1. Cellular Respiration and Fermentation9
Cellular Respiration and Fermentation

2. Life Is Work Living cells require energy from outside sources
Some animals, such as the giraffe, obtain energy by eating plants, and some animals feed on other organisms that eat plants

3. Energy flows into an ecosystem as sunlight and leaves as heat
Photosynthesis generates O2 and organic molecules, which are used in cellular respiration
Cells use chemical energy stored in organic molecules to generate ATP, which powers work

4. Light energy ECOSYSTEM Photosynthesis in chloroplasts Organic
Figure 9.2
Light
energy
ECOSYSTEM
Photosynthesis
in chloroplasts
Organic
molecules
CO2 +
H2O + O2
Cellular respiration
in mitochondria
Figure 9.2 Energy flow and chemical recycling in ecosystems
ATP powers
most cellular work
ATP
Heat
energy

5. Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration
Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP + heat)

6. The Stages of Cellular Respiration: A Preview
Harvesting of energy from glucose has three stages
Glycolysis (breaks down glucose into two molecules of pyruvate) occurs in cytoplasm
The citric acid cycle (completes the breakdown of glucose)occurs in mitochondria
Oxidative phosphorylation (accounts for most of the ATP synthesis) occurs in mitochondria
Accounts for almost 90% of the ATP generated

7. Electrons via NADH Electrons via NADH and FADH2 GLYCOLYSIS PYRUVATE
Figure 9.6-3
Electrons
via NADH
Electrons
via NADH
and FADH2
GLYCOLYSIS
PYRUVATE
OXIDATION
OXIDATIVE
PHOSPHORYLATION
CITRIC
ACID
CYCLE
Glucose
Pyruvate
Acetyl CoA
(Electron transport
and chemiosmosis)
CYTOSOL
MITOCHONDRION
Figure An overview of cellular respiration (step 3)
ATP
ATP
ATP
Substrate-level
Substrate-level
Oxidative

8. Concept 9.2: Glycolysis harvests chemical energy by oxidizing glucose to pyruvate
Glycolysis (“sugar splitting”) breaks down glucose into two molecules of pyruvate
Glycolysis occurs in the cytoplasm
Glycolysis occurs whether or not O2 is present
In the presence of O2, pyruvate enters the mitochondrion (in eukaryotic cells) where the oxidation of glucose is completed

9. Citric Acid/ Krebs cycle
The citric acid cycle, also called the Krebs cycle, completes the break down of pyruvate to CO2
CO2 is released

10. Figure 9.11
PYRUVATE OXIDATION
Pyruvate (from glycolysis,
2 molecules per glucose)
The citric acid cycle has eight steps, each catalyzed by a specific enzyme
CO2
NAD+
CoA
NADH
+ H+
Acetyl CoA
CoA
CoA
CITRIC
ACID
CYCLE
Figure 9.11 An overview of pyruvate oxidation and the citric acid cycle 2
CO2
FADH2 3
NAD+
FAD
CoA 3
NADH +
3 H+
ADP + P i
ATP

11. CITRIC ACID CYCLE Acetyl CoA 1 Oxaloacetate 8 2 Malate Citrate
Figure
Acetyl CoA
CoA-SH
NADH
H2O
+ H+ 1
NAD+
Oxaloacetate 8 2
Malate
Citrate
Isocitrate
CITRIC
ACID
CYCLE
NAD+
NADH 3 7
+ H+
H2O
CO2
Fumarate
CoA-SH
-Ketoglutarate
Figure A closer look at the citric acid cycle (step 8) 4 6
CoA-SH
FADH2 5
CO2
NAD+
FAD
Succinate
NADH P i
+ H+
GTP
GDP
Succinyl
CoA
ADP
ATP

12. Concept 9.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis
Oxygen is converted to water
32 ATP molecules are produced.

