Presentation on theme: "Metabolic Pathways Several steps Oxidations paired with reductions Specific enzymes for each step Multiple ways to “enter” or “exit” pathway Allows links."— Presentation transcript:
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
Figure 6.9 Energy coupling by phosphate transfer
Basic Energy molecules ATP/GTP Electron Carriers – NADH, FADH 2, NADPH –Ways of moving energy around;
Oxidative phosphorylation Involves the oxidation of electron carriers, chemiosmosis and oxygen. We’ll elaborate more on this later.
Figure 9.2 A review of how ATP drives cellular work
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:coenzymes 1. ADP traps chemical energy to make ATP.energy 2. NAD + traps the energy released in redox reactions to make NADHenergyredox reactions 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
Figure 9.1 Energy flow and chemical recycling in ecosystems
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 9.6 An overview of cellular respiration (Layer 3)
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 O 2 NAD + + H 2 O 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