Cellular Respiration: Harvesting Chemical Energy

Respiration is the process of extracting stored energy from glucose to make ATP.

Cellular Respiration Equation C 6 H 12 O O 2 6 CO H 2 O and energy As a result of respiration, energy is released from the chemical bonds found in complex organic molecules (food).

Aerobic Respiration u Aerobic Respiration is respiration which takes place in the presence of oxygen

Respiration is controlled by Enzymes …rate is controlled by enzymes

Cell Respiration is divided into 3 stages 1. Glycolysis 2. Krebs Cycle 3. Oxidative Phosphorylation

Glycolysis u Glyco- glucose, -lysis: to split u Universal step in all forms of respiration u Likely used to supply energy for the ancient cells.

Glycolysis u Function - To split glucose and produce NADH, ATP and Pyruvate (pyruvic acid). u Location - Cytoplasm. u Occurs in 9 steps…. 6 of the steps use magnesium Mg as cofactors.

NAD + Energy carrier u Nicotinamide Adenine Dinucleotide NAD e - NADH NAD + = oxidized form NADH = reduced form

Requirements for Glycolysis u Glucose u 2 ATP…. As activation energy u 4 ADP u 2 NAD + u Enzymes

The Products of Glycolysis u 2 Pyruvic Acids (a 3C acid) u 4 ATP u 2 NADH

Net Energy Result u 2 ATP per glucose u 2 NADH u In summary, glycolysis takes one glucose and turns it into 2 pyruvate, 2 NADH and a net of 2 ATP.

Krebs Cycle Also called: Citric Acid Cycle or Tricarboxylic Acid Cycle u Function: Oxidize pyruvic acid to CO 2 u Produce: 3NADH, 1FADH 2 and 1ATP u Location: Mitochondria matrix

Formation of Acetyl CoA: Acetyl CoA is formed when the pyruvate, from glycolysis, combines with Coenzyme A… tis takes place in the matrix.

Requirements for Krebs Cycle u Pyruvic acid (3C acid) u Coenzyme A u 3 NAD + u 1 ADP u 1 FAD u Double this list for each glucose.

Products of Krebs Cycle u 3 CO 2 u Acetyl CoA u 3 NADH u 1 ATP u 1 FADH 2 u Double this list for each glucose.

Krebs Cycle u Produces most of the cell's energy in the form of NADH and FADH 2 … not ATP u Does NOT require O 2 u The CO 2 produced by the Krebs cycle is the CO 2 animal exhale when they breathe.

Oxidative Phosphorylation u Process of extracting to energy from NADH and FADH 2 to form ATP. u Function: Convert NADH and FADH 2 into ATP. u Location: Mitochondria cristae.

Oxidative Phosphorylation u NADH or FADH 2 u ADP uO2uO2

Oxidative Phosphorylation u Requires the Electron Transport Chain… the Electron Transport Chain is a collection of proteins, embedded in the inner membrane, used to transport the electrons from NADH and FADH 2

Cytochrome c u Cytochrome c: is one of the proteins of the electron transport chain… often used by geneticists to determine relatedness… exists in all living organisms. u The Cytochromes alternate between RED and OX forms and pass electrons down to O 2

ATP Yield u Each NADH energizes 3 ATP u Each FADH 2 energizes 2 ATP

Chemiosmotic Hypothesis u ETC energy is used to move H + (protons) across the cristae membrane. u ATP is generated as the H + diffuse back into the matrix through ATP Synthase

ATP Synthase u Uses the flow of H + to make ATP. u Works like an ion pump in reverse, or like a waterwheel under the flow of H + “water”.

Alcoholic Fermentation u Carried out by yeast, a kind of fungus.

Alcoholic Fermentation u Uses only Glycolysis. u An incomplete oxidation - energy is still left in the products (alcohol). u Does NOT require O 2 u Produces ATP when O 2 is not available.

Lactic Acid Fermentation u Uses only Glycolysis. u An incomplete oxidation - energy is still left in the products (lactic acid). u Does NOT require O 2 u Produces ATP when O 2 is not available.

Lactic Acid Fermentation u Done by human muscle cells under oxygen debt. u Lactic Acid is a toxin and causes soreness and stiffness in muscles.

Fermentation - Summary u Way of using up NADH so Glycolysis can still run. u Provides ATP to a cell even when O 2 is absent.

Aerobic vs Anaerobic u Aerobic - Respiration with O 2 u Anaerobic - Respiration without O 2 u Aerobic - All three Respiration steps. u Anaerobic - Glycolysis only.

Strict vs. Facultative Respiration u Strict - can only carry out Respiration one way… aerobic or anaerobic. u Facultative - can switch respiration types depending on O 2 availability. Ex - yeast

ATP yields by Respiration type u Anaerobic - Glycolysis only Gets 2 ATPs per glucose. u Aerobic - Glycolysis, Krebs, and Oxidative Phosphorylation (electron transport chain) Generates many more ATPs per glucose.

Aerobic ATP yield u Glycolysis - 2 ATPS, 2 NADHs u Krebs - 2 ATPS, 8 NADHs, 2 FADH 2 u Each NADH = 3 ATP u Each FADH 2 = 2 ATP

ATP Sum u 10 NADH x 3 = 30 ATPs u 2 FADH 2 x 2 = 4 ATPs u 2 ATPs (Gly) = 2 ATPs u 2 ATPs (Krebs) = 2 ATPs u Max = 38 ATPs per glucose

However... u Some energy is used in shuttling the NADH from Glycolysis into the mitochondria. u Actual ATP yield ~ 36/glucose

Yeast u Would rather do aerobic Respiration; it has 18x more energy per glucose. u But, anaerobic will keep you alive if oxygen is not present.

Importance of Respiration u Alcohol Industry - almost every society has a fermented beverage. u Baking Industry - many breads use yeast to provide bubbles to raise the dough.

Swiss Cheese u Holes are bubbles of CO 2 from fermentation.

Exergonic/Endergonic

Biological Examples u Exergonic - respiration u Endergonic - photosynthesis

Cell - Types of Work u Mechanical - muscle contractions u Transport - pumping across membranes u Chemical - making polymers

Cells use ATP as their energy source u Adenosine Triphosphate u Made of: - Adenine (nitrogenous base) - Ribose (pentose sugar) - 3 phosphate groups

Adenine Ribose Phosphates

Key to ATP u Is in the high energy bonds between the three phosphate groups. u Negative charges on the phosphate groups repel each other and makes the phosphates unstable.

ATP Cycles u Energy released from ATP drives anabolic reactions. u Energy from catabolic reactions “recharges” ATP.

ATP Cycle ATP ADP + P + Energy

ATP in Cells u A cell's ATP content is recycled every minute. u Humans use close to their body weight in ATP daily. u No ATP production equals quick death.