Topic 8.2 Chap. 7 in Falcon Book Cell Respiration Topic 8.2 Chap. 7 in Falcon Book

8.2 Cell Respiration Oxidation (8.2.1) Reduction Loss of electrons from an element Oxygen is gained Hydrogen is lost OIL – Oxidation is Loss of energy Reduction Gain of electrons from an element Oxygen is lost Hydrogen is gained RIG – Reduction is Gain of energy

Cell Respiration Occurs in the mitochondria of animal cells Reactants are glucose and oxygen; products are water and carbon dioxide Aerobic respiration occurs in three steps: Glycolysis Krebs Cycle (aka Citric Acid Cycle) Oxidative Phosphorylation (aka Electron Transport Chain)

Glycolysis Occurs in the cytoplasm, just outside of the mitochondria Begins with phosphorylation: 2 ATP lose a phosphate to glucose (a six carbon sugar) and thus become ADP The added phosphates makes the sugar unstable, thus allowing it to be broken down more easily

Glyceraldehyde-3- phosphate After phosphorylation is lysis six carbon glucose is broken down into two three-carbon molecules called G3P Glyceraldehyde-3- phosphate G3P is oxidized results in the production of two triose phosphate molecules and two NADH molecules 2 NAD+ 2

Substrate level phosphorylation of ATP 4 ADP  4 ATP

G3P G3P

Glycolysis Summary 2 ATP used at start Total of 4 ATP’s produced. Net gain of 2 2NADH are produced 2 Pyruvates are produced Phosphorylation, lysis, oxidation Controlled by enzymes, increase in ATP levels will result in end product inhibition and slow or stop process.

8.2 Anaerobic Respiration (no oxygen present) pyruvate will be converted to lactic acid (animals) or ethanol and carbon dioxide (yeast) Aerobic Respiration (oxygen present) pyruvate will go into the mitochondria to participate in the Kreb’s Cycle

8.2 The fluid filled matrix contains the enzymes necessary for the Krebs cycle to take place

Link Reaction Once inside the matrix of the mitochondria (via active transport) each pyruvate is decarboxylated (CO2 is removed) The remaining two-carbon molecule (acetyl) reacts with reduced co-enzyme A (carbohydrate metabolism only), and at the same time NADH + H+ is formed

Krebs Cycle Each acetyl group (CH3CO)(2C) combines with oxaloacetate(4C) with the removal of Coenzyme A (CoA) to make citrate (6C) a.k.a. citric acid

Citrate(6C) is oxidized and a carbon is lost to become CO2 Result is a compound called a-ketoglutarate (5C)

a–ketoglutarate is oxidized and another carbon is lost to make carbon dioxide, thus leaving succinate (4C)molecule. NAD+ is reduced to NADH

This Succinate (4C) molecule goes through a series of reactions in which hydrogens are removed then collected by hydrogen carrying coenzymes such as FADH2 and NADH. One ATP is created from ADP + Pi The final molecule left at the end of the cycle is called oxaloacetate (4C)

In summary, one turn of the krebs cycle yields: 2 CO2 3 NADH + H+ 1 FADH2 1 ATP

Krebs Cycle Review Krebs Cycle will run twice for each glucose molecule entering cellular respiration! Totals from one Glucose molecule 4 CO2 6 NADH + H+ 2 FADH2 2 ATP

Oxidative Phosphorylation (chemiosmosis) Third and final step of cellular respiration Electron transport carriers (proteins)are strategically arranged over the inner membrane of the mitochondrian (called the electron transport chain) Electrons get passed through a series of proteins of increasing electronegativity The final electron acceptor is oxygen(high electronegativity) which then binds with hydrogen to form water As these carriers oxidize NADH + H+ and FADH2 (products of the Krebs cycle), energy is released

This energy forces hydrogen ions to move across the concentration gradient from the mitochondrial matrix (inner portion) to the space between the two membranes (intermembrane space)

Oxidative Phophorylation Animation Eventually the hydrogen ions flow back into the matrix through protein channels in specialized molecules called ATP Synthase As the ions flow down the gradient (via the ATP Synthase protein channels) energy is released and ATP is made Oxidative Phophorylation Animation

Structure and Function of Mitochondria The mitochondria is specially designed to promote efficiency of respiration: Membranes fold in upon themselves to form cristae Cristae provide a larger surface area for the electron transport chain The space between the outer and inner membranes provides room for the accumulation of hydrogen ions