Photosynthesis Notes PDF

General Biology I PHOTOSYNTHESIS  LESSON OBJECTIVES At the end of the lesson, students should be able to: 1 2 3 describe the process explain the show the process of of light-depe...

General Biology I PHOTOSYNTHESIS  LESSON OBJECTIVES At the end of the lesson, students should be able to: 1 2 3 describe the process explain the show the process of of light-dependent importance of light-dependent and and light-independent chlorophyll; light-independent reactions in reactions through a photosynthesis; and game. THE PHOTOSYNTHESIS SONG THE PHOTOSYNTHESIS SONG https://www.youtube.com/watch?v=C1_uez5WX1o  PART 1: CHLOROPHYLL PART 2: OVERVIEW OF PHOTOSYNTHESIS PART 3: ELECTRONS & ENERGY  PART 1: CHLOROPHYLL PIGMENTS Substances that absorb visible light.  PART 1: CHLOROPHYLL CHLOROPHYLL The green pigment found in the thylakoid membrane inside the chloroplast of a plant cell.  PART 1: CHLOROPHYLL KINDS OF CHLOROPHYLL Chlorophyll a – directly participates in converting solar energy into chemical energy Chlorophyll b – accessory pigment that absorb light and transfer it to chlorophyll a carotenoids are also accessory pigments  PART 1: CHLOROPHYLL PHOTOSYSTEM Aggregate of pigments and proteins in the thylakoid membrane responsible for absorption of photons and transfer of energy and electrons.  PART 1: CHLOROPHYLL PHOTOSYSTEM Composed of Light-harvesting complex Reaction center complex  PART 1: CHLOROPHYLL PHOTOSYSTEM Light-harvesting complex ‘antenna’ complex consists of different pigments bounded with proteins.  PART 1: CHLOROPHYLL PHOTOSYSTEM Reaction center complex composed of pair of chlorophyll a and a primary electron acceptor.  PART 1: CHLOROPHYLL 2 TYPES OF PHOTOSYSTEMS Photosystem II Photosystem I WATER-SPLITTING NADPH-PRODUCING PHOTOSYSTEM PHOTOSYSTEM  PART 1: CHLOROPHYLL 2 TYPES OF PHOTOSYSTEMS Photosystem II functions first in the light reaction of photosynthesis but discovered later, after the discovery of Photosystem I. AKA P680 WATER-SPLITTING PHOTOSYSTEM NADPH-PRODUCING PHOTOSYSTEM  PART 1: CHLOROPHYLL 2 TYPES OF PHOTOSYSTEMS Photosystem I functions after Photosystem II but discovered first. AKA P700 WATER-SPLITTING NADPH-PRODUCING PHOTOSYSTEM PHOTOSYSTEM  PART 2: OVERVIEW OF PHOTOSYNTHESIS  OVERVIEW OF PART 2: PHOTOSYNTHESIS IMPORTANCE OF PHOTOSYNTHESIS Photosynthesis is vital because it stores energy in solar radiation and synthesize carbohydrates. Those carbohydrates are the energy source of animals. Therefore, photosynthesis powers 99% of the Earth’s ecosystems.  OVERVIEW OF PART 2: PHOTOSYNTHESIS IMPORTANCE OF PHOTOSYNTHESIS Photosynthesis is a multi-step process that requires sunlight, carbon dioxide, and water. It releases oxygen and carbohydrate after the process.  OVERVIEW OF PART 2: PHOTOSYNTHESIS UNLOCKING OF TERMS Photosynthesis generally happens in leaves. In the leaves, it happens in the middle layer of cells called mesophyll.  OVERVIEW OF PART 2: PHOTOSYNTHESIS  OVERVIEW OF PART 2: PHOTOSYNTHESIS  OVERVIEW OF PART 2: PHOTOSYNTHESIS 2 PARTS OF PHOTOSYNTHESIS Photosynthesis happens in 2 stages: the light-dependent and light-independent reactions  OVERVIEW OF PART 2: PHOTOSYNTHESIS LIGHT-DEPENDENT REACTIONS take place in the thylakoid membrane requires light energy produces NADPH and ATP (to be used in dark reactions)  OVERVIEW OF PART 2: PHOTOSYNTHESIS LIGHT-INDEPENDENT REACTIONS also called Calvin cycle or Dark reactions Take place in stroma Produces carbohydrates Returns ADP and NADP+ to the light reactions PART 3: ELECTRONS & ENERGY Most of the energy stored in atoms is in the form of high- energy electrons. PART 3: ELECTRONS & ENERGY ELECTRON CARRIERS Electron carriers – function as electron shuttles: bind and carry electrons between compounds and energy pathways.  PART 3: ELECTRONS & ENERGY OXIDATION AND REDUCTION Oxidation happens in a chemical reaction when there is a loss of electrons. Reduction happens in a reaction when there is a gain of electrons.  PART 3: ELECTRONS & ENERGY OXIDATION AND REDUCTION Whenever a molecule is oxidized, another molecule must be reduced. Redox Reaction  PART 3: ELECTRONS & ENERGY ELECTRON CARRIER EXAMPLES NADP: Nicotinamide Adenine Dinucleotide Phosphate. The oxidized form of NADP is NADP+ and the reduced form is NADPH. NAD and FAD are also examples of electron carriers. PART 4: LIGHT-DEPENDENT REACTIONS  PART 4: LIGHT-DEPENDENT REACTION https://www.youtube.com/watch?v=Le7KOX91w7U&list=PPSV  PART 4: LIGHT-DEPENDENT REACTION The process starts in photosystem II. When PSII absorbs light, the electrons in chlorophyll get excited (gain energy).  