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PowerPoint Lectures for Biology, Seventh Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero

Chapter 10

Photosynthesis

The Process That Feeds the Biosphere

Photosynthesis plants, algae and some prokaryotes

Autotrophs = Producers

Heterotrophs = Consumers

Obtain their organic material from other organisms

The Sites of Photosynthesis in Plants

The leaves of plants are the major sites of photosynthesis

The Sites of Photosynthesis in Plants

The leaves of plants are the major sites of photosynthesis

The Sites of Photosynthesis in Plants

The leaves of plants are the major sites of photosynthesis

Chloroplast Structure

Tracking Atoms Through Photosynthesis: Scientific Inquiry

Photosynthesis:

6 CO2 + 12 H2O + Light energy  C6H12O6 + 6 O2 + 6 H2 O

What is oxidized?

What is reduced?

Cellular Respiration:

C6H12O6 + 6O2  6CO2 + 6H2O + ATP

The Two Stages of Photosynthesis: A Preview

Photosynthesis consists of two processes

1. The Light reactions

2. The Calvin cycle

The Two Stages of Photosynthesis: A Preview

Photosynthesis consists of two processes

1. The Light reactions

Solar Energy  ATP and NADPH

2. The Calvin cycle

Use ATP and NADPH

CO2  Sugar

The light reactions

The Calvin Cycle

The Nature of Sunlight

Light

Form of electromagnetic energy

Travels in waves

The electromagnetic spectrum

Photosynthetic Pigments: The Light Receptors

Pigments= Substances that absorb visible light
Reflected Light = the colors we see

What pigments (wavelengths of light) are used to drive photosynthesis?

The absorption spectra of 3 types of pigments in chloroplasts

Chlorophyll a - Main photosynthetic pigment
Chlorophyll b- Accessory pigment

What happens when chlorophyll absorbs light?

Isolated solution of chlorophyll Illuminated

= Fluoresce, gives off light and heat

Figure 10.11 B

Photosystem: Reaction Center associated with Light-Harvesting Complexes

Where and how does photosynthesis take place?

Light Reactions!

2 Photosystems and 2 Electron Transport Chains

Photosystem II

1. Light absorbed by chlorophyll chlorophyll 680

Photosystem II

1. Light absorbed by chlorophyll chlorophyll 680
2. electron excited caught by primary electron acceptor

Photosystem II

3. Enzyme splits H2O  O2 + H+ + electrons
Electrons pulled to chlorophyll 680

Photosystem II and Electron transport chain 1

4. Electron pulled down electron transport chain 1=

5. Make ATP

Photosystem I

Electrons pulled by chlorophyll 700 in PS I

Photosystem I

6. Light absorbed by chlorophyll in PS I chlorophyll 700

Photosystem I and Electron transport chain 2

7. Excited electron caught by primary electron acceptor and pulled down electron transport chain 2

Photosystem I and Electron transport chain 2

8. NADP+ + 2 electrons and 1 H+ = NADPH

Mechanical analogy for the light reactions

Chloroplasts and Mitochondria

Generate ATP by the same basic mechanism: Chemiosmosis

Compare/Contrast:

2. Movement of H+ (between what spaces, what direction?)

2 Photosystems and 2 Electron Transport Chains

Chloroplasts and Mitochondria

Generate ATP by the same basic mechanism: Chemiosmosis

Compare/Contrast:

2. Movement of H+ (between what spaces, what direction?)

Concept 10.3

Calvin Cycle:

Uses ATP and NADPH to convert CO2 to sugar

Occurs in the stroma

The Calvin cycle has 3 phases

1. Carbon fixation

2. Reduction

3. Regeneration of the CO2 acceptor

The Calvin cycle: 1. Carbon fixation

2. Reduction

3. Regeneration of RuBP

REVIEW!

Ch. 10 Photosynthesis:
What organisms? Where?
Chloroplast structure
Light reactions and Calvin cycle (where and what?)
Light reactions 2 photosystems, 2 electron transport chains