CELLULAR RESPIRATION C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + 36 ATP ∆G = kJ/mol

The Big Picture Where it all came from: Chemoautotroph = organisms that can build all organic compounds necessary for life from simple inorganic materials, without using light (photosynthesis hadn’t evolved yet) Chemo = chemical, auto = self, troph = eat Photoautotroph = use photosynthesis to build organic compounds necessary for life by transforming light energy Photo = life, auto = self, troph = eat Heterotroph = obtain energy through consuming autotrophs Hetero = other, troph = eat (“other feeders”)

The Big Picture Besides chemoautotrophs, all organisms use glucose as their primary energy source A series of redox reactions is used to break the covalent bonds and reform new, more stable configurations ALL REACTIONS ARE EXOTHERMIC / EXERGONIC Products have less energy than reactants Free energy is transferred via energy carrier molecules (NAD+ and FAD)

The Big Picture AEROBIC CELLULAR RESPIRATION C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + energy (heat and ATP) Aerobic = with oxygen present Accomplished through roughly 20 reactions where the product of one step becomes the reactant in the next step Each step is catalyzed by a enzyme Ex. Glucose  Glucose-6-phosphate via hexokinase The 12 hydrogen atoms from glucose are oxidized and attach to 6 oxygen atoms to form 6 H 2 O Considered oxidation because the hydrogens are removing é from carbon The 6 carbon atoms from glucose attach to the remaining 6 oxygen atoms to form 6 CO 2 Considered oxidation because electrons are pulled towards oxygen

The Big Picture When glucose is burned in a test tube, CO2 and H2O are formed (normal combustion products) Energy is given off as heat and light (flames) When glucose is burned in a cell, CO2 and H2O are formed but… The energy is trapped in the form of ATP ATP is then used as a source of free energy for further reactions

The Big Picture When glucose and O 2 come together, they don’t react until there is enough activation energy. Why do they need the E A ? Oxygen is not strong enough of an oxidizing agent to steal the electrons from the C-H bonds in glucose at body temperature If Oxygen could, then life would not exist. All C-H bonds would just be oxidized immediately due to the high [O 2 ] Activation energy prevents spontaneous combustion. In a test tube heat must be provide to start the reaction However, in a cell, the excess heat would prove fatal Thus, specific enzymes catalyze smaller intermediary steps that lower the overall activation energy

The Big Picture Obligate Anaerobes: obligate = must, an= without, aerobe= O 2 Organisms that cannot live in the presence of oxygen and obtain energy by oxidizing inorganic substances Use NO 2, SO 4, CO 2, and Fe 3+ as oxidizing agents Obligate Aerobes: obligate = must, aerobe = O 2 Organisms that obtain energy by oxidizing organic substances through oxygen Facultative Anaerobes: facultative = adapt organisms that obtain energy by oxidizing inorganic substances with or without O 2

The Big Picture There are two major processes that are used to convert energy from the C-C bonds in glucose into the ATP we need for cellular processes: 1. Substrate-Level Phosphorylation 2. Oxidative Phosphorylation

The Big Picture 1.Substrate Level Phosphorylation -ATP is formed directly in an enzyme-catalyzed reaction -Phosphate containing compounds transfer a phosphate group directly to ADP to form ATP -For each glucose molecule, 4 ATP molecules are produced using this process

The Big Picture 2. Oxidative Phosphorylation -ATP is formed indirectly -Considered oxidative as it is composed of a series of redox reactions, where oxygen is final electron acceptor -Uses two CO-ENZYMES to help in the process **Both of these molecules are used to carry electrons which eventually produce ATP 1.NAD+ (Nicotinamide Adenine Dinucleotide) – - is reduced by accepting 2 electrons and 1 proton from two hydrogen atoms on glucose – - forms NADH + H + 2.FAD (Flavin adenine dinucleotide) - is reduced by accepting 2 electrons and 2 protons from two hydrogen atoms on glucose - Forms FADH 2

CELLULAR RESPIRATION So where does all of this occur? All 4 steps in this process occur in the MITOCHRONDRION 1.Glycolysis 2.Pyruvate Oxidation 3.Krebs Cycle 4.ETC/Chemiosmosis

Stage1: Glycolysis **Occurs in the Cytoplasm *Glycolysis means = GLYCO (sugar) + LYSIS (break down) - Thus, the breaking down of sugar *In the 10 reactions of glycolysis, the 6-carbon glucose molecule is broken down into two 3-carbon molecules called PYRUVATE *However, we will split Glycolysis up into two parts: Glycolysis I & Glycolysis II

Stage1: Glycolysis I

Step 1: Glucose is phosphorylated by ATP to form GLUCOSE – 6 – PHOSPHATE [G6P] *The glucose is added to the 6 th carbon Step 2: G6P undergoes isomerization to form FRUCTOSE – 6 – PHOSPHATE [F6P]

Stage1: Glycolysis I Step 3: F6P is phosphorylated to form FRUCTOSE – 1,6 – BISPHOSPHATE [F1,6-BP] Step 4: F1,6-BP is split into two molecules: - DHAP (dihydroxyacetone phosphate) - G3P (glyceraldehyde – 3- phosphate) **DHAP is then converted into two G3P molecules.

Stage1: Glycolysis I GLYCOLYSIS I SUMMARY -We have converted glucose into two 3-carbon molecules that will further be converted -2 ATP molecules have been used in the process – ** It is very important in this process to keep track of all the ATP molecules that are used and produced. – ** Remember, the goal of glycolysis is to produce ATP – ENERGY TALLY thus far ATP USEDATP PRODUCEDNADH PRODUCEDFADH 2 PRODUCED 2000