81. Photosynthesis Uses Light Energy to Make Food

Katrina Garibotto

Objectives Describe the structure of a chloroplast. Identify the overall reactants and

products of photosynthesis.

Vocabulary chloroplast: organelle where photosynthesis

occurs chlorophyll: chemical compound inside

chloroplasts mesophyll: cells containing chloroplasts stroma: liquid inside a chloroplast thylakoid: disk-like structure inside

chloroplasts light reactions: release oxygen Calvin cycle: create sugar

Photosynthesis Location plant

leaf mesophyll (cells)

chloroplasts (organelles) stroma (liquid) thylakoids (disks inside chloroplasts, surrounded by

stroma)

Leaf Structure

Leaf Structure

Leaf Structure epidermis – skin (protection) mesophyll – cells containing chloroplasts veins – allow substances to move

around a plant (xylem for water, phloem for sugar)

stomata (plural for stoma) – allow gases to enter and exit the leaf (like pores)

air space – allows gases to diffuse through leaf

The Structure of Chloroplasts chloroplast: organelle inside cell of a

plant found in mesophyll cells contain chemical chlorophyll (green) If it’s green on a plant, it contains

chlorophyll.

The Structure of Chloroplasts

stroma (liquid)

thylakoids (discs)

Overview of Photosynthesis Plants use energy from the sun to break

apart water (H2O) and recombine it with carbon dioxide (CO2) to create sugar (C6H12O6) for food.

Leftover oxygen (O2) is released into the air.

Reactants (input): sunlight, CO2, H2O Products (output): C6H12O6, O2

Overview of Photosynthesis

Overview of Photosynthesis Light reactions yield O2. Calvin cycle yields sugar. These two processes depend on each

other. Products of light reactions are reactants

for Calvin cycle. Products of Calvin cycle are reactants

for light reactions.

Light Reactions The light reactions convert solar energy to

the chemical energy of ATP and NADPH. occur in the thylakoids1. Chlorophyll molecules capture light energy.2. Energy used to separate H and O from

water.3. O2 released – waste

4. Hydrogen used to create NADPH.5. Energy used to create ATP.

Calvin Cycle Makes sugar using atoms from CO2 and

hydrogen and electrons from NADPH. Uses ATP created in light reactions Occurs in stroma (liquid)

Light Reactions and Calvin Cycle