Cellular Respiration: Process and Equation

• Cellular respiration is the process of analyzing the relationships between structures and functions in living cells
• Photosynthesis and respiration cycle matter and flow of energy within the cell

Overview of Cellular Respiration

• Cellular respiration converts chemical energy in food, such as glucose, into chemical energy stored in ATP
• Carbohydrates are used first for energy, but any food can be processed as an energy source

Chemical Equation for Cellular Respiration

• C6H12O6 + 6O2 yields 6H2O + 6CO2 + Energy (ATP)
• Reactants: C6H12O6 (glucose) and O2 (oxygen)
• Products: CO2 (carbon dioxide) and H2O (water)
• Energy is released as ATP but isn't considered a product

Structure of Mitochondria

• Cellular respiration takes place in the mitochondria, which contains two main parts:
• Inner membrane: Folded membranes
• Matrix: Fluid-like substance that fills the space

Glycolysis: The First Stage

• Glycolysis is the first stage in cellular respiration; the breakdown of glucose
• It is a 10-step process that splits the 6-carbon molecule of glucose in half, forming two 3-carbon molecules called pyruvate
• Glycolysis occurs in the cytoplasm and is anaerobic, meaning it doesn't require oxygen
• Glycolysis produces a net of 2 ATP and 2 NADH
• One glucose molecule yields two pyruvate molecules and 4 ATP, but nets only 2 ATP because two are used

Decision Time: Aerobic vs. Anaerobic Respiration

• After glycolysis, the cell decides whether to proceed with aerobic or anaerobic respiration
• If oxygen is present, the cell undergoes aerobic respiration, a two-step process to obtain energy
• If oxygen is absent, the cell undergoes anaerobic respiration, a.k.a. fermentation

Aerobic Respiration

• Oxygen is available

Citric Acid Cycle (Krebs Cycle): 1st Step Details

• The citric acid cycle's purpose is to make electron carriers, NADH and FADH2, to move on to the ETC
• The location is in the mitochondrial matrix
• Process: Involves 8 steps of chemical reactions where 2 pyruvate molecules from glycolysis are chemically converted to make 2 ATP (along with some NADH and FADH2
• Pyruvate from glycolysis are converted into acetyl-CoA for the Citric Acid Cycle
• NAD+ and FAD become NADH and FADH₂ to carry e- into the final step
• The cycle happens twice, each time, one pyruvate yields 4 NADH, 1 ATP, 1 FADH2, and 3 CO2

Citric Acid Cycle Total

• 8 NADH, 2 ATP, 2 FADH2 and 6 CO2 are produced in the citric acid cycle

Electron Transport Chain: 2nd Step

• The electron transport chain (oxidative phosphorylation and chemiosmosis) is the second step in aerobic respiration
• Chemiosmosis combines electron transport to ATP synthesis
• This occurs in the inner membrane of the mitochondria (cristae)
• Process: It features a series of reactions using electrons and hydrogens carried by NADH and FADH2 formed during the Krebs Cycle
• The enzyme ATP synthase helps to assemble ATP
• Oxygen serves as the final electron acceptor and combines with electrons and H+ to make water
• The electron transport chain produces 34 ATP and H2O

Anaerobic Respiration (Fermentation)

• Oxygen is unavailable
• In the absence of oxygen, a cell goes through anaerobic respiration, known as fermentation
• There are two main types of fermentation: lactic acid fermentation and alcohol fermentation

Lactic Acid Fermentation

• Lactic acid fermentation occurs in some bacteria and animal cells, like muscle cells
• Pyruvate from glycolysis is converted into lactic acid and 2 ATP

Alcohol Fermentation

• Alcohol fermentation occurs in yeast when oxygen is unavailable
• Pyruvate from glycolysis is broken down into alcohol, CO2, and 2 ATP

ATP Production: Aerobic vs Anaerobic Respiration

• Aerobic respiration produces 36-38 ATP:
  • 2 ATP from Glycolysis
  • 2 ATP from Krebs Cycle
  • 34 ATP from Electron Transport Chain
• Anaerobic Respiration = 2-4 ATP

An overview of cellular respiration, focusing on how living cells analyze relationships between structures and functions. The respiration and photosynthesis cycle and the flow of energy within the cell are also described. It also explains the chemical equation, structure of mitochondria and glycolysis.