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