Photosynthesis

LN #15

California State Standards for Cell Biology1f. usable energy is captured from sunlight by chloroplasts and is stored

through the synthesis of sugar from carbon dioxide.

Overview of Photosynthesis

glucose

6 CO2 + 6 H2O C6H12O6 + 6 O2 Light energy

CO2

H2O

C6H12O6

O2

Purpose of photosynthesis is to turn light energy into chemical energy. Chemical energy is stored in glucose.

Where does Photosynthesis take place?

• Photosynthesis takes place in the leaves of plants.

• Chloroplast is the organelle responsible for carrying out photosynthesis. – In the figure circle the

chloroplast.

Leaf and Chloroplast Structure

Leaf and Chloroplast Structure• Leaf structure

– Stomata = tiny pores in the leaf, carbon dioxide enters and oxygen exits.

• Inside the chloroplast– stroma = thick fluid enclosed in the inner membrane of the

chloroplast. The stroma is where glucose is made from carbon dioxide.

– thylakoids = disk like sacs within the stroma. Thylakoids are connected in stacks called grana. Chlorophyll molecules are built into the thylakoid membrane.

• chlorophyll molecules are a pigment that capture light energy.

Photosynthesis Occurs In Two Parts

Part One: The Light Reactions

• Light energy is changed into chemical energy.– Oxygen gas is a waste product of this reaction.

• The light reactions happen in the thylakoid membrane of the chloroplast.

• Light energy is caught by the chlorophyll and used to make ATP from ADP and phosphate.

• Light energy is also stored in a molecule called NADPH.

Part Two: The Calvin Cycle

• During the Calvin cycle sugar is made using carbon dioxide and the energy storing molecules (ATP and NADPH) made during the light reactions.

• Calvin cycle takes place in the stroma of the chloroplast.

Summary

• What is photosynthesis?• Where does photosynthesis take place?• How many parts does photosynthesis have?• What occurs during the light reactions?• What occurs during the Calvin cycle?