Cellular Respiration- 3.6

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Differ between aerobic and anaerobic respiration pathways


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Differ between aerobic and anaerobic respiration pathways

Aerobic Respiration- The breakdown of organic molecules using oxygen

Anaerobic Respiration- The breakdown of organic molecules WITHOUT using oxygen

Describe redox reactions. What is oxidation? What is reduction?

A redox reaction involves the transfer of electrons from one molecule to another resulting is an oxidized molecule and a reduced molecule

Oxidation is when a molecule LOSES an electron and donates the e- to another molecule

Reduction is when a molecule GAINS an electron and accepts the e- from another molecule

LEO goes GER (Lose Electron ->oxidation, Gain Electron -> Reduction)

What is the role of redox reaction in cellular respiration?

In reducing NAD+ and FAD into NADH and FADH2, and creating the proton motive force by oxidizing NADH and FADH2 on the ETC

Name the major processes involved in cellular respiration

(location in a eukaryotic cell, primary inputs (reactants), primary outputs (products), whether the ATP produced is substrate-level phosphorylation or oxidative phosphorylation)


  • Location: Cytoplasm (outside the mitochondria)

  • Primary Inputs (reactants): Glucose, 4 ATP, 2 NAD+

  • Primary Outputs (products): 2 Pyruvates, 2 ATP, 2 NADH

  • ATP: Substrate-level phosphorylation

Pyruvate Modification

  • Location: Matrix (inside the mitochondria)

  • Primary Inputs (reactants): 2 Pyruvates

  • Primary Outputs (products): 2 CO2, 2 Acetyl Co-A, 2 NADH

  • ATP: none produced

Citric Acid Cycle/Krebs Cycle

  • Location: Matrix

  • Primary Inputs (reactants): 2 Acetyl Co-A

  • Primary Outputs (products): 4 CO2, 2 ATP, 2 FADH2, 6 NADH

  • ATP: substrate-level phosphorylation

Oxidative Phosphorylation

  • Location: ACROSS the Inner Membrane of the Mitochondria

  • Primary Inputs (reactants): NADH, FADH2, Oxygen (O2)

  • Primary Outputs (products): H2O, ATP, NAD+, FAD+

  • ATP: Oxydative Phosphorylation

Describe the difference between substrate-level phosphorylation and oxidative phosphorylation

Substrate-level phosphorylation uses ENZYMES to combine ADP and Pi to make ATP

Oxidative Phosphorylation uses a series of REDOX REACTIONS (Electron Transport Chain) to combine ADP and Pi to make ATP

Differentiate between the energy investment and the energy payoff phases of glycolysis

The energy investment phase happens first and requires an input of ATP in order for the reactions of this phase to continue

The energy payoff phase happens after the investment phase and releases ATP after the reactions of this phase occur

Describe the modification of pyruvate that occurs before the citric acid cycle. Why is this necessary?

The carboxyl group (COOH) of pyruvate is removed and releases CO2 as a result. The enzyme acetyl Co-A binds where the carboxyl group previously was. This step is necessary so that the citric acid cycle can occur since pyruvate cannot enter as it is

Describe the initial reactions of the citric acid cycle

  • The Co-A of acetyl Co-A is removed leaving acetyl (2 C)

  • The acetyl (2 C) combines with oxaloacetate (4 C) to create citrate (6 C)

  • Then a series of enzyme-catalyzed reactions occur

The citric acid cycle begins and ends with the same molecule- oxaloacetate. How is this possible?

As the citric acid cycle occurs, the carbons and electrons of citrate get removed eventually ending with 4 Carbons left which make up oxaloacetate, and the carbons of oxaloacetate get used again to create citrate. Creating a cycle

Summarize the processes involved in oxidative phosphorylation need to know in more detail than other steps

  1. Electron Transport Chain

  • NADH and FADH2 oxidize by attaching to the starting transport proteins of the electron transport chain, releasing electrons and H+

  • The electrons travel down the ETC and "lose" some potential energy (P.E) as they move towards the highly electronegative oxygen at the end of the chain

  • Once the electrons reach the end of the ETC, H+ and e- combine with O2 to create water

  • As the electron moved through the ETC, the P.E "lost" was used to pull the H+ against their gradient and into the high [H+] in the IMS


  1. Chemiosmosis

  • The high [H+] in the Intermembrane Space (IMS) travels with the gradient through the enzyme ATP synthase

  • The movement of H+ rotates the ATP synthase, providing energy to catalyze ADP and Pi into ATP

  • Produces significantly more ATP than the other steps of cellular respiration

What role for oxygen play in oxidative phosphorylation?

Oxygen is highly electronegative so it plays the role of attracting electron to itself through the ETC; which results in the creation of the proton motive force

How is the proton motive force generated in oxidative phosphorylation?

As electrons move through the ETC, the P.E that is generated helps the H+ in the matrix move against their gradient into the IMS which creates a high to low concentration gradient from the IMS to the Matrix

What purpose does the proton motive force play in oxidative phosphorylation?

For H+ to travel from a [high] to [low] through the ATP synthase so that the enzyme can rotate and produce a lot of ATP

Differ between the two main types of fermentation pathways

  1. Alcoholic Fermentation

  • Creates ethanol -Carried out by bacteria/fungi

  1. Lactic Acid Fermentation

  • Creates lactate -Carried out by bacteria/human muscle cells (when low on O2)

How do carbohydrates, proteins, and fats compare in terms of their ease of use in metabolic pathways and their energy content?

Order of ease (easiest to hardest)

  1. Carbohydrates

  2. Proteins

  3. Fats *2 and 3 require prior processing

Order of energy content (highest to lowest)

  1. Fats

  2. Proteins & Carbohydrates