Breathing (Pulmonary Respiration) versus Cellular Respiration

Cellular Respiration General Equation: C6H12O6 + 6O2  6CO2 + 6H2O + ~38 ATP Glucose + Oxygen  Carbon Dioxide + Water + Energy Cellular respiration is how all eukaryotic cells gain energy, in the form of ATP, from macromolecules, such as glucose (sugar).

Types of Respiration Aerobic Respiration – cellular respiration using oxygen (O2). Anaerobic Respiration (Fermentation) – cellular respiration in the absence of O2. There are 2 types of Anaerobic Respiration – Lactic Acid Fermentation and Alcoholic Fermentation.

Which variable (X or Y) is being reduced/oxidized? REDOX reactions: A series of reactions where molecules are reduced then oxidized or vice-versa, resulting in the transfer of energy. Reduction: When a molecule gains an electron (e-) thereby reducing its charge (increasing energy). Oxidation: When a molecule loses an electron (e-) thereby gaining a charge (decreasing energy).   Which variable (X or Y) is being reduced/oxidized? X- + Y+  X+ + Y-

Cellular respiration consists of 3.5 steps: 1. Glycolysis (splitting of sugar) 1.5 Prep-Step 2. Krebs Cycle or Citric acid cycle 3. Electron transport chain

Mitochondrial Anatomy

1. Glycolysis Occurs in the cytosol of the cell, regardless of the presence of oxygen (O2) Involves the splitting of a glucose (sugar) molecule into two, 3-carbon molecules (pyruvate) Uses 2 ATP molecules to split glucose but creates 4 ATP molecules from this splitting. Also reduces 2 NAD+ into 2 NADH’s

1.5 Prep-Step Occurs in the matrix of the mitochondria ONLY if oxygen (O2) is present in the mitochondrion. Converts the 2 pyruvates (from glycolysis) into 2 acetyl-CoA’s Generates 2 NADH’s & 2 CO2

2. Krebs Cycle Occurs in the matrix of the mitochondrion. Turns twice for each glucose broken down in glycolysis Adds acetyl-CoA to a 4-carbon molecule, which is then oxidized (electrons taken away from) in multiple steps into 2CO2 per turn (or 4 CO2 per glucose molecule) Generates 3 NADH’s, 1 ATP, and 1 FADH2 per turn

3. Electron Transport Chain (ETC) Occurs in the inner membrane of the mitochondrion. Series of REDOX reactions between molecules that take electrons from NADH & FADH2 and passes them to the FINAL ELECTRON ACCEPTOR (OXYGEN!!!) When oxygen receives these electrons it becomes H2O Electrons that travel through the ETC generate energy that powers proton pumps.

ETC Continued… Proton pumps pump H+ from the matrix into the intermembrane space (IMS) which generates a chemiosmotic gradient of H+ (between the intermembrane space and the matrix) This gradient allows H+ to travel back (down their gradient) to the matrix through a membrane protein, ATP Synthase.

ETC Continued… Each NADH that gives ETC electrons results in the generation of 3 ATP Each FADH2 that gives ETC electrons results in the generation of 2 ATP Energy generated (proton motive force) from H+ traveling down their gradient is used to power ATP Synthase to create ATP.

Anaerobic Respiration Fermentation and Respiration Compared 1. Both produce ATP from food, cellular respiration is aerobic while fermentation is anaerobic. Both use glycolysis; have a net production of 2 ATP by substrate phosphorylation, and both used NAD+ as the oxidizing agent. Respiration yields up to 19 times more ATP per glucose molecule than fermentation does.

Types of Fermentation Alcoholic fermentation- pyruvate is converted to ethanol to regenerate the supply of NAD+. (Done by yeast) C6H12O6  2C2H5OH +2CO2 +NAD+ Lactic acid fermentation- pyruvate is reduced to NADH to form lactate, no release of CO2. C6H12O6  2C3H6O3 + NAD+

Diagram of Both Biochemical Pathways

CR vs PS