13. CITRIC ACID CYCLE OXIDATIVE PHOSPHORYL- ATION PYRUVATE OXIDATION ATP
Figure 9.UN09
CITRIC
ACID
CYCLE
OXIDATIVE
PHOSPHORYL-
ATION
PYRUVATE
OXIDATION
GLYCOLYSIS
Figure 9.UN09 In-text figure, mini-map, oxidative phosphorylation, p. 172
ATP

14. Concept 9.5: Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen
Most cellular respiration requires O2 to produce ATP
Without O2, the electron transport chain will cease to operate
In that case, glycolysis couples with anaerobic respiration or fermentation to produce ATP

15. The Evolutionary Significance of Glycolysis
Ancient prokaryotes are thought to have used glycolysis long before there was oxygen in the atmosphere
Very little O2 was available in the atmosphere until about 2.7 billion years ago, so early prokaryotes likely used only glycolysis to generate ATP
Glycolysis is a very ancient process

16. The Versatility of Catabolism
Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration
Glycolysis accepts a wide range of carbohydrates
Proteins and Fats are used in cellular respiration in absence of glucose

17. Proteins Carbohydrates Fats Amino acids Sugars Glycerol Fatty acids
Figure
Proteins
Carbohydrates
Fats
Amino
acids
Sugars
Glycerol
Fatty
acids
GLYCOLYSIS
Glucose
Glyceraldehyde 3- P
NH3
Pyruvate
Figure The catabolism of various molecules from food (step 5)
Acetyl CoA
CITRIC
ACID
CYCLE
OXIDATIVE
PHOSPHORYLATION

18. Regulation of Cellular Respiration via Feedback Mechanisms
Feedback inhibition is the most common mechanism for metabolic control
If ATP concentration begins to drop, respiration speeds up; when there is plenty of ATP, respiration slows down

19. Overview Cellular respiration occurs in 3 steps:
Glycolysis: Glucose converted to pyruvate and it occurs in cytoplasm
Krebs/Citric acid cycle: CO2 is produced which is exhaled (occurs in Mitochondria)
Oxidative Phosphorylation: O2 is converted to H2O and 32 ATP produced (occurs in Mitochondria)

20. The Process That Feeds the Biosphere
Photosynthesis is the process that converts solar energy into chemical energy
Directly or indirectly, photosynthesis nourishes almost the entire living world

21. Autotrophs sustain themselves without eating anything derived from other organisms
Autotrophs are the producers of the biosphere, producing organic molecules from CO2 and other inorganic molecules
Almost all plants are photoautotrophs, using the energy of sunlight to make organic molecules

22. Figure 10.1
Figure 10.1 How does sunlight help build the trunk, branches, and leaves of this broadleaf tree?

23. Photosynthesis occurs in plants, algae, certain other unicellular eukaryotes, and some prokaryotes
These organisms feed not only themselves but also most of the living world

24. (b) Multicellular alga 1 μm
Figure 10.2
(d) Cyanobacteria 40 μm
(a) Plants
Figure Photoautotrophs
(b) Multicellular alga
1 μm
(e) Purple sulfur
bacteria
10 μm
(c) Unicellular eukaryotes

25. Heterotrophs obtain their organic material from other organisms
Heterotrophs are the consumers of the biosphere
Almost all heterotrophs, including humans, depend on photoautotrophs for food and O2

26. Chloroplasts: The Sites of Photosynthesis in Plants
Leaves are the major locations of photosynthesis
Chloroplasts are found mainly in cells of the mesophyll, the interior tissue of the leaf
Each mesophyll cell contains 30–40 chloroplasts

27. Leaf cross section Chloroplasts Vein Mesophyll Stomata Chloroplast
Figure 10.4
Leaf cross section
Chloroplasts
Vein
Mesophyll
Stomata
CO2 O2
Chloroplast
Mesophyll
cell
Outer
membrane
Figure 10.4 Zooming in on the location of photosynthesis in a plant
Thylakoid
Intermembrane
space
Thylakoid
space
Stroma
Granum
20 μm
Inner
membrane
1 μm

28. Tracking Atoms Through Photosynthesis: Scientific Inquiry
Photosynthesis is a complex series of reactions that can be summarized as the following equation:
6 CO2 + 6 H2O + Light energy → C6H12O6 + 6 O2
The overall chemical change during photosynthesis is the reverse of the one that occurs during cellular respiration

29. Photosynthesis as a Redox Process
Photosynthesis reverses the direction of electron flow compared to respiration
Photosynthesis is a redox process in which H2O is oxidized and CO2 is reduced
becomes reduced
becomes oxidized

30. The Two Stages of Photosynthesis: A Preview
Photosynthesis consists of the light reactions (the photo part) and Calvin cycle (the synthesis part)
In light reaction: H2O is converted to O2

31. The Calvin cycle (in the stroma) forms sugar from CO2, using ATP and NADPH
The Calvin cycle begins with carbon fixation, incorporating CO2 into organic molecules
CO2 is converted to glucose

