Photosynthesis & Chloroplasts

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Slide 1

Photosynthesis

Slide 2

Overview

All energy on earth comes from the sun.

We depend on:

Plants

Algae (underwater plants)

Cyanobacteria (photosynthetic bacteria)

To provide this energy to us!

Slide 3

Overview

Slide 4

Overview

Carbon dioxide and water are taken in by plants

Plants absorb light energy and convert it to a usable form.

ATP

Energy is used to “fix” carbon dioxide into sugar molecules

Chemical energy

Sugar is converted to starch and stored for use by the plant, and by animals when they eat plants.

Slide 5

Chloroplasts

Have TWO membranes

A “bi-bilayer!”

The inner membrane is called the thylakoid.

The thylakoid is folded and looks like stacks of coins called granum (grana singular).

The stroma is the space surrounding the granum

Image source: http://www.daviddarling.info/encyclopedia/C/chloroplasts.html

Slide 6

Chloroplasts

Chlorophyll molecules are embedded in the thylakoid membrane

Act like a light “antenna”

These molecules can absorb sunlight energy.

Image from Biology 11: College Preparation. Pg 73. Nelson, Toronto. 2003.

Slide 7

Light (dependent)Reactions

Happen ONLY in sunlight

Hence they depend on light!

Light is absorbed by chlorophyll molecules

The energy generates molecules of ATP

Image from: Biology 11: College Preparation. Pg 74. Nelson, Toronto. 2003.

Slide 8

Light Independent Reactions (formerly the “dark reactions”)

Happen in sunlight, and in the dark.

Hence “independent of light”

ATP generated by sunlight drives the Calvin Cycle.

Monosaccarides (eg. glucose) are manufactured in the cycle.

Monosaccarides are used to “build” polysaccharides (eg. Starch).

Image from: Biology 11: College Preparation. Pg 74. Nelson, Toronto. 2003.

Slide 9

Overall Reaction

What is the equation for photosynthesis?

carbon dioxide + water  glucose + oxygen + energy

6CO2 + 6H2O  C6H12O6 + 6O2 + energy

Slide 10

Summary