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Cell Energy: Photosynthesis and Respiration 1 Energy and Life l Energy is the ability to do work – l l 2 All living organisms need energy Autotrophs – make their own food Heterotrophs – obtain energy from food they consume Chemical Energy and ATP • Energy is stored as phosphate groups are added to Adenosine • Adenosine Monophosphate (AMP) • Adenosine Diphosphate (ADP) • Adenosine Triphosphate (ATP) • Energy is released when bonds are broken 3 continued • Adenosine Triphosphate or ATP – Composed of: Adenine (base) Ribose (5 C sugar) 3 Phosphate Groups 4 Photosynthesis: An Overview 5 l Van Helmont – (1643) trees gain most of their mass from water l Priestly - (1771) plants release oxygen l Ingenhousz – (1779) plants need sunlight Photosynthesis continued l 6 Photosynthesis – is the process in which plants convert the energy of sunlight into the energy of chemical bonds of carbohydrates Photosynthesis continued • Requirements for photosynthesis: 6 CO2 + 6 H2O Light C6H12O6 + 6 O2 Sunlight- almost all organism depend on energy from the sun 7 Pigments – continued • Pigments– Plants absorb light via pigments in individual cells – Pigments are colored substances that absorb or reflect light – Primary pigment of green plants is chlorophyll • Absorbs red and blue • Reflects green (and other wavelengths such 8 The Reactions of Photosynthesis l Inside the chloroplast – – l l 9 Thylakoid – sac-like structure Grana – stacks of thylakoid In the thylakoid membrane pigments are arranged in clusters called photosystems Stroma- region outside the thylakoid membrane l Electron Carriers – – – – – – Sun light excites electrons in chlorophyll e- gain energy and require a special carrier Something that can accept a pair of high energy e-’s NADP+ Will then become NADPH and carry e- elsewhere in the cell Photosynthesis: The Light and Dark Reactions l Photosynthesis is divided into two reactions – Light Reaction Requires light (thylakoid) l Uses sunlight to make energy storing compounds l – Dark Reaction Does not require light (stroma) l Uses energy stored by light reaction to make glucose l 10 continued l Photosynthesis occurs in the chloroplast – Within the chloroplast are photosynthetic membrane l – – 11 Contain chlorophyll Light Reactions take place in the photosynthetic membrane Dark Reactions take place outside the membrane Light Dependent Reaction page 210 l l The energy of sunlight is absorbed and then converted into the energy of chemical bonds Light Reactions are broken down into four basic parts 1. 2. 3. 4. 12 Light Absorption Electron Transport Oxygen Production ATP Formation Light Absorption –continued l Takes place in clusters of pigment molecules within the photosynthetic membrane (photosystems) – 13 There are two types of photosystems Photosystem I and Photosystem II l Each photosystem contain several hundred chlorophyll molecules and accessory pigments l Absorption of light causes electrons in pigments to become “excited” l Energy is passed to specialized chlorophyll molecules in the reaction center of the photosystem 14 Electron Transport –continued l High energy electrons are released from the reaction center and are transferred along a series of electron carriers in the photosynthetic membrane. – Electron carriers are known as the electron transport chain – At the end of the chain an enzyme passes electrons to NADP+ -converting it to NADPH (1st way energy trapped by chemical bonds) 15 Oxygen Production –continued Water is broken down l Electrons are taken from water molecules l 4 electrons are removed from 2 water molecules – – 16 4 H+ and 2 O atoms 2 O atoms form O2 ATP Formation –continued l When water decomposes – – Electrons are passed from chlorophyll to NADP+ H+ are pumped across membrane l – An enzyme use energy to add a phosphate group to ADP forming ATP l 17 Difference in charge across membrane is a source of energy 2nd way energy is trapped in a chemical bond 18 continued l Summary – – Light reactions use H2O, ADP, and NADP+ Light Reactions produce O2, ATP, and NADPH l 19 ATP and NADPH are energy storing compounds Dark Reaction " The dark reaction is known as the Calvin Cycle 1. 2. a 5 C sugar bonds with CO2 to form two 3 C compounds ATP and NADPH are used and the 3 C compounds are converted to PGAL " " " " " Most of the PGAL is recycled 1 out of 6 is used to make glucose or other molecules Calvin cycle must go around twice to make 1 glucose Intermediate compounds are produced Dark reaction provides the raw materials to produce almost everything the cells needs 20 21 Glycolysis and Respiration § Respiration occurs in all living cells. It involves breaking the chemical bonds in organic food molecules and releasing energy (ATP). The food molecules are produced by plants during the process of photosynthesis. 22 Glycolysis –continued § Glycolysis is the first phase of respiration § § § § § Occurs independent of oxygen (anaerobic) is the breaking down of glucose into pyruvic acid Occurs in the cytoplasm 2 ATP molecules needed to start reaction 4 ATP molecules are synthesized 23 Aerobic Respiration – continued § This process involves O2 in the breakdown of food molecules to release energy § Uses pyruvic acid § Captures most of the energy in glucose § 34 ATP molecules § Occurs in both plants and animal § Takes place in the mitochondria 24 Krebs Cycle –continued § 1st step in aerobic respiration 1. Pyruvic acid moves from the cytoplasm into the mitochondria § Broken down into CO2 & 2C Compound § Coenzyme A combines with 2C Compound to form acetyl-CoA § acetyl-CoA combines with 4C molecule to form Citric Acid 25 26 Krebs Cycle continued § 9 intermediate reactions take place § More CO2 is released § NAD+ and FAD are converted to NADH and FADH2 § GDP converted to GTP to assist in making ATP § Page 227, Fig 9-6 27 continued- Electron Transport and ATP Formation § Electron Transport § Oxygen is the final electron receptor § It is needed to obtain energy from NADH and FADH2 § Electrons, H+, and Oxygen combine and form water § ATP Formation § Similar to photosynthesis, H+ are pumped through a membrane § Movement of H+ powers ATP formation § In total 36 ATP 28 Electron Transport Chain Electron Transport Hydrogen Ion Movement Channel Mitochondrion Intermembrane Space ATP synthase Inner Membrane Matrix ATP Production 29 Fermentation n n Fermentation is an anaerobic process Allows cells to produce energy in absence of oxygen 30 Fermentation continued n Lactic Acid n Pyruvic Acid n n n n n Lactic Acid Exercise Yogurt Sour Cream Sourdough Bread n Alcoholic Pyruvic Acid n Yeast n n n Alcohol + CO2 Carbon Dioxide = air spaces in bread Alcohol found in wine and beer Bubbles in Champagne 31 32