1. How Cells Harvest Chemical Energy
Chapter 6
How Cells Harvest Chemical Energy

2. Cellular respiration: aerobic harvesting of energy

3. 6.1 Photosynthesis and Cellular Respiration provide energy for life
In Cellular Respiration
Glucose broken down to co2 and h2o and
Cell captures some of released energy to make ATP
Cell resp. takes place in the Mitochondria of Eukaryotic cells
In Photosynthesis
Some energy in sun is captured by chloroplasts
Atoms of CO2 and H2O are rearranged
Glucose and Oxygen are produced

4. 6.3 Cellular Respiration Banks Energy in ATP Molecules
Cellular Respiration is exergonic process that transfers energy from the bonds in Glucose to form ATP
Cellular Respiration
Produces up to 32 ATP molecules from each Glucose molecule
Captures only 34% of the energy originally stored in Glucose
It is overall an Exergonic process
Other foods (organic molecules) can also be used as source of energy

5. + + + C6H12O6 6CO2 6O2 6H2O ATP Glucose Carbon Dioxide Oxygen Heat
Water

6. 6.5 Cells tap energy from electrons “falling’ from organic fuels to oxygen
On the other hand, cellular respiration is the controlled breakdown of organic molecules
Energy is
Gradually released in small amounts
Captured by a biological system
Stored in ATP

7. 6.5 Redox Stuff
The movement of electrons from one molecule to another is an oxidation-reduction reaction, or Redox Reaction
In a redox reaction:
Loss of electrons from one substance is oxidation
Addition of electrons to another substance is called reduction
A molecule is oxidized when it loses one+ electrons
A molecules is reduced when it gains one+ electrons

8. 6.5
A cellular respiration equation is helpful to show changes in Hydrogen atom distribution
Oxygen
Gains Hydrogen atoms
Becomes reduced to H2O
Glucose
Loses its H atoms
Becomes oxidized to CO2

9. 6.5 Enzymes are necessary to oxidize glucose and other foods NAD+
Important enzyme in oxidizing glucose
Accepts electrons
Becomes reduced to NADH
There are other electron “carrier” molecules that function like NAD+
Form staircase where the electrons pass from one to the next down the staircase
These electron carriers collectively are called the Electron Transport Chain
As electrons are transported down the chain, ATP is generated

10. Stages of Cellular Respiration

11. 6.6 Cellular Respiration Occurs in 3 main Stages
Glycolysis
Stage 2
Pyruvate Oxidation and Citric Acid Cycle
Stage 3
Oxidative Phosphorylation

12. Stage 1 = Glycolysis Occurs in Cytoplasm Begins Cellular Respiration
Breaks down Glucose into two molecules of a 3-Carbon compound called Pyruvate

13. Stage 2 = Citric Acid Cycle
Takes place in Mitochondria
Oxidizes Pyruvate to a 2-Carbon compound
Supplies the 3rd stage with electrons

14. Stage 3 = Oxidative Phosphorylation
Involves electrons carried by NADH and FADH2
Shuttles these electrons to electron transport Chain embedded in inner mitochondrial membrane
Involves Chemiosmosis
Generates ATP through Oxidative Phosphorylation, associated with Chemiosmosis

16. 6.7 Glycolysis Harvests Chem Energy by Oxidizing Glucose to Pyruvate
In Glycolysis
A single molecule of glucose is enzymatically cut in half through a series of steps
2 molecules of pyruvate are produced
2 molecules of NADH+ are reduced to 2 molecules of NADH
A net of 2 molecules of ATP is produced

17. 6.7 ATP is formed in glycolysis by Substrate-Level Phosphorylation
An enzyme transfers a Phosphate Group from a substrate molecule to ADP
ATP is formed
The compounds that form btwn the initial reactant, glucose, and the final product, pyruvate, are called Intermediates

18. 6.7 Steps of Glycolysis grouped into 2 main phases
In Steps 1-4: The Energy Investment Phase
Energy is consumed as two ATP molecules are used to energize a glucose molecule
Which is then split into two small sugars
In Steps 5-9: The Energy Payoff
2 NADH molecules are produced for each initial glucose molecule
4 ATP molecules generated

19. 6.8 Pyruvate is Oxidized prior to the Citric Acid Cycle
The pyruvate formed in glycolysis is transported from the cytoplasm into a mitochondrian where
The citric acid cycle and
Phosphorylation will occur

20. 6.9 The Citric Acid Cycle completes the oxidation of organic molecules, generating many NADH and FADH2 Molecules
Citric Acid Cycle
Also called “Krebs Cycle”
Completes oxidation of organic molecules
generates many NADH and FADH2 Molecules

21. 6.9
The Citric Acid Cycle processes two molecules of acetyl CoA for each initial Glucose
Thus after 2 turns of the Citric Acid Cycle, the overall yield per Glucose molecule is
2 ATP
6 NADH
2 FADH2

22. 6.10 Most ATP production occurs by Oxidative Phosphorylation
(From 5.12) Hydrolysis of ATP releases energy by transferring its 3rd phosphate from ATP to some other molecules in a process called Phosphorylation
Oxidative Phosphorylation
Involves electron transport and Chemiosmosis and
Requires adequate supply of oxygen

23. 6.11 interrupting cellular respiration can have both harmful and beneficial affects
3 categories of cellular poisons obstruct process of Oxidative Phosphorylation
1. Block electron transport chain
2. Inhibit ATP synthase
3. make membrane leaky to 4 ions