1. Cellular Respiration

2. Principles of Energy Harvest
Ultimately, the NRG in an ecosystem begins as sunlight and leaves as heat
Chemical elements are recycled
Photosynthesis and Respiration are essential processes that allow NRG to flow through an ecosystem

3. NRG from food Catabolic pathways produce ATP from organic compounds
Fermentation
Partially degrades sugars
Occurs when no O2 present
Cellular Respiration
C6H12O6 + 6O2  6CO2 + 6H2O + E (ATP + heat)

4. Redox reactions In order to make ATP, electrons must be rearranged
Oxidation/Reduction
LEO the lion says GER
Lose Electrons = Oxidation
Gain Electrons = Reduction
Reducing agent: e- donor
Oxidizing agent: e- acceptor

5. Oxidizing agent in Respiration
NAD+ (nicotinamide adenine dinucleotide)
Removes electrons from food (series of reactions)
NAD+ is reduced to NADH
Enzyme action: dehydrogenase (removes 2 e- and 2 H+)
NRG in NADH is used to make ATP (controlled production of NRG)

6. Electron Transport Chains
Electron carrier molecules (membrane proteins)
Shuttle e- that release NRG used to make ATP
Sequence of reactions that prevents NRG release in one explosive step
Electron route:
food NADH  ETC O2
Oxygen is the final e- acceptor

7. Cellular respiration Glycolysis: Citric Acid (Kreb’s) Cycle:
cytosol
degrades glucose into pyruvate
Citric Acid (Kreb’s) Cycle:
mitochondrial matrix
pyruvate into CO2
Electron Transport Chain:
inner membrane of mitochondrion
electrons passed to oxygen
NRG trapped to make ATP

8. Glycolysis 1 Glucose ---> 2 pyruvate molecules
Energy investment phase: cell uses 2 ATP to phosphorylate fuel
Energy payoff phase: 4 ATP produced by substrate-level phosphorylation and NAD+ is reduced to NADH by food oxidation
Net NRG yield per glucose: ATP, 2 NADH

9. Kreb’s Cycle For each pyruvate: If molecular O2 is present…
Each pyruvate (2 from glycolysis) converted into acetyl CoA
CO2 released
NAD+ ---> NADH
coenzyme A (from B vitamin) attached; makes molecule very reactive
In each turn, 2 C atoms enter (pyruvate) and 2 exit (CO2)
For each pyruvate:
3 NAD+ reduced to NADH
1 FAD+ reduced to FADH2
1 ATP molecule

11. Electron Transport Chain
e- carriers, NADH and FADH2 donate e- to the chain
e- passed “downhill” to more electronegative molecules as they move on
Most carrier molecules are cytochromes
have a heme group that accepts and donates e-

12. Chemiosmosis
Electron Transport chain sets up a H+ concentration gradient
e- flow is exergonic; released NRG is used to pump protons across the membrane
“proton-motive force”
As H+ diffuses back in, ATP synthase makes ATP
Chemiosmosis: energy coupling mechanism
NRG of H+ gradient drives cellular work

13. ATP Production ATP synthase: produces ATP using the H+ gradient
harnesses flow of H+ back into matrix
phosphorylates ADP to ATP (oxidative phosphorylation)
Produces molecules of ATP

15. Review: Cellular Respiration
Glycolysis:
2 ATP (substrate-level phosphorylation)
Kreb’s Cycle:
Electron transport & oxidative phosphorylation:
2 NADH (glycolysis) = 6 ATP
2 NADH (acetyl CoA) = 6 ATP
6 NADH (Kreb’s) = ATP
2 FADH2 (Kreb’s) = 4 ATP
38 TOTAL ATP/glucose

16. Fermentation Occurs when no O2 is present
Produces some ATP and replenishes NAD+
Keeps glycolysis going so some ATP can be produced
Facultative anaerobes (yeast/bacteria) can survive off of fermentation alone

17. Types of fermentation Alcoholic Lactic acid pyruvate to ethanol
Bacteria, yeast, most plants
Production of bread and alcoholic beverages
Lactic acid
pyruvate to lactate
Fungi, bacteria, human muscle cells
Production of cheese and yogurt
Causes muscle fatigue and pain during strenuous exercise

18. Other Metabolic Pathways
Proteins
broken down into amino acids
Converted into intermediates used in glycolysis and Kreb’s
Lipids
Broken down into glycerol and fatty acids
Glycerol transformed into an intermediate in glycolysis
Fatty acids broken down by beta-oxidation and transformed into Acetyl Co-A