Lysosomes The cell’s recycling centers

Lysosome Structure Membrane-bound Membrane-bound Contains powerful digestive enzymes Contains powerful digestive enzymes If membrane broke open, enzymes would destroy cell If membrane broke open, enzymes would destroy cell Size Size 0.05 to 0.5 micrometers in diameter 0.05 to 0.5 micrometers in diameter Proteins embedded in membrane Proteins embedded in membrane protect activity of enzymes by regulating internal acidity protect activity of enzymes by regulating internal acidity Transport digested materials away from lysosome Transport digested materials away from lysosome

Lysosome Structure (cont.)

Lysosome Production Enzymes made in rough endoplasmic reticulum Enzymes made in rough endoplasmic reticulum Hydrolytic enzymes Hydrolytic enzymes Enzymes delivered to Golgi apparatus via transport vesicles Enzymes delivered to Golgi apparatus via transport vesicles Sacs formed by rough ER Sacs formed by rough ER Golgi apparatus processes enzymes Golgi apparatus processes enzymes Lysosomes bud from Golgi apparatus w/ enzymes inside Lysosomes bud from Golgi apparatus w/ enzymes inside

Lysosome Production (cont.)

Lysosome Function Newly formed lysosomes can perform one of three tasks Newly formed lysosomes can perform one of three tasks Endocytosis Endocytosis Phagocytosis Phagocytosis Autophagocytosis Autophagocytosis

Endocytosis Endocytosis Endocytosis Cell membrane surrounds large nutritional molecule, forming an endosome Cell membrane surrounds large nutritional molecule, forming an endosome Complex lipids Complex lipids Polysaccharides Polysaccharides Nucleic acids Nucleic acids Proteins Proteins Lysosome fuses with endosome, delivering enzymes needed to break down molecules Lysosome fuses with endosome, delivering enzymes needed to break down molecules Broken-down molecules delivered to cytoplasm by membrane proteins for later use Broken-down molecules delivered to cytoplasm by membrane proteins for later use

Endocytosis (cont.)

Phagocytosis Phagocytosis Phagocytosis Cell membrane surrounds disease-causing bacteria or large object, forming phagosome Cell membrane surrounds disease-causing bacteria or large object, forming phagosome Lysosome joins with phagosome, breaking down the object or bacteria with enzymes Lysosome joins with phagosome, breaking down the object or bacteria with enzymes

Phagocytosis (cont.)

Autophagocytosis Autophagocytosis Autophagocytosis ER wraps around spent cell structure, forming autophagosome ER wraps around spent cell structure, forming autophagosome i.e. mitochondrion i.e. mitochondrion Lysosome joins autophagosome, destroys structure, delivers products to cytoplasm Lysosome joins autophagosome, destroys structure, delivers products to cytoplasm

Autophagocytosis (cont.)

Vacuoles Found within plant cells Found within plant cells Classified by some scientists as large lysosomes Classified by some scientists as large lysosomes Much larger than other lysosomes Much larger than other lysosomes 20 µm 20 µm Membrane-bound Membrane-bound Maintain turgor, or water pressure, inside cell to prevent wilting Maintain turgor, or water pressure, inside cell to prevent wilting Storage for nutrients, pigments, and harmful materials (opium, rubber) used to deter predators Storage for nutrients, pigments, and harmful materials (opium, rubber) used to deter predators

Vacuoles (cont.)