Photosynthesis & Cell Molecular Biology PDF

8/27/24, 8:20 PM Platform | Study Fetch Photosynthesis and Cell Molecular Biology (00:00:00 - 00:00:13) Introduction by Tyler Overview of Photosynthesis (00:00:13 - 00:00:24) Photosynthesis is a process that converts li...

8/27/24, 8:20 PM Platform | Study Fetch Photosynthesis and Cell Molecular Biology (00:00:00 - 00:00:13) Introduction by Tyler Overview of Photosynthesis (00:00:13 - 00:00:24) Photosynthesis is a process that converts light energy into chemical energy to fuel the activity of living organisms. Lesson Overview (00:00:24 - 00:00:35) First, we'll discuss photosynthesis. Then, we'll cover non-cyclic and cyclic photophosphorylation, and the Calvin cycle. Finally, we'll discuss alternative photosynthetic pathways. What is Photosynthesis? (00:00:35 - 00:00:48) Photosynthesis is a process by which carbon dioxide, water, and sunlight combine to produce sugar or food for the plant. This also outputs oxygen, which helps to sustain all life on Earth. Chloroplasts (00:00:48 - 00:01:01) Photosynthesis is carried out in chloroplasts, the organelles in the cell that contain chlorophyll. Chloroplasts have an envelope with an outer and inner membrane. Thylakoids are the structures where photosynthesis takes place. Photosynthesis Process (00:01:01 - 00:01:11) Photosynthesis consists of two main parts: Light-dependent reactions Calvin cycle Inputs and Outputs (00:01:11 - 00:01:25) https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6bc78ab287f54e41f2a6/document?go=note 1/6 8/27/24, 8:20 PM Platform | Study Fetch Inputs: water and carbon dioxide Outputs: activated molecules that will be used in the Calvin cycle to produce sugar Energy Carriers and Photosynthesis Light-Dependent Reactions (00:01:25 - 00:01:36) Energy carriers are molecules that help manufacture sugars, generate ATP and NADPH in the light-dependent reactions. These energy carriers are activated and will occur in the thylakoid membrane of the chloroplast. The diagram shown represents the Calvin cycle, which occurs in the stroma of the chloroplast. The Calvin Cycle (00:01:36 - 00:01:47) The Calvin cycle has three phases: carbon fixation, reduction, and regeneration. Chlorophyll absorbs light within a narrow range of blue and red wavelengths. Chlorophyll Absorption (00:01:47 - 00:01:58) Chlorophyll absorbs light most strongly at wavelengths of 687 and 700 nanometers, along with other pigments. Photosystems (00:01:58 - 00:02:08) Chlorophyll P700 forms a pigment cluster called Photosystem I. Chlorophyll P680 forms Photosystem II. These two photosystems are large multi-protein complexes that absorb light energy. Photosystem Structure (00:02:08 - 00:02:22) Each photosystem consists of: Antenna complexes that capture light energy A reaction center that converts light energy into chemical energy Non-Cyclic and Cyclic Photophosphorylation (00:02:22 - 00:02:32) https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6bc78ab287f54e41f2a6/document?go=note 2/6 8/27/24, 8:20 PM Platform | Study Fetch We will now discuss non-cyclic and cyclic photophosphorylation, as well as the Calvin cycle. Non-Cyclic Photophosphorylation (00:02:32 - 00:02:42) "First, let's talk about non-cyclic photophosphorylation." Cyclic Photophosphorylation (00:02:42 - 00:02:52) "Next, let's discuss cyclic photophosphorylation." The Calvin Cycle (00:02:52 - 00:03:02) "Finally, we'll cover the Calvin cycle." Cyclic Photophosphorylation (00:02:42 - 00:02:58) Electrons are trapped by Photosystem II and energized by light The primary electron acceptor, plastoquinone, accepts the first pair of electrons (00:02:58 - 00:03:11) The electron transport chain transfers high-energy electrons to a protein proton pump This generates an electrochemical proton gradient, similar to the process in mitochondria (00:03:11 - 00:03:24) As electrons travel down the electron transport chain, they lose energy This lost energy is used to phosphorylate ADP into ATP The electron transport chain ends with Photosystems (00:03:24 - 00:03:39) Electrons energized by the sun are passed to a different primary electron acceptor Electrons pass through a short electron transport chain Two electrons combine with NADP+ and H+ to form NADPH (00:03:39 - 00:03:50) The loss of two electrons from Photosystem II is replaced by the splitting of one water molecule into two H+ and half an oxygen This process must be doubled to account for the full reaction