Respiration, Fermentation, and Photosynthesis

1. Respiration, Fermentation, and Photosynthesis

2. Free Energy • Free energy is the energy needed to do work. • It takes work to keep the cell organized and functioning properly! • Ex: Active transport, muscle contractions, nerve impulses…

3. Endergonic & Exergonic Reactions • In a chemical reaction, the amount of energy in the reactants is usually different from the amount of energy in the products. • Energy is stored in the bonds between atoms within a molecule. • There are 2 type of reactions: • Endergonic – energy must be supplied • The products have more energy than the reactants • Exergonic – energy is released • The products have less energy than the reactants • Activation energy is still required!

4. Endergonic & Exergonic Reactions

5. Coupling Reactions • Endergonic and exergonic reactions are often coupled, or linked, to each other. • The energy released from the exergonic reaction is the same energy that is supplied for the endergonic reaction.

6. ATP • ATP (adenosine triphosphate) is the energy “currency” for living things • ATPhas 3 parts: • Adenine (a nitrogenous base) • Ribose (the same sugar that is found in RNA) • 3 phosphate groups Adenine *** Energy is stored in the bonds between the phosphate groups. The last bond (between the second and third phosphates) stores tons of energy!! The energy from food is not useful for the cell until it has been converted and stored in one of these high-energy bonds.

7. ATP & ADP • Energy is released when the bond between the second & third phosphate groups is broken. • This also produces ADP (adenosine diphosphate) • We need to turn ADP back into ATP to do more work! • Energy is required to reattach the 3rd phosphate group. • ATP  ADP + Pi Exergonic • ADP + Pi  ATP Endergonic • (Pi = inorganic phosphate)

8. ATP & ADP

9. ATP & ADP • ATP  ADP + Pi Exergonic • ADP + Pi  ATP Endergonic 2. Energy from food is then stored as a phosphate bond in ATP. ATP 3. Energy is then released when the phosphate bond is broken, and can be used to fuel our everyday activities. 1. Energy from food is required to push a third phosphate group onto ADP. energy hill energy in energy out P + ADP P + ADP Figure 7.1

10. Aerobic Respiration • (Aerobic = oxygen is required) • In aerobic respiration, glucose provides the energy to make ATP from ADP and inorganic phosphate. • The formula for cellular respiration is: C6H12O6 + 6O2 + 38 ADP + 38 Pi  6CO2 + 6H2O + 38 ATP

11. 3 Stages of Aerobic Respiration: • Glycolysis • An anaerobic process that occurs in the cytosol • Uses 2 ATP but creates 4, for a net total of 2 ATP • Krebs cycle (citric acid cycle, TCA cycle) • Takes place in the mitochondria • Produces 2 ATP • Electron transport chain (ETC) • Takes place across the inner mitochondrial membrane • Produces up to 34 ATP • Oxygen is the terminal electron acceptor in the ETC. • Without oxygen, BOTH the ETC AND the Krebs cycle shut down!

12. Cellular Respiration (b) In schematic terms products reactants glycolysis (a) In metaphorical terms 2 ATP insert 1 glucose glucose cytosol 2 NADH glucose derivatives 2 energy tokens glycolysis CO2 2 NADH CO2 2 energy tokens 6 NADH Krebs cycle 2 ATP Krebs cycle 2 FADH2 34 energy tokens electron transport chain O2 electron transport chain 34 ATP mitochondrion H2O 38 ATP maximum per glucose molecule Figure 7.4

13. Aerobic Respiration

14. Anaerobic Respiration • Anaerobic = Oxygen is NOT required. • Anaerobic respiration is also called fermentation. • There are 2 types of fermentation: • A) Lactic acid fermentation • C6H12O6 + 4 ADP + 4 Pi2 lactic acid + 4 ATP • This happens inside our muscles when we cannot get oxygen to them quickly enough (during strenuous exercise) • Also used by many bacteria • This is how yogurt, buttermilk, and sauerkraut are made!

15. Anaerobic Respiration • B) Alcoholic fermentation • C6H12O6 + 4 ADP + 4 Pi2 ethanol + 2 CO2+ 4 ATP • Used by yeast and some other microorganisms • Used to produce beer, wine, and bread

16. Autotrophs vs. Heterotrophs • Autotrophs are organisms that can produce their own food (sugars) from CO2. • Turning CO2 to sugar is an endergonic process. • Photoautotrophs use energy from sunlight • Chemoautotrophs use energy from inorganic chemicals • Heterotrophs are organisms that must consume food.

17. Photosynthesis • During photosynthesis, photoautotrophic organisms like plants and cyanobacteria use energy from sunlight to convert carbon dioxide and water to glucose. • Light is a form of electromagnetic radiation. • Sunlight contains all wavelengths of the visible spectrum.

18. Electromagnetic Spectrum

19. Chloroplasts • In plants, photosynthesis takes place in the chloroplasts. • Chloroplasts contain the pigment chlorophyll, which makes them appear green. • There are 2 types of chlorophyll that absorb light in the red and blue wavelengths. • Green and yellow wavelengths are reflected, so this is what we see! • Chloroplasts also contain pigments called carotenoids that reflect orange and yellow wavelengths of light. • These become visible when chlorophyll degrades in the fall.

20. 2 Stages of Photosynthesis • The Light Reactions (Light-Dependent Reactions): • Sunlight absorbed by chlorophyll is used to activate electrons, which enter an electron transport chain, producing ATP. • The electrons come from water, forming oxygen as a by-product • Takes place across the membranes of coin-shaped thylakoids that are stacked inside the chloroplasts - a stack of thylakoids is called a granum (plural = grana) • The Calvin Cycle (Light-Independent Reactions): • Uses the ATP generated during the light reactions to produce glucose from carbon dioxide (an endergonic reaction!) • Takes place in the stroma, the liquid that fills chloroplasts.