1. Chapter 9: Cellular Respiration
9-1 Chemical Pathways

2. Chemical Energy and Food
Cellular respiration happens slowly and in many steps.
If all the energy was release in one step Most would be lost as light and heat!
Cellular respiration breaks down glucose molecules and banks their energy in ATP

3. Chemical Energy and Food
PHOTOSYNTHESIS
___________ + _________ + ___________ →_______________ + __________
6 CO2
6 H2O
C6H12O6
6O2
CELLULAR RESPIRATION
C6H12O6
6 CO2
_____________ + _________ →________ + __________ + __________
6O2
6 H2O
The two equations are exact opposites!

4. Chemical Energy and Food
Amount of heat it takes to raise 1 gram of water 1o Celsius = calorie
Unit for measuring energy in food = Calorie
1 Calorie = 1,000 calories

5. Overview of Cellular Respiration
Occurs in three main stages
Stage 1: Glycolysis
Occurs in the cytoplasm
Breaks down glucose into pyruvate, producing a small amount of ATP
Stage 2: The citric acid cycle (Krebs cycle)
Takes place in the mitochondria
Completes breakdown of glucose, produces a small amount of ATP
Provides third stage of cell respiration with electrons
Stage 1
Stage 2
Stage 3

6. Overview of Cellular Respiration
Stage 3: Oxidative phosphorylation (ETC)
Occurs in the mitochondria
Uses the energy released by “falling” electrons to pump H+ across a membrane
Harnesses the energy of the H+ gradient through chemiosmosis, producing ATP
Stage 3

7. Understanding Oxidation and Reduction
Oxidation is the loss of electrons; electrons are removed from hydrogen atoms contained in glucose.
Reduction is the gain of electrons; oxygen atoms accept hydrogen and electrons forming water H2O.
Remember OIL RIG (oxidation is loss, reduction is gain)

8. Electron Carriers (enzymes) Involved
NAD+ (Nicotinamide adenine dinucleotide)
Accepts H+ to become NADH
FAD (Flavin adenine dinucleotide)
Accepts 2H+ to become FADH2

9. Overview of Cellular Respiration
NADH
FADH2
GLYCOLYSIS
Glucose
Pyruvate
CITRIC ACID CYCLE
OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis)
Substrate-level phosphorylation
Oxidative phosphorylation
Mitochondrion
and
High-energy electrons carried by NADH
ATP
CO2
Cytoplasm
Stage 1
Stage 3
Stage 2
Krebs

10. (Glykos = sweet, Lysis = split apart)
9.2 Glycolysis
(Glykos = sweet, Lysis = split apart)
The first step in cellular respiration = Glycolysis
Happens in the CYTOPLASM outside the mitochondria
Does not require oxygen, BUT it needs some energy to get it started.
What molecule is going to supply the energy?
ATP

11. ____________________ + _______________
Glycolysis
________ ↓
___________ → → _____________
____________________ + _______________
GLUCOSE
2 PYRUVIC ACID
ATP ATP ATP ATP
NADH NADH
PUT IN 2 ATP and GET BACK 4 ATP
Net gain of 2 ATP and 2 NADH

12. Glycolysis Produces pyruvic acid (pyruvate – a 3 carbon compound)
Cell needs to invest some energy to get a higher return (2 ATP gained)
Occurs quickly, in miliseconds to respond to increased energy demand

13. 9-2 The Krebs Cycle and Electron Transport

14. Mitochondria Structure
Has a double membrane, with an intermembrane space between the two layers.
Cristae are folds of the inner membrane
The matrix is the innermost compartment, which is filled with a gel-like fluid.
Krebs Cycle occurs in the matrix of the mitochondria.

15. The Krebs Cycle Pyruvic acid enters the mitochondria matrix
Pyruvic acid is converted into an intermediate 2 carbon molecule called Acetyl-CoA before entering the Krebs Cycle.
The Krebs cycle breaks down carbon compounds into carbon dioxide (waste), ATP, NADH, and FADH2

16. The Krebs Cycle Carbon dioxide is lost to the atmosphere as waste
ATP can be used directly to supply energy for the cell
High energy electron carriers move into the ELECTRON TRANSPORT CHAIN

17. Electron Transport Chain
Enzymes (protein complexes) for the electron transport chain are located on the inner mitochondrial membrane. Several complexes are called cytochromes.
Virtual Cell ETC Animation

18. Electron Transport Chain
Electrons from NADH and FADH2 travel down the electron transport chain, between protein complexes to oxygen (final electron acceptor), which picks up H+ to form water
Energy released by the redox reactions is used to pump H+ into the space between the mitochondrial membranes
H2O
NAD+
NADH
ATP H+
Controlled release of energy for synthesis of ATP
Electron transport chain 2 O2
2e + 1

19. Chemiosmosis
In chemiosmosis, the H+ diffuses back through the inner membrane through ATP synthase complexes. Driving the synthesis of ATP
Intermembrane space
Inner mitochondrial membrane
Mitochondrial matrix
Protein complex
Electron flow
Electron carrier
NADH
NAD+
FADH2
FAD
H2O
ATP
ADP
ATP synthase H+ + P O2
Electron Transport Chain
Chemiosmosis .
OXIDATIVE PHOSPHORYLATION
+ 2 1 2

21. Fermentation Pyruvic acid moves to the next step
If there is no oxygen = anaerobic
If there is oxygen = aerobic

22. Fermentation
Fermentation – process by which cells release energy in the absence of oxygen
Two types of fermentation:
Alcoholic Fermentation
Lactic Acid Fermentation

23. Alcoholic Fermentation
_______ +_____ →__________ + ______ + _____
PYRUVIC ACID
ALCOHOL
CO2
NAD+
Happens when yeast makes bread dough rise, CO2 bubbles make air spaces in bread.
(Alcohol evaporates during cooking)
Happens when:
Yeast make beer
Bacteria make wine

24. Lactic Acid Fermentation
_______ +_____ →______________ + ________
PYRUVIC ACID
LACTIC ACID
NAD+
Happens in muscles during exercise when body can’t get oxygen to tissues fast enough.
Lactic acid builds up in muscles causing soreness.
Bacteria use lactic acid fermentation to make:
yogurt, cheese, sour cream, pickles, sauerkraut, kimchi

26. The Totals Cellular Respiration (aerobic: with oxygen)
1 glucose → 36 ATP
Fermentation (anaerobic: without oxygen)
1 glucose → 2 ATP

27. Respiration Questions
List the reactants and products of respiration
List the three steps (stages) involved in respiration
Name two electron carriers involved
What step produces the most ATP

28. Respiration Questions
In your group:
See if you can write the chemical equation for respiration (inputs and outputs)
What is the organelle in cells that is “releasing” energy during respiration?
What primary molecule is energy being “released” from?
How is the sun indirectly involved in respiration?

29. Fermentation Questions
List two types of fermentation
List the reactants for both types of fermentation
List the products for fermentation used to brew beer
List the products for fermentation used to make yogurt
What important molecule cycles back from fermentation to keep glycolysis going?
What process starts fermentation?

30. Krebs Cycle 1.___________ 2.___________ 3.________ 7.________
4.________
6.________
5.________

31. Electron Transport Chain (ETC)
Intermembrane space
Inner mitochondrial membrane
Mitochondrial matrix
Protein complex
Electron flow
Electron carrier
NADH
NAD+
FADH2
FAD
H2O
ATP
ADP
ATP synthase H+ + P O2
Electron Transport Chain
Chemiosmosis .
OXIDATIVE PHOSPHORYLATION
+ 2 1 2