1. Cellular Respiration

2. C6H12O6 + 6O2 -----> 6CO2 + 6H2O + ATP
Cellular Respiration
A series of chemical reactions needed to break down carbohydrates and other molecules in order to release the energy they contain.
C6H12O6 + 6O > 6CO2 + 6H2O + ATP

3. Energy in Living Organisms
Energy harvested from the breakdown of sugar is stored in energy carrier molecules:
adenosine triphosphate (ATP)
nicotinamide adenine dinucleotide (NADH)
flavin adenine dinucleotide (FADH2).

4. Energy Carrier Molecule: ATP
ATP consists of adenine (red), ribose (purple) and three phosphate groups (blue).

5. Energy Carrier Molecule: ATP
The bonds between the phosphate groups are high energy bonds. When energy is needed, the bond between the 2nd and 3rd phosphate groups is broken.
About 30 kJ/mol of ATP is released. The remaining molecule is now called adenosine diphosphate (ADP).
ATP <-----> ADP + P + energy

6. Energy Carrier Molecules: NADH & FADH2
NADH carries an amount of energy equivalent to 3 ATP.
FADH2 carries an amount of energy equivalent to 2 ATP.

7. Types of Cellular Respiration
Aerobic respiration:
the process that requires sufficient O2
produces 36 ATP
Anaerobic respiration:
The process that occurs when there is insufficient O2 supply
Produces ONLY 2 ATP
C6H12O6 + 6O > 6CO2 + 6H2O + ATP
Sufficient: Aerobic
Insufficient: Anaerobic

8. Aerobic Cellular Respiration
3 Main Phases:
Glycolysis
Krebs Cycle
Electron Transport Chain

9. Phase 1: Glycolysis
A series of 10 steps that breaks down glucose (6-carbon molecule) into two pyruvate molecules (3-carbon molecules)
This process does not use oxygen.

10. Phase 1: Glycolysis Energy Yield 2 ATP are used 4 ATP are made
(net of 2 ATP)
2 NADH are made
The 2 ATP can be used directly, however, the 2 NADH need to go into the 3rd phase (ETC) to be converted into ATP.
The process occurs in the cytoplasm.

11. Phase 2: Krebs Cycle
A process by which 2 pyruvate molecules are sent through a cycle to release CO2.
During the cycle, a 6-carbon molecule of citrate is produced, thus this cycle is also known as the citric acid cycle.

12. Phase 2: Krebs Cycle Energy Yield / pyruvate 1 ATP 4 NADH 1 FADH2
Since glycolysis produces 2 pyruvate molecules, the energy yield should be doubled.
ADP
ATP

13. Phase 2: Krebs Cycle
This phase occurs in the matrix of a mitochondria.
The 2 ATP can be used directly.
The 8 NADH and 2 FADH2 go into the 3rd phase (ETC) to be converted into ATP.
CO2 is a waste product that is blown off when breathing.

14. Phase 3: The Electron Transport Chain (ETC)
Process by which NADH and FADH2 are converted into ATP. H2O molecules are also formed during this phase. This phase occurs on the cristae of the mitochondria.

15. Phase 3: ETC Details
NADH and FADH2 that are formed during glycolysis and Krebs cycle each have a pair of electrons.
These electrons are brought to the cristae of the mitochondria and transferred to proteins called cytochromes.
The electrons are passed down through a series of cytochromes known as the ETC.
As the electron pairs move through each cytochrome, 2 hydrogen ions (H+) are pumped out of the matrix into the intermembrane space.
This causes the intermembrane space to have a high concentration of H+ and so H+ want to diffuse back into the matrix.
They do this through a protein known as ATP synthase. Energy from H+ is provided to join ADP+ P > ATP .
At the end of the ETC, the electrons join with oxygen and 2 H+ to produce H2O.

16. Phase 3: ETC
The electrons from NADH start at the beginning of the chain and pump 3 pairs of H+ across.
The electrons from FADH2 start farther down the chain and only pump 2 pairs of H+ across.
Since each pair of electrons passes through ATP synthase to make 1 ATP, each NADH can produce 3 ATP and FADH2 can produce 2 ATP.

17. Energy Yield Overview 2 ATP (glycolysis) 2 ATP (Krebs cycle)
2 NADH (glycolysis) ----> 4 ATP in ETC**
8 NADH (Krebs cycle) --> 24 ATP in ETC
2 FADH2 (Krebs cycle) --> 4 ATP in ETC
36 ATP from glucose molecule
**Krebs cycle and ETC both occur in the mitochondria therefore NADH made in Krebs cycle is converted into 3 ATP each.
Glycolysis occurs in the cytoplasm and therefore the 2 NADH produced there must enter the mitochondria to get to the ETC. This costs energy. Therefore, each NADH from glycolysis is only worth 2 ATP each.

18. Question
How many ATP could a prokaryotic cell get from 1 glucose molecule? Explain.
Answer:
A prokaryotic cell could get 38 ATP from 1 glucose molecule because prokaryotes do not have mitochondrial membranes.
Therefore, glycolysis, Krebs cycle, and ETC all happen in the cytoplasm. ALL NADH are worth 3 ATP. Since the NADH produced in glycolysis does not have to enter the mitochondria, there in NO energy cost!

19. Review: Cellular Respiration
C6H12O6 + 6O > 6CO2 + 6H2O + ATP
Glycolysis
ETC
Krebs Cycle
ETC
All Phases:
2 from glycolysis
2 from Krebs cycle
32 from ETC

20. Anaerobic Cellular Respiration
Glucose is converted into 2 pyruvate molecules in glycolysis which will then go to the Krebs cycle IF O2 if available.
Sometimes, the amount of O2 available is insufficient and the 2 pyruvate molecules undergo a process called fermentation.

21. Anaerobic Cellular Respiration
During fermentation in eukaryotic cells, pyruvate will either be converted into:
Ethanol through Alcoholic Fermentation
Lactic Acid through Lactic Acid Fermentation

22. Alcoholic Fermentation
Ethanol:
produced when yeast cells ferment
A source of ethyl alcohol (beer and wine)
Glucose > 2 pyruvate > ethanol + CO2
fermentation
glycolysis
2 ATP

23. Lactic Acid Fermentation
Produced by cells of multicellular organisms during O2 deficient times (exercise)
Lactic acid causes the “burn” felt in muscle cells
Blood circulation moves excess lactic acid
fermentation
glycolysis
Glucose > 2 pyruvate > lactic acid
2 ATP

24. Anaerobic Respiration
Consider that aerobic respiration can produce 36 ATP/ glucose molecule.
Therefore, how efficient is anaerobic respiration at getting energy from glucose?
2 ATP / 36 ATP * 100% = 5.6% efficient