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Metabolic Pathways. Several steps Oxidations paired with reductions Specific enzymes for each step Multiple ways to “enter” or “exit” pathway Allows links to other pathways. Thermodynamics. First law? All about energy TRANFER, need to be able to trace where all the energy ends up
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Metabolic Pathways • Several steps • Oxidations paired with reductions • Specific enzymes for each step • Multiple ways to “enter” or “exit” pathway • Allows links to other pathways
Thermodynamics • First law? • All about energy TRANFER, need to be able to trace where all the energy ends up • Usually a partial transfer • Combustion on a SLOW scale • Energy coupling
Basic Energy molecules • ATP/GTP • Electron Carriers – NADH, FADH2, NADPH • Ways of moving energy around;
Oxidative phosphorylation • Involves the oxidation of electron carriers, chemiosmosis and oxygen. • We’ll elaborate more on this later.
Oxidation and Reduction • Always Paired together • What happens in a reduction reaction? • What happens in an oxidation? • What happens to the free energy of a molecule when it is reduced? VERY IMPORTANT!!!!
Figure 9.3 Methane combustion as an energy-yielding redox reaction
We can summarize the two energy-coupling coenzymes as follows: 1. ADP traps chemical energy to make ATP. 2. NAD+ traps the energy released in redox reactions to make NADH Catabolism vs. Anabolism - What’s going on with the energy? - Which would be paired with ATP ADP - Which might be paired with NAD+ NADH
BUT energy in NADH can not be used directly • Oxidative Phosphorylation couples the oxidation of NADH (energy out) with the Phosphorylation of ADP (energy in) • Requires Chemiosmosis – using potential energy in H+ gradient to drive ADP ATP • This process is essential to both photosynthesis AND aerobic cell respiration
Aerobic Cell Respiration • Complete oxidation of glucose • Glucose CO2 endo or exo? • What are the reactions that break glucose down likely to be paired with? • Reduction or oxidation of electron carriers? • Phosphorylation or hydrolysis of ATP?
Figure 9.9 A closer look at glycolysis: energy investment phase (Layer 2)
Figure 9.9 A closer look at glycolysis: energy payoff phase (Layer 4)
Know your enzymes • Kinases • Linked with? • Isomerases • Dehydrogenases • Linked with?
Glycolysis Summary • Started with? • Ended with? • Where is the bulk of the energy? • Location? • Aerobic?
Figure 9.10 Oxidation of Pyruvate ** remember we have TWO pyruvates per glucose, so everything from here on out is doubled!!**
Keep the tally going! • What do we have now?
Krebs Cycle (a.k.a. citric acid cycle) - complete oxidation of Acetyl CoA’s carbons into CO2
Figure 9.12 So after Krebs what are we left with? Where is the energy? Can we use it all?
Electron carriers need to be oxidized • NADH + H+ + ½ O2 NAD+ + H2O • Requires Electron Transport Chain (respiratory chain) • Electrons are passed from membrane bound protein to membrane bound protein in a series of oxidations • EXERGONIC! • Energy released actively transports H+ across membrane establishing a gradient
Final Tally • What do we have now? • Why is oxygen needed? • What happens in absence of O2? • Solution?
Figure 10.2 Focusing in on the location of photosynthesis in a plant
Figure 10.4 An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle (Layer 3)
Figure 10.6 Why leaves are green: interaction of light with chloroplasts
Photons absorbed by molecules raise the molecule to an excited state.
Figure 10.8 Evidence that chloroplast pigments participate in photosynthesis: absorption and action spectra for photosynthesis in an alga
Figure 10.9 Location and structure of chlorophyll molecules in plants
