1. 9.1 Cellular Respiration: An Overview
Lesson Overview
9.1 Cellular Respiration: An Overview

2. Chemical Energy and Food
Energy flows into an ecosystem & exits as heat. The chemical elements essential to life are recycled!!
Light energy
CO2 + H2O
Organic molecules + O2
Cellular Respiration in mitochondria
ATP
Heat Energy

3. Chemical Energy in Food
Food Provides:
Source of raw materials used to make new molecules
Source of energy
calorie – the amount of energy needed to raise the temperature of one gram of water one degree Celsius calories = 1 kilocalorie, or Calorie.
Cells don’t burn glucose - gradually release energy from it.
Cells break down food molecules gradually and use energy stored in chemical bonds to produce compounds such as ATP that power the activities of the cell.

4. 6O2 + C6H12O6 6CO2 + 6H2O + ENERGY (ATP)
Cellular Respiration
Overview
Cellular Respiration – process that releases energy from food in the presence of oxygen.
Contains 3 Pathways:
Glycolysis
Krebs cycle
Electron transport
6O2 + C6H12O CO2 + 6H2O + ENERGY (ATP)

5. Cellular Respiration Overview
If cellular respiration took place in one step, all the energy would be released at once and most lost as heat.
Each of the three stages of cellular respiration captures some of the chemical energy available in food molecules and uses it to produce ATP or energy.

8. Stages of Cellular Respiration
Step 1: Glycolysis
-Occurs in the cytoplasm.
- 1 molecule of glucose is broken in half, producing 2molecules of pyruvic acid.
- uses 2 stored ATP molecules as energy
- 4 ATP molecules are made during glycolysis, so a total of 2 ATP molecules are released by glycolysis as energy
net gain: 2 ATP
NAD+ (electron carrier) is converted to NADH.
This is only 2% of the total chemical energy in glucose.

9. Glycolysis
Glycolysis happens quickly & can produce 1000’s of ATPs in milliseconds.
Glycolsis does not require oxygen!

10. Out 2 pyruvate; 2(3-C) 2NADH a net of 2 ATP
Summary Of Glycolysis
Out 2 pyruvate; (3-C) 2NADH a net of 2 ATP In
Glucose (6-C)
2 ATP

11. Oxidative Respiration
To get the rest of the energy from the food molecules, the cell uses oxygen.
Aerobic – requires oxygen.
The energy-releasing pathways require oxygen, and that is the reason we need to breathe, to respire.
Respiration - process that involves oxygen and breaks down food molecules to release energy.
rap

12. Step 2: Kreb’s Cycle
Takes place in: matrix (innermost compartment)of mitochondria.
Also called the Citric acid cycle.
Carbon contained in pyruvic acid is broken down into carbon dioxide.
This CO2 is considered a waste product and is released from the cell.
Two high energy electron carriers are also generated by the Krebs cycle:
NADH
FADH2
krebs

13. Step 2: Kreb’s Cycle Citric acid production:
1 carbon from pyruvic acid becomes part of CO2 & is released.
2 other carbons from pyruvic acid rearrange to form acetyl-CoA.
Acetyl-CoA combines with a 4C molecule to form citric acid.
Energy extraction:
Citric acid broken- more CO2 release and production of electrons.
Electrons transferred to electron carriers NAD+ and FAD creating NADH and FADH2.

14. Kreb’s Cycle
NADH and FADH2 go on to make huge amounts of ATP (via electron transport) in the presence of oxygen, and the CO2 is eventually released when you exhale.

15. Kreb’s Cycle: energy generated
Each glucose = 2 pyruvate
Each glucose= 2 complete turns of Kreb’s cycle = 2 ATP

16. Summary of Kreb’s Cycle
Out
CO2 (as waste)
NADH
Acetyl-CoA In
Pyruvate
NAD
CoA

17. Step 3: ETC
Electron transport occurs in the intermembrane of the mitochondria.
High energy electrons are passed from carriers in the Krebs cycle (NADH, FADH2) to ETC.
ETC uses these high energy electrons to convert ADP into ATP or energy.

18. ETC
As electrons pass down chain, H+ ions are pumped into inter-mitochondrial space making a charge gradient.
Gradient provides energy for ATP synthase to add the P group.
At the end of the chain, an enzyme combines the electrons with H+ and oxygen to form water, a by-product of electron
** Final e- acceptor
is O2

19. ETC
O2 is essential for removing low energy e-, H+ ions, & wastes of cellular respiration
Every time a pair of high energy e- move down ETC, energy is used to move H+ ions across the membrane.
Cellular respiration:
Total ATP= 36
32 ATP

20. Total Energy
In the presence of oxygen, the complete breakdown of glucose through cellular respiration results in the production of 36 ATP molecules.
This represents about 36 percent of the total energy of glucose. The remaining 64 percent is released as heat.

21. Comparing Photosynthesis and Cellular Respiration
Photosynthesis & cellular respiration- opposite processes.
Photosynthesis “deposits” energy, and cellular respiration “withdraws” energy.
The reactants of cellular respiration are the products of photosynthesis and vice versa.

22. Comparing Photosynthesis and Cellular Respiration
The release of energy by cellular respiration takes place in plants, animals, fungi, protists, and most bacteria.
Energy capture by photosynthesis occurs only in plants, algae, and some bacteria
glycolysis jam

23. Energy & Exercise
Aerobic cellular respiration produces 36 total ATP molecules from each glucose molecule (37% efficient).
Remainder of energy from glucose is released as heat (body feels warm after exercise).
Eating food: Complex carbs broken down to simple sugars that are converted to glucose.
Lipids and proteins broken down to molecules that enter glycolysis or Krebs cycle.
Breathing and respiration:
Remember- final electron acceptor for electrons produced in respiration is oxygen.
Without oxygen, all ATP synthesis in mitochondria stops and body tries to make ATP by glycolysis alone (not sufficient for most cells).