Photosynthesis

6H2O + 6CO2 ----------> C6H12O6+ 6O2

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 sunlight2. Light energy is converted to chemical energy(ATP/NADPH)3. ATP and NADPH power the formation of glucose using carbon from CO2

Molecules in Photosynthesis

Chlorophyll aChlorophyll b

Green pigments that absorb light energy

Carbon Dioxide - CO2, source of carbon for sugar formation

Water - H2O, source of hydrogen for sugar formation and important for moving energy during photosynthesis

Oxygen - O2, by-product of photosynthesis

ATP(ADP+P) - Energy carrying molecule

NADPH(NADP+H) - Energy carrying moleculeElectron 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 buildglucose

RBP - 5 carbon molecule used to build glucose

Glucose - C6H12O6, 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 (103 m or one-thousand meters)

Radiant Energy travels in tiny “packets” called photons

Electromagnetic spectrum

Back it up

Chlorophyll Absorbs Photons

There are 2 types of chlorophyll molecules in the thylakoid membrane

Chlorophyll aChlorophyll 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 OrangeChlorophyll b - Indigo/Blue and Orange/Red

What colors of light are least absorbed by the chlorophyll molecules?

Green and Yellow

Absorption Spectra

Back it up

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-H2O molecules are split into:

O2 - released as a by-product into the atmosphereH+ - used to form NADPH

Chemical Energy is Stored in GlucoseThe 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 CycleATP - releases energy to keep cycle going

NADPH - releases energy to keep cycle going -provides the hydrogen for the glucose

moleculeRuBP -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

CO2 - 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.