.
Cells break down food to slowly release energy.
Glycolysis is the starting point of breaking down food. This process only releases a small amount of energy but is necessary to move to 2 other pathways that release a lot more energy.

3. Overview of Cellular Respiration
If oxygen is available then after glycolysis we will have the Krebs cycle and the electron transport chain. These three processes together make up cellular respiration.
Cellular respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.
Equation for cell respiration:
6O2 + C6H12O6  6CO2 + 6H2O + Energy

4. Cell respiration must have oxygen, food molecules, and it gives off water, carbon dioxide, and energy.
It is a very important process that controls the release of energy.

5. Glycolysis
This is the process in which one molecule of glucose is broken in half, producing 2 pyruvic acid, a 3-carbon compound.

6. ATP Production
The cell has to put in some energy to get the process going. It must start with 2 ATP.
The process of glycolysis makes 4 ATP so that is a net gain of 2 ATP.

7. NADH Production
NAD+ is an electron carrier. It will take an shuttle electrons to other parts of the process.
Glycolysis moves 4 electrons to shuttle to other parts of cell respiration.
Glycolysis does not require oxygen.

8. Fermentation
When oxygen is not available there has to be a way to keep supplying NAD+. This is done by fermentation.
Fermentation releases energy from food molecules by making ATP without oxygen.
Fermentation will convert NADH back to NAD+ to keep being used by glycolysis.
This process is called anaerobic because it is without oxygen.
There are 2 types of fermentation: alcoholic fermentation and lactic acid fermentation.

9. Alcoholic Fermentation
Yeast uses alcoholic fermentation.
This process causes bread dough to rise. When yeast runs out of oxygen, it starts fermentation. This gives off carbon dioxide bubbles and makes the bread rise.

10. Lactic Acid Fermentation
This type of fermentation produces lactic acid.
Lactic acid is produced in your muscles during rapid exercise because your muscles do not get enough oxygen.
The buildup of lactic acid can cause painful, burning sensations and make muscles sore.
Some bacteria can produce lactic acid and are used to make cheese, yogurt, buttermilk, and sour cream.