1. How Cells Harvest Energy
Chapter 9 Outline
Cellular Energy Harvest
Cellular Respiration
Glycolysis
Oxidation of Pyruvate
Krebs Cycle
Electron Transport Chain
Catabolism of Protein and Fat
Fermentation

2. Cellular Respiration
Cells harvest energy by breaking bonds and shifting electrons from one molecule to another.
aerobic respiration - final electron acceptor is oxygen
anaerobic respiration - final electron acceptor is inorganic molecule other than oxygen
fermentation - final electron acceptor is an organic molecule

3. ATP
Adenosine Triphosphate (ATP) is the energy currency of the cell.
used to drive movement
used to drive endergonic reactions

4. ATP
Most of the ATP produced in cells is made by the enzyme ATP synthase.
Enzyme is embedded in the membrane and provides a channel through which protons can cross the membrane down their concentration gradient.
ATP synthesis is achieved by a rotary motor driven by a gradient of protons.

5. NAD+ & NADH
Nicotinamide adenine dinucleotide, NAD+, is a coenzyme found in all living cells.
The compound is a dinucleotide, since it consists of two nucleotides joined through their phosphate groups: with one nucleotide containing an adenosine ring, and the other containing nicotinamide.
In metabolism, NAD+ is involved in redox reactions, carrying electrons from one reaction to another.
The coenzyme is therefore found in two forms in cells: NAD+ is an oxidizing agent – it accepts electrons from other molecules and becomes reduced,
this reaction forms NADH, which can then be used as a reducing agent to donate electrons. These electron transfer reactions are the main function of NAD+.

6. NAD+ & NADH

7. The Cellular isms
Metabolism: is the set of chemical reactions that occur in living organisms in order to maintain life.
These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments.
Usually divided into two categories.
Catabolism and Anabolism
Catabolism – breaking down
Anabolism – building up

8. The Cellular isms
Catabolism: the set of metabolic pathways which break down molecules into smaller units and release energy.
Large molecules such as polysaccharides, lipids, nucleic acids and proteins are broken down into smaller units such as monosaccharides, fatty acids, nucleotides and amino acids, respectively.
These processes produce energy

9. The Cellular isms
Anabolism: the set of metabolic pathways that construct molecules from smaller units.
These reactions require energy.
Anabolism is powered by catabolism. Many anabolic processes are powered by adenosine triphosphate (ATP).
Anabolic processes tend toward "building up" organs and tissues.
These processes produce growth and differentiation of cells and increase in body size, a process that involves synthesis of complex molecules.

10. Glucose Catabolism
Cells catabolize organic molecules and produce ATP in two ways:
substrate-level phosphorylation
aerobic respiration
in most organisms, both are combined
glycolysis
pyruvate oxidation
Krebs cycle
electron transport chain

11. Aerobic Respiration

12. Stage One - Glycolysis
For each molecule of glucose that passes through glycolysis, the cell nets two ATP molecules.
Priming
glucose priming
cleavage and rearrangement
Substrate-level phosphorylation
oxidation
ATP generation

13. Priming Reactions

14. Cleavage Reactions

15. Energy-Harvesting Reactions

16. Recycling NADH
As long as food molecules are available to be converted into glucose, a cell can produce ATP.
Continual production creates NADH accumulation and NAD+ depletion.
NADH must be recycled into NAD+.
aerobic respiration
fermentation

17. Recycling NADH

18. Stage Two - Oxidation of Pyruvate
Within mitochondria, pyruvate is decarboxylated, yielding acetyl-CoA, NADH, and CO2.

19. Stage Three - Krebs Cycle
Acetyl-CoA is oxidized in a series of nine reactions.
two steps:
priming
energy extraction

21. Overview of Krebs Cycle
1: Condensation
2-3: Isomerization
4: First oxidation
5: Second oxidation
6: Substrate-level phosphorylation
7: Third oxidation
8-9: Regeneration and oxaloacetate

22. Krebs Cycle

23. Krebs Cycle

24. Harvesting Energy by Extracting Electrons
Glucose catabolism involves a series of oxidation-reduction reactions that release energy by repositioning electrons closer to oxygen atoms.
Energy is harvested from glucose molecules in gradual steps, using NAD+ as an electron carrier.

25. Electron Transport

26. Stage Four: The Electron Transport Chain
NADH molecules carry electrons to the inner mitochondrial membrane, where they transfer electrons to a series of membrane-associated proteins.

27. Electron Transport Chain

28. Chemiosmosis

29. ATP Generation
This process begins with pyruvate, the product of glycolysis, and ends with the synthesis of ATP

30. Theoretical ATP Yield of Aerobic Respiration

31. Regulating Aerobic Respiration
Control of glucose catabolism occurs at two key points in the catabolic pathway.
glycolysis - phosphofructokinase
Krebs cycle - citrate synthetase

33. Control of Glucose Catabolism

34. Catabolism of Proteins and Fats
Proteins are utilized by deaminating their amino acids, and then metabolizing the product.
Fats are utilized by beta-oxidation.

35. Cellular Extraction of Chemical Energy

36. Fermentation
Electrons that result from the glycolytic breakdown of glucose are donated to an organic molecule.
regenerates NAD+ from NADH
ethanol fermentation
lactic acid fermentation