https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6bc78ab287f54e41f2a6/document?go=note 3/6 8/27/24, 8:20 PM Platform | Study Fetch Key Terms and Concepts: Cyclic Photophosphorylation Photosystem II Plastoquinone Electron Transport Chain Proton Pump Electrochemical Proton Gradient Photosystem NADP+ Water Splitting Tables: Step Description 1 Electrons trapped and energized by Photosystem II 2 Plastoquinone accepts first pair of electrons 3 Electron transport chain transfers electrons to proton pump 4 Proton gradient used to phosphorylate ADP to ATP 5 Electrons passed to different primary acceptor 6 Electrons combine with NADP+ and H+ to form NADPH 7 Water splitting replaces electrons lost from Photosystem II Footnotes:^1 The water splitting process must be doubled to account for the full reaction. Code Block: # Pseudocode for Cyclic Photophosphorylationwhile True: trap_electrons(photosystem_II) energize_electrons(light) accept_electrons(plastoquinone) transfer_electrons(electron_transport_chain) generate_gradient(proton_pump) phosphorylate_ADP(gradient) pass_electrons(photosystem) combine_electrons(NADP+, H+) replace_electrons(water_splitting) Photosynthesis: Cyclic Photophosphorylation and the Calvin Cycle https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6bc78ab287f54e41f2a6/document?go=note 4/6 8/27/24, 8:20 PM Platform | Study Fetch Cyclic Photophosphorylation (00:04:01 - 00:04:15) Cyclic photophosphorylation occurs at the same time as non-cyclic photophosphorylation The difference is that the energized electrons are recycled and returned to photosystems Both photosystems work in tandem to produce ATP and NADPH Photosystems and Electron Transport (00:04:15 - 00:04:26) Photosystem II gets electrons from water Photosystem I gets electrons from Photosystem II This is an important distinguishing factor to remember Summary of Photophosphorylation (00:04:26 - 00:04:36) Photophosphorylation takes the energy from light and the electrons from water to make the energy-rich molecules ATP and NADPH Diagram of Photophosphorylation (00:04:36 - 00:04:50) H2O + Phosphate + ADP + NADP+ + Light → ATP + NADPH + O2 + H+ The Calvin Cycle (00:04:50 - 00:05:09) The Calvin cycle is where carbon dioxide from the atmosphere is combined with the ATP and NADPH produced in the light reactions This process converts the carbon dioxide into organic compounds like glucose Key Points to Remember: Cyclic photophosphorylation recycles electrons, while non-cyclic produces ATP and NADPH Photosystem II gets electrons from water, Photosystem I gets electrons from Photosystem II Photophosphorylation uses light energy to produce ATP and NADPH The Calvin cycle uses the ATP and NADPH to convert carbon dioxide into organic compounds The Calvin Cycle: Photosynthesis's Carbon Fixation Process https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6bc78ab287f54e41f2a6/document?go=note 5/6 8/27/24, 8:20 PM Platform | Study Fetch (00:05:09 - 00:05:36) Bisco is a 5-carbon molecule The Calvin cycle produces 23 carbon molecules of 3-phosphoglycerate (3-PG) in the chloroplast stroma 12 ATP and 12 NADPH are used to convert 12 3-PG to 12 G3P (glyceraldehyde 3-phosphate) ADP, phosphate, and NADP+ are released and reenergized in non-cyclic photophosphorylation Rubisco is regenerated, allowing the cycle to repeat (00:05:36 - 00:05:56) 3-phosphoglycerate (3-PG) is the 3-carbon sugar that is the final product of the Calvin cycle 3-PG is the starting material for the synthesis of many other sugars and organic molecules (00:05:56 - 00:06:07) The Calvin cycle takes CO2 from the atmosphere and uses the energy in ATP and NADPH to create a glucose molecule The energy in ATP and NADPH represents the energy from the sun captured during photophosphorylation (00:06:07 - 00:06:21) C4 photosynthesis and CAM photosynthesis are alternative photosynthetic pathways that don't use the traditional Calvin cycle mechanism (00:06:21 - 00:06:29) Congratulations! You've mastered photosynthesis and the Calvin cycle. You're now prepared to do well on tests and answer plant-related questions correctly. Alternative Photosynthetic Pathways C4 Photosynthesis Overview of the C4 photosynthesis mechanism CAM Photosynthesis Overview of the CAM photosynthesis mechanism These alternative pathways are mechanisms of photosynthesis that don't use the traditional Calvin cycle. https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6bc78ab287f54e41f2a6/document?go=note 6/6