Photosynthesis

Using Light Energy to Make Food

Photosynthesis

Plants use energy to change carbon dioxide and water into glucose and oxygen (waste product)

Who performs Photosynthesis?

Plants and a few bacteriaThese are called autotrophs

Three major events take place in two stages:– Absorption of light energy– Conversion of light energy into

chemical energy (ATP and NADPH)– Storage of energy in the form of

carbohydrates

Where does it happen?

Chloroplasts:– Thylakoids (a single

pancake) Contain chlorophyll

– Grana (stacks) Granum is one stack.

– Stroma (thick fluid that surrounds the grana)

omega.dawsoncollege.qc.ca/ ray/cell/401cell.htm

Light Dependent Reaction– Temperature

independent– Light Reaction

Light Independent Reaction– Calvin-Benson Cycle– Dark Reaction

www.emc.maricopa.edu/faculty/ farabee/BIOBK/BioBookPS.html

Light Reaction

Requires direct light energy Occurs in the thylakoids of chloroplasts 2 steps occur here:

1. Absorption of light by pigments

2. Splitting of water

Electron carriers

Light dependent reaction They gain tons of energy! Cells use electron carriers to transport this energy

to other molecules– Called electron transport (name of process)

2 types in photosynthesis– NADP+

Carriers 2 high energy electrons and hydrogen ions Create NADPH

– ATP

Light Dependent Reaction (depends on light)

Inputs=sun and waterProducts formed

– Oxygen gas-formed by splitting water– Electrons transported to create

NADPH and ATPused in the Calvin-Benson cycle

Calvin Cycle

Occurs in the stroma (filler in chloroplasts)Also called the dark reaction

– Carbon dioxide is the input and the NADPH and ATP from the light reaction

The output is glucose– It is used for food and energy.– Formula for glucose

C6H12O6

The Equation

Sunlight+ 6CO2 + 6H20

---->C6H12O6 + 6 02

Factors that effect the rate of photosynthesis

Temperature Enzymes are important for photosynthesis to work.

– Enzymes work best in certain temperatures.– If the temp is too low or too high, it can decrease it or stop

photosynthesis.

Light intensity– Increase light will increase photosynthesis to a point.

Amount of Carbon Dioxide Amount of water

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