Chapter 8: Photosynthesis Section 3: Process of Photosynthesis

A. General Formula: Reactants: Carbon Dioxide and Water Products: Glucose (Food) and Oxygen During Photosynthesis, the Suns energy will be converted through a series of chemical reactions to glucose. This requires an input of CO2 and produces O2 as a waste product!

Two Sets of Chemical Reactions The Light Dependents Reactions (Light Reactions): Require Light (hence the name) These reactions take place in chlorophyll Utilize water and sunlight Produce ATP (Energy) and NADPH (Energy Storing Electron Carrier) to be used later on!! The Light Independent Reactions (Dark Reactions or Calvin Cycle) Do not require light (Hence the Dark Part) Take place in the Stroma Utilize ATP, NADPH, and CO2 from the atmosphere Produce Glucose and O2 by using the energy gained from light reactions

2. Light Reactions: 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 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)

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? What are the inputs of the Calvin cycle? 1. H2O (Water) 1. Energy (ATP and NADPH) 2. Sunlight 2. CO2 (from Atmosphere) What are the outputs of the Light reactions? What are the outputs? ATP Glucose (Food) 2. NADPH 2. ADP and NADP+ (To go get more energy from light reactions

Factors Effecting Photosynthesis Temperature: Enzymes for Photosynthesis work best between 0 and 95 degrees Fahrenheit Above this we get DENATURATION of Enzymes

Light Intensity: The brighter the light, the greater the rate of photosynthesis. (Unless it is too hot!) Water Availability: No water…No photosynthesis

How do Plants in Extreme Conditions Survive! C4 Plants such as corn and sugar cane Open stomata at night to let CO2 in when temps are low- prevents evaporation of water! CAM Plants such as cacti and pineapples also only open their stomata at night and store CO2 as something else. When light is available to produce ATP and NADPH- PS 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)