Cellular Energetics

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Fermentation, Cellular Respiration, Photosynthesis

Fermentation, Cellular Respiration, Photosynthesis

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  • Where did the CO2 come from? Why is this called a cycle?
  • Where does the water come from?

Transcript

  • 1. What we will learn about ENERGY
    • How does ATP store energy for our cells?
    • How do plants make their own food, using just sunlight, air and water?
    • Why do a lot of “energy” drinks or foods have B vitamins in them?
    • Why do we need oxygen?
  • 2. ATP Notes
    • ATP is A denosine T ri p hosphate. It is able to store energy in the bonds between phosphate
    • groups.
      • The “~” represents high energy bonds
  • 3. ATP is similar to DNA and RNA
    • “ Adenosine” is an adenine plus a ribose.
    • Adenine is a nitrogen base found in DNA and RNA.
    • Ribose is a 5-carbon sugar found in RNA.
    • Instead of having one phosphate group like in RNA or DNA, ATP has three phosphate groups.
    • However, ATP does not form polymers like DNA and RNA.
  • 4. The ATP-ADP Cycle
    • Breaking one phosphate group off of ATP releases energy.
    • ATP  ADP + P i + energy
    • We can put the phosphate back on, with the help of an enzyme called ATP synthase.
    • Energy + P i + ADP  ATP
  • 5. Is this really efficient?
    • The ATP-ADP cycle is efficient because we get more energy from splitting
    • ATP  ADP + P i
    • than is required for making
    • ADP + P i  ATP.
  • 6.
    • The cycle is so efficient that a working muscle cell recycles ALL of its ATP once each minute !
    • If ATP couldn’t be recycled, you would have to eat your body weight in ATP each day!
    • We tend to think of glucose as the starting point for making ATP, in fact your BRAIN prefers glucose as food.
    • The brain will use over 50% of the glucose in your blood.  (Whether you are thinking or not!)
  • 7. What happens to glucose?
    • Glycolysis (cytoplasm)
    • A. A 6-carbon sugar (glucose)
    • is broken down into 2
    • pyruvates, each with 3
    • carbons
    • B. There is a net gain of 2
    • ATP (from ADP + P i ) and 2
    • NADH (from NAD + and H + )
    • molecules.
  • 8.  
  • 9.
    • C. Glycolysis does not require
    • oxygen .
    • D. For simplicity, we use glucose as the starting point (and it is the cell’s main source of energy) but proteins and lipids can be broken
    • down for energy later on in cellular
    • respiration.
  • 10. After glycolysis….
    • Depending on the type of cell and whether or not oxygen is present…
    • No oxygen Oxygen present
    • fermentation aerobic cellular
    • (anaerobic respiration) respiration
  • 11. Anaerobic Respiration
    • a.k.a. “Fermentation”
    • Why use fermentation?
    • -Not all cells have oxygen available to them.
    • - Not all cells have the structures to carry out aerobic respiration
    • -The cells still have to regenerate NAD + to keep glycolysis going.
  • 12.
    • Some cells are strictly aerobic:
    • Example: nervous tissue
    • Some cells are strictly anaerobic:
    • Example: some bacteria
    • Some cells can switch back and forth.
    • Example: some bacteria, muscle cells (though not for long!)
  • 13. I. Glycolysis occurs first,
    • producing 2 ATPs and 2 NADH.
    • II. Pyruvates stay in the cytoplasm and enter a pathway that does not require oxygen.
  • 14. III. Two major end products exist.
    • Lactic Acid : C 3 H 6 O 3
    • we’ve ‘domesticated’ some organisms to help us make yogurt, sauerkraut, pickles, and some cheeses.
    • You’ll make it too….
  • 15.
    • YOUR muscles switch to lactic acid fermentation when they run out of oxygen, and has been blamed for muscle soreness, but there is evidence that this is not true (too much may be evidence that your are not in shape)
    • Within an hour, it either diffuses into your blood and your liver breaks it down, or it can be converted back to pyruvate – then when oxygen is available it can enter aerobic respiration.
  • 16. B. Ethanol (ethyl alcohol) & CO 2
    • Ethanol and carbon dioxide are given off by some organisms, such as yeast (a single-celled fungus)
    • CO 2 bubbles help bread rise and put the bubbles in some alcoholic beverages.
    • Ethyl alcohol fermentation is also used for making from cacao beans
  • 17. C. Acetic Acid:
    • CH 3 COOH
    • In some cases, oxygen combines with alcohol to produce acetic acid (vinegar)
    • Many bacteria produce acetic acid by breaking down ethanol.
    • We use it for vinegar, but also for pickling foods, making aspirin, rayon, film,etc. But we know how to do it without bacteria.
  • 18.
    • If oxygen is present (and the organism has the ability to perform cellular respiration), then
    • Glycolysis is followed by aerobic cellular respiration instead of fermentation.
  • 19. II. Formation of Acetyl-CoA (mitochondria)
    • A. Pyruvate moves into the mitochondria and enters the mitochondrial matrix.
  • 20. (still A)
    • In the matrix, the 3-Carbon pyruvate reacts with a Coenzyme-A molecule (this requires thiamine, or Vitamin B 1 ) to form Acetyl-CoA, which has 2 carbons .
