© Cengage Learning 2015

Biology Concepts and Applications | 9e

Starr | Evers | Starr

© Cengage Learning 2015

Chapter 6

Where It Starts – Photosynthesis

© 2016 Pearson Education, Inc.

Figure 7.1

PHOTOSYNTHETIC AUTOTROPHS

Plants

(mostly on land)

Photosynthetic Protists

(aquatic) Photosynthetic Bacteria

(aquatic)

Micrograph of cyanobacteria Kelp, a large, multicellular alga Forest plants

LM

Autotrophs = self feeders

Photoautotrophs – use light energy

© Cengage Learning 2015 Figure 6-1a p100

Properties of Light

Light behaves as waves and discrete packets of

energy called photons, fixed quantities of light

energy.

A pigment absorbs light of a specific wavelength

(chlorophyll a is most common).

© Cengage Learning 2015 Figure 7.6

Properties of Light

Chlorophyll absorbs light in the blue-purple and

red-orange wavelengths, but not in the green

wavelengths

WHAT is Photosynthesis?

The simplified equation for photosynthesis. A

chemical transformation of light energy to

chemical energy.

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Photosynthesis is a Redox Reaction

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Chloroplast

In the chloroplasts!

Figure 4.3-2

Chloroplast

WHERE does photosynthesis

occur?

Plant Cell

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© 2016 Pearson Education, Inc. Figure 6-4 p103

• Stroma Thick fluid inside the chloroplast

• Thylakoids Connected sacs within the chloroplast

• Grana Stacks of thylakoids

• Chlorophyll Pigment molecules that capture light energy, built into thylakoid membrane

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Photosynthesis has 2 stages:

Light-Dependent Reactions & Calvin-Benson Cycle

© 2016 Pearson Education, Inc.

Figure 7.8-1

Excited state The electron falls to its ground state.

Heat

Absorption of a

photon excites an electron.

Light

Light

(fluorescence) Photon

(a) Absorption of a photon

Ground

state

e

Chlorophyll

molecule

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Photosystem: group of chlorophyll,

accessory pigments, and other molecules

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Electron Transport Chain

Provides energy for ATP synthesis

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TWO Photosystems (II and I)

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Summary of Light-Dependent

Reactions

Products = O2 (waste); ATP & NADPH (to C-B cycle)

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Photosynthesis has 2 stages:

Light-Dependent Reactions & Calvin-Benson Cycle

© Cengage Learning 2015 Figure 6-8 p106

Calvin-Benson Cycle

Product = Sugar

BioFlix Animation: Photosynthesis

© 2016 Pearson Education, Inc.