Aerobic Cellular Respiration Process and Stages

Primary purpose of aerobic cellular respiration

To convert glucose into usable energy (ATP) for the cell.

Location of aerobic cellular respiration

It takes place in the cytoplasm (glycolysis) and mitochondria (Krebs cycle and electron transport chain).

Four main stages of aerobic cellular respiration

Glycolysis, pyruvate oxidation, the Krebs Cycle, and the Electron Transport Chain (ETC).

Glycolysis process

Glucose is broken down into 2 pyruvate, net 2 ATP and 2 NADH.

Location and oxygen requirement of glycolysis

It occurs in the cytosol and does not require oxygen (anaerobic process).

Pyruvate Oxidation process

Pyruvate is converted into 2 acetyl-CoA, releasing 2 CO₂ and generating 2 NADH.

Purpose of the Krebs cycle

To produce electron carriers (NADH and FADH₂) that will be used in the electron transport chain.

Location of the Krebs cycle

In the mitochondrial matrix.

Electron transport chain (ETC)

The ETC is a series of protein complexes in the inner mitochondrial membrane that transfer electrons to create a proton gradient.

ATP generation in the electron transport chain

The proton gradient drives ATP synthase, which produces ATP through chemiosmosis.

Role of oxygen in aerobic cellular respiration

Oxygen is the final electron acceptor in the electron transport chain, forming water.

ATP produced from one molecule of glucose

Approximately 36-38 ATP molecules.

Chemiosmosis

The process of using a proton gradient to drive the synthesis of ATP.

Waste products of aerobic respiration

Carbon dioxide (CO₂) and water (H₂O).

Substrate-level phosphorylation

A way of generating ATP by directly transferring a phosphate group to ADP from an intermediate substrate in metabolic pathways, primarily occurring in glycolysis and the Krebs cycle.

Oxidative phosphorylation

ATP production linked to the electron transport chain, where energy from electrons is used to pump protons, creating a gradient that powers ATP synthase.

Net gain of ATP from glycolysis

2 ATP molecules, as 4 are produced but 2 are used during glycolysis.

Electron carriers in cellular respiration

NAD⁺ and FAD, which become NADH and FADH₂ when they gain electrons.

Role of NADH and FADH₂

They carry electrons to the electron transport chain, where they help produce ATP.

Krebs cycle turns per glucose

Twice, because each glucose molecule produces two molecules of pyruvate, leading to two acetyl-CoA molecules.

Fate of carbon dioxide produced during respiration

It is a waste product and diffuses out of the cell, eventually being exhaled by the organism.

Inner mitochondrial membrane structure

Folded into cristae to increase surface area for the electron transport chain and ATP synthesis, allowing more energy production.

Proton gradient generation in the electron transport chain

By using the energy from electrons to pump protons from the mitochondrial matrix into the intermembrane space.

Potential energy stored in the proton gradient

Proton motive force, which drives ATP production through chemiosmosis.

ATP synthase function

As protons flow back into the mitochondrial matrix through ATP synthase, the enzyme rotates, facilitating the addition of a phosphate group to ADP to form ATP.

Oxygen's importance for the electron transport chain

Without oxygen to accept electrons at the end of the chain, the ETC would back up, and ATP production would stop.

Effect of oxygen unavailability on cellular respiration

Cells may switch to anaerobic respiration or fermentation, which produces much less ATP.

Comparison of aerobic and anaerobic respiration in ATP production

Aerobic respiration produces up to 38 ATP per glucose, while anaerobic processes produce only 2 ATP per glucose.

Role of coenzyme A in cellular respiration

It binds to acetyl groups from pyruvate, forming acetyl-CoA, which enters the Krebs cycle.

High-energy electrons in the electron transport chain

They are transferred through a series of proteins, releasing energy that pumps protons across the membrane.

Glucose as a high-energy molecule

It has many chemical bonds that can be broken to release energy used to produce ATP.

Proton Gradient

electrochemical gradient → the difference in hydrogen ion concentration and electrical potential from one side of a membrane to the other.

Why is glycolysis considered to be the most fundamental and ancient metabolic pathway?

Glycolysis is ancient because it happens in almost all organisms and doesn't need oxygen, so it could work in early Earth's low-oxygen environment. It's a basic way for cells to make energy.

What happens when electron transport and ATP synthesis are uncoupled?

Energy released during electron transport is not used to produce ATP but is instead released as thermal energy.

How do uncoupling proteins affect proton flow in the mitochondria?

They create an alternative pathway for protons to re-enter the mitochondrial matrix without generating ATP.

Why is the thermal energy generated by uncoupling proteins important in certain animals?

It helps maintain body temperature in hibernating mammals, birds in cold environments, and young offspring, including human infants.