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2007-2008 Photosynthesis: Life from Light and Air.

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Presentation on theme: "2007-2008 Photosynthesis: Life from Light and Air."— Presentation transcript:

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3 Photosynthesis: Life from Light and Air

4 Energy needs of life  All life needs a constant input of energy  Heterotrophs (Animals)  get their energy from “eating others”  eat food = other organisms = organic molecules  make energy through respiration  Autotrophs (Plants)  produce their own energy (from “self”)  convert energy of sunlight  build organic molecules (CHO) from CO 2  make energy & synthesize sugars through photosynthesis consumers producers

5 How are they connected? glucose + oxygen  carbon + water + energy dioxide C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ Heterotrophs + water + energy  glucose + oxygen carbon dioxide 6CO 2 6H 2 O C 6 H 12 O 6 6O 2 light energy  +++ Autotrophs making energy & organic molecules from light energy making energy & organic molecules from ingesting organic molecules Where’s the ATP? oxidation = exergonic reduction = endergonic

6 N P K … H2OH2O What does it mean to be a plant  Need to…  collect light energy  transform it into chemical energy  store light energy  in a stable form to be moved around the plant or stored  need to get building block atoms from the environment  C,H,O,N,P,K,S,Mg  produce all organic molecules needed for growth  carbohydrates, proteins, lipids, nucleic acids ATP glucose CO 2

7 Plant structure  Obtaining raw materials  sunlight  leaves = solar collectors  CO 2  stomates = gas exchange H2OH2O  uptake from roots  nutrients  N, P, K, S, Mg, Fe…  uptake from roots

8 stomate transpiration gas exchange

9 Stomates

10 Chloroplasts chloroplasts in plant cell cross section of leaf leaves chloroplast absorb sunlight & CO 2 make energy & sugar chloroplasts contain chlorophyll CO 2

11  Chloroplasts  double membrane  stroma  fluid-filled interior  thylakoid sacs  grana stacks  Thylakoid membrane contains  chlorophyll molecules  electron transport chain  ATP synthase  H + gradient built up within thylakoid sac Plant structure H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ outer membrane inner membrane thylakoid granum stroma thylakoid chloroplast ATP

12 Photosynthesis  Light reactions  light-dependent reactions  energy conversion reactions  convert solar energy to chemical energy  ATP & NADPH  Calvin cycle  light-independent reactions  sugar building reactions  uses chemical energy (ATP & NADPH) to reduce CO 2 & synthesize C 6 H 12 O 6 It’s not the Dark Reactions!

13 Pigments of photosynthesis  Chlorophylls & other pigments  embedded in thylakoid membrane  arranged in a “photosystem”  collection of molecules  structure-function relationship How does this molecular structure fit its function?

14 A Look at Light  The spectrum of color ROYGBIV

15 Light: absorption spectra  Photosynthesis gets energy by absorbing wavelengths of light  chlorophyll a  absorbs best in red & blue wavelengths & least in green  accessory pigments with different structures absorb light of different wavelengths  chlorophyll b, carotenoids, xanthophylls Why are plants green?

16 Photosystems of photosynthesis  2 photosystems in thylakoid membrane  collections of chlorophyll molecules  act as light-gathering molecules  Photosystem II  chlorophyll a  P 680 = absorbs 680nm wavelength red light  Photosystem I  chlorophyll b  P 700 = absorbs 700nm wavelength red light reaction center antenna pigments

17 You can grow if you Ask Questions!

18 ATP Making energy! The point is to make ATP!

19 The energy needs of life  Organisms are endergonic systems  What do we need energy for?  synthesis  building biomolecules  reproduction  movement  active transport  temperature regulation

20 Where do we get the energy from?  Work of life is done by energy coupling  use exergonic (catabolic) [energy out] reactions to fuel endergonic (anabolic) [energy in] reactions ++ energy + + digestion synthesis

21 ATP Living economy  Fueling the body’s economy  eat high energy organic molecules  food = carbohydrates, lipids, proteins, nucleic acids  break them down  digest = catabolism  capture released energy in a form the cell can use  Need an energy currency  a way to pass energy around  need a short term energy storage molecule Whoa! Hot stuff!

22 ATP high energy bonds How efficient! Build once, use many ways  Adenosine TriPhosphate  modified nucleotide  nucleotide = adenine + ribose + P i  AMP  AMP + P i  ADP  ADP + P i  ATP  adding phosphates is endergonic

23 How does ATP store energy? P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O  Each negative PO 4 more difficult to add  a lot of stored energy in each bond  most energy stored in 3rd P i  3rd P i is hardest group to keep bonded to molecule  Bonding of negative P i groups is unstable  spring-loaded  P i groups “pop” off easily & release energy Instability of its P bonds makes ATP an excellent energy donor I think he’s a bit unstable… don’t you? AMP ADPATP

24 How does ATP transfer energy? P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O 7.3 energy + P O–O– O–O– O –O–O  ATP  ADP  releases energy  ∆G = -7.3 kcal/mole  Fuel other reactions  Phosphorylation  released P i can transfer to other molecules  destabilizing the other molecules  enzyme that phosphorylates = “kinase” ADPATP

25 It’s never that simple! An example of Phosphorylation…  Building polymers from monomers  need to destabilize the monomers  phosphorylate! C H OH H HOHO C C H O H C + H2OH2O kcal/mol C H OH C H P + ATP + ADP H HOHO C + C H O H CC H P + PiPi “kinase” enzyme -7.3 kcal/mol -3.1 kcal/mol enzyme H OH C H HOHO C synthesis

