1. CHAPTER 6 How Cells Harvest Chemical Energy

2. How is a Marathoner Different from a Sprinter?
Long-distance runners have many slow fibers in their muscles
Slow fibers break down glucose for ATP production aerobically (using oxygen)
These muscle cells can sustain repeated, long contractions

3. Sprinters have more fast muscle fibers
Fast fibers make ATP without oxygen— anaerobically
They can contract quickly and supply energy for short bursts of intense activity

4. The dark meat of a cooked turkey is an example of slow fiber muscle
Leg muscles support sustained activity
The white meat consists of fast fibers
Wing muscles allow for quick bursts of flight

5. Without Oxygen (Anaerobic)
Fermentation occurs when cells do not have oxygen.
The electron transport chain is stopped.
Glycolysis is the only ATP producing mechanism.
Lactic Acid and Alcoholic fermentation.

6. INTRODUCTION TO CELLULAR RESPIRATION
Nearly all the cells in our body break down sugars for ATP production
Most cells of most organisms harvest energy aerobically, like slow muscle fibers
The aerobic harvesting of energy from sugar is called cellular respiration
Cellular respiration yields CO2, H2O, and a large amount of ATP

7. 6.1 Breathing supplies oxygen to our cells and removes carbon dioxide
Breathing and cellular respiration are closely related
BREATHING O2
CO2
Lungs
CO2
Bloodstream O2
Muscle cells carrying out
CELLULAR RESPIRATION
Sugar + O2  ATP + CO2 + H2O
Figure 6.1

8. 6.2 Cellular respiration banks energy in ATP molecules
Cellular respiration breaks down glucose molecules and banks their energy in ATP
The process uses O2 and releases CO2 and H2O
Glucose
Oxygen gas
Carbon dioxide
Water
Energy
Figure 6.2A

9. The efficiency of cellular respiration (and comparison with an auto engine)
Energy released from glucose banked in ATP
Energy released from glucose (as heat and light)
Gasoline energy converted to movement
100%
About 40%
----- Meeting Notes (11/15/12 15:18) -----
Human: banks about 40% of glucose nrg in ATP
Cars: convert about 25% of nrg in gas into KE nrg
25%
Burning glucose in an experiment
“Burning” glucose in cellular respiration
Burning gasoline in an auto engine
Figure 6.2B

10. ATP powers almost all cell and body activities
6.3 Connection: The human body uses energy from ATP for all its activities
ATP powers almost all cell and body activities
Table 6.3

11. BASIC MECHANISMS OF ENERGY RELEASE AND STORAGE
6.4 Cells tap energy from electrons transferred from organic fuels to oxygen
Glucose gives up energy as it is oxidized
Loss of hydrogen atoms
Energy
Glucose
Gain of hydrogen atoms
Figure 6.4

12. Dehydrogenase and NAD+
6.5 Hydrogen carriers such as NAD+ shuttle electrons in redox reactions
Enzymes remove electrons from glucose molecules and transfer them to a coenzyme
OXIDATION
Dehydrogenase and NAD+
----- Meeting Notes (11/15/12 15:18) -----
Oxidation: loss of electrons
Reduction: addition of electrons
NAD: made by the cell from the vitamin niacin
REDUCTION
Figure 6.5

13. 6.6 Redox reactions release energy when electrons “fall” from a hydrogen carrier to oxygen
NADH delivers electrons to a series of electron carriers in an electron transport chain
As electrons move from carrier to carrier, their energy is released in small quantities
Energy released and now available for making ATP
ELECTRON CARRIERS of the electron transport chain
Electron flow
Figure 6.6

14. Energy released as heat and light
In an explosion, 02 is reduced in one step
Energy released as heat and light
Figure 6.6B

15. 6.7 Two mechanisms generate ATP
Cells use the energy released by “falling” electrons to pump H+ ions across a membrane
The energy of the gradient is harnessed to make ATP by the process of chemiosmosis
High H+ concentration
ATP synthase uses gradient energy to make ATP
Membrane
Electron transport chain
ATP synthase
Chem ee osmosis
Energy from
Low H+ concentration
Figure 6.7A

16. Chemiosmosis
NAD+ H+ :
NADH

17. Chemiosmosis : H+

18. Chemiosmosis H+
NAD+ H+ :
NADH

19. H+ H+ H+ H+
Chemiosmosis H+ H+ H+ H+ : H+

20. H+ H+ H+ H+
Chemiosmosis H+ H+ H+ H+ :
ATP
ADP P

21. H+ H+
Chemiosmosis H+ H+ H+ H+ : O
ATP H+ H+

22. H+ H+
Chemiosmosis H+ H+ H+ H+
H2O
ATP

23. Organic molecule (substrate) New organic molecule (product)
ATP can also be made by transferring phosphate groups from organic molecules to ADP
Enzyme
Adenosine
Organic molecule (substrate)
This process is called substrate-level phosphorylation
Adenosine
New organic molecule (product)
Figure 6.7B

24. 6.8 Overview: Respiration occurs in three main stages
STAGES OF CELLULAR RESPIRATION AND FERMENTATION
6.8 Overview: Respiration occurs in three main stages
Cellular respiration oxidizes sugar and produces ATP in three main stages
Glycolysis occurs in the cytoplasm
The Krebs cycle and the electron transport chain occur in the mitochondria

25. An overview of cellular respiration
High-energy electrons carried by NADH
GLYCOLYSIS
ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS
KREBS CYCLE
Glucose
Pyruvic acid
Cytoplasmic fluid
Mitochondrion 2 2 32
Figure 6.8

26. 6.9 Glycolysis harvests chemical energy by oxidizing glucose to pyruvic acid
Figure 6.9A

