1. Cell Organelles Section 3.3

2. The Nucleus The nucleus is an internal compartment that houses the cell’s DNA. Most functions of a eukaryotic cell are controlled by the cell’s nucleus. The nucleus is surrounded by a double membrane called the nuclear envelope Scattered over the surface of the nuclear envelope are many small channels called nuclear pores

3. The Nucleus, continued Ribosomal proteins and RNA are made in the nucleus Ribosomes are partially assembled in a region of the nucleus called the nucleolus

4. Ribosomes and the Endoplasmic Reticulum Ribosomes are the cellular structures on which proteins are made. The Endoplasmic Reticulum or ER is an extensive system of internal membranes that move proteins and other substances through the cell.

5. Ribosomes and the Endoplasmic Reticulum, continued The part of the ER with attached ribosomes is called the rough ER The rough ER helps transport proteins that are made by the attached ribosomes New proteins enter the ER The portion of the ER that contains the completed protein pinches off to form a vesicle A vesicle is a small, membrane-bound sac that transports substances in cells

6. Ribosomes and the Endoplasmic Reticulum, continued Packaging and Distribution of Proteins Vesicles that contain newly made proteins move through the cytoplasm from the ER to an organelle called the Golgi apparatus The Golgi apparatus is a set of flattened, membrane-bound sacs that serve as the packaging and distribution center of the cell

7. Ribosomes and the Endoplasmic Reticulum, continued

8. Mitochondria Mitochondria are organelles that harvest energy from organic compounds to make ATP ATP is the main energy currency of cells. Most ATP is made inside the mitochondria

9. Mitochondria, continued Mitochondria have two membranes. The outer membrane is smooth. The inner membrane is greatly folded, and has a large surface area. Mitochondria have their own DNA. Mitochondria reproduce independently of the cell. Mitochondrial DNA is similar to the DNA of prokaryotic cells. Mitochondria are thought to be descendents of primitive prokaryotes.

10. Summary of Organelles