1. Chapter 9 Cellular Respiration
How Cells Harvest Chemical Energy

2. All life activities need energy
a. Maintain homeostasis; do life functions
breathing, blood circulation
active transport, biosynthesis
regulate temperature, etc.
b. Physical and mental activity
c. Cells use energy in ATP molecules

3. Food energy is measured in calories
Food labels:
Calorie (Kcal) = 1000 calories
calorie = energy needed to raise the temperature of one mL water 1 degree Celsius

5. Breathing supplies oxygen to cells
1. Breathing brings oxygen into the body
2. Oxygen in lungs diffuses into blood
6. Blood carries CO2 back to lungs - exhaled
3. Blood delivers oxygen to all body cells
5. CO2 diffuses out of cells into blood
4. Oxygen diffuses into body cells, is used in cell respiration.

6. Gas exchange is by diffusion
In the lungs:
Oxygen from air in air sacs
- into blood in capillaries
- carried to all body cells
Carbon dioxide from blood
- into air in air sacs (alveoli)
- removed from body
In body cells: oxygen diffuses in; CO2 diffuses out

7. Overview of Cellular Respiration
Breaks down glucose in many small steps
a biochemical pathway
Energy released is stored in molecules of ATP
Each ATP has enough energy for one cell task
One glucose molecule yields ATP

8. Mitochondria – “power house”
Compartments
- for different stages
Matrix
Space enclosed by inner membrane
Inner membrane
Deeply folded for more surface area
Many reactions at the same time
Cristae - folds in membrane
Intermembrane space
Between inner and outer membrane

9. Electron Acceptors NAD and FAD Accept hydrogen ions and electrons
from glucose as it breaks down
Transfer them to another molecule
in Electron Transport Chain
makes ATP

10. Stages of Cell Respiration
Glycolysis
Splits glucose in half
In cytoplasm
Kreb’s Cycle
In mitochondria
Finishes glucose breakdown
3. Electron Transport Chain
Generates the most ATP

11. Oxygen and Energy
Aerobic respiration harvests the most ATP from glucose
Aerobic Anaerobic
Breaks down glucose completely Glucose only partly broken down
Yields maximum amount of ATP Yields only 2 ATP/ glucose molecule
Most organisms Only a few microorganisms
3 stages of breakdown stages of breakdown
glycolysis glycolysis
Kreb’s cycle fermentation
Electron transport Chain

12. Glycolysis 1st stage in cell respiration
Glycolysis = “sugar splits” Glucose  two smaller molecules - small amount of energy released USE 2 ATP to start a. Two ATP are added to glucose b. Glucose splits  PGAL (3-C) c. Some hydrogens go to NAD d. Several more reactions

13. Final Products of Glycolysis
Glucose splits a. forms 2 molecules of pyruvic acid (3-C) (further breakdown in aerobic) b. 2 NADH (these will make ATP later) c. net 2 ATP (made 4 but used 2 to start)

14. Advantages of glycolysis
All life forms do glycolysis
Need no oxygen or special organelles
Probably evolved very early in history of life
Can meet energy needs of some simple organisms

15. Pyruvic Acid Breakdown
NOT a separate stage
PREPARES pyruvic acid for Kreb’s cycle
3) 2-carbon acetyl
attaches to Coenzyme A
Hydrogens removed
 NADH
Carbon removed
 CO2
4) Acetyl-Co A begins Kreb’s cycle

16. Sir Hans Krebs 1900-1981 German chemist
Described the cycle of reactions that make energy in cells
1930s
Received Nobel in 1953
“Krebs Cycle” or “Citric Acid Cycle”

17. Kreb’s citric acid cycle Stage 2 in aerobic respiration
Completes breakdown of glucose to CO2
- generates many molecules of NADH and FADH2

18. 2) starting molecule – acetyl CoA
1) Pyruvic acid: broken down  acetyl (2-C)
- joins to coenzyme A
3) 4-C compound in matrix + acetyl
 6 C citric acid
7) 4-C compound recycled
6). Hydrogens removed
to carriers NAD, FAD
4) two carbons removed as CO2
5) one ATP forms

19. Final Products of Kreb’s Cycle
2 ATP/glucose molecule
2. Many molecules of NADH and FADH2
These will yield energy in stage 3
3. Last carbons in glucose form CO2
- diffuse out of cell

20. Electron Transport Chain Stage 3 in aerobic respiration
What is it?
Chemiosmosis same as in photosynthesis
Series of proteins in inner membrane (cristae)
Pass electrons along chain
Electron energy makes ATP
Only proceeds if oxygen is available to take
electrons at end of chain
O H e-  H2O

21. 6. Final electron acceptor is oxygen
O + H+ + e-  H2O 1
Starting molecules NADH, FADH2
release H+ and electrons 5
ADP + P  ATP 2
Electrons pass from one protein in transport chain to next 4
H+ ions diffuse through ATP synthase
(chemiosmosis) 3
Electron energy pumps H+ across membrane
- make H+ gradient

22. Energy Yield In Aerobic Resp.
Total Energy yield/ glucose:
Glycolysis – 2 ATP
Krebs – 2 ATP
ETC ATP
Total/glucose = ATP

23. Summary of Aerobic Respiration
PATHWAYS
REACTANTS
PRODUCTS
# ATP
LOCATION
GLYCOLYSIS
Glucose + O2
2 pyruvic acid
2 NADH   2
cytoplasm
KREBS CYCLE
acetyl CoA
2 CO2
8 NADH,FADH2 2 
matrix 
ELECTRON TRANSPORT
NADH, FADH2
 H2O
 cristae
Total ATP
34-36

24. Fermentation is anaerobic respiration
Fermentation is anaerobic respiration
Needs no oxygen
Makes no additional ATP after glycolysis
Hydrogens on NADH return to pyruvic acid
NAD can be reused
Pyruvate is rearranged into a final product

25. Lactic Acid Fermentation
Pyruvic acid (3-C)  lactic acid (3-C)
Anaerobic bacteria -make lactic (and other) acids
Commercial uses: cheese, yogurt, soy products, sauerkraut, vinegars
Muscle cells – can do fermentation temporarily
lactic acids builds up  Muscles fatigue, cramp
“oxygen debt”
With fresh oxygen: Lactic acid  converted back to pyruvate  Kreb’s  finish aerobic

26. Alcohol Fermentation Some yeasts Baking, brewing beer and wine
pyruvic acid (3-C)  ethyl alcohol (2-C) + CO2
Baking, brewing beer and wine
CO2 gas makes bread dough rise, bubbles in beer and champagne
NAD returned for reuse
No additional ATP made

27. Comparing Photosynthesis and Respiration
Photosynthesis – makes food
Light energy  chemical energy
6 H2O + 6 CO2  C6 H12 O O2
Respiration – breaks down food for cell energy
C6 H12 O O2  6 H2O + 6 CO2
Energy in food  energy in ATP
All living things
Aerobic or anaerobic
Energy flow is one-way
Nutrient chemicals recycle