1. Chapter 5: Cellular Respiration:
Releasing Chemical Energy

2. 5.1 Metabolism & Cell Respiration
Metabolism involves synthesis (consumes energy) & decomposition (releases energy).
ATP = the major energy carrier in metabolism
ATP is made during decomposition & is used during biosynthesis (links the 2 processes).

3. 5.1 Metabolism & Cell Respiration

4. 5.1 Metabolism & Cell Respiration
Cell Respiration – a decomposition pathway; a series of reactions that release energy as they break down sugars & other substances into CO2 & H2O
Each step is catalyzed by an enzyme.
Releases the energy by oxidizing the sugars/other substances.
Some of that energy is conserved as ATP, which is used to power life processes

5. 5.1 Metabolism & Cell Respiration
Aerobic respiration – occurs in the presence of OXYGEN; O2 is the oxidizing agent that receives the electrons
Anaerobic respiration – occurs WITHOUT OXYGEN; substrate is only partly decomposed, releasing less energy with a Nitrogen or Sulfur compound replacing the oxygen

6. Aerobic vs. Anaerobic Respiration

7. 5.1 Metabolism & Cell Respiration
Raw materials for respiration = sugars, fats, & proteins; we’ll concentrate on GLUCOSE primarily
Glucose Production
Produced when animals digest carbs or glycogen; gets transported in blood
Produced when plants break down sucrose & starch; main transport carb = sucrose

8. 5.1 Metabolism & Cell Respiration
Summarized Reaction:
1 C6H12O6 + 6 O2  6 CO2 + 6 H2O + Energy
Oxidizing 1 glucose – releases more energy than a single reactions needs, so glucose is NOT useful as a direct source of energy
To release all the energy in glucose at once would waste most of the energy, so it’s done in a series of small steps

9. 5.1 Metabolism & Cell Respiration
Car Analogy
When all energy in glucose When the energy is released
released at once slowly in a controlled manner

10. 5.2 Stages of Aerobic Respiration
Three Major Stages:
Glycolysis – Enzymes split glucose into two 3-carbon molecules – called pyruvate (uses some ATP & releases a small amount ATP)
Krebs cycle – carbon molecules are completely oxidized to CO2 (releases a few more ATP)
Electron Transport System – regenerates a supply of NAD+, releasing p+& e- , which are transferred to oxygen, forming water

11. 5.2 Stages of Aerobic Respiration
When something is oxidized (lose e-), something else has to be reduced (gain
e-).
Glucose is oxidized; NAD+ (Nicotinamide adenine dinucleotide) is reduced to NADH – similar to NADP+  NADPH in photosynthesis
NAD+  NADH Occurs in the Glycolysis & Krebs cycle

12. 5.2 Stages of Aerobic Respiration
Another molecule that gets reduced:
FAD (flavin adenine dinucleotide)  FADH2
Happens in Krebs Cycle
Hydrogen carriers in cells: NADH, NADPH (only photosynthesis), & FADH2
At end of ETS: NADH & FADH2 reduce oxygen to form water (releasing energy to form ATP).

13. 5.2 Stages of Aerobic Respiration
Most ATP is synthesized in the 3rd step: the Electron Transport System
Oxygen is the final e- acceptor, so stages 2 and 3 CANNOT proceed without oxygen – they are considered aerobic.

14. 5.2 Stages of Aerobic Respiration

15. Your assignment….
I have photocopied section 5.3 from your books, but have left out the pictures of the 1st step of respiration: Glycolysis
You are going to read/highlight the descriptions of the major steps of this stage and then try to draw what is occuring…..
For Example:

16. If we did this for the Calvin cycle last unit, the book says, “At a, the beginning of the cycle, a molecule of carbon dioxide combines with the 5 carbon sugar-phosphate RuBP….This produces an unstable 6 carbon molecule that….”