Cytosol

The cytosol or intracellular fluid (or cytoplasmic matrix) is the liquid found inside cells.The cytosol is a complex mixture of substances dissolved in water. Although water forms the large majority of the cytosol, its structure and properties within cells is not well understood.

The concentrations of ions such as sodium and potassium are different in the cytosol than in the extracellular fluid; these differences in ion levels are important in processes such as osmoregulation and cell signaling. The cytosol also contains large amounts of macromolecules, which can alter how molecules behave, through macromolecular crowding.

The cytosol has no single function and is instead the site of multiple cell processes

The cytosol is the site of most metabolism in prokaryotes, and a large proportion of the metabolism of eukaryotesMajor metabolic pathways that occur in the cytosol in animals are protein biosynthesis, pentose phosphate pathway, glycolysis gluconeogenesis

The Golgi apparatus

• The Golgi apparatus consists of flattened membranous sacs and small membrane-enclosed vesicles.

• The Golgi apparatus has three roles:

– Receive proteins from the ER and further modify them.

– Concentrate, package, and sort proteins before they are sent to their destinations.

– Some polysaccharides for plant cell walls are synthesized.

The Golgi Apparatus Golgi body or the Golgi complex

Functions of Golgi Apparatus• Sphingolipid processing (sphingomyelin,

glycolipids);• Protein glycosylation (terminal glycosylation of N-

linked glycans, O-linked glycans producing);• Glycosaminoglycans (GAG) biosynthesis;• Sulfation of some sugars (glycoproteins, GAGs);

• Synthesis of the mannose-6-phosphate marker on lysosomal hydrolases, and lysosome biogenesis;

• Protein maturation;• Sorting and transport of biomolecules to

final cellular location.

N.B. Step by step ordered biochemical events in Golgi apparatus