PART 4: LIGHT-DEPENDENT REACTION Excited electrons will be passed to the first electron transport chain.  PART 4: LIGHT-DEPENDENT REACTION The first electron pq pc transport chain is composed of plastoquinone (pq), cytochrome and plastocyanin (pc). cytochrome  PART 4: LIGHT-DEPENDENT REACTION Electrons in PSII should be replaced. This is done through photolysis – water is split and its electrons go to chlorophyll.  PART 4: LIGHT-DEPENDENT REACTION Electrons → PSII Hydrogen ion → lumen Oxygen → exit (through the stomata)  PART 4: LIGHT-DEPENDENT REACTION (Back to the electron transport chain!!!!!!!) Electrons are transported from the plastoquinone (pq) to cytochrome. As it does, energy in the electrons is used to transfer H ions from stroma to lumen.  PART 4: LIGHT-DEPENDENT REACTION H ions to diffuse passively across the membrane through the ATP synthase. H ions act as the fuel for the ATP synthase to work and produce ATP (first key product).  PART 4: LIGHT-DEPENDENT REACTION Electrons from cytochrome go to plastocyanin (pc) and go to photosystem I.  PART 4: LIGHT-DEPENDENT REACTION In PS I, light excites them once again. The electrons travel down a second, shorter ETC.  PART 4: LIGHT-DEPENDENT REACTION Fd NADP+ REDUCTASE The second ETC is composed of Ferredoxin (Fd) and NADP+ Reductase.  PART 4: LIGHT-DEPENDENT REACTION Here, the electrons are accepted by NADP+. When it accepts electrons, it also accepts H ion and it becomes NADPH (second key product).  PART 4: LIGHT-DEPENDENT REACTION The 2 key products ATP and NADPH will go the next set of reaction: The Calvin Cycle. PART 4: LIGHT-DEPENDENT REACTION PART 5: CALVIN CYCLE  PART 5: CALVIN CYCLE https://www.youtube.com/watch?v=SltE4zP8-9w  PART 5: CALVIN CYCLE Second set of reactions in photosynthesis that occurs after the light- dependent reactions Uses key products of light-dependent reactions (ATP, NADPH)  PART 5: CALVIN CYCLE Unlocking of Terms: RuBP, a 5-carbon molecule (Ribulose biphosphate) RuBisCO, an enzyme (Ribulose biphosphate carboxylase) 3PGA, a 3-carbon molecule (3-phosphoglycerate) G3P, a 3-carbon molecule (glyceraldehyde-3-phosphate)  PART 5: CALVIN CYCLE 3 Phases: 1. Carbon Fixation 2. Reduction 3. Regeneration of RuBP  PART 5: CALVIN CYCLE 1. CARBON FIXATION: CO2 is used The CO2 will be attached to the starting compound RuBP (Ribulose biphosphate, a 5- carbon molecule) with the help of the RuBisCO (Ribulose biphosphate carboxylase) Enzyme.  PART 5: CALVIN CYCLE 1. CARBON FIXATION: This results to an unstable 6-carbon molecule that quickly splits into two 3-carbon molecules called 3- phosphoglycerate, or 3PGA. This phase will happen 3 times. So, the end product of this phase is six 3PGA molecules.  PART 5: CALVIN CYCLE 2. REDUCTION: The process of creating carbohydrate begins This phase will add electrons and energy to the 3PGA molecules Each 3PGA will be reduced to G3P (glyeceraldehyde-3-phosphate, a carbohydrate).  PART 5: CALVIN CYCLE 2. REDUCTION: ATP and NADPH will be used up and become ADP and NADP+ The end product of this phase is 6 G3P molecules 1 of the G3P will be set aside as a building block for glucose 5 of the G3P will move to the next phase.  PART 5: CALVIN CYCLE How many carbons does an RuBP have? 5 G3P Molecules x 3 Carbons = 15 5 Carbons  PART 5: CALVIN CYCLE If we have 5 G3P molecules, which has 3 carbons each, how many carbon atoms do we have? 5 Carbons  PART 5: CALVIN CYCLE So out of 15 carbons from the 5 G3Ps, how many RuBP can we create? 155Carbons G3P Molecules x 3 Carbons ÷ 5 Carbons = 15= 3 per RuBP 5 Carbons  PART 5: CALVIN CYCLE Key product: G3P Molecule 1 Calvin Cycle = 1 G3P 1 G3P = 3 carbon atoms 1 Glucose (C6H12O6) = 6 carbon atoms  PART 5: CALVIN CYCLE A G3P molecule has 3 carbon atoms and glucose needs 6 carbon atoms, so we need 2 G3P. Therefore, THE ENTIRE CYCLE HAS TO GO THROUGH TWICE to create 1 glucose molecule (C6H12O6), because only 1 G3P will be set aside during reduction. PART 4: LIGHT-DEPENDENT REACTIONS Takes place in the Thylakoid Membrane Needs sunlight and water Key products: ATP and NADPH Byproduct: Oxygen gas PART 5: CALVIN CYCLE Takes place in the Stroma Needs CO2, ATP, and NADPH Key product: G3P (Carbohydrate) 3 Phases: Carbon Fixation, Reduction, Regeneration Thank you for listening!