1. Chapter 9 Chemical Pathways
Cellular Respiration
Ms. Lew Biology
Chapter 9
Chemical Pathways

2. Vocabulary Aerobic Anaerobic calorie Cellular respiration Fermentation
Glycolysis

3. Basic Need for Energy
Energy in Food: What is the difference between a: calorie(lower case c) and Calorie (upper case C)?
A calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1 degree C.
A Calorie is a kilocalorie, or 1000 calories
For example, 1 gram of glucose releases 3811 calories, on a food label 3.8 Calories

4. Basic Need for Energy
Energy in Food: Organisms cannot use glucose directly, it must be broken down into smaller units.
This process in living things begins with glycolysis.
If oxygen is present, glycolysis is followed by the Krebs Cycle and electron transport chain – This is called Cellular Respiration

5. An Overview: Cellular Respiration
The equation for cellular respiration is exactly the opposite of photosynthesis.
Equation:
6O2 + C6H12O6  6CO2 + 6H2O and energy

6. Breaking Down Energy Slowly:
Glucose needs to be broken down in small steps so that energy is not wasted.

7. Glycolysis
Definition: The process of breaking glucose in half to form 2 molecules of pyruvate (a 3 carbon chain).
Uses 2 ATP to start reaction
Produces 4 ATP and 2 NADH

8. Glycolysis Does not require oxygen
Very Fast – thousands of ATP produced in milliseconds
Stops when it runs out of NAD+ (electron carrier)
If oxygen is available: Cellular respiration starts
If oxygen is NOT available, to make more NAD+, your body goes through fermentation.
This way ATP can be made even without Oxygen.

9. Why use ATP in Glycolysis if you want ATP?
You have to use a little energy to make even more energy.
Like a bank, you put money in to earn interest.
NAD+ and NADH are like NADP+ and NADPH . They can hold electrons.
Animation

10. Fermentation
Fermentation is releasing energy in the absence of oxygen. It is an ANAEROBIC process.
Ultimately it allows NADH to be converted to NAD+, allowing glycolysis to continue.
There are two main types of fermentation
Alcoholic Fermentation
Lactic Acid Fermentation

11. Alcoholic Fermentation
Alcoholic fermentation is found in Yeasts, and a few other microorganisms.
The equation is:
Pyruvic acid + NADH  alcohol + CO2 + NAD+
Note: Carbon Dioxide is also produced, so when yeast conducts fermentation, there is the release of carbon dioxide as well as alcohol.

12. Alcoholic Fermentation
Alcoholic fermentation diagram

13. Lactic Acid Fermentation
Pyruvic acid from glycolysis can be converted to lactic acid.
This conversion regenerates NAD+ for glycolysis to continue
The equation is:
Pyruvic acid + NADH  lactic acid + NAD+
Lactic acid fermentation is used by muscles when they run out of oxygen, ultimately causing soreness.
Lactic acid is also created by unicellular organisms in the production of cheese, pickles, kimchi and other foods.

14. Lactic Acid Fermentation
Lactic Acid fermentation diagram

15. Krebs Cycle
In the Krebs Cycle, pyruvic acid is broken down into carbon dioxide.

16. Krebs Cycle Where does it occur: Mitochondria
It requires oxygen – it is AEROBIC
It is also known as the Citric Acid Cycle

17. Krebs Cycle So far, from 1 glucose Glycolysis produced:
2 NADH and 2 ATP
Krebs Cycle produced:
8 NADH and 2 FADH2 and 2 ATP
Animation

18. Krebs Cycle What happens to the Krebs cycle products?
Carbon Dioxide is released to the atmosphere
ATP is used for cellular activities
NADH and FADH2 are used in the electron transport chain to produce large amounts of ATP

19. Electron Transport Chain
Uses the high energy electrons from the Krebs cycle to convert ADP into ATP

20. Electron Transport Chain
Where does it occur: Inner membrane of the Mitochondria
It requires oxygen – it is AEROBIC

21. Electron transport chain

22. Cellular Respiration totals
So far, from 1 glucose
Glycolysis: 2 ATP +
Krebs Cycle: 2 ATP +
Electron Transport: 32 ATP
Totals: ATP from 1 glucose
This is 38% efficiency
The rest of the energy is released as heat

23. Energy use by humans Cells contains small amounts of ready ATP
About 5 seconds worth
After that, your body uses lactic acid formation
This lasts for about 90 seconds
You breathe hard to get rid of the lactic acid buildup
For exercise longer than 90 seconds, cellular respiration is used
This is a slow method to generate ATP
Glycogen (a form of carbohydrate) is used for the first minutes of cellular respiration
After that other molecules, such as fats, are broken down