1. Chapter 6
Acquiring Energy

2. Energy for Life All energy comes from the sun
Producers convert light into chemical energy (glucose bonds)
Consumers eat/break bonds to release energy
Energy coupling reactions recycle components
Cellular respiration (break):
6O2 + C6H12O6  6CO2 + 6H2O + ATP
Photosynthesis (make):
ATP + 6CO2 + 6H2O  C6H12O6 + 6O2
Which reaction term applies to each?

3. Redox Reactions
Coupled reactions that move electrons between molecules
Review: electrons form bonds and energy is released when they break (endergonic or exergonic?)
LEO goes GER
Lose an electron = oxidation
Glucose oxidized to CO2
Gain an electron = reduction
O2 reduced to H20
NAD+ reduced to NADH
What do all these reactions have in common?

4. Electron Carriers NADH and NADPH hold e-’s = high energy bonds
Carry 2 e-’s and a H+
Precursor = NAD + and NADP +
Molecules oxidized  e-’s released & captured
Dehydrogenase

5. Cellular Respiration Aerobic respiration Anaerobic respiration
Requires O2
High energy (ATP) yield
Glycolysis
Common to all paths
Energy from sugar (glucose)
Citric acid cycle (Kreb’s cycle)
Oxidative phosphorylation (ETS and Chemiosmosis)
Anaerobic respiration
Doesn’t require O2
Organisms w/o mitochondria
Low energy yield

6. Step 1: Glycolysis Aerobic and anaerobic In the cytoplasm Starts with:
Glucose (6C’s)
2 ATP
Ends with:
2 pyruvate (3C’s)
Important products of this process:
Net 2 ATP
4 ATP  substrate-level phosphorylation
2 NADH

7. Intermediate Step: ‘Grooming’
Starts with:
2 Pyruvate (3C’s)
High energy product
Ends with:
2 Acetyl-CoA (2C’s)
Important products of this process:
2 CO2
Decarboxylation
2 NADH

8. Step 2: Citric Acid Cycle
In the mitochondrial matrix
Starts with:
2 Acetyl CoA
Ends with:
4 CO2
Important products of this process:
2 ATP  substrate level phosphorylation
6 NADH
2 FADH2
6 C’s
4 C’s

9. Step 3: Electron Transport System (ETS)
In the inner mitochondrial membrane
Starts with:
10 NADH (previous steps)
2 FADH2 (citric acid cycle) O2
Ends with:
H2O
Important products of
this process:
H + gradient

10. Electrons and the Importance of Oxygen
Review
Electron energy determined by arrangement
e-’s further from the nucleus = more PE
e-’s dropping levels release E
Oxygen is highly electronegative
Integral protein complexes use a little less energy to ‘hold’ the electrons
Extra energy transports a H+ across out of the matrix into the intermembrane space
O2 is the last molecule to accept e-’s to become water
Electrons from reactions in glycolysis and Kreb’s cycle

11. Step 4: ATP Generation (Chemiosmosis)
In the inner mitochondrial membrane
Starts with:
H + gradient
Ends with:
32 – 34 ATP
ATP synthase facilitates

12. A Review of Cellular Respiration
Substrate level
phosphorylation

13. Fermentation If no O2 available Starts with: Ends with:
Glucose
Ends with:
Lactate or
CO2 and ethanol
Important products of this process:
2 pyruvate
2 ATP
2 NADH/NAD+
Makes yogurt, bread, alcoholic beverages