Photosynthesis

What is the ultimate source of all energy

How does the energy get from the sun into the foods we eat? energy

Plants must break down food just like humans. However, they don’t ingest their food, they make it using photosynthesis.

Autotrophs use sunlight to create food –Since they can’t move they need to get their energy from the sun’s light Heterotrophs get energy from either autotrophs or other heterotrophs –They cannot create their own energy

Photosynthesis takes place in the chloroplast of the plant

Where do we find chloroplasts?

stoma Chloroplast containing chlorophyll Chloroplasts are found in cells of leaves.

Chloroplast structure Disks called GRANA contain the pigment CHLOROPHYLL. The liquid portion of a chloroplast is the STROMA

Found in the thylakoid membranes of the chloroplast Makes plant appear green Traps sunlight

What process captures the light energy and uses it to make food?

OVERVIEW OF PHOTOSYNTHESIS PLANTS TAKE IN CO 2 AND H 2 O PLANTS MAKE GLUCOSE AND OXYGEN SUNLIGHT PROVIDES THE ENERGY FOR PHOTOSYNTHESIS

What is photosynthesis? Photosynthesis is the process by which: water carbon dioxide oxygen glucose TAKE INAND USINGMAKE PLANTS (producers) light chlorophyll

Reactants Products

Carbohydrate formed during photosynthesis –Made of oxygen, hydrogen, and carbon Chemical formula –C 6 H 12 O 6

Photosynthesis includes two main groups of reactions: –Light reactions –Dark reactions (aka Calvin cycle) Light ReactionDark Reaction

Who was Calvin anyway? A member of the faculty at UC Berkeley since 1937, Melvin Calvin received the 1961 Nobel prize in chemistry for identifying the path of carbon in photosynthesis. The cycle of reactions in the dark phase of photosynthesis was named after him for his work in identifying the processes taking place.

Light reaction: –Occurs in the grana –Must have light light Light Reaction Dark Reaction LIGHT REACTION Dark Reaction grana (chlorophyll)

Where does the light go? Light reactions –Water molecules are split –Produces Hydrogen Ions ATP and NADPH (energy sources used in Calvin Cycle) Oxygen (released by plant)

Dark reactions (aka Calvin cycle) : –Occurs in the stroma –Occurs in the light and dark Light Reaction Dark Reaction Light Reaction DARK REACTION stroma (liquid)

Calvin Cycle Energy from light reactions, carbon dioxide and hydrogen ions combine: –Glucose formed Glucose

Step 1: Light Reactions H2OH2O O2O2 O2O2 O2O2 O2O2 O2O2 HH How does the O 2 leave the leaf? ENERGY light energy reacts with the chlorophyll water is split by the light energy H is kept for the dark reaction O 2 is released OH2OH2

Step 2: Dark Reactions AKA: CALVIN CYCLE CO 2 H C 6 H 12 O 6 How does CO 2 enter the plant? H from the water split in the light reaction is present CO 2 enters the chloroplast the reactants H and CO 2 combine H H + CO 2 glucose is the product Other carbohydrates besides glucose may be made in photosynthesis

Photosynthesis Review Light reactions: H 2 O split into H 2 + O Dark reactions: H + CO 2 = C 6 H 12 O 6 H2OH2O Light ReactionDark Reaction CO 2 C 6 H 12 O 6 O2O2 chlorophyll

Photosynthesis Formula How would this be written as a chemical equation? What goes in? (the reactants) What comes out? (the products) H2OH2O Light Reaction Dark Reaction CO 2 C 6 H 12 O 6 O2O2 chlorophyll H2OH2OCO 2 C 6 H 12 O 6 O2O2

Photosynthesis Formula What’s wrong with this equation? The number of atoms is not equal on both sides of the equation. Balance the equation so that the number of atoms of each element is equal on both sides. H2OH2OCO 2 C 6 H 12 O 6 O2O2 one carbon atom reactant 6 carbon atoms product 6 66(1) Now balance it as if TWO glucose molecules were being produced.

In the End The complete equation for photosynthesis in the end Is this balanced?

The Balanced Equation

Photosynthesis Review What goes in? (the reactants) What comes out? (the products) H2OH2O Light Reaction Dark Reaction CO 2 C 6 H 12 O 6 O2O2 chlorophyll 6CO 2 + 6H 2 O 6O 2 + C 6 H 12 O 6 light chlorophyll

REVIEW and REFLECT 1.Where does photosynthesis take place in the plant cell? 2.What is the simple sugar formed during photosynthesis? 3.How many oxygen molecules does it take to make one glucose molecule? 4.What are the two cycles of photosynthesis?