CONCEPT 8.1) Photosynthesis Uses Light Energy to make food.

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KEY TERMS:

Chloroplast: organelle found in some plant cells and certain unicellular organisms where photosynthesis takes place. These contain chemical compounds called chlorophylls.
Chlorophyll: pigment that gives a chloroplast its green color; uses light energy to split water molecules during photosynthesis.
Stroma: thick fluid contained in the inner membrane of a chloroplast
Thylakoid: disk-shaped sac in the stroma of a chloroplast; site of the light reactions of photosynthesis.
Light reactions: chemical reactions that convert the sun's energy to chemical energy; take place in the membranes of thylakoids in the chloroplast.
Calvin cycle: cycle in plants that makes sugar from carbon dioxide, H+ ions, and high-energy electrons carried by NADPH.

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SUMMARY

Looking at the structure of a plant leaf.....
- Leafs in a plant contain the most chloroplasts and are the major sites for photosynthesis to take place.
- Chloroplasts are concentrated in the cells of the mesophyll (inner layer of tissure).
- On the surface of the leaf, there are pores called stomata, where CO2 enters and O2 exits through.
-Veins carry water and nutrients, and also other organic molecules produced in the leaves, through stomatas and to other parts of the plant.

Looking inside the chloroplasts' structure...
Chloroplast
~ inner& outer membrane
~ inner: thick fluid - stroma
~ stroma: Many disk-shaped sacs: thylakoids
~ Thylakoids:
+ each has a membrane surrounding the interior space.
+ Thylakoids arranged in stacks are called grana.

- Photosynthesis is a process of plants and other producers, or autotrophs, converting the energy of sunlight into useful energy that is stored in organic molecules. - Photosynthesis is the opposite of cellular respiration.

- The chloroplast uses "excited" electrons, along with CO2 and hydrogen ions, to produce sugar molecules.

-Photosynthesis occurs in 2 main stages: theLight Reactions & the Calvin Cycle.

The Light Reaction

1. Sun light energy>> chemical energy

2. Chlorophyll molecules in the membrane captures energy.

3. Chloroplasts use these energy to remove electrons from water. ---> Splits H2O --> Oxygen ("waste product" go out through stomata) & Hydrogen ions

4. Electron & Hydrogen ions in chloroplast ---> NADPH (energy carrier)

5. Chloroplast use the stored energy to make ATP too.

+++ Overall: Light energy stored ---> chemical energy ---> NADPH & ATP

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The Calvin Cycle

- NADPH & ATP made by light reactions provides energy to make sugar from the atoms in:

CO2 + Hydrogen ions + high-energy electrons carried by NADPH

- Enzymes for the process located outside the thylakoids, dissolved in stroma.

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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: Glucose, Oxygen
6 O2 + 6 H2O ->->-> C6H12O6 + 6 O2

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

Two main stages: the light reactions, the Calvin Cycle

They are related in that the light reactions recieve is the process of storing the sun light energy and converting them into chemical energy, making NADPH and ATP rich in energy. Then the Calvin Cycle uses these NADPH and ATP to make sugar for the chloroplast.