protein synthesis

the nucleus

• DNA contains genetic instructions for proteins

• sequence of bases in DNA will determine the sequence of amino acids in a polypeptide

ribosomes & RER

• ribosomes in the cytoplasm & RER join amino acids together to form a polypeptide. this requires energy from ATP.

• polypeptide folded and processed in the lumen of the RER

• vesicles bud off from the RER carrying the protein

• vesicles fuse with the golgi apparatus for further processing

golgi apparatus

• proteins are modified

• proteins then sorted & packaged into secretory vesicles

• hydrolytic enzymes are packaged into vesicles called lysosomes which remain in the cell

transport to cell surface/other locations

• secretory vesicles move towards cell surface membrane

• proteins can then be secreted out of the cell via exocytosis

exocytosis at the cell surface membrane

• vesicles fuse with the plasma membrane

• proteins are released outside the cell