Photosynthesis 2024 PDF

Photosynthesis  2 Stages of Photosynthesis Light Dependent Stage Light Independent Stage (Calvin Cycle) 2  Light-Dependent Reactions {Textbook Pages 210-211} Where? ~ on the thylakoid membranes...

Photosynthesis  2 Stages of Photosynthesis Light Dependent Stage Light Independent Stage (Calvin Cycle) 2  Light-Dependent Reactions {Textbook Pages 210-211} Where? ~ on the thylakoid membranes Reactants? : light and water  Light-Dependent Reactions Overview Light is absorbed by chlorophyll Water is split into (2) H & Oxygen atoms Oxygen is released through Stomata in leaves ATP & NADPH are made to drive the next stage – These are energy carrying molecules Water splitting What cell transport process allows gases to diffuse in and out of cells?  Light-Dependent Reactions A. Light energy is used to break up water molecules into hydrogen ions (H+) and oxygen.  Light-Dependent Reactions B. The energized electrons then bind with NADP+ to form NADPH (NADPH is acting as a carrier of energy that will be needed in the Calvin Cycle to make sugar) C. The inside of the thylakoid membrane (the lumen) is now filling up with positively charged H+ causing an electrochemical gradient (lumen positively charged and stroma negatively charged) Where are all of these H+ coming from???? Light-Dependent Reactions (LUMEN)  Light-Dependent Reactions Using your knowledge of transport, what do you think will occur when there becomes an abundance of H + on one side of a membrane?  Light-Dependent Reactions D. Yes!!! Hydrogen ions will pass through an ion channel (passively moving from high to low). As this occurs, energy is produced and used to convert ADP into ATP  Light-Dependent Reactions Products from this stage – ATP {adenosine triphosphate} used in the Calvin Cycle – NADPH {nicotinamide adenine dinucleotide phosphate} used in the Calvin Cycle – Oxygen Released into the atmosphere NADPH  Light-Independent Reactions (also called Calvin Cycle or Dark Reactions) Not directly dependent on light Where? : stroma – Liquid region of Chloroplast Animation  Calvin Cycle Reactants??: {what the Calvin Cycle needs} – ATP (made in light dependent stage ) – NADPH (made in light dependent stage ) – CO2 How did CO2 get into plant? What organisms provide CO2 for plants? 13  Calvin Cycle Known as Carbon Fixation Carbon dioxide is “fixed” into the sugar glucose (C6H12O6) Most plants use the Calvin (C3) cycle to fix carbon Calvin Cycle Product Carbohydrates~ Stored in plant C6H12O6 = Glucose!!!!!! What do animals use glucose for?????  The Calvin Cycle 3 5 6 6 5 6 1 G3P  Step 1 Carbon Fixation 1. THREE Carbon dioxide (3-C) is joined to three RuBP (5-C) using the enzyme Rubisco, forming an unstable 6-C molecule 2. The 6-C molecule quickly splits into 6 3-C PGA molecules 3 6 3  Step 2 Reduction (the gaining of e-’s 3. ATP adds a ‘P’ to 6 PGAs forming 6 BPGAs 4. 6 BPGAs gets the energized electrons from NADPH to convert it to 6 G3Ps  Step 3: Regeneration of RuBP 5. One G3P (3-C) molecule exits the cycle 6. The 5 G3P (3-C) molecules join to become 3 Ribulose-5-P (5-C) 7. ATP adds ‘P’ to the 3 Ribulose-5-P to regenerate 5 RuBP (5- C) to continue cycle!!  Summary Video (7 min 30 secs) Click picture for video  Plant Adaptations Because of photorespiration, plants have special adaptations to limit the effect of photorespiration: Ex. CAM plants Photorespiration is when a plant does not have enough CO2 so oxygen jumps into the Calvin Cycle. This results in no glucose production and instead, a bad chemical for the plant 21  CAM Plants Hot, dry environments 5% of plants (cactus and succulents) Day- Stomates closed Night- Stomates open Light reaction - occurs during the day Calvin Cycle - occurs when CO2 is present (over time) 22  Factors Affecting Photosynthesis CO2 Concentration Light Intensity Temperature 23 Animation  plateau CO2 is a substrate in an enyme-catalysed light- dependent reaction. At low CO2 concentration, rate is positively correlated with concentration  plateau At low light intensity, rate of photosynthesis is proportional to light intensity.  Optimum temperature Above the optimum temp., Increased temp. enzymes are gives increased denatured and energy and rate drops increased rate of steeply. photosynthesis Which enzymes are used in respiration?