Endomembrane System and Related Organelles

Endomembrane System

  • Components: nuclear envelope, ER, Golgi, vesicles, endosomes, vacuoles/lysosomes, plasma membrane, extracellular space.

Vesicle Movement

  • Endocytosis: Internalizes outside contents via vesicles and delivers them into the endosome.

  • Exocytosis: Secretes inside contents via vesicles outside of the cell.

Lysosomes

  • Contain hydrolytic enzymes for molecule degradation.

  • Optimal hydrolytic enzyme activity at low pH (4.5−54.5-5).

  • Formed from the aggregation of vesicles.

Vacuoles

  • Serve as storage compartments for enzymes, organic, and inorganic compounds.

  • Can occupy up to 80%80\% of a plant cell’s volume.

Peroxisomes

  • Important in lipid metabolism, photorespiration, oxidizing enzymatic reactions, and scavenging reactive oxygen species (synthesis and degradation of H<em>2O</em>2H<em>2O</em>2), facilitating detoxification.

  • Enclosed in a single lipid bilayer.

Apicoplasts

  • Found in the Apicomplexa (eukaryotic parasites).

  • Surrounded by four membranes.

  • Involved in lipid, isoprenoid, and heme metabolism.

  • Have lost the ability to photosynthesize.