Section 2: Photosynthesis Light energy is trapped and converted into chemical energy during photosynthesis.

Essential Questions What are the two phases of photosynthesis? What is the function of a chloroplast during the light reactions? How can electron transport be described and diagramed? Copyright © McGraw-Hill Education Photosynthesis

Day 1 Vocabulary Review New carbohydrate thylakoid granum Stroma Electron transport molecules pigment NADP+ Photosynthesis Copyright © McGraw-Hill Education

Carbohydrate

Overview of Photosynthesis Most autotrophs make organic compounds using photosynthesis. Photosynthesis is the process of converting light energy into chemical energy. Copyright © McGraw-Hill Education Photosynthesis

Overview of Photosynthesis Photosynthesis occurs in two phases. In the light-dependent phase, light energy is converted into chemical energy. In the light-independent phase, chemical energy used to synthesize glucose. Copyright © McGraw-Hill Education Photosynthesis

Phase One: Light Reactions The absorption of light is the first step in photosynthesis. Once light energy is captured, it can be stored as ATP or NAPDH. Copyright © McGraw-Hill Education Photosynthesis

Phase One: Light Reactions Chloroplasts Organelles that capture light energy Copyright © McGraw-Hill Education Photosynthesis

Phase One: Light Reactions Chloroplasts Contain two main compartments: Thylakoids: flattened saclike membranes Stacks of thylakoids are called grana. Copyright © McGraw-Hill Education Photosynthesis

Phase One: Light Reactions Chloroplasts Contain two main compartments: The fluid filled space outside the grana called the stroma. Copyright © McGraw-Hill Education Photosynthesis

Phase One: Light Reactions Pigments Light-absorbing colored molecules called pigments are found in the thylakoid membranes. Copyright © McGraw-Hill Education Photosynthesis

Phase One: Light Reactions Pigments Different pigments absorb specific wavelengths of light. Most common pigment in plants is chlorophyll. Plants also have accessory pigments. Copyright © McGraw-Hill Education Photosynthesis

Phase One: Light Reactions Electron transport Takes place across the thylakoid membrane This includes a large number of electron transporting molecules and two types of protein complexes called photosystems. Photosystems house the light-capturing pigments. Copyright © McGraw-Hill Education Photosynthesis

Phase One: Light Reactions Electron transport Light energy excites electrons in photosystem II. This light energy causes a water molecule to split – releasing an electron into the electron transport system, a hydrogen ion (H+ or proton) into the thylakoid space, and oxygen as a waste product. Copyright © McGraw-Hill Education Photosynthesis

Phase One: Light Reactions Electron transport The activated electrons move from photosystem II to an acceptor molecule in the thylakoid membrane. The electron acceptor molecule transfers the electrons along a series of electron carriers to photosystem I. Copyright © McGraw-Hill Education Photosynthesis

Phase One: Light Reactions Electron transport In the presence of light, photosystem I transfers the electrons to a protein called ferrodoxin. Ferrodoxin transfers the electrons to the carrier molecule NADP+, forming the energy storage molecule NADPH. Copyright © McGraw-Hill Education Photosynthesis

Phase One: Light Reactions Electron transport ATP is produced in conjunction with the electron transport system through chemiosmosis. ATP is produced through the flow of electrons down a concentration gradient. The breakdown of water provides the necessary protons for ATP synthesis. Copyright © McGraw-Hill Education Photosynthesis

Review Essential Questions Vocabulary What are the two phases of photosynthesis? What is the function of a chloroplast during the light reactions? Vocabulary thylakoid granum stroma Pigment NADP+ Photosynthesis Copyright © McGraw-Hill Education

Quiz 5 What are the two phases of photosynthesis? What is the function of a chloroplast during the light reactions? How can electron transport be described and diagramed? Copyright © McGraw-Hill Education Photosynthesis

Day 2 Essential Questions What role does CO2 play in the Calvin Cycle? What is the end result of the Calvin Cycle? Copyright © McGraw-Hill Education Photosynthesis

Day 2 Vocabulary Review New Electron Transport Chain Calvin cycle thylakoid granum stroma pigment NADP+ New Calvin cycle rubisco Photosynthesis Copyright © McGraw-Hill Education

Review: Electron Transport Chain Copyright © McGraw-Hill Education Photosynthesis

Phase Two: The Calvin Cycle In the second phase of photosynthesis, called the Calvin cycle, energy is stored in organic molecules such as glucose. Copyright © McGraw-Hill Education Photosynthesis

Phase Two: The Calvin Cycle The first step of the Calvin cycle is called carbon fixation. CO2 molecules combine with 5-carbon molecules to form 3- phosphoglycerate (3-PGA) Copyright © McGraw-Hill Education Photosynthesis

Phase Two: The Calvin Cycle In the second step, chemical energy stored in ATP and NADPH is transferred to the 3-PGA to form glyceraldehyde 3-phospate (G3P). Copyright © McGraw-Hill Education Photosynthesis

Phase Two: The Calvin Cycle In the third step, some G3P molecules leave the cycle to be used for the production of glucose and other organic compounds. Copyright © McGraw-Hill Education Photosynthesis

Phase Two: The Calvin Cycle In the fourth and final step, an enzyme called rubisco converts the remaining G3P molecules into 5-carbon molecules called ribulose 1,5-bisphospates (RuBP). These molecules combine with new CO2 and continue the cycle. Copyright © McGraw-Hill Education Photosynthesis

The Calvin Cycle Copyright © McGraw-Hill Education Photosynthesis

Alternative Pathways CAM plants Crassulacean acid metabolism (CAM) is found in desert plants. Collect CO2 at night and store it in organic compounds During the day, release CO2 from organic compounds for the light-dependent cycle of photosynthesis Copyright © McGraw-Hill Education Photosynthesis

Copyright © McGraw-Hill Education Photosynthesis

Photosynthesis Review Sunlight hits receptors in the thylakoid membrane This with the combination of H2O and starts the electron transport chain

Photosynthesis Review The electron transport chain sets up the production of ATP

Photosynthesis Overview

Review Essential Questions Vocabulary What role does CO2 play in the Calvin Cycle? What is the end result of the Calvin Cycle? Vocabulary thylakoid granum stroma pigment NADP+ Calvin cycle rubisco Copyright © McGraw-Hill Education Photosynthesis