27. PREPARATORY PHASE (energy investment)
Steps – A fuel molecule is energized, using ATP.
Glucose 1 3
Details of glycolysis
Step 1
Glucose-6-phosphate 2
Fructose-6-phosphate 3
Fructose-1,6-diphosphate
Step A six-carbon intermediate splits into two three-carbon intermediates. 4 4
Glyceraldehyde-3-phosphate (G3P)
ENERGY PAYOFF PHASE 5
Step A redox reaction generates NADH. 5
1,3-Diphosphoglyceric acid (2 molecules) 6
Steps – ATP and pyruvic acid are produced.
3-Phosphoglyceric acid (2 molecules) 6 9 7
2-Phosphoglyceric acid (2 molecules) 8
2-Phosphoglyceric acid (2 molecules) 9
Pyruvic acid
Figure 6.9B
(2 molecules per glucose molecule)

28. 6.10 Pyruvic acid is chemically groomed for the Krebs cycle
Each pyruvic acid molecule is broken down to form CO2 and a two-carbon acetyl group, which enters the Krebs cycle
Pyruvic acid
Acetyl CoA (acetyl coenzyme A)
CO2
Figure 6.10

29. 6.11 The Krebs cycle completes the oxidation of organic fuel, generating many NADH and FADH2 molecules
Acetyl CoA
The Krebs cycle is a series of reactions in which enzymes strip away electrons and H+ from each acetyl group 2
KREBS CYCLE
CO2
Figure 6.11A

30. Alpha-ketoglutaric acid
2 carbons enter cycle
Oxaloacetic acid 1
Citric acid
CO2 leaves cycle 5
KREBS CYCLE 2
Malic acid 4
Alpha-ketoglutaric acid 3
CO2 leaves cycle
Succinic acid
Step
Acetyl CoA stokes the furnace
Steps and
NADH, ATP, and CO2 are generated during redox reactions.
Steps and
Redox reactions generate FADH2 and NADH. 1 2 3 4 5
Figure 6.11B

31. 6.12 Chemiosmosis powers most ATP production
The electrons from NADH and FADH2 travel down the electron transport chain to oxygen
Energy released by the electrons is used to pump H+ into the space between the mitochondrial membranes
In chemiosmosis, the H+ ions diffuse back through the inner membrane through ATP synthase complexes, which capture the energy to make ATP

32. ELECTRON TRANSPORT CHAIN
Chemiosmosis in the mitochondrion
Protein complex
Intermembrane space
Electron carrier
Inner mitochondrial membrane
Electron flow
Mitochondrial matrix
ELECTRON TRANSPORT CHAIN
ATP SYNTHASE
Figure 6.12

33. Cyanide, carbon monoxide ELECTRON TRANSPORT CHAIN
6.13 Connection: Certain poisons interrupt critical events in cellular respiration
Rotenone
Cyanide, carbon monoxide
Oligomycin
----- Meeting Notes (11/16/12 07:45) -----
Read pp101
ELECTRON TRANSPORT CHAIN
ATP SYNTHASE
Figure 6.13

34. 6.14 Review: Each molecule of glucose yields many molecules of ATP
For each glucose molecule that enters cellular respiration, chemiosmosis produces up to 38 ATP molecules
Cytoplasmic fluid
Mitochondrion
Electron shuttle across membranes
KREBS CYCLE
GLYCOLYSIS
2 Acetyl CoA
2 Pyruvic acid
KREBS CYCLE
ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS
Glucose
32 ATP
by substrate-level phosphorylation
used for shuttling electrons from NADH made in glycolysis
by substrate-level phosphorylation
by chemiosmotic phosphorylation
Maximum per glucose:
36 ATP
Figure 6.14

35. 6.15 Fermentation is an anaerobic alternative to aerobic respiration
Under anaerobic conditions, many kinds of cells can use glycolysis alone to produce small amounts of ATP
But a cell must have a way of replenishing NAD+

36. In alcoholic fermentation, pyruvic acid is converted to CO2 and ethanol
This recycles NAD+ to keep glycolysis working
released
GLYCOLYSIS
2 Pyruvic acid
2 Ethanol
Glucose
Figure 6.15A
Figure 6.15C

37. In lactic acid fermentation, pyruvic acid is converted to lactic acid
As in alcoholic fermentation, NAD+ is recycled
Lactic acid fermentation is used to make cheese and yogurt
GLYCOLYSIS
2 Pyruvic acid
2 Lactic acid
Glucose
Figure 6.15B

38. Cellular Respiration
Cellular Respiration – releases energy from the bonds of organic molecules
C6H12O6 + O2  H2O + CO2 + Energy
3 Stages
Glycolysis
Kreb’s (Citric Acid Cycle)
Electron Transport Chain

39. Glycolysis
Glycolysis – sugar breakdown
Glucose is split into 2 pyruvate molecules
2 net ATP are produced (-2 +4 = 2)
2 NADH are also produced

40. Kreb’s Cycle
Oxidation of Acetyl CoA
Each glucose (2 pyruvates) yields
2 ATP
6 NADH
2 FADH2

41. Electron Transport Chain and Chemiosmosis
The electron transport chain is the part of respiration that produces the most ATP and requires oxygen.
The electrons that are carried in NADH and FADH2 molecules are used to produce ATP through Chemiosmosis.

42. Net Yield of Cellular Respiration
Glycolysis – 2 ATP
Krebs Cycle – 2 ATP
Electron Transport – 32 ATP
Each glucose yields 36 ATP

43. Glycolysis (fermentation); ETC
Watch utube video #34(ATP& respiration cc),
**see iPad: photo**