Photosynthesis chapter 10
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Photosynthesis Chapter 10. Photosynthesis. P rocess that converts solar energy into chemical energy Directly or indirectly, photosynthesis food for almost the entire living world. Photosynthesis.

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Photosynthesis Chapter 10

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PhotosynthesisChapter 10


Photosynthesis

  • Process that converts solar energy into chemical energy

  • Directly or indirectly, photosynthesis food for almost the entire living world


Photosynthesis

Photosynthesis is a complex series of reactions that can be summarized as the following equation:

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


  • Autotrophs= produce own food

  • Autotrophs are the producers of the biosphere, producing organic molecules from CO2 and other inorganic molecules

  • Almost all plants are photoautotrophs

    • Uses the energy of sunlight to make organic molecules


Photosynthesis

  • Initial Source of Energy for Most Systems

  • Primary Producers= source of organic molecules for most other organisms

    • Terrestrial Systems= Plants

    • Aquatic Systems= Phytoplankton

  • Consumers= heterotrophs= consume organic material from other organisms

    • Cellular Respiration

Primary Producers

Consumers

Decomposers


Photosynthesis

  • Plants use ~50% of sugars produced for cellular respiration to fuel own cellular processes

  • Rest of sugar is used as building blocks for other organic molecules

  • Ultimately, consumed by heterotrophs and used for cellular respiration


Figure 10.2

(b)

Multicellularalga

(c)

Unicellularprotists

(e)

Purple sulfurbacteria

Primary Producers: plants, algae, protists, and some prokaryotes

(a) Plants

These organisms feed not only themselves but also most of the living world.

(d) Cyanobacteria

40 m

10 m

1 m


Consumers

  • Heterotrophs are the consumers of the biosphere

    • Heterotrophs= obtain organic material from other organisms

  • Almost all heterotrophs, including humans, depend on photoautotrophs for food and O2


Humans rely on primary producers for other types of fuel

  • The Earth’s supply of fossil fuels was formed from the remains of organisms that died hundreds of millions of years ago

    • In a sense, fossil fuels represent stores of solar energy from the distant past

  • Biofuels


Chloroplasts

  • Energy-producing organelle in plants

    • Converts solar energy into chemical energy

  • Contains green pigment known as chlorophyll

    • Light absorbing pigment

    • Gives leaves the green color

  • All green parts of plant have chloroplasts

    • Chloroplasts are found mainly in cells of the mesophyll, the interior tissue of the leaf

      • Cells can have 30-40 chloroplasts


Figure 10.4a

Leaf cross section

Chloroplasts

Vein

Mesophyll

Stomata

CO2

O2

Chloroplast

Mesophyllcell

20 m


Figure 10.4b

Chloroplast

Outermembrane

Thylakoid

Intermembranespace

Granum

Stroma

Thylakoidspace

Innermembrane

1 m


Photosynthesis

  • Photosynthesis is a complex series of reactions that can be summarized as the following equation:

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

  • Chloroplasts split H2O into hydrogen and oxygen, incorporating the electrons of hydrogen into sugar molecules and releasing oxygen as a by-product


Figure 10.5

Photosynthesis

Reactants:

6 CO2

12 H2O

6 H2O

Products:

C6H12O6

6 O2


Photosynthesis

  • Endergonic reaction

    • Sunlight

  • Energy stored in bonds of glucose

  • Redox Reaction

    • Photosynthesis reverses the direction of electron flow compared to respiration

    • Oxidation= loss of electrons

      • Water is oxidized

    • Reduction= gain of electrons

      • Carbon dioxide is reduced


Figure 10.UN01

Photosynthesis

becomes reduced

C6 H12 O6 6 O2

Energy  6 CO2  6 H2O

becomes oxidized


Photosynthesis occurs in 2 stages

  • Light Reactions (“photo)

    • Occurs in thylakoids

    • Split H2O

    • Release O2

    • Reduce NADP+ to NADPH

    • Generate ATP from ADP by photophosphorylation


Figure 10.6-1

H2O

Light

NADP

ADP

+P i

LightReactions

Chloroplast


Figure 10.6-2

H2O

Light

NADP

ADP

+P i

LightReactions

ATP

NADPH

Chloroplast

O2


Photosynthesis occurs in 2 stages

  • Dark Reactions: Calvin Cycle (“synthesis”)

    • Occurs in the stroma

      • Uses ATP and NADPH from light reaction to reduce CO2 and produce sugars

      • Begins with carbon fixation, incorporating CO2 into organic molecules


Figure 10.6-3

CO2

H2O

Light

NADP

ADP

+P i

CalvinCycle

LightReactions

ATP

NADPH

Chloroplast

O2


Figure 10.6-4

CO2

H2O

Light

NADP

ADP

+P i

CalvinCycle

LightReactions

ATP

NADPH

Chloroplast

[CH2O](sugar)

O2


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