26 That’s the rest of my story! Any Questions?

27 Cellular Respiration Harvesting Chemical Energy ATP

28 Harvesting stored energy  Energy is stored in organic molecules  carbohydrates, fats, proteins  Heterotrophs eat these organic molecules  food  digest organic molecules to get…  raw materials for synthesis  fuels for energy  controlled release of energy  “burning” fuels in a series of step-by-step enzyme-controlled reactions

29 Harvesting stored energy  Glucose is the model  catabolism of glucose to produce ATP C 6 H 12 O 6 6O 2 ATP6H 2 O6CO 2  + ++ CO 2 + H 2 O + heat fuel (carbohydrates) COMBUSTION = making a lot of heat energy by burning fuels in one step RESPIRATION = making ATP (& some heat) by burning fuels in many small steps CO 2 + H 2 O + ATP (+ heat) ATP glucose glucose + oxygen  energy + water + carbon dioxide respiration O2O2 O2O2 + heat enzymes ATP

30 How do we harvest energy from fuels?  Digest large molecules into smaller ones  break bonds & move electrons from one molecule to another  as electrons move they “carry energy” with them  that energy is stored in another bond, released as heat or harvested to make ATP e-e- ++ e-e- +– loses e-gains e-oxidizedreduced oxidationreduction redox e-e-

31 How do we move electrons in biology?  Moving electrons in living systems  electrons cannot move alone in cells  electrons move as part of H atom  move H = move electrons p e + H + H +– loses e-gains e-oxidizedreduced oxidationreduction C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ oxidation reduction H e-e-

32 Coupling oxidation & reduction  REDOX reactions in respiration  release energy as breakdown organic molecules  break C-C bonds  strip off electrons from C-H bonds by removing H atoms  C 6 H 12 O 6  CO 2 = the fuel has been oxidized  electrons attracted to more electronegative atoms  in biology, the most electronegative atom?  O 2  H 2 O = oxygen has been reduced  couple REDOX reactions & use the released energy to synthesize ATP C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ oxidation reduction O2O2

33 Oxidation & reduction  Oxidation  adding O  removing H  loss of electrons  releases energy  exergonic  Reduction  removing O  adding H  gain of electrons  stores energy  endergonic C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ oxidation reduction

34 Moving electrons in respiration  Electron carriers move electrons by shuttling H atoms around  NAD +  NADH (reduced)  FAD +2  FADH 2 (reduced) + H reduction oxidation P O–O– O–O– O –O–O P O–O– O–O– O –O–O C C O NH 2 N+N+ H adenine ribose sugar phosphates NAD + nicotinamide Vitamin B3 niacin P O–O– O–O– O –O–O P O–O– O–O– O –O–O C C O NH 2 N+N+ H NADH carries electrons as a reduced molecule reducing power! How efficient! Build once, use many ways H like $$ in the bank

35 Overview of cellular respiration  3 metabolic stages  Anaerobic respiration 1. Glycolysis  respiration without O 2  in cytosol  Aerobic respiration  respiration using O 2  in mitochondria 2. Krebs cycle 3. Electron transport chain C 6 H 12 O 6 6O 2 ATP6H 2 O6CO 2  +++ (+ heat )

36 What’s the point? The point is to make ATP ! ATP

37 Cellular Respiration Stage 1: Glycolysis

38 What’s the point? The point is to make ATP ! ATP

39 Glycolysis glucose      pyruvate 2x2x 6C3C In the cytosol? Why does that make evolutionary sense? That’s not enough ATP for me!  Breaking down glucose  “glyco – lysis” (splitting sugar)  ancient pathway which harvests energy  where energy transfer first evolved  transfer energy from organic molecules to ATP  still is starting point for ALL cellular respiration  but it’s inefficient  generate only 2 ATP for every 1 glucose  occurs in cytosol

40 Glycolysis summary endergonic invest some ATP exergonic harvest a little ATP & a little NADH net yield 2 ATP 2 NADH 4 ATP ENERGY INVESTMENT ENERGY PAYOFF G3P C-C-C-P NET YIELD like $$ in the bank -2 ATP

41 Fermentation (anaerobic)  Bacteria, yeast 1C 3C2C pyruvate  ethanol + CO 2  Animals, some fungi pyruvate  lactic acid 3C  beer, wine, bread  cheese, anaerobic exercise (no O 2 ) NADHNAD + NADHNAD + back to glycolysis 

42 What’s the point? The point is to make ATP ! ATP

43 NO! There’s still more to my story! Any Questions?

44 Cellular Respiration Stage 2: The Kreb’s Cycle

45 Cellular respiration

46  Coordination of chemical processes across whole organism  digestion  catabolism when organism needs energy or needs raw materials  synthesis  anabolism when organism has enough energy & a supply of raw materials  by regulating enzymes  feedback mechanisms  raw materials stimulate production  products inhibit further production Metabolism CO 2

47 Cellular Respiration Stage 3: Electron Transport Chain

48 ATP accounting so far…  Glycolysis  2 ATP  Kreb’s cycle  2 ATP  Life takes a lot of energy to run, need to extract more energy than 4 ATP! A working muscle recycles over 10 million ATPs per second There’s got to be a better way! I need a lot more ATP!

49 There is a better way!  Electron Transport Chain  series of proteins built into inner mitochondrial membrane  along cristae  transport proteins & enzymes  transport of electrons down ETC linked to pumping of H + to create H + gradient  yields ~36 ATP from 1 glucose!  only in presence of O 2 (aerobic respiration) O2O2 That sounds more like it!

50 Mitochondria  Double membrane  outer membrane  inner membrane  highly folded cristae  enzymes & transport proteins  intermembrane space  fluid-filled space between membranes Oooooh! Form fits function!

51 Electrons flow downhill  Electrons move in steps from carrier to carrier downhill to oxygen  each carrier more electronegative  controlled oxidation  controlled release of energy make ATP instead of fire!

52 You can grow if you Ask Questions!


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