    • B. Lost carbon is given off as CO 2
    • C. NADH is produced from NAD +
    • Niacin (Vitamin B 3 ) is a component of NADH
  • 21. III. The Kreb’s Cycle (mitochondria)
    • a.k.a. “Citric Acid Cycle”
    • A. Each acetyl-CoA (2-carbon) combines with a 4-carbon molecule (oxaloacetate) to form a 6-carbon molecule (citric acid ). Quite a few reactions follow…
  • 22.  
  • 23. B. At the end of the Kreb’s cycle,
    • 2 GTP (works like ATP), and some NADH and FADH 2 are produced. Riboflavin (Vitamin B 2 ) is a component of FADH 2 )
    • Two carbons are given off as CO 2 .
    • The remaining 4 carbons are recycled (as oxaloacetate) to do the cycle again.
  • 24. IV. Electron Transport Chain (mitochondria)
    • A. All those NADH and FADH 2 molecules produced from the first three steps are hydrogen carriers. The hydrogens are split into hydrogen ions and electrons:
    • H 2  2 H + + 2 e -
  • 25. B. The electrons are
      • passed along a series of electron acceptors on the inner membrane. This regenerates NAD + and FADH +
      • The final electron acceptor is
      • OXYGEN.
  • 26.
    • C. Oxygen combines with hydrogen to form WATER.
    • See http://vcell.ndsu.nodak.edu/animations/etc/movie-flash.htm
  • 27. Simultaneously…
    • remember this? H 2  2 H + + 2 e -
    • D. The hydrogens are pumped across the inner membrane, OUT of the matrix by a proton pump. The energy for this comes from the E.T.C. This causes a H + ion gradient (a.k.a. proton gradient).
  • 28. E. As the hydrogen ions flow back in (WITH the gradient)
    • they pass through an enzyme (ATP synthase). One part of ATP synthase is a channel, the other part actually spins as H+ ions pass it. This gives the cell energy to put the phosphate back on to ADP to make ATP.
    • ATP synthase movie
    • See http://vcell.ndsu.nodak.edu/animations/atpgradient/movie-flash.htm
  • 29.
    • Adding phosphate to ADP is called “phosphorylation”
    • Approximately 36 – 38 ATP molecules are produced at this step!
    • Other B vitamins (B6, B12, Pantothenic acid, folic acid, and biotin) serve as coenzymes at various points in metabolizing our food.
    • Summary Formula
    • C 6 H 12 O 6 + O 2  CO 2 + H 2 O (+energy)
  • 30. PHOTOSYNTHESIS
    • Energy is captured
    • by sunlight (in
    • chloroplasts –
    • specifically in the
    • thylakoids).
    • A. Pigments are any substances that absorb light energy.
    • 1. Chlorophyll a and Chlorophyll b are the
    • most common plant pigments.
    • 2. Chlorophyll appears green because it absorbs red and blue.
  • 31.
      • 3. Other pigments (such as carotenoids) exist.
      • 4. Pigments are clustered and are called “photosystems”
      • B. Electrons are “excited” when light energy in the proper wavelengths is absorbed.
      • “ Excited” means that the electrons jump up to a higher energy level. They will leave chlorophyll and enter an electron transport chain.
  • 32. Electromagnetic Spectrum
  • 33.  
  • 34. C. H 2 O is split by sunlight:
    • 2 H 2 O  4 H + + 4 e - + O 2
    • The electrons are used
    • to replace the ones excited
    • (and lost) by the pigments.
    • The Oxygen is released as a waste product, although plants will use some of it for their own cellular respiration.
  • 35. II. Light Energy is converted to chemical energy in the thylakoids.
      • Excited electrons enter a series of electron acceptors called an electron transport chain.
      • As they are transferred “down” this chain, they lose energy…but that energy is used to pump H + ions across the thylakoid membrane, creating a gradient.
      • 2 H 2 O  4 H + + 4 e - + O 2
  • 36. B. ATP and NADPH are produced from ADP and NADP +
        • As H + ions flow back in. They pass through an ATP synthase enzyme, which catalyzes the reaction to…
        • Add phosphate to ADP, which makes ATP
        • Add the hydrogen ion to NADP +, which makes NADPH
        • For ATP and NADPH, think… STORES ENERGY
  • 37. III. Calvin Cycle : Does not require light, but does need products (ATP and NADPH) of the “light reactions”. (this is why it is often called the “dark reactions”)
    • A. Chemical energy from ATP and NADPH is used to “fix” carbon into organic compounds.
    • 1. CO 2 combines with a 5-carbon molecule
    • (RuBP), then splits into two 3-carbon
    • molecules called G3P (aka: PGAL)
    • 2. Most of this is converted back into the 5-
    • carbon molecule (so cycle can continue)
    • B . The 3-carbon G3P can be converted
    • into glucose, sucrose, starch, and other
    • organic molecules.
  • 38.  
  • 39. B. G3P can be a building block for glucose, but also for other carbohydrates, amino acids and lipids.
    • The summary equation:
    ☼ CO 2 + H 2 O  O 2 + C 6 H 12 O 6
  • 40. All plants use the Calvin cycle, but…
    • C. Because the initial product is a 3-carbon sugar, plants that only use the Calvin cycle are called C 3 plants.
    • C 4 plants (corn, sugarcane) have a 4-carbon sugar as their first product.
    • CAM plants (cacti, pineapples) are even more specialized, allowing for a storage of carbon acquired at night to be fixed later, when light is available.