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Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
Metabolismo ii fotossintese
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Metabolismo ii fotossintese

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  • 1. Fats Other Metabolic Pathways Glycogen Protein
  • 2. The body fat is our major source of stored energy • Our adipose tissue is made of fat cells adipocytes. • A typical 70 kg person has about 135 000 kcal of energy stored as fat, 24 000 kcal as protein, 720 kcal as glycogen reserves, and 80 kcal as blood glucose. • The energy available from stored fats is about 85 % of the total energy available in the body.
  • 3. Lipolysis via β-oxidation Lipases
  • 4. Beta-oxidation of fatty acids • β-oxidation of FA produces acetyl CoA and NADH and FADH2, which are sources of energy (ATP) • First, FA are converted to acyl CoA in the cytoplasm:
  • 5. Carnitine shuttle • For transport into mitochondria, CoA is replaced with carnitine by acylcarnitine transferase I • Inside mitochondria a corresponding enzyme (II) forms acyl CoA • Malonyl CoA inhibits acylcarnitine transferase I • So, when FA synthesis is active, FA are not transported into mitochondria • Defects in FA transport (including carnitine deficiency) are known
  • 6. Beta-Oxidation of Fatty Acids In reaction 1, oxidation: • Removes H atoms from the α and β carbons. • Forms a trans C=C bond. • Reduces FAD to FADH2. β α
  • 7. Beta-Oxidation of Fatty Acids In reaction 2, hydration: • Adds water across the trans C=C bond. • Forms a hydroxyl group (—OH) on the β carbon. βα
  • 8. Beta (β)-Oxidation of Fatty Acids In reaction 3, a second oxidation: • Oxidizes the hydroxyl group. • Forms a keto group on the β carbon. βα
  • 9. Beta (β)-Oxidation of Fatty Acids In Reaction 4, acetyl CoA is cleaved: • By splitting the bond between the α and β carbons. • To form a shortened fatty acyl CoA that repeats steps 1 - 4 of βoxidation.
  • 10. Beta (β)-Oxidation of Myristic (C14) Acid
  • 11. Beta (β)-Oxidation of Myristic (C14) Acid (continued) 6 cycles 7 Acetyl CoA
  • 12. β-oxidação dos ácidos gordos – uma via em espiral
  • 13. Cycles of β-Oxidation The length of a fatty acid: • Determines the number of oxidations and • The total number of acetyl CoA groups. Carbons in Acetyl CoA β-Oxidation Cycles Fatty Acid 12 14 16 18 (C/2) 6 7 8 9 (C/2 –1) 5 6 7 8
  • 14. β-Oxidation and ATP Activation of a fatty acid requires: • 2 ATP One cycle of oxidation of a fatty acid produces: • 1 NADH 3 ATP • 1 FADH2 2 ATP Acetyl CoA entering the citric acid cycle produces: • 1 Acetyl CoA 12 ATP
  • 15. ATP for Lauric Acid C12 ATP production for lauric acid (12 carbons): Activation of lauric acid -2 ATP 6 Acetyl CoA 6 acetyl CoA x 12 ATP/acetyl CoA 72 ATP 5 Oxidation cycles 5 NADH x 3ATP/NADH 5 FADH2 x 2ATP/FADH2 15 ATP 10 ATP Total 95 ATP
  • 16. Oxidation of Unsaturated Fatty Acids. • Oxidation of monounsaturated fatty acyl-CoA requires additional reaction performed with the help of the enzyme isomerase. • Double bonds in the unsaturated fatty acids are in the cis configuration and cannot be acted upon by enoyl-CoA hydratase (the enzyme catalyzing the addition of water to the trans double bond generated during β-oxidation. • Enoyl-CoA isomerase repositions the double bond, converting the cis isomer to trans isomer, a normal intermediate in β-oxidation.
