Cellular Metabolic Pathways

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rica_ross
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226506
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Cellular Metabolic Pathways
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2013-07-13 19:59:32
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Biology GRE
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Biology GRE
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  1. Cellular metabolism
    is the sub of all chemical reactions that take place in a cell
  2. Anabolic
    Requires input of energy, complex compounds synthesized from smaller compounds
  3. Catabolic
    Releases energy from the break down of complex compounds
  4. Photosynthesis Chemical Formula
    Sun+6CO2+6H20--> C6H12O6+O2
  5. Cellular Respiration Chemical Formula
    C6H12O6+6O2-->6CO2+6H20+ATP
  6. Energy Carriers
    • Durring metabolism the cell uses a number of molecular carriers to shuffle electrons between reactions. 
    • -ATP
    • Coenzymes:
    • -NAD+
    • NADP+
    • FAD
  7. ATP- Adenosine Triphosphate
    Structure
    Formation and dehydration of ATP allow for quick way of releasing and storing energy, energy is stored in covalent bonds

    synthesized during glucose catabolism

    ATP= Adenine, sugar (ribose) and three phospate groups
  8. Hydrolysis of ATP
    ATP-->ADP + Pi + E

    Pi-inorganic phosphate
  9. Coenzymes: NAD+ and NADP+ and FAD, general function
    H+ atoms are removed and accepted by carried coenzymes, as a way to transfer high energy electrons.

    Coenzymes store and release energy via oxidations and reductions
  10. Oxidation/Reduction
    Oxidation is loss of electrons

    Reduction is gain of electrons

    When oxidizing agents gain electrons they are reduced
  11. Examples of coenzyme reducing agents
    NADH NADPH FADH, transport electrons (H+ ions) to the first unit of electron transport chain

    Reducing agents lose electrons and become oxidized
  12. Glucose Catabolism: Two General stages
    • Glycosis
    • Cellular respiration
  13. Glycosis: General Idea
    • Series of reactions that lead to oxidative breakdown of glucose
    • occurs in the cytoplasm
    • Leading to two molecules of pyruvate and production of ATP and reduction of NAD+ -->NADH
  14. Glycosis: Overall rxn
    • Glucose--> 2pyruvate
    •  2 ATPS are used and 4 are generated
    • 4 because steps 5-9 happens two times
    • Net ATP gain: 2 ATP/glucose molecule
  15. Glycosis/Substrate Level Phosphorlation: Net Rxn
    glucose + 2ADP +2Pi+ 2NAD+--> 2 pyruvate +2ATP +2 NADH + 2H+ +H20
  16. Phosphorlation
    Adding a phosphate molecule
  17. Pyruvate degradation is either ____ or ____, one releases more energy.
    Anaerobic fermentation

    Aerobic Cellular Respiration
  18. Fermentation
    Pyruvate is reduced to ethanol/lactic acid, releasing 2ATP/glucose
  19. Alcohol Fermentation: Summary
    Performed by yeast and some bacteria, pyruvate is decarboxlyated to acetaldehyda

    Then reduced to NADH in step 5 of Glycolysis to ethanol, NAD+ is regenerated so Glycolysis can continue
  20. Alcohol Fermentation Equation
    Pyruvate ----> Acetaldhyde--> Ethanol 

    • Step one produces CO2
    • Step two reduced NADH-->NAD+ so Glycolysis can continues
  21. Lactic Acid Fermentation: Summary
    Performed by fungi and bacteria and in human muscle cells during strenuous activity (low oxygen conditions) 

    NAD+ is regenerated when pyruvate is reduced

    Increase of lactic acid decreased blood pH and leads to muscle fatigue
  22. Oxygen debt
    The amount of oxygen that is needed to oxidized lactic acid back to pyruvate and continue cellular respiration, instead of lactic acid fermentation
  23. ATP generation: Summary
    • Glycolysis--> Net 2 ATP/Glucose
    • Fermentation--> 2ATP/glucose
    • Respiration---> 36-38 ATP/Glucose
  24. Cellular Respiration: Oxygens Role
    Oxygen acts as the final acceptor of electrons during glucose oxidation, occurs in mitochondris with specific enzymes

    if oxygen is not there to except the electrons, the chain gets backed up and sparks lactic acid fermentation.
  25. Respiration: Basic Stages
    • -Pyruvate Decarboxylation
    • -Citric acid cycle/krebs cycle
    • -e- transport chain
  26. Pyruvate Decarboxylation
    Pyruvate is transportated from cytoplasm into the mitochondrial matix, where it is decarboxlycated (looses a CO2 and acetyl group is transferred to co enzyme A--> Acetyl Co A)
  27. Pyruvate Decarboxylation Equation
    Pyruvate + Co Enzyme A---> Acetyl CO A 

