Cellular Respiration Harvesting Chemical Energy 2006 2007 Cellular

Cellular Respiration Harvesting Chemical Energy 2006 -2007

Cellular Respiration Stage 1: Glycolysis Today I will… 1. Describe the process of glycolysis. 2. State the reactants and products of glycolysis. Modified from Kim Foglia

What’s the point? ATP The Point is to Make ATP! 2006 -2007

Glycolysis � Breaking down glucose ◦ “glyco – lysis” (splitting sugar) glucose pyruvate 2 x 3 C 6 C ◦ most ancient form of energy capture �starting point for all cellular respiration ◦ inefficient �generate only 2 ATP for every 1 glucose ◦ occurs in cytosol �why does that make evolutionary sense?

Evolutionary perspective � Life on Earth first evolved without free oxygen (O 2) in atmosphere ◦ energy had to be captured from organic molecules in absence of O 2 � Prokaryotes that evolved glycolysis are ancestors of all modern life ◦ ALL organisms still utilize glycolysis

Overview 10 reactions ◦ convert 6 C glucose to two 3 C pyruvate ◦ produce 2 ATP & 2 NADH glucose C-C-C-C 2 ATP 2 ADP ac t en ivat erg ion y fructose-6 P P-C-C-C-P DHAP P-C-C-C 2 Pi G 3 P = glyceraldehyde-3 -phosphate DHAP = dihydroxyacetone phosphate G 3 P (PGAL) C-C-C-P 2 NAD+ pyruvate C-C-C 2 NADH 4 ADP 4 ATP

Glycolysis summary endergonic invest some ATP exergonic harvest a little ATP & a little NADH yield 2 ATP 2 NADH

1 st half of glycolysis (5 reactions) �Glucose “priming” ◦ get glucose ready to split �phosphorylate glucose �rearrangement ◦ split destabilized glucose PGAL

2 nd half of glycolysis (5 reactions) � Energy Harvest ◦ NADH production �G 3 P donates H �oxidize sugar �reduce NAD+ �NAD+ NADH ◦ ATP production �G 3 P pyruvate �sugars donate P �ADP ATP

Energy accounting of glycolysis 2 ATP 2 ADP glucose pyruvate 2 x 3 C 6 C 4 ADP � Net 4 ATP gain = 2 ATP ◦ some energy investment (-2 ATP) ◦ small energy return (+4 ATP) � 1 6 C sugar 2 3 C sugars

Is that all there is? � Not a lot of energy… ◦ for 1 billon years+ this is how life on Earth survived… Why? �slow growth, slow reproduction �only harvest 3. 5% of energy stored in glucose �more carbons to strip off = more energy to harvest O 2 O 2 O 2 glucose pyruvate 2 x 3 C 6 C

We can’t stop there…. glucose + 2 ADP + 2 Pi + 2 NAD+ Glycolysis 2 pyruvate + 2 ATP + 2 NADH glucose + 2 ADP + 2 Pi + 2 NAD+ 2 pyruvate + 2 ATP + 2 NADH � Going to run out of NAD+ ◦ without regenerating NAD+, energy production would stop ◦ another molecule must accept H from NADH How is NADH recycled to NAD+? NADH

How is NADH recycled to NAD+? � Another molecule must accept H from NADH ◦ aerobic respiration O 2 �to Electron Transport Chain in mitochondria ◦ anaerobic respiration �ethanol fermentation �lactic acid fermentation NADH which path you use depends on who you are… O 2

Fermentation (anaerobic) � Bacteria, yeast pyruvate ethanol + CO 2 3 C NADH § beer, wine, bread 2 C NAD+ to glycolysis § Animals, some fungi pyruvate lactic acid 3 C NADH 3 C NAD+to glycolysis § cheese, anaerobic exercise (no O 2) 1 C

Alcohol Fermentation pyruvate ethanol + CO 2 3 C NADH 2 C NAD+ § Dead end process § at ~12% ethanol, kills yeast § can’t reverse the reaction 1 C bacteria yeast

Lactic Acid Fermentation pyruvate lactic acid NADH 3 C NAD+ 3 C § Reversible process § once O 2 is available, lactate is converted to pyruvate by liver O 2 animals

Pyruvate is a branching point Pyruvate O 2 fermentation Kreb’s cycle mitochondria

What’s the point? ATP The Point is to Make ATP! 2006 -2007

And how do we do that? H+ H+ � Set up a H+ gradient � Allow the H+ to flow through ATP synthase ADP + Pi ATP ADP + Pi ATP Have we done that yet? H+ H+