  • 17. Protein Catabolism The liver is the major site of protein degradation in mammals Proteins are degraded into amino acids Ammonium ion is converted to urea in most mammals First step in protein degradation is the removal of the nitrogen
  • 18. Protein Catabolism Catabolism of proteins: -amino acids undergo deamination to remove the amino group -remainder of the amino acid is converted to a molecule that enters glycolysis or the Krebs cycle -for example: alanine is converted to pyruvate aspartate is converted to oxaloacetate
  • 19. Amino acid Catabolism
  • 20. THE BASICS OF PHOTOSYNTHESIS • Almost all plants are photosynthetic autotrophs, as are some bacteria and protists – Autotrophs generate their own organic matter through photosynthesis – Sunlight energy is transformed to energy stored in the form of chemical bonds (c) Euglena (b) Kelp (a) Mosses, ferns, and flowering plants (d) Cyanobacteria
  • 21. Light Energy Harvested by Plants & Other Photosynthetic Autotrophs 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2 Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water
  • 22. Experimental evidence • Where did the O2 come from? – radioactive tracer = O18 Experiment 1 6CO2 + 6H2O +light → energy C6H12O6 6 12 6 + 6O2 Water is oxidized Experiment 2 6CO2 + 6H2O +light → energy C6H12O6 + 6O2 Carbon dioxide is reduced Proved O2 came from H2O not CO2 = plants split H2O
  • 23. THE COLOR OF LIGHT SEEN IS THE COLOR NOT ABSORBED • Chloroplasts absorb light energy and convert it to chemical energy Blue and red wavelengths are absorved Light Reflected light Transmitted light Chloroplast Absorbed light
  • 24. WHY ARE PLANTS GREEN? PLANTS GREEN? Plant Cells have Green Chloroplasts The thylakoid membrane of the chloroplast is impregnated with photosynthetic pigments (i.e., chlorophylls, carotenoids).
  • 25. Chloroplasts: Sites of Photosynthesis • Photosynthesis – Occurs in chloroplasts, organelles in certain plants – All green plant parts have chloroplasts and carry out photosynthesis • The leaves have the most chloroplasts • The green color comes from chlorophyll in the chloroplasts • The pigments absorb light energy
  • 26. Photosynthesis occurs in chloroplasts • In most plants, photosynthesis occurs primarily in the leaves, in the chloroplasts • A chloroplast contains: – stroma, a fluid – grana, stacks of thylakoids • The thylakoids contain chlorophyll – Chlorophyll is the green pigment that captures light for photosynthesis
  • 27. The location and structure of chloroplasts Chloroplast LEAF CROSS SECTION MESOPHYLL CELL LEAF Mesophyll CHLOROPLAST Intermembrane space Outer membrane Granum Grana Stroma Inner membrane Stroma Thylakoid Thylakoid compartment
  • 28. Chloroplast Pigments • Chloroplasts contain several pigments – Chlorophyll a – Chlorophyll b – Carotenoids (carotenes and xanthophylls) Chlorophyll a and b CHO in chlorophyll b Phyto tail
  • 29. Different pigments absorb light differently Violet Blue Green Yellow Red Orange Chlorophyll a • Is only pigment that directly participates in the light reactions • Other pigments add energy to chlorophyll a or dissipate excessive light energy • Absorption of light elevates an electron to a higher energy orbital (increased potential energy)
  • 30. AN OVERVIEW OF PHOTOSYNTHESIS • The light reactions convert solar energy to chemical energy Light Chloroplast – Produce ATP & NADPH • The Calvin cycle makes sugar from carbon dioxide – ATP generated by the light reactions provides the energy for sugar synthesis – The NADPH produced by the light reactions provides the electrons for the reduction of carbon dioxide to glucose NADP+ ADP +P Light reactions Calvin cycle
  • 31. In the light reactions, electron transport chains generate ATP, NADPH, & O2 • Two connected photosystems collect photons of light and transfer the energy to chlorophyll electrons • The excited electrons are passed from the primary electron acceptor to electron transport chains – Their energy ends up in ATP and NADPH
  • 32. Photosystems • Collection of pigments and proteins found associated with the thylakoid membrane that harness the energy of an excited electron to do work • Captured energy is transferred between photosystem molecules until it reaches the chlorophyll molecule at the reaction center
