08 Photosynthesis Presentation

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Photosynthesis

Lecture 08

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Objectives

At the end of this series of lectures, you should be able to:

Define terms. Describe the structure of chloroplasts and their location

in a leaf. Compare the reactants and products of the light

reactions and the Calvin cycle.

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Objectives

Explain how the electron transport chain and chemiosmosis generate ATP, NADPH, and oxygen in the light reactions.

Compare the mechanisms that C3, C4, and CAM plants use to obtain and use carbon dioxide.

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Trophic Levels

Autotrophs

Primary producers Photoautotrophs

Heterotrophs

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Diversity of Photosynthesis

Plants Protists (protozoa) Bacteria

Kelp

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Chloroplasts

Chloroplasts are located in green parts of plants.

The green color comes from the pigment chlorophyll located in the chloroplasts. Important role in converting light to chemical energy.

Leaves are the major site of photosynthesis and contain large numbers of chloroplasts in each cell. Within a leaf, the chloroplasts are concentrated in the mesophyll Stomata allow CO2 to enter the leaf and O2 to exit the leaf.

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Biology by OpenStax College is licensed under a Creative Commons Attribution 3.0

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Chloroplasts

Chloroplasts have a double membrane. Stroma is a thick fluid that fills the inner membrane Thylakoids are a system of interconnected

membranous sacs

Stack of thylakoids are called granum (grana) Thylakoid membranes are the location of much of

photosynthesis. Chlorophyll is built into the thylakoid membrane. 8

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Miguelsierra, CC BY-SA 3.0,

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6CO 12H O Light C H O 6O 6H O C H O 6O 6CO 6H O 32 ATP Heat

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Redox Reactions

Cellular respiration uses redox reactions to harvest the chemical energy stored in a glucose molecule. Glucose is oxidized and O2 is reduced to H2O. Electrons lose potential as they travel down the electron transport chain.

In photosynthesis, Water is oxidized and CO2 is reduced. Light is captured by chlorophyll molecules to boost the energy of electrons. Chemical energy is stored in the chemical bonds of sugars.

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Photosynthetic Reactions

Light reactions

Occur on the thylakoids Convert light energy to high energy intermediates (ATP

and NADPH). Produces O2

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Photosynthetic Reactions

Calvin Cycle

Occurs in the stroma Uses high energy intermediates and CO2 to synthesize

glucose. Carbon fixation

Light Reactions and Calvin Cycle are linked by the high energy intermediates.

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Daniel Mayer, CC BY-SA 3.0,

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Light

Light is a small part of the electromagnetic spectrum.

Wavelengths: 380-750 nm Photon ? packet of light energy

Shorter the wavelength the more energy the photon has

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Philip Ronan, Gringer, CC BY 3.0,

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