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;

Figure 9.7 Substrate-level phosphorylation

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)

Figure 9.8 The energy input and output of glycolysis

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 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

Figure 9.14 ATP synthase, a molecular mill

Final Tally What do we have now? Why is oxygen needed? What happens in absence of O2? Solution?

Figure 9.18 Pyruvate as a key juncture in catabolism

Figure 9.20 The control of cellular respiration

Figure 9.19 The catabolism of various food molecules

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 10.5 The electromagnetic spectrum

Figure 10.6 Why leaves are green: interaction of light with chloroplasts

Figure 10.7 Determining an absorption spectrum

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

Figure Excitation of isolated chlorophyll by light

Figure How a photosystem harvests light

Figure How noncyclic electron flow during the light reactions generates ATP and NADPH (Layer 5)

Figure A mechanical analogy for the light reactions

Figure Cyclic electron flow

Figure Comparison of chemiosmosis in mitochondria and chloroplasts

Figure The light reactions and chemiosmosis: the organization of the thylakoid membrane

Figure The Calvin cycle (Layer 3)

Figure C 4 and CAM photosynthesis compared

Figure C 4 leaf anatomy and the C 4 pathway

Figure A review of photosynthesis