  • 33. What Next? • At the reaction center are 2 molecules – Chlorophyll a – Primary electron acceptor • The reaction-center chlorophyll is oxidized as the excited electron is removed through the reduction of the primary electron acceptor • Photosystem I and II
  • 34. Electron Flow • Two routes for the path of electrons stored in the primary electron acceptors • Both pathways – begin with the capturing of photon energy – utilize an electron transport chain with cytochromes for chemiosmosis • Noncyclic electron flow – uses both photosystem II and I – electrons from photosystem II are removed and replaced by electrons donated from water – synthesizes ATP and NADPH – electron donation converts water into ½ O2 and 2H+ • Cyclic electron flow – Uses photosystem I only – electrons from photosystem I are recycled – synthesizes ATP only
  • 35. Photophosphorylation cyclic photophosphorylation noncyclic photophosphorylation
  • 36. Noncyclic Photophosphorylation • Photosystem II regains electrons by splitting water, leaving O2 gas as a by-product Primary electron acceptor Primary electron acceptor Photons Energy for synthesis of PHOTOSYSTEM I PHOTOSYSTEM II by chemiosmosis
  • 37. Noncyclic Electron Flow Electrons at reaction-center are energized H2O split via enzyme catalysed reaction forming 2H+, 2e-, and 1/2 O2. Electrons move to fill orbital vacated by removed electrons Each excited electron is passed along an electron transport chain fueling the chemiosmotic synthesis of ATP The electrons are now lower in energy and enters photosystem I via plastocyanin (PC) where they are re-energized The electrons are then passed to a different electron transport system that includes the iron containing protein ferridoxin. The enzyme NADP+ reductase assists in the oxidation of ferridoxin and subsequent reduction of NADP+ to NADPH
  • 38. Chemiosmosis powers ATP synthesis in the light reactions • The electron transport chains are arranged with the photosystems in the thylakoid membranes and pump H+ through that membrane – The flow of H+ back through the membrane is harnessed by ATP synthase to make ATP – In the stroma, the H+ ions combine with NADP+ to form NADPH
  • 39. • The production of ATP by chemiosmosis in photosynthesis Thylakoid compartment (high H+) Light Light Thylakoid membrane Antenna molecules Stroma (low H+) ELECTRON TRANSPORT CHAIN PHOTOSYSTEM II PHOTOSYSTEM I ATP SYNTHASE
  • 40. Where are the photosystems found on the thylakoid membrane?
  • 41. Chemiosmosis in 2 Organelles Both the Mitochondria and Chloroplast generate ATP via a proton motive force resulting from an electrochemical imbalance across a membrane Both utilize an electron transport chain primarily composed of cytochromes to pump H+ across a membrane. Both use a similar ATP synthase complex Source of “fuel” for the process differs
  • 42. Calvin Cycle • Starts with CO2 and produces Glyceraldehyde 3-phosphate • Three turns of Calvin cycle generates one molecule of product • Three phases to the process: I) Carbon Fixation; II) Reduction of CO2; III) Regeneration of RuBP
  • 43. Calvin Cycle Phase 1 A molecule of CO2 is converted from its inorganic form to an organic molecule (fixation) through the attachment to a 5C sugar (ribulose bisphosphate or RuBP). –Catalysed by the enzyme RuBP carboxylase (Rubisco). The formed 6C sugar immediately cleaves into 3phosphoglycerate
  • 44. Calvin Cycle Phase 2 Each 3-phosphoglycerate molecule receives an additional phosphate group forming 1,3Bisphosphoglycerate (ATP phosphorylation) •NADPH is oxidized and the electrons transferred to 1,3-Bisphosphoglycerate cleaving the molecule as it is reduced forming Glyceraldehyde 3phosphate
  • 45. Calvin Cycle Phase 3 The final phase of the cycle is to regenerate RuBP •Glyceraldehyde 3phosphate is converted to RuBP through a series of reactions that involve the phosphorylation of the molecule by ATP
  • 46. Variations Anyone? • In hot/arid regions plants may run short of CO2 as a result of water conservation mechanisms • C4 Photosynthesis CO2 may be captured by conversion of PEP (Phosphoenolpyruvate) into oxaloacetate and ultimately malate that is exported to cells where the Calvin cycle is active • CAM Photosynthesis CO2 may be captured as inorganic acids that my liberate CO2 during times of reduced availability

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