4.6 The nucleus is the cell’s genetic control center ORGANELLES OF THE ENDOMEMBRANE SYSTEM 4.6 The nucleus is the cell’s genetic control center The largest organelle is usually the nucleus The nucleus is separated from the cytoplasm by the nuclear envelope The nucleus is the cellular control center It contains the DNA that directs the cell’s activities

Two membranes of nuclear envelope NUCLEUS Chromatin Two membranes of nuclear envelope Nucleolus Pore ROUGH ENDOPLASMIC RETICULUM Ribosomes Figure 4.6

Ribosomes-non-membrane bound organelles Ribosomes are free or attached to the endomembranous system of endoplamic reticulum They are where proteins are built.

The endomembrane system is a collection of membranous organelles 4.7 Overview: Many cell organelles are related through the endomembrane system The endomembrane system is a collection of membranous organelles These organelles manufacture and distribute cell products The endomembrane system divides the cell into compartments Endoplasmic reticulum (ER) is part of the endomembrane system

4.8 Rough endoplasmic reticulum makes membrane and proteins The rough ER manufactures membranes Ribosomes on its surface produce proteins 1 2 3 4 Transport vesicle buds off Ribosome Sugar chain Glycoprotein Secretory (glyco-) protein inside transport vesicle ROUGH ER Polypeptide Figure 4.8

4.9 Smooth endoplasmic reticulum has a variety of functions Smooth ER synthesizes lipids In some cells, it regulates carbohydrate metabolism and breaks down toxins and drugs

SMOOTH ER ROUGH ER Nuclear envelope Ribosomes SMOOTH ER ROUGH ER Figure 4.9

4.10 The Golgi apparatus finishes, sorts, and ships cell products The Golgi apparatus consists of stacks of membranous sacs These receive and modify ER products, then send them on to other organelles or to the cell membrane

The Golgi apparatus Golgi apparatus Golgi apparatus “Receiving” side of Golgi apparatus Transport vesicle from ER New vesicle forming “Shipping” side of Golgi apparatus Transport vesicle from the Golgi Figure 4.10

4.11 Lysosomes digest the cell’s food and wastes Lysosomes are sacs of digestive enzymes budded off the Golgi LYSOSOME Nucleus Figure 4.11A

Lysosomal enzymes digest food destroy bacteria recycle damaged organelles function in embryonic development in animals

Transport vesicle (containing inactive hydrolytic enzymes) Rough ER Transport vesicle (containing inactive hydrolytic enzymes) Plasma membrane Golgi apparatus Engulfment of particle Lysosome engulfing damaged organelle “Food” LYSOSOMES Digestion Food vacuole Figure 4.11B

4.12 Connection: Abnormal lysosomes can cause fatal diseases Lysosomal storage diseases are hereditary They interfere with other cellular functions Examples: Pompe’s disease, Tay-Sachs disease

4.13 Vacuoles function in the general maintenance of the cell Plant cells contain a large central vacuole The vacuole has lysosomal and storage functions Central vacuole Nucleus Figure 4.13A

Protists may have contractile vacuoles These pump out excess water Nucleus Contractile vacuoles Figure 4.13B

4.14 A review of the endomembrane system The various organelles of the endomembrane system are interconnected structurally and functionally Transport vesicle from Golgi Transport vesicle from ER Rough ER Plasma membrane Vacuole Nucleus Lysosome Golgi apparatus Smooth ER Nuclear envelope Figure 4.14