Energy transformations in cells


Published on

Published in: Education, Technology, Business
  • Be the first to comment

  • Be the first to like this

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide
  • Photoautotrophs – capture solar energyChemoautotrphs – use inorganic molecules to produce storable chemical energy
  • Limiting factors
  • Limiting factors
  • Energy transformations in cells

    1. 1. Ian Anderson (2013)Saint Ignatius College Geelong06. Energy transformations.
    2. 2. Energy. All living organisms require a constant supply ofenergy to survive e.g. for cellular processes (incl.protein synthesis, active transport, digestionetc.), growth, movement, reproduction, etc. Energy = capacity to do work.
    3. 3. Energy. In plants and animals glucose is the main source ofchemical energy. If there is insufficient glucose available, fatty acids andamino acids can be used instead. Chemical energy is present in the chemical bonds. When the bonds break, energy is released (i.e. exergonicreaction).
    4. 4. ATP – ADP cycle. Adenosine triphosphate (ATP) is the energy currencyof a cell. ATP is needed for every activity that requires energy. ATP structure – adenosine attached to a sugar group(ribose), which is bound to a chain of three phosphategroups. = nucleotide (sugar, N containing base and a phosphategroup). Immediate energy source lies in the energy rich bondholding the third phosphate to the rest of themolecule.
    5. 5. ATP – ADP cycle.Source: Sadava et al. (2011)
    6. 6. ATP – ADP cycle. Cells make their own ATP in a cyclic process. When energy is used ATP is broken down intoAdenosine diphosphate (ADP) and inorganicphosphate, with energy released. ATP is then reformed during cellular respiration.
    7. 7. ATP – ADP cycle.Source: Sadava et al. (2011)
    8. 8. Cellular respiration. The process that releases energy from glucosemolecules in the form of ATP. Cellular respiration is the most important andcommon catabolic reaction to all living organisms. Occurs in several stages [Biochemical/metabolic pathway = each step beginswith a substrate, which is then converted to aproduct, which then becomes the substrate for anotherchemical reaction (each enzyme controlled)].Source: Campbell et al. (2011)
    9. 9. Cellular respiration. First stage = Glycolysis. Occurs in cytosol. Anaerobic (without oxygen) pathway. Glucose is broken down into two pyruvatemolecules, with a net production of two ATP molecules. H+ and e- are released as glucose is split and collected byelectron carrier molecule (nictoninamide adeninedinucleotide).Glucose  2 pyruvate + 2H2O + 2NADH + 2ATP(6 carbon sugar) (2 x 3 carbon sugar)
    10. 10. Electron carrier molecule. H+ and e- are not stable and are quickly picked up byNAD (nictoninamide adenine dinucleotide) whichacts as an electron carrier.NAD+  NADHSource: Russell et al. (2011)
    11. 11. Cellular respiration.Next stage of cellular respiration depends on whether ornot oxygen is available. Oxygen available  aerobic pathway. Oxygen not available  anaerobic pathway.
    12. 12. Cellular respiration– aerobic pathway. Most efficient way of producing ATP. Occurs in mitochondria in eukaryotes. Pyruvate enters via active transport. (Occurs in cytoplasm of prokaryotes). Involves two steps Krebs cycle (Citric acid cycle). Electron-transport chain.
    13. 13. Cellular respiration– aerobic pathway.Krebs cycle. Occurs in fluid matrix of mitochondria. Pyruvate molecules converted to two molecules ofacetyl CoA, one molecule of CO2 and 2 H+. Acetyl CoA then enters Krebs Cycle where eachmolecule is converted into 2 CO2, 4 H+ & 1 ATP. H+ are picked up by electron carriers (NAD & FADH). A total of 2 ATP molecules produced per initial glucosemolecule.
    14. 14. Cellular respiration– aerobic pathway.Electron-transport chain. Occurs on the cristae (inner membrane) ofmitochondria. Energy from the NADH and FADH2 produced inglycolysis and Krebs cycle used to produce ATP. H+ combine with O2 to form H2O. A total of 32-34 ATP from each original glucosemolecule. 34 ATP in prokaryotes & 32 ATP in eukaryotes (2 ATPused as as NADH produced via glycolysis pass acrossmitochondrial membrane).
    15. 15. Cellular respiration– aerobic pathway. Total ATP produced via aerobic pathway Glycolysis = 2 ATP Krebs cycle = 2 ATP Electron transport chain = 32-34 ATP = total 36-38ATPSummary reaction of cellular respiration via aerobicpathwayC6H12O6 + 6O2  6CO2 + 6 H2O + 36-38 ATP
