Photosynthesis 6H 2 O + 6CO > C 6 H 12 O 6 + 6O 2

What is photosynthesis? Photosynthesis is arguably the most important biological process on earth. By liberating oxygen and consuming carbon dioxide, it has transformed the world into the hospitable environment we know today. "putting together with light."

Importance of Photosynthesis If we can understand and control the intricacies of the photosynthetic process, we can learn how to increase crop yields of food, fiber, wood, and fuel, and how to better use our lands. The energy-harvesting secrets of plants can be adapted to man-made systems which provide new, efficient ways to collect and use solar energy.

Photosynthesis takes place in three stages: 1. Energy is captured from sunlight 2. Light energy is converted to chemical energy(ATP/NADPH) 3. ATP and NADPH power the formation of glucose using carbon from CO 2

Molecules in Photosynthesis Chlorophyll a Chlorophyll b Green pigments that absorb light energy Carbon Dioxide - CO 2, source of carbon for sugar formation Water - H 2 O, source of hydrogen for sugar formation and important for moving energy during photosynthesis Oxygen - O 2, by-product of photosynthesis

ATP(ADP+P) - Energy carrying molecule NADPH(NADP+H) - Energy carrying molecule Electron Acceptors - proteins that move electrons during photosynthesis Proton Pump - protein that moves protons (H+) during photosynthesis Molecules in Photosynthesis, continued

PGAL - 3 carbon molecule used to build glucose RBP - 5 carbon molecule used to build glucose Glucose - C 6 H 12 O 6, Food product of photosynthesis Enzymes (e.g. ATP synthetase) - proteins that speed up the chemical reactions Molecules in Photosynthesis, continued

Photosynthesis takes place in the chloroplast

Inside the Cholorplast Thylakoid - membrane “sac” holds the chlorophyll molecules *photosynthesis takes place here Grana - column of thylakoids Stroma - liquid that fills the chloroplast

Energy is captured from sunlight Light is a form of radiant energy - emitted in waves that can travel through a vacuum The complete range of radiant energy is called the electromagnetic spectrum Units: nm = nanometer (10 -9 m or one-millionth of a millimeter) Km = kilometer (10 3 m or one-thousand meters) Radiant Energy travels in tiny “packets” called photons Electromagnetic spectrum

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Chlorophyll Absorbs Photons There are 2 types of chlorophyll molecules in the thylakoid membrane Chlorophyll a Chlorophyll b They both produce a green color- but absorb slightly different wavelengths of light energy

Processing :Based on What colors of light are best absorbed by the chlorophyll molecules? Chlorophyll a - Indigo and Orange Chlorophyll b - Indigo/Blue and Orange/Red What colors of light are least absorbed by the chlorophyll molecules? Green and Yellow Absorption Spectra

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How does this data support the fact that the chlorophyll molecules give plants their green color? Because green and yellow are NOT absorbed, they are reflected to your eye giving chlorophyll the green color.

Photosystems-are clusters of Chlorophyll molecules in the thylakoid membrane. There are two clusters called: photosystem I and photosystem II These Photosystems start the process of photosynthesis by absorbing photon energy This energy is captured by electrons in the cholorphyll molecules.

Light Energy is Converted into Chemical Energy This stage of photosynthesis is also called the “Light Reaction”because light energy is required. 1. Photons reach the chlorophyll molecules in the photosystems found on the thylakoid membrane and are absorbed by these molecules. 2. Electrons in the chlorophyll become “energized” from these photons and are passed from Photosystem II to Photosystem I.

3. In the process of “passing” electrons -energy is stored in ATP and NADPH molecules -H 2 O molecules are split into: O 2 - released as a by-product into the atmosphere H + - used to form NADPH

Chemical Energy is Stored in Glucose The other stage of photosynthesis is also called the “Dark Reaction” or the Calvin Cycle -no light energy is required -occurs in the stroma of a chloroplast

Molecules Important to the Calvin Cycle ATP - releases energy to keep cycle going NADPH - releases energy to keep cycle going -provides the hydrogen for the glucose molecule RuBP -5 carbon molecule used over and over in the cycle to form glucose PGAL - 3 carbon molecule used over and over in cycle to form glucose CO 2 - carbon source for cycle

What affects the rate of photosynthesis? Light intensity - as light intensity increases the initial rate will increase and eventually level off as all of the electrons in the photosystems are “excited.” Carbon dioxide - increasing levels of CO2 will increases the rate initially. So, talking to your plants is a good thing. :) Temperature - increasing temperature increases all chemical reactions, including those in photosynthesis.