Chapter 8: Chapter 8: PhotosynthesisPhotosynthesisSection 3: Process of PhotosynthesisSection 3: Process of Photosynthesis

A. General Formula:A. General Formula:Reactants: Carbon Dioxide and WaterReactants: Carbon Dioxide and Water

Products: Glucose (Food) and OxygenProducts: Glucose (Food) and Oxygen

During Photosynthesis, the Suns energy will be converted through a series of During Photosynthesis, the Suns energy will be converted through a series of chemical reactions to glucose. This requires an input of CO2 and chemical reactions to glucose. This requires an input of CO2 and produces O2 as a waste product!produces O2 as a waste product!

1.1. Two Sets of Chemical ReactionsTwo Sets of Chemical ReactionsA.A. The Light Dependents Reactions (Light Reactions):The Light Dependents Reactions (Light Reactions):

Require Light (hence the name)Require Light (hence the name)

These reactions take place in chlorophyllThese reactions take place in chlorophyll

Utilize water and sunlightUtilize water and sunlight

Produce ATP (Energy) and NADPH (Energy Storing Produce ATP (Energy) and NADPH (Energy Storing Electron Carrier) to be used later on!!Electron Carrier) to be used later on!!

B.B. The Light Independent Reactions (Dark Reactions or The Light Independent Reactions (Dark Reactions or Calvin Cycle)Calvin Cycle)

Do not require light (Hence the Dark Part)Do not require light (Hence the Dark Part)

Take place in the StromaTake place in the Stroma

Utilize ATP, NADPH, and CO2 from the atmosphereUtilize ATP, NADPH, and CO2 from the atmosphere

Produce Glucose and O2 by using the energy gained Produce Glucose and O2 by using the energy gained from light reactionsfrom light reactions

2. Light Reactions:

A. Steps in the Process:

1. Photosystem II: collection of chloroplast molecules

Absorbs light energy (photons)

Breaks down water into 3 things

- an Oxygen atom (Which is ½ of O2)

- 2 Hydrogen ions (Important Later)

- 2 Electrons that have absorbed suns energy (Crazy, Mad

Important!)

2. Electron Transport Chain: A collection of molecules on the thylakoid membrane

As electrons travel down this chain they lose energy

That energy is used to make ATP!

3. Photosystem I: Captures energy from the sun to re-energize those two electrons

So they don’t lose energy they need to be stored in a molecules called NADP+

When NADP+ stores those electrons it is called NADPH- This is another form of energy!

Inputs: Water, Sunlight

Outputs: ATP, and NADPH (Both forms of energy for the next step)

2.2. Dark Reactions/Calvin Cycle: Dark Reactions/Calvin Cycle:

Take Place in the stroma

Use energy from light reactions to turn CO2 from the atmosphere into Glucose!

This an enzyme catalyzed reaction:

Rubisco is the most abundant protein on the planet!!!

Input: ATP, NADPH (both from Light Reactions)

CO2 from the atmosphere

Output: Glucose- Food for plants (this was the purpose)

ADP, NADP+ Left over after their energy was used

Return to Light Reactions to get more energy

Oxygen

Review:General Formula

What are the inputs of

the Light reactions?

1. H2O (Water)

2. Sunlight

What are the outputs of the Light reactions?

1. ATP2. NADPH

What are the inputs of the Calvin cycle?

1. Energy (ATP and NADPH)

2. CO2 (from Atmosphere)

What are the outputs?

1. Glucose (Food)

2. ADP and NADP+ (To go get more energy from light reactions

Factors Effecting Factors Effecting PhotosynthesisPhotosynthesis

Temperature:Temperature:

Enzymes for Photosynthesis work Enzymes for Photosynthesis work best between 0 and 95 degrees best between 0 and 95 degrees FahrenheitFahrenheit

Above this we get DENATURATION Above this we get DENATURATION of Enzymesof Enzymes

Light Intensity:Light Intensity:

The brighter the light, the greater The brighter the light, the greater the the rate of photosynthesis.rate of photosynthesis.

(Unless it is too hot!)(Unless it is too hot!)

Water Availability:Water Availability:

No water…No photosynthesisNo water…No photosynthesis

How do Plants in Extreme How do Plants in Extreme Conditions Survive!Conditions Survive!

C4 Plants such as corn and sugar caneC4 Plants such as corn and sugar caneOpen stomata at night to let CO2 in Open stomata at night to let CO2 in

when temps are low- prevents when temps are low- prevents evaporation evaporation of water!of water!

CAM Plants such as cacti and pineapplesCAM Plants such as cacti and pineapplesalso only open their stomata at night and also only open their stomata at night and store CO2 as something else. When store CO2 as something else. When

light light is available to produce ATP and NADPH- is available to produce ATP and NADPH- PS continuesPS continues

Sugar Cane: C4 Plant

Grows in Tropical climates- Very hot, lots of sunlight

(Dominican Republic, Costa Rica, Hawaii)

Organ Pipe Cactus: CAM Plant

Grows in deserts

(Southwestern US, Mexico)