The breakdown of pyruvate to give carbon dioxide, water and energy takes place in (a) cytoplasm. (c) chloroplast. (b) mitochondria. (d) nucleus.

Pyruvate oxidation is a key step in cellular respiration. It happens right after glycolysis and before the citric acid cycle. In this process, pyruvate (produced from glycolysis) is transformed into acetyl-CoA. This is vital for the continuation of cellular respiration.
Pyruvate oxidation takes place in the mitochondria of eukaryotic cells. During this step, pyruvate is transported from the cytoplasm into the mitochondria. Once inside, it is converted into acetyl-CoA. This process also releases carbon dioxide and reduces NAD+ to NADH.
The main objectives of pyruvate oxidation are to link glycolysis with the citric acid cycle and to produce molecules that will help generate ATP later on in the process.

Mitochondria are often called the 'powerhouses' of the cell. This is because they generate most of the cell’s supply of ATP, which is used as a source of chemical energy.
Mitochondria have a double membrane structure, with an outer membrane and a highly folded inner membrane. These folds are called cristae, and they increase the surface area for biochemical reactions.
The main functions of mitochondria in cellular respiration include:

• Hosting the citric acid cycle (Krebs cycle)
• Conducting the electron transport chain
• Facilitating ATP synthesis via oxidative phosphorylation

These processes occur in various parts of the mitochondria. The citric acid cycle takes place in the mitochondrial matrix, while the electron transport chain is embedded in the inner membrane.

The citric acid cycle, also known as the Krebs cycle, is a crucial metabolic pathway that generates energy through the oxidation of acetyl-CoA. This cycle takes place in the mitochondrial matrix.
The citric acid cycle has several important functions:

• Production of electron carriers like NADH and FADH2
• Release of carbon dioxide
• Regeneration of oxaloacetate for the continuation of the cycle

Here’s a brief overview of the key steps in the citric acid cycle:

• Acetyl-CoA combines with oxaloacetate to form citrate.
• Citrate undergoes several transformations, leading to the release of two molecules of carbon dioxide.
• During these transformations, high-energy electron carriers (NADH and FADH2) are produced.
• Oxaloacetate is regenerated to start the cycle over again.

The NADH and FADH2 produced here play significant roles in the electron transport chain, where their high-energy electrons are used to make ATP.