Concept 8.1 Summary

Chloroplast-the cellular organelle where photosynthesis takes place

*The leaves contain the most chloroplasts and are the major sites of photosynthesis:

1. the chloroplasts are concentrated in the cells of the mesophyll

2. carbon dioxide enters and oxygen exits the leaf through the stomata (located on the surface)

3. Veins carry water and nutrients from the roots to the leaves. They also deliver organc molecules produced in the leaves to other parts of the plant.

*Some of the steps of photosynthesis take place in the thylakoid membranes, while others take place in the stroma.

1. The Light Reactions (takes plae in thylakoids' membranes)-
-converts the sunlight energy to chemical energy
-steps: 1. chlorophyll molecules (in the membrane) capture light energy
2. the chloroplasts use the captured energy to remove electrons from water
--> it splits H2O into O2 and H+
3. O2 goes out into the atmosphere through the stomata
4. the chloroplasts use electron and H+ to make NADPH
5. the chloroplasts use the captured enrgy to generate ATP
*NADPH is an electron carrier, similar to NADH, an energy-rich molecule.
-results=light energy-->chemical energy-NADPH
-ATP

2. The Calvin Cycle (takes place in the stroma)-
-makes sugar from the atoms in CO2 and H+ and high-energy electrons in NADPH
-the enzymes for the cycle are outside the thylakoids and dissolved in the stroma

Concept Check 8.1

1. Draw and label a simple diagram of a chloroplast that includes the following structures: outer and inner membranes, stroma, thylakoids.

2. What are the reactants for photosynthesis? What are the products?

Reactants: CO2, H2O

Products: C6H12O6, O2

3. Name the two main stages of photosynthesis. How are the two stages related?

The light reaction, and the Calvin cycle.

The Calvin cyce process needs the supply of ATP and NADPH from the light reaction process, in order to make sugar.

Vocabulary 8.1

Chloroplast-the cellular organelle where photosynthesis takes place

Chlorophyll-chemical compounds inside chloroplasts that give these organelles a green colour

Stroma-a thick fluid enclosed by the inner membrane of a chloroplast

Thylakoid-a disk-shaped sac suspended in the stroma

Light reaction-a process that converts te energy in sunlight to chemical energy

Calvin cycle-a process that makes sugar from the atoms in carbon dioxide plus the hydrogen ions and high-energy electrons carried by NADPH