1. Energy Flow and Chemical Recycling in Ecosystems
The chemical elements of life are
recycled but energy is not – it flows
into an ecosystem as light and
leaves as heat

3. Electrons “fall” from organic molecules to oxygen during cellular respiration
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
Oxidation of C6H12O6 coupled to the reduction of O2.
Controlled release of energy to form ATP.
The remainder of the energy is released as heat.
This process is called oxidative phosphorylation.

4. Overview of Cellular Respiration

5. Overview of Cellular Respiration
Glucose →
glycolysis
2 ATP
2 Pyruvate
Overview of Cellular Respiration
The first step is called glycolysis. It occurs in the cytosol.
During glycolysis, a glucose molecule (6 carbons) is converted to two pyruvate molecules (3 carbons each).
It does not require oxygen (it is anaerobic).
A total of 2 ATP are gained as a result of these reactions. 6

6. The Glycolytic Pathway

7. Summary of Glycolysis 4 ATP produced - 2 ATP consumed 2 ATP net
glucose (C6)
2 ATP
2 ADP
4 ATP produced
- 2 ATP consumed
2 ATP net
2 NADH are also produced
2C3
2 NAD+
2 ADP
2 ATP
2 NADH
2 ADP
2 ATP
2 pyruvate (C3) 15

8. Efficiency of Glycolysis
Compare the kilocalories of glucose with the kilocalories in the ATP that is made.
The 2 ATP molecules made during glycolysis account for only 2% of the energy in glucose
Where does the rest go?
It’s still in pyruvic acid
This small amount of energy is enough for bacteria, but more complex organisms need more of glucose’s energy.

9. Fermentation
If there is no oxygen some cells can convert pyruvic acid into other compounds and get more NAD+
No ATP is made, but the NAD+ can keep glycolysis going to make a little ATP
2 kinds of fermentation: Lactic acid fermentation and Alcoholic Fermentation

10. Anaerobic
Aerobic

11. Evolutionary Significance of Glycolysis
Glycolysis is the most widespread pathway, so it probably evolved early.
The first prokaryotes evolved over 3.5 billion years ago, before there was much O2 in the atmosphere.
Glycolysis occurs in the cytosol and does not require membrane-bound organelles.
Eukaryotic cells with organelles probably evolved about 2 billion years after prokaryotic cells.

12. A transport protein built into the membrane facilitates the movement of pyruvate into the mitochondrion

13. Overview of Cellular Respiration

14. The Krebs Cycle

18. The conversion of pyruvate to acetyl CoA and the Krebs cycle produce large quantities of electron carriers.

19. The inner mitochondrial membrane couples
electron transport to ATP synthesis
Proton-motive force
Oxidative phosphorylation

20. A protein complex, ATP synthase, in the cristae actually makes ATP from ADP and Pi.
ATP used the energy of an existing proton gradient to power ATP synthesis.
This proton gradient develops between the intermembrane space and the matrix.

21. Feedback mechanisms control cellular respiration

22. How are food molecules other than glucose oxidized to ATP?

23. RESPIRATION CYTOPLASMGLYCOLOSIS HAPPENS HERE! CO2 IS RELEASED
PROTEINS
CARBO’S
(SUGARS)
FATS
(LIPIDS)
GLUCOSE
C6H12O6
AMINO
ACIDS
MAKES
2 ATPS
GLYCOLOSIS
IN CYTOPLASM
NO OXYGEN!
ATP TOTALS
GLYCOLOSIS=2
RESPIRATION=34
BOTH=36!
PYRUVIC
ACID
CO2 IS RELEASED
ACETYL-CoA
O2 ENTERS HERE
KREBS CYCLE
AND
ELECTRON
TANSPORT
MAKES
34 ATPS
MITOCHONDRIARESPIRATION HAPPENS IN THIS ORGANELLE!