Biology 4A-2Photosynthesis

Start-Up Work Answer the Question on a separate sheet of paper: Answer the Question on a separate sheet of paper: Where do you ultimately get your energy from? Explain the process. Objectives Objectives Define Photosynthesis Write a simple equation for photosynthesis Explain how light energy is captured for use in photosynthesis Describe the light-dependent and light-independent reactions List the final products of photosynthesis Explain how the environment affects photosynthesis Distinguish between the C3- C4- and CAM pathways

What is Photosynthesis? Defined: the absorption of light and the process of converting it into energy Defined: the absorption of light and the process of converting it into energy

How does Photosynthesis work? Equation (write on board) Equation (write on board)

How is light Energy Captured and turned into usable Energy? (8 Steps) 1. Chlorophyll captures light energy and uses it for photolysis 2. The excited electron leaves the chlorophyll and is picked up by the electron acceptor molecule 3. As electron passes through the transport chain, some of the energy is used to pump hydrogen ions across the membrane

Continued 4. After passed through the chain, it is accepted by the by a molecule of chlorophyll. At the same time, light energy excites the newly arrived electron 5. The excited electron is passed to a different electron transport receptor in a different chain

Continued 6. Carries the electron to stroma side of the thylakoid membrane where it combines with hydrogen ion and forms NADPH 7. Hydrogen produced in by photolysis and those brought in step 3 form a large concentration gradient between the inside of the thylakoid and the stoma in the chloroplast 8. The hydrogen builds up inside the thylakoid. The H+ passes through an enzyme (ATP synthase) similar to osmosis!

Light Dependent Reactions Input: sunlight (energy) and water Input: sunlight (energy) and water Products: Products: Oxygen is give off Oxygen is give off Hydrogen Hydrogen Electrons Electrons Energy (Held in ATP) Energy (Held in ATP)

Light-Independent Reactions Input: Input: Hydrogen (from light Phase) Hydrogen (from light Phase) Energy (From ATP) Energy (From ATP) Carbon Dioxide and RuBP Carbon Dioxide and RuBP Output: Output: PGAL=glucose PGAL=glucose

The Results are in! Results of photosynthesis: Results of photosynthesis: Light independent Phase- PGAL Light independent Phase- PGAL Used as the building block of organic compounds such as glucose Used as the building block of organic compounds such as glucose Light Dependent Phase- Oxygen Light Dependent Phase- Oxygen

How does the Environment Effect Photosynthesis? The right amount of wavelengths and intensity is needed for photosynthesis to occur The right amount of wavelengths and intensity is needed for photosynthesis to occur If they do not absorb enough energy the chlorophyll will not become energized If they do not absorb enough energy the chlorophyll will not become energized This leads to a plateau where the chlorophyll a molecules are working at maximum capacity This leads to a plateau where the chlorophyll a molecules are working at maximum capacity

Environmental Factors Continued Temperature Temperature Proper temperature for photosynthesis varies, but for most room temperature (approx. 70 F) is just right Proper temperature for photosynthesis varies, but for most room temperature (approx. 70 F) is just right Above 90 F most photosynthesis stops Above 90 F most photosynthesis stops The result is a peak model (SB 103) The result is a peak model (SB 103)

Environmental Continued Water Water A lack of water will cause photosynthesis to stop A lack of water will cause photosynthesis to stop This limits the ability of the plant to transport water to the leaves, which is needed for photosynthesis This limits the ability of the plant to transport water to the leaves, which is needed for photosynthesis

C3 Pathway Also known as the Calvin cycle Also known as the Calvin cycle Most commonly used to fix carbon Most commonly used to fix carbon Starts with PGA (a 3 carbon compound) Starts with PGA (a 3 carbon compound) These plants close their stomata when temperatures are too high- causing photosynthesis to cease These plants close their stomata when temperatures are too high- causing photosynthesis to cease

C4 Pathway Fix carbon dioxide to allow photosynthesis to occur even though conditions are not ideal Fix carbon dioxide to allow photosynthesis to occur even though conditions are not ideal They partially close their stomata during the hottest part of the day They partially close their stomata during the hottest part of the day

CAM Pathway Fix carbon dioxide to allow photosynthesis to occur even though conditions are not ideal Fix carbon dioxide to allow photosynthesis to occur even though conditions are not ideal They close their stomata during the day They close their stomata during the day

Terms _______-Made of Membranes that contain chlorophyll _______-Made of Membranes that contain chlorophyll _______-Requires an input of sunlight and water _______-Requires an input of sunlight and water _______- Requires carbon dioxide and RuBP _______- Requires carbon dioxide and RuBP _______-the place where the entire process of photosynthesis takes place _______-the place where the entire process of photosynthesis takes place

Terms and Questions ______-Place where the light-dependent phase of photosynthesis takes place ______-Place where the light-dependent phase of photosynthesis takes place ______- Alternate photosynthesis pathway ______- Alternate photosynthesis pathway Which is an autotrophic organism? A cow, A man, A mushroom, An Oak Tree Which is an autotrophic organism? A cow, A man, A mushroom, An Oak Tree What are the two major products of photosynthesis? What are the two major products of photosynthesis? What is RuBP What is RuBP Who discovered most of the information about photosynthesis? Who discovered most of the information about photosynthesis?

Questions What is the most important function of Chlorophyll? What is the most important function of Chlorophyll? Which phase of photosynthesis takes place in either the presence or absence of darkness Which phase of photosynthesis takes place in either the presence or absence of darkness Which is the most directly involved in photosynthesis-Chlorophyll a or Chlorophyll b? Which is the most directly involved in photosynthesis-Chlorophyll a or Chlorophyll b? ________- The process of obtaining energy from inorganic materials ________- The process of obtaining energy from inorganic materials

True/False Photosynthesis is the essential step between solar energy and life Photosynthesis is the essential step between solar energy and life Plants grown in increased light or iron rich soil lack chlorophyll and appear whitish or pale yellow Plants grown in increased light or iron rich soil lack chlorophyll and appear whitish or pale yellow