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PhotosynthesisPhotosynthesis

Table of Contents

PhotosynthesisPhotosynthesis

Trapping the Sun’s EnergyTrapping the Sun’s Energy

Chapter 9 Section 2 Pgs. 225-230

How do WE harness energy from the How do WE harness energy from the sun???sun???

What is Photosynthesis?What is Photosynthesis?• Photosynthesis is the process plants use to trap and make energy from sunlight.

• The energy is then used to make simple sugars.

• These simple sugars are then converted to complex carbohydrates

• These complex carbs are then able to store energy.

Where Does Photosynthesis Where Does Photosynthesis Take Place?Take Place?

Photosynthesis takes place in the chloroplast. Photosynthesis takes place in the chloroplast.

ChlorophyllChlorophyll

Chloroplasts contain a Chloroplasts contain a pigment called pigment called chlorophyll. chlorophyll.

ChlorophyllChlorophyll absorbs absorbs most wavelengths of most wavelengths of light except for green. light except for green.

The Two Phases of PhotosynthesisThe Two Phases of Photosynthesis

The Light-Dependent The Light-Dependent ReactionsReactions

• Requires sunlightRequires sunlight

• End productsEnd products• Oxygen releasedOxygen released• ATPATP• NADPHNADPH

The Light-Independent The Light-Independent ReactionsReactions

• Does not require Does not require sunlightsunlight

• End ProductEnd Product• NADPNADP++

• sugarsugar

Light Dependent ReactionsLight Dependent Reactions

• Light is trapped by chlorophyll in the plant’s leaves

• The energy from the sunlight is transferred to electrons

• The electrons move to an electron transport chain (a line of proteins embedded in a membrane)

Electron Transport Chain (ETC)Electron Transport Chain (ETC)

• Electrons are passed protein to protein

• As the electrons are passed along this line, some energy is lost.

What Happens to the Lost Energy?What Happens to the Lost Energy?

•The energy lost can be used to form ATP from ADP

•Energy not used is stored in an electron carrier called NADPH.

•NADPH carries the energy to the light-independent reactions.

Restoring ElectronsRestoring Electrons

• Electrons are lost at the beginning of photosynthesis and must be restored

• Without restoration chlorophyll can’t absorb light and light dependent reactions stop, causing lack in production of ATP

• To replace lost electrons, PHOTOLYSIS occurs.

PhotolysisPhotolysis

• Splitting of water molecules in the first photosystem

• Produces

• ½ molecule of oxygen (released into the air WE breathe)

• 2 electrons (returned to chlorophyll)

• 2 hydrogen ions (help provide energy for ATP production)

Light-Independent ReactionsLight-Independent Reactions

• Does not Require Light

• Called the Calvin Cycle

Calvin CycleCalvin Cycle

• Series of reactions that uses carbon dioxide, ATP, and NADPH to form sugars, which become stored energy

•It takes 6 rounds of the cycle to form one sugar