    IN the process NAD+ H+--> NADH

    *Two Pyruvates are generated during Glycolysis, so two Acteyl CO A's are generated
  28. Citric Acid Cycle:General
    Acetyl Co A+ Oxalocatetate --> Cirtate

    for each turn 1 ATP is produced by substrate level phosphorylation (GDP--> GTP, then ADP-->ATP) 

    • The citric acid cycle is a series of 8 oxidations
    • Electrons move from NAD+-->NADH, FAD-->FADH2.
  29. Citric Acid Cycle yields . . .
    • Yields two CO2 molecules
    • A GTP molecule, which is converted to ATP
    • Three NADH molecules and one FADH2 molecule
    • These Coenzymes are sent to the electron transport chain
    • ** For one molecule of Acteyl Co A, however two are generated so the cycle goes twice
  30. Electron Transport Chain: General Idea
    Occurs in the inner mitochondrial membrane

    oxidative phosphorylation produces ATP vis high energy electrons transferred from coenzymes to carrier molecules 

    As electrons go from carrier to carrier energy is released and changed to ATP
  31. Cytochromes, Electron transport chain
    • electron carriers that resemble hemoglobin
    • i.e. undergoes reversible redox reactions, can be alternatively reduced and oxidized

    each carrier is reduced (gains e-) as it accepts e-, and is oxidized as it passes them on
  32. Cytochrom a3
    last molecule of electron transport chain and passes electron oxygen
  33. Oxygen in ETC
    Oxygen is the last electron acceptor in the ETC

    picks up a pair of H+ ions and forms H2O

    • without oxygen ETC gets backlogged and NAD+ is not regenerated, 
    • -----> therefore, glycolysis cannot continue until it switches to lactic acid fermentation
  34. Cyanide or Dinitrophenol
    Cyanide - respirtory poisons that center a cell and stop e- transfer

    Dinitrophenol uncouples ETC from proton gradient across the mitochondrial membrane
  35. ATP Generation/ Proton Pump: General
    • There are energy losses as the electrons go from one complex to the next.
    • Energy is used to synthesis 1 ATP/complexThree total complexes=3ATP
  36. Three main electron protein complexes
    • NADH Dehydrogenase
    • B-c Complex
    • Cyctochrome Oxidase
  37. NADH and FADH2 electron delivery
    NADH delivers electrons to the front of the chain at NADH Dehydrogenase and electrons move through the three complexes

    FADH 2 delivers electrson to Q (obiquinone) which is between the first and second main complex, therefore electrons only pass through two protein complexes and therefore only yields 2 ATP/e- instead of three
  38. Coupling of ATP production and Oxidative phosphorylation
    As NADH passes its electrons to ETC hydrogen atoms are pumped out of the mitochondrial matrix across the inner mitochondrial membrane and into the inner membrane space

    happens at each of the three complexes

    This creates a positively charged acidic environment in the inner membrane space, and yields the proton motive force, which pushes H+ ions back across the membrane via ATP Synthase
  39. Proton Motive Force
    when protons are pumped out of the membrane into the inner membrane space, a gradient is created= Proton Motive force

    Protons pass back into the matrix via channel proteins called ATP Synthase
  40. ATP Synthase
    as protons pass through the ATP synthase and down the concentraion gradient, ATP synthase uses the energy that is liberated to phosphorylate ADP -->ATP.

