Cellular respiration involves the breakdown of glucose to produce energy in the form of ATP. It occurs in both plants and animals and takes place in three main stages: glycolysis, the Krebs cycle, and the electron transport chain. Glycolysis breaks down glucose and occurs in the cytoplasm, producing a net gain of 2 ATP. In the presence of oxygen, glycolysis is followed by the Krebs cycle and electron transport chain, where more ATP is produced. Without oxygen, fermentation occurs instead to regenerate NAD+ and allow glycolysis to continue.

1. Cellular Respiration

2. Description/definition of
cellular respiration
When an organism breaks down glucose
and transfers glucose or chemical energy
into ATP or cellular energy/usable energy.
Both plants AND animals use cellular
respiration to transfer energy.

3. Cellular Aerobic Respiration
C6H12O6 + 6O2 6CO2 + 6H2O + energy

4. Mitochondrial Structure
Intermembrane Space Outer Membrane
Matrix
Inner Membrane Cristae

6. Mitochondria
• Double membrane & Cristae
– Increases surface area for cellular respiration to
occur
– Location of the Electron Transport Chain
• Matrix
– Location of the Krebs cycle

7. Recall
Electron Carrier Molecules
• NADH
• FADH2

8. Process of Cellular Respiration
Glycolysis
Without O2 With O2
Krebs Cycle
Alcoholic Lactic Acid
Fermentation Fermentation
Electron
Transport
Chain

9. The First Process of Cellular Respiration
Glycolysis
• Occurs in the Cytoplasm
• Does not require oxygen
• Breakdown of glucose or glycogen
• “Splitting of sugar”

11. Glycolysis
• Series of 10 reactions
• Glucose is split into two smaller molecules
called PYRUVATE or pyruvic acid
• 2 ATP are used but 4 ATP are produced
• Net gain of ATP? 2 ATP molecules
• Glycolysis Process
C6H12O6 + 2ATP + 2NAD+ 2 Pyruvate + 4ATP + 2NADH + H+

12. Glycolysis Animation
Click on the link above to view the animation

13. Process of Cellular Respiration
Glycolysis
Without O2

14. Without Oxygen
Anaerobic Respiration

15. Anaerobic Fermentation
• Occurs in the cytoplasm
• Does not produce ANY ATP
• Regenerates NAD+ for reuse in glycolysis
• Two types
– Alcoholic Fermentation
– Lactic Acid Fermentation

16. Alcoholic Fermentation
• Plants Cells
• Used to produce alcoholic beverages and to make bread
• Pyruvic acid (pyruvate) is converted into ethyl
alcohol, carbon dioxide, NAD+.
• Alcoholic Fermentation Equation
Pyruvic acid + NADH ethyl alcohol + CO2 + NAD+

18. Lactic Acid Fermentation
• Animal Cells
• Used to produce yogurt and cheese
• Cause soreness in muscle cells
• Pyruvic acid (pyruvate) is converted into lactic
acid, & NAD+
• Lactic Acid Fermentation Equation
Pyruvic acid + NADH Lactic acid + NAD+

20. What’s the point of fermentation?
Glycolysis – 2 ATP
Fermentation – 0 ATP
Total – 2 ATP
• Regenerate the electron carrier, NAD+
• NAD+ can allow for cellular respiration to
continue