Organelles and Other Internal Structures: Nucleus 3 22 Nuclear Changes During Mitosis 23 Internal Structures: Endoplasmic Reticulum Two types: • Rough endoplasmic reticulum (RER) – originates from the outer membrane of the nuclear envelope and extends in a continuous network through cytoplasm; rough due to ribosomes; proteins synthesized and shunted into the ER for packaging and transport; first step in secretory pathway • Smooth endoplasmic reticulum (SER) – closed tubular network without ribosomes; functions in nutrient processing, synthesis, and storage of lipids 24 Rough Endoplasmic Reticulum 25 Internal Structures: Golgi Apparatus 1 Modifies, stores, and packages proteins Consists of a stack of flattened sacs called cisternae 26 Internal Structures: Golgi Apparatus 2 27 Synthesis and Transport Machine 1 The nucleolus provides ribosomes that travel to the RER Transport vesicles from the ER containing proteins go to the Golgi apparatus for modification and maturation Condensing vesicles transport proteins to organelles or into secretory vesicles to be exported outside 28 Synthesis and Transport Machine 2 29 Synthesis and Transport Machine 3 Lysosomes Vesicles containing enzymes that originate from Golgi apparatus • Involved in intracellular digestion of food particles and in protection against invading microbes Vacuoles Membrane bound sacs containing particles to be digested, excreted, or stored Phagosomes Vacuoles merged with a lysosome 30 Synthesis and Transport Machine 4 31