Photosynthesis Wrap-up Onto Cellular Respiration! Today: Photosynthesis Wrap-up Onto Cellular Respiration!

How did we do with our questions? Are there different types of photosynthesis? Is it possible at night? Do other organisms besides plants do PS? What’s the best light for PS? How is it regulated? What types of sugars are formed? Do all plants photosynthesize?

Onto Respiration: Note that Energy Flow is Directional, but Matter is Cycled

Cellular Respiration What form of Energy?? Enzyme –Mediated Catabolic Yields Energy! Organic Compounds Carbon Dioxide + Oxygen + Water + Energy! What form of Energy??

ATP!

Cellular RESPIRATION: An Overview

Requires an input of energy! Step 1: Glycolysis Requires an input of energy! In the cytosol… 1. Glucose (6C) is split into 2, 3-Carbon Sugars 2. These 2, 3-Carbon sugars are then oxidized two form 2 molecules of pyruvate Releases Energy!

Step 1: Glycolysis

Step 2: The Citric Acid Cycle

Step 2: The Citric Acid Cycle

The Citric Acid Cycle Each Turn: Two carbons enter as acetate Two completely oxidized carbons leave (CO2) For each acetate, 3 molecules of NADH, 1 FADH2, and 1 ATP

The Citric Acid (Kreb’s) Cycle: A Friendlier View German scientist Hans Krebs deciphers the Krebs Cycle in 1957.

All ATP Generated by Glycolysis and the Citric Acid Cycle is through Substrate-level Phosphorylation

Step 3: Oxidative Phosphorylation So far, only 4 molecules of ATP from each Glucose Where’s the rest of the energy?? How can we capture it??

Reviewing Electron Transport Chains

The Electron Transport Chain in the Inner Mitochondrial Membrane

This exergonic flow of electrons pumps H+ into the intermembrane space, creating a concentration gradient

ATP Synthase Generates ATP (Oxidative Phosphorylation!) http://www.sp.uconn.edu/%7Eterry/images/movs/synthase.mov

Energetic Summary of Cellular Respiration: Efficiency = ~40%

Can we generate ATP under anaerobic conditions?? How?? Aerobic = oxygen present Anaerobic = without oxygen

Can this proceed indefinitely? Why or why not? Glycolysis! Can this proceed indefinitely? Why or why not?

Anaerobic Respiration: Alcohol Fermentation

Anaerobic Respiration: Lactic Acid Fermentation

Anaerobic Respiration Cellular Respiration usually requires OXYGEN as the final electron acceptor. But ANAEROBIC respiration can occur with an alternate electron acceptor. You Try: Diagram the process of cellular respiration. Use your diagram to trace the movement of a single electron through this process!

Evolutionary Implications Why do we think RUBISCO is sloppy? What does this suggest about the earliest mechanisms for generating ATP??

The Fluid Nature of Catabolic Pathways

Do you want to regulate cellular respiration? When? Where? How? Why?

Regulating Respiration Phosphofructokinase is an allosteric enzyme inhibited by ATP and stimulated by AMP. It also may be inhibited by citrate from the Citric Acid Cycle.

Applying Your Understanding of Photosynthesis and Respiration Am I a carbon source or sink?? What does it mean to be a carbon source? What does it mean to be a carbon sink?

The Biology of the Carbon Cycle

More Applications… The fat-soluble compound 2, 4-dinitrophenol (DNP, shown above) acts as a proton ionophore. In this role, it can bind protons on one side of a membrane and drift through the membrane, effectively transporting protons across a membrane. The probability of this happening is greatest on the side of the membrane with the highest concentration of protons.

More Applications… Based on this information, what effect do you think DNP would have on mitochondrial function? Use your drawing of cellular respiration to explain this effect! What short –term and long-term effects do you think exposure to DNP would have on a human? Explain!