32. H2O Light NADP+ ADP + P i LIGHT REACTIONS Stroma Thylakoid Chloroplast
Figure
Light
H2O
NADP+
ADP +
LIGHT
REACTIONS
P i
Thylakoid
Stroma
Figure An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle (step 1)
Chloroplast

33. H2O Light NADP+ ADP + P i LIGHT REACTIONS ATP Stroma Thylakoid NADPH
Figure
Light
H2O
NADP+
ADP +
LIGHT
REACTIONS
P i
ATP
Thylakoid
Stroma
NADPH
Figure An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle (step 2)
Chloroplast O2

34. LIGHT REACTIONS CALVIN CYCLE
Figure
Light
H2O
CO2
NADP+
ADP +
LIGHT
REACTIONS
P i
CALVIN
CYCLE
ATP
Thylakoid
Stroma
NADPH
Figure An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle (step 3)
Chloroplast O2

35. LIGHT REACTIONS CALVIN CYCLE [CH2O] (sugar)
Figure
Light
H2O
CO2
NADP+
ADP +
LIGHT
REACTIONS
P i
CALVIN
CYCLE
ATP
Thylakoid
Stroma
NADPH
Figure An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle (step 4)
Chloroplast O2
[CH2O]
(sugar)

36. The Nature of Sunlight
Light is a form of electromagnetic energy, also called electromagnetic radiation
Like other electromagnetic energy, light travels in rhythmic waves
Wavelength is the distance between crests of waves
Wavelength determines the type of electromagnetic energy

37. The electromagnetic spectrum is the entire range of electromagnetic energy, or radiation
Visible light consists of wavelengths (including those that drive photosynthesis) that produce colors we can see

38. Figure 10.7
1 m
10− nm
10− nm
1 nm 10 nm 10 nm
(10
nm) 10 m 5 3 3 6 9 3
Gamma
rays
Micro-
waves
Radio
waves
X-rays UV
Infrared
Visible light
Figure 10.7 The electromagnetic spectrum
380
450
500
550
600
650
700
750 nm
Shorter wavelength
Longer wavelength
Higher energy
Lower energy

39. Photosynthetic Pigments: The Light Receptors
Pigments are substances that absorb visible light
Different pigments absorb different wavelengths
Wavelengths that are not absorbed are reflected or transmitted
Leaves appear green because chlorophyll reflects and transmits green light

40. Light Reflected light Chloroplast Absorbed Granum light Transmitted
Figure 10.8
Light
Reflected
light
Chloroplast
Figure 10.8 Why leaves are green: interaction of light with chloroplasts
Absorbed
light
Granum
Transmitted
light

41. The Importance of Photosynthesis: A Review
The energy entering chloroplasts as sunlight gets stored as chemical energy in organic compounds
Sugar made in the chloroplasts supplies chemical energy and carbon skeletons to synthesize the organic molecules of cells
Plants store excess sugar as starch in structures such as roots, tubers, seeds, and fruits
In addition to food production, photosynthesis produces the O2 in our atmosphere

42. REACTIONS: Photosystem II
Figure 10.22a O2
CO2
H2O
Sucrose
(export)
Mesophyll cell
Chloroplast
H2O
CO2
Light
NADP+
Figure 10.22a A review of photosynthesis (part 1)
ADP
3-Phosphoglycerate
LIGHT
REACTIONS: Photosystem II
Electron transport
chain + P
CALVIN
CYCLE i
RuBP
ATP
G3P
Photosystem I
Electron transport
chain
NADPH
Starch
(storage)
Sucrose (export) O2
H2O

43. MAKE CONNECTIONS The Working Cell Figure 10.23
Flow of Genetic Information
in the Cell:
DNA → RNA → Protein
(Chapters 5–7)
Movement Across
Cell Membranes
(Chapter 7)
Energy Transformations in the Cell:
Photosynthesis and Cellular
Respiration (Chapters 8–10)
The Working Cell
DNA 1
Nucleus
mRNA
Nuclear
pore 2
Protein
Rough endoplasmic
reticulum (ER) 3
Protein
in vesicle
Ribosome
mRNA
Vacuole 4
Vesicle
forming 7
Photosynthesis
in chloroplast
CO2
Golgi
apparatus
Protein
H2O
ATP 6
Plasma
membrane
Organic
molecules
Transport
pump 8
ATP
Figure Make connections: the working cell 5 O2
Cellular respiration
in mitochondrion
ATP 11
ATP 10 9
Cell wall O2
CO2
H2O