AP BIOLOGY

Detailed explanation-1: -Pyruvate can be formed in the cytosol by glycolysis, or conversion from alanine by ALT, from lactate by LDH-B or from malate by malic enzyme (ME). Pyruvate crosses the outer mitochondrial membrane (OMM) probably via the VDAC into the intermembrane space (IMS). Pyruvate is then transported across the IMM by the MPC.

Detailed explanation-2: -Pyruvate, also called pyruvic acid, is a polar molecule with a negative charge. Charged polar molecules are unable to pass through the phospholipid bilayer due to the large span of non-polar fatty acid tails in the middle. Therefore these types of molecules require a transport protein to cross a cell membrane.

Detailed explanation-3: -Pyruvic acid is transported into the mitochondria via a monocarboxylic acid cotransporter and is then metabolized by PDH into acetyl-CoA. Metabolism of acetyl-CoA follows the pathway described previously.

Detailed explanation-4: -The transport of pyruvate to mitochondria is via the transport protein translocase of pyruvate. Pyruvate translocase transports pyruvate in a symport fashion with a proton and is therefore active, consuming energy.

Detailed explanation-5: -Normally, pyruvate is involved in the production of ATP via the TCA cycle, following its transportation into mitochondria.