    16. 16. Cellular respiration– aerobic pathway.Source: Raven et al. (2011)
    17. 17. Cellular respiration– anaerobic pathway. Occurs in the cytoplasm of cells. No further ATP is produced during the anaerobicpathway. i.e. only 2 ATP produced as a result of glycolysis. Anaerobic pathway known as fermentation.
    18. 18. Cellular respiration– anaerobic pathway. In animals Pyruvate produced by glycolysis is converted to lacticacid. NADH (produced during glycolysis) converted back toNAD+ (thus allowing it to be reused).Pyruvate + NADH  lactic acid + NAD+Source: Campbell et al. (2011)
    19. 19. Cellular respiration– anaerobic pathway. In most plants, yeast & bacteria Pyruvate is converted to ethanol and carbon dioxide. NADH (produced during glycolysis) converted back toNAD+ (thus allowing it to be reused).Source: Campbell et al. (2011)Pyruvate + NADH  ethanol + CO2 + NAD+
    20. 20. Energy. The sun provides this energy either directly orindirectly for nearly all life forms. Autotrophs – manufacture organic material frominorganic material [self feeding] e.g. plants, algae &cyanobacteria. Heterotrophs – obtain organic material by feeding onother organisms (or their products) [feed on others] e.g.animals, fungi, most bacteria & some protists.
    21. 21. Photosynthesis. Autotrophs (photoautotrophs) capture solar energy tohelp drive the reactions that convert inorganic C toorganic C. Overall process = photosynthesis6CO2 + 12H2O  C6H12O6 + 6O2 + 6H2O
    22. 22. Photosynthesis.6CO2 + 12H2O  C6H12O6 + 6O2 + 6H2O Reaction is anabolic Larger molecules made from smaller molecules & endergonic Needs energy to proceed. Equation is a summary of 100’s of reactions that makeup photosynthesis (i.e. it is a biochemical pathway).
    23. 23. Photosynthesis. Occurs in the chloroplasts Membrane bound organelles – inner & outer membrane. Stroma – gel-like matrix that fills the interior of achloroplast. Rich in enzymes. Thylakoid membranes – suspended in the stroma.Flat, sac-like structures that are stacked like pancakesknown collectively as grana.
    24. 24. Chloroplasts.Source: Russell et al. (2011)
    25. 25. Photosynthesis. Two main stages Light dependent reactions. Light independent reactions. Each stage confined to specific sites within thechloroplast.
    26. 26. Photosynthesis- Light dependent reactions. Light is essential for these reactions to occur. Occurs on the thylakoid membranes of thechloroplast. Chlorophyl absorbs light energy, which is then used toproduce ATP and split water molecules into H+ ionsand O2 gas. O2 gas is a waste product. ATP, H+ ions and electrons are used in the lightindependent reactions.
    27. 27. Photosynthesis- Light independent reactions. Also know as the Calvin Cycle. Occurs in the stroma of the chloroplast. Carbon dioxide is combined with the H+ ions usingenergy provided by ATP, to form glucose and water.
    28. 28. Photosynthesis. Summary reaction of photosynthesis6CO2 + 12H2O  C6H12O6 + 6H2O + 6O2
    29. 29. Photosynthesis.Factors that affect the rate of photosynthesis. Light intensity CO2 availability Temperature Indirect factors Lacking nitrogen/magnesium reduces the amount ofchlorophyll produced. Dehydration causes stomata to close.
    30. 30. Variations in photosynthesis.Plants adapt to their environment C3 plants C4 plants CAM plants‘the norm’Adapted to arid conditions
    31. 31. C3 plants. Called C3 because the CO2 is first incorporated into a3-carbon compound. Stomata are open during the day. Photosynthesis takes place throughout the leaf. Adaptive value = more efficient than C4 and CAMplants under cool and moist conditions and undernormal light because requires less machinery (fewerenzymes and no specialized anatomy).. Most plants are C3.
    32. 32. C4 plants. Called C4 because the CO2 is first incorporated into a4-carbon compound. Use a different enzyme to capture & convert CO2. Adaptive value = reduces the time the stomates areopen and therefore reduces water loss. C4 plants include several thousand species in at least19 plant families. E.g. fourwing saltbush, corn, andmany of our summer annual plants.
    33. 33. CAM plants. Open their stomates at night. Convert the CO2 to an acid that is stored. During the day the acid is broken down back into CO2and used during photosynthesis. Adaptive value = stomates are not open during day andtherefore reduces water loss. CAM plants include succulents, some orchids andsome bromeliads.