1. Cellular Respiration
Definition: Gradual release of energy by the break-down of food molecules in aerobic conditions
(= O2 present)

2. Energy in Food Where does the energy in food come from?
________________________
Light provides the energy to make molecules from…

3. Water +

4. 6CO2 +H2O  C6H12O6 +6O2 Occurs in grasses (and other plants) growing…
Which are eaten by cattle

5. And end up as food on our Plates
(Or vegetarians fill their plates with products made from green plants)

6. Question 1: Where does the energy in food come from?
Originates in sunlight  During photosynthesis light energy is converted into chemical energy in food molecules

7. How does energy get released from food?
In humans and many other vertebrates:
Food particles get broken down in the digestive system.
Chewing - teeth
Acids - stomach
Enzymes – small intestine

8. Role of the small intestine
Tiny projections called villi line the small intestine (increases surface area), which absorb digested food into the capillaries (small blood vessels).*

9. Food, Energy and Blood
Tiny food particles (glucose) is carried in the blood to each cell in the body.
Glucose enters each cell by the process of _______________________
Facilitated diffusion

10. Which organelle releases the energy from glucose?

11. What happens next? 6O2 + C6H12O6  6H2O + 6CO2 __________
The chemical reaction for cellular respiration:
6O2 + C6H12O6  6H2O + 6CO2 __________
High energy bonds low energy bonds
What is missing from the equation?
+ ENERGY

12. Cellular respiration Occurs in THREE STAGES
This allows the energy found in glucose to be released slowly rather than all at once.
The energy in glucose is found in chemical bonds.
When the bonds are broken, the energy is released and stored in molecules of ATP.

13. What is missing from the equation?
Stage 1 - Glycolysis
What happens? molecule of glucose is broken into 2 molecules of pyruvic acid. Bonds are broken and energy is released 
C6H12O  C3H4O3 + 4H+ _____________ (glucose) (pyruvic acid)
What is missing from the equation?
+ ENERGY

14. Glycolysis (Cont)
Glycolysis releases energy. The energy is stored in the chemical bonds of two molecules.
ADP (low energy) is converted to ATP (high energy) and
NAD+ (nicotinamide adenine dinucleotide) is converted into NADH (holds high energy electrons)

15. Glycolysis (cont)
The amount of energy produced from glycolysis is small but the process occurs quickly. Glycolysis nets 2 ATP molecules

16. Stage 2 – Krebs Cycle or Citric Acid Cycle
Hans Krebs (1900–1980)
Discovered the citric acid cycle, (aka) Krebs Cycle, in 1937.
Awarded the Nobel Prize for his discovery in 1953.

17. Krebs Cycle
Under aerobic conditions (O2 present), pyruvic acid, passes to the second stage of cellular respiration
What happens?
Pyruvic acid is broken down into CO2 (this is the CO2 we breathe out).
A small amount of energy is stored in ATP

18. Krebs Cycle (cont) Occurs in the mitochondrion of Eukaryotes
Occurs in the cytoplasm of Prokaryotes

19. Stage 3 – Electron Transport Chain
Electron transport chain – series of reactions
What happens? High energy NADH converts low energy ADP into ATP.
About 34 ATP molecules are formed from the Krebs cycle and electron transport chain combined.
Occurs in the mitochondrion of Eukaryotes
Occurs in the cytoplasm of Prokaryotes

20. Question!
Why are mitochondria called the
POWERHOUSE OF THE CELL?

21. Cell Respiration
Together ____________, the _______________and the _________________________________________ make up cell respiration.
Glycolysis
Krebs Cycle
Electron Transport Chain
In most cells, 1 molecule of glucose produces 36 molecules of ATP.
This amounts to 38% of the total energy stored in glucose. The rest of the energy is released as body heat.
Complete worksheet on Cell Respiration!

22. Aerobic vs. Anaerobic
Aerobic = O2 present
Anaerobic = No O2 present
Can organisms break down glucose and release its energy in anaerobic conditions?

23. YES!
Fermentation – an anaerobic cellular process by which glucose is broken down.
Fermentation - used by organisms that need small quantities of energy: unicellular organisms or simple multicellular organisms AND
Fermentation – used when energy is needed very quickly by muscle cells in animals.

24. Fermentation Two types of fermentation a) lactic acid fermentation
b) alcohol fermentation.

25. Lactic Acid Fermentation
Stage 1 - Glycolysis occurs.
Glucose  ____________________ 
Stage 2 – Lactic acid fermentation
Pyruvic acid broken down into lactic acid + NAD+
Lact = milk!
pyruvic acid

26. Lactic Acid Fermentation
The NAD+ restarts the glycolysis reaction which produces 2ATP molecules from 2ADP molecules.
Used by bacteria for the breakdown of glucose. Used to produce yogurt and cheeses.
Used by muscles when energy is needed quickly (a sprint), and O2 is in short supply.
Lactic acid build up causes a burning sensation resulting in “sore muscles”.  

27. Alcoholic Fermentation
Stage 1 - Glycolysis occurs.
Glucose  pyruvic acid
Stage 2 – Alcoholic fermentation - In yeast occurs.
Pyruvic acid broken into CO2 + ethanol alcohol.
When yeast is added to bread dough, the CO2 that’s produced is released and trapped in the dough—causes bread to rise.*
The alcohol produced in the reaction evaporates when the bread is baked!

28. Breaking down Glucose Cellular Respiration Fermentation Aerobic
3 Stages
Glycolysis
Krebs Cycle
Electron Transport Chain
Nets 36 ATP molecules
Anaerobic
Glycolysis followed by
Lactic Acid Fermentation OR
Alcoholic Fermentation
Nets 2 ATP molecules