PhotosynthesisChapter 8

Vocabulary—Breaking Down the Definitions• Photosynthesis• Pigment• Chlorophyll• Thylakoid• Stroma• NADP+• Light Dependent Reactions• ATP Synthase• Calvin Cycle

Photosynthesis—What Do We Already Know?

Photosynthesis Brain Pop

Chemical Equation—Quiz on this Next Meeting!

6 6

Photosynthesis

•Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into oxygen and high-energy sugars.

Light and Pigments

•In addition to water and carbon dioxide, photosynthesis also requires LIGHT and CHLOROPHYLL. •CHLOROPHYLL= a molecule within a chloroplast•Chlorophyll is a pigment that absorbs light

IVF to Analyze the Graph!

2 Stages of Photosynthesis

Light Reactions—In the Thylakoids• Light Energy (from the sun) is converted to

chemical energy, which is temporarily stored in ATP and the energy carrier molecule NADPH.

Calvin Cycle—In the Stroma• A series of enzyme-assisted chemical reactions

that produces a three-carbon sugar.

Inside a Chloroplast

•Photosynthesis takes place inside a chloroplast• The chloroplast contains saclike membranes called

THYLAKOIDS• THYLAKOIDS are arranged in stacks called GRANA• The Chlorophyll is inside the thylakoids• The STROMA is the region outside of the thylakoids

Light Reactions

1.The first stage of photosynthesis is the LIGHT REACTIONS.

2.Light is absorbed by the chloroplasts3.Light Energy is converted to Chemical

Energy (stored in ATP and NADPH)

Light Reactions Continued

4. Oxygen is given off during this reaction. --Leaf Demo--

5.Chlorophyll in the chloroplast contains pigments (compounds that absorb light) that absorb a lot of blue and red light but reflect green light (giving plants their green color.

Light Reactions Continued

6. An oxidation reaction takes place, losing electrons and the primary electron acceptor takes on the lost electrons in a reduction reaction.

7. The primary electron acceptor donates the electrons to a series of molecules in the thylakoid membrane of the chloroplast.

Oxygen as Byproduct Demo

Label the diagram

Dark Reactions/Calvin Cycle

•In the second set of reactions in photosynthesis plants use the energy that was stored in ATP and NADPH during the light reactions to produce sugars.•Most common way this is done is called the CALVIN CYCLE.•Calvin Cycle Song!

4 Steps of the Calvin Cycle•3 CO2 molecules diffuse into the stroma and combine with a 5-Carbon molecule, RuBP. This molecule is very unstable and it quickly splits into 2 3-Carbon molecules called 3-PGA.•Each 3-PGA is converted into another 3 Carbon molecule, G3P after receiving a phosphate group from ATP and a proton from NADPH.

Step 1

Step 2

4 Steps of the Calvin Cycle•One of the G3P molecules leave the Calvin Cycle to make carbohydrates which are stored for later use.

•The remaining 3GP molecules are converted back into RuBP by adding phosphate groups from ATP and then the Calvin Cycle begins again.

Step 3

Step 4

Calvin CycleStep 1—3 CO2 molecules combine to

form RuBP (6 carbon molecule) which splits into 3 PGA

Step 2—Each molecule of 3 PGA is converted to G3P

Step 3– One molecule of G3P leaves the cycle to make sugars

Step 4– The rest of the G3P is converted back into RuBP/Rubisco

Factors Affecting Photosynthesis

•Water, Temperature, Intensity of Light all affect the rate of photosynthesis

Thinking Visually

• Complete the flowchart on page 216 of your book.

Investigation Photosynthesis