PhotosynthesisChapter 6

Vocabulary—Breaking Down The Definitions•Photosynthesis• Light Reactions• Thylakoids•Grana• Stroma•Photosystem•Primary electron acceptor

• Electron transport chain•Pigment•Chloroplast•Calvin cycle•Carbon fixation

Photosynthesis—What Do We Already Know?

Photosynthesis—Obtaining Energy

•Autotrophs use the process of photosynthesis to convert light energy into organic compounds.

Chemical Equation—Quiz on this Next Meeting!

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Photosynthesis Brain Pop

Overview Photosynthesis

1. Water2. Carbon Dioxide3. Sunlight/Photons4. Chloroplast5. Light Reactions

a) Photosystem IIb) Cytochrome Complexc) ATP Synthased) Photosystem I

6. Dark Reactions/Calvin Cyclea) Phase 1-Carbon Fixationb) Reductionc) Regeneration

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.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.

Light Reactions Continued6. These molecules are called an electron

transport chain.7. As the electrons pass through the chain they

lose energy.8. Light is absorbed at this point and the

electrons combine with a proton and NADP+9. NADP+ is then reduced through another

reduction reaction to NADPH.

Making ATP in Light Reactions

•ATP is the energy in cells. •The movement o protons into the stroma of the chloroplast releases energy, which is used to produce ATP. •The energy is harnessed by an enzyme, ATP Synthase, which is in the thylakoid membrane

Photosynthesis—Light Reactions Video Clip

Label the diagram

Label Another Diagram…

INTERACTIVE

• 100-200 Words• Summarize the LIGHT REACTIONS of photosynthesis

Light Reactions Video Clips

• Add to your summary if you need to!

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!

Calvin Cycle

•A series of enzyme-assisted chemical reactions that produce a 3-Carbon Sugar.•Occurs in the STROMA of the chloroplast.

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

Calvin Cycle Video Clip

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Let’s hear that song again…

Light Color and Intensity and its effect on Photosynthesis