BIO NMDCAT

The conversion of amino acid carbon skeletons into metabolic intermediates like alpha-ketoglutarate requires enzymes located within the mitochondrial matrix.

Porins render the outer membrane freely permeable to small molecules and metabolic substrates, unlike the highly selective inner membrane.

Mitochondria possess independent circular DNA genomes and bacterial-like 70S ribosomes, allowing independent transcription and translation of select proteins.

Electron flow drives complexes I, III, and IV to pump protons out of the matrix into the intermembrane space, creating a reservoir of high proton concentration.

Mitochondria are the powerhouses of the cell because they regenerate adenosine triphosphate (ATP) from ADP and inorganic phosphate.

Premature electron transfers to oxygen at complexes I and III form superoxide radicals, making the mitochondrion the chief producer of intracellular ROS.

Cardiolipin is a double-phospholipid compound unique to the inner mitochondrial membrane that acts as an electrical insulator to block proton leakage.

The electron transport chain pumps protons into the intermembrane space, building a proton-motive force (proton electrochemical gradient) that drives ATP synthase mechanically.

Mitochondrial outer membrane permeabilization releases Cytochrome c into the cytosol, where it activates the apoptosome and executioner caspases.

The soluble enzymes of the Krebs cycle reside inside the fluid matrix, with the sole exception of succinate dehydrogenase (bound to the inner membrane).

The electron transport chain complexes (I-IV) are embedded within the inner membrane folds (cristae) to easily interact with the chemical environment.

These prokaryotic-like genetic traits strongly confirm that mitochondria evolved from ancient alpha-proteobacteria engulfed by primitive cells.

While N-linked glycosylation begins in the ER, O-linked glycosylation occurs exclusively within the compartments of the Golgi apparatus.

The trans-Golgi network is the sorting hub where exit vesicles are packaged and targeted to the plasma membrane, lysosomes, or extracellular space.

Without the mannose-6-phosphate (M6P) tag, lysosomal enzymes miss their sorting receptors in the trans-Golgi, routing into the default secretory pathway instead (I-cell disease).

The Golgi has a slightly lower pH than the ER. This acidic environment increases the affinity of KDEL receptors for ER proteins, facilitating their capture into retrograde COPI vesicles.

Rab GTPases serve as molecular tags on transport vesicles, interacting with specific tethering complexes on target membranes to ensure docking accuracy.

The sulfation of proteoglycans and proteins is a specialized maturation step carried out by sulfotransferase enzymes located in the trans-Golgi.

Cristae are folds of the inner mitochondrial membrane that house the respiratory chain and ATP synthase complexes.