Experiment 5: Cellular Aerobic Respiration (Biology)

Experiment 5 Cellular Aerobic Respiration GENERAL BIOLOGY LABORATORY Introduction Cellular aerobic respiration is a metabolic process by which cells convert biochemical energy from nutrients (like glucose) into adenosine triphosphate (ATP), a molecule that cells use to fuel various fu...

Experiment 5 Cellular Aerobic Respiration GENERAL BIOLOGY LABORATORY Introduction Cellular aerobic respiration is a metabolic process by which cells convert biochemical energy from nutrients (like glucose) into adenosine triphosphate (ATP), a molecule that cells use to fuel various functions. This process requires oxygen and occurs in the mitochondria of eukaryotic cells. Aerobic respiration is essential for producing the majority of ATP that organisms need to survive. Stages of Aerobic Respiration 1. Glycolysis Location: Cytoplasm of the cell. Process: Glucose, a six-carbon molecule, is broken down into two molecules of pyruvate (three carbons each). Products: 2 ATP (net), 2 NADH, and 2 pyruvate molecules. Oxygen Requirement: Anaerobic (does not require oxygen). Key Points: Glycolysis is the first step in both aerobic and anaerobic respiration. Stages of Aerobic Respiration 2. Pyruvate Oxidation Location: Mitochondrial matrix (in eukaryotes). Process: Each pyruvate is converted into acetyl-CoA, releasing one molecule of carbon dioxide per pyruvate. Products: 2 CO₂, 2 NADH and 2 acetyl-CoA (one from each pyruvate). Oxygen Requirement: Aerobic (requires oxygen). Stages of Aerobic Respiration 3. Citric Acid Cycle (Krebs Cycle) Location: Mitochondrial matrix. Process: Acetyl-CoA combines with oxaloacetate to form citrate, which undergoes a series of reactions to produce energy-rich molecules. Products: 2 ATP, 6 NADH, 2 FADH₂, and 4 CO₂ (for every glucose molecule). Oxygen Requirement: Aerobic (requires oxygen). Stages of Aerobic Respiration 4. Electron Transport Chain (ETC) and Oxidative Phosphorylation Location: Inner mitochondrial membrane. Process: Electrons from NADH and FADH₂ pass through a series of protein complexes, releasing energy used to pump protons across the membrane. This creates a proton gradient that drives ATP synthesis. Products: Around 32-34 ATP molecules and water (from oxygen accepting electrons and protons). Oxygen Requirement: (requires oxygen as the final electron acceptor). 1 Proton Gradient: Imagine a dam holding back a large amount of water. The water behind the dam has potential energy because it wants to flow downhill. This is like the proton gradient across the mitochondrial membrane. The protons in the intermembrane space have potential energy because they want to move back into the matrix. 2 ATP Synthase: ATP synthase is like a small turbine that sits within the dam. It has a channel that allows protons to flow through it. 3 Flowing Protons: When the protons flow through the channel of ATP synthase, it's like water flowing through a water wheel. The flow of protons causes the turbine-like structure of ATP synthase to spin, creating mechanical energy. 4 ATP Production: This mechanical energy is harnessed by ATP synthase to add a phosphate group to ADP, creating ATP. This is like the water wheel turning a generator to produce electricity. Summary of ATP Yield Total ATP Production: Approximately 36-38 ATP per glucose molecule under ideal conditions in eukaryotic cells. The Practical Part + Heat Four experiments will be carried out: 1. Water condensation by aerobic respiration. 2. CO₂ Liberation by aerobic respiration. 3. Heat Produced by aerobic respiration. 4. Dehydrogenase activity. 1. Water condensation by aerobic respiration Water condensation, or water formation, is a byproduct of aerobic respiration and occurs during the final stage of the process: the electron transport chain (ETC) and Oxidative phosphorylation. The presence of condensed water or water droplets on cold glass or after blowing on it indicates that the water is liberated by aerobic respiration. 1. Water condensation by aerobic respiration 2. CO₂ Liberation by aerobic respiration Barium hydroxide (Ba(OH)₂) is often used in laboratory settings to demonstrate the release of carbon dioxide (CO₂) during aerobic respiration. Barium hydroxide is a strong base that reacts with carbon dioxide to form barium carbonate (BaCO3), a white precipitate, and water. Ba(OH)₂ +CO₂ BaCO3 +H₂ O The white precipitate (BaCO3) confirms the presence of CO₂ because it only forms when CO₂ is bubbled through or introduced to the barium hydroxide solution. 3. Heat Produced by aerobic respiration. Heat is a natural byproduct of aerobic respiration due to the energy transformations involved in breaking down glucose and forming ATP. The breakdown of glucose is an exergonic reaction, meaning it releases energy. This energy is only partially captured as ATP (about 40% of the total energy). The remaining energy is lost as heat. 4. Dehydrogenase activity. Dehydrogenases are enzymes that catalyze oxidation reactions, typically by transferring hydrogen atoms from glucose to an electron acceptor (NAD+). 4. Dehydrogenase activity. If we force the yeast to use methylene blue (Blue in oxidized form) as a proton acceptor, it will convert to leukomethylene (Reduced form, colorless), as in the following reaction: Thank you very much!