    Total number of ATP's created is 30
  41. Alternative E sources when hte body is low on glucose
    • 1- Other Cards
    • 2-Fats
    • 3- Protiens

    they are all converted into glucose and then enter glycolysis
  42. Photosynthesis: General
    Occus in the chloroplast, in prokaryotes it occurs in plasma membrane/inter foldings of membrane
  43. Mesophyll
    Green tissue on interior of leaf
  44. Stomata
    Pores on surface that allow CO2 in and O2 out
  45. Stroma
    Chloroplast inner membrane fluid
  46. Thylakoid
    Membrane bound sack inside chloroplast, the membrane forms stacks called grana
  47. Two main parts of photosynthesis
    • -Light reactions : Thylakoid
    • -Calvin Benson Cycle : Stroma
  48. Chloroplast Picture
  49. Mitochondria
  50. Light Reactions: general
    Light energy is used to generate ATP, oxygen and NADPH
  51. Chlorophyll
    molecules that captures light
  52. Photosystem 1 and 2
    each photosystem is a system of proteins that when light stikes chlorophyll electrons are excited and transfered to the reaction center, at the reaction center electrons enter the electron transport chain and are used to generate chemical energy as ATO or NADPH
  53. Cyclic Photophosphorlation
    photosystem 1: P700 700nm

    Electrons move through the reaction center to ETC and back to the same reaction center 

    No oxygen production because no NADPH
  54. Non Cyclic Photophosphorlyation
    Photosystem 2 680 nm

    Electrons move through the reaction center at 680 nm and go to electron transport chain and then go to the reaction center of photosytem 1 700 nm

    photosystem 2 replaces the electron is lost from water, and produces 02 as a result

    electrons that go into photosystem 1 from photosystem 2 are used to produces NADPH
  55. Calvin Bension Cycle
    fixes CO2 into glucose

    NADPH provides reducing power by giving electrons to CO2

    CO2 yields RUBP (Ribulose Biphosphate) this reactions is catalyzed by Rubisco
  56. Photorespiration
    Rubisco is not totally specific for CO2, it will also catalyze reactions between RUBP and oxygen

    ---> Reduces the efficiency of photosynthesis by competitive inhibition

    *Some plants can bypass this vis C4 photosynthesis
  57. C4 photosynthesis
    • C4 plants have enzyme called PEP carboxlyase. Rubisco has a lower affinity for CO2 than PEP so reduces photorespiration 
    • PEP does not react with O2 so decreases photorespiration

    perform calvin benson cycle in different cells

    • Calvin benson cycle occurs in bundel sheath cells
    • C4 pathway occurs in mesophyll cells, close to the surface of the leaf. 
    • ---> This alsos C4 plants to pump CO2 into bundel sheath cell, farther from 02 and maintain a high concentration of CO2 and decrease the chance of photorespiration
  58. C4 plants vs C3 plants
    Tend to live in hot environments, plants close stomata and limit CO2 exchange

    C3 plants are more efficient at cooler temps
  59. CAM plants
    • like hot dry conditions
    • keep stomata cosed during the day to conserve water, but keep up c fixation with PEP

    Open stomata at night to store up CO2
  60. Paracrine Signaling
    Signaling only nearby cells
  61. Synaptic Signaling
    Only in nerve cells in synapse, electrical signals each axon terminals and release neurotransmitters
  62. Endocrine Signaling
    • Secretion of chemical messengers into blood stream
    • widespread signaling
  63. Hormones
    Any molecule that signal things
  64. Steroid Hormones
    • Lipid cholesterol based signals
    • Can pass through cell membrane and act directly on cell's nucleus 
    • lipid based therefore do not disolve in water and effects can last for hours or days
  65. NO
    • Nitrious oxide
    • not a lipid/steroid but can pass through cell membrane because its so small
    • creates cyclic GMP which causes smooth muscle cells to relax
  66. Non steriod hormones
    • cannot cross plasma membrane
    • act via signal transduction, i.e. binding of hormones to cell surface receptor and signaling a intracellular change
  67. Cell surface receptors come in three forms:
    • ion channel linked
    • G protein linked
    • Enzyme linked
  68. Ion channel linked
    • ligand gated channels 
    • membrane spanning protein undegoes a change when ligand binds to them that opens up tunnel or passage to membrane
  69. Ligand
    chemical Signal
  70. G Protein linked
    • channels cause G proteins to dissociate from cytoplasmic side of receptor protein and bind to nearby enzyme 
    • activates a second messenger, which activate enzyme transcription factors

  71. Enzyme linked
    act directly as enzymes catalyzing a reaction inside the cell
  72. Kinases
    add free floating phosphate groups to proteins
  73. Signal Integration
    • G linked and enzyme linked 
    • complex relays of signals 
    • sometimes requiring two receptors to become activated
    • leads to measure of control over reaction and ability to use multiple inputs
  74. Cellular Respiration Picture
  75. Photosynthesis  Diagram

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