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Biology 3.3 Cell Organelles

Biology 3.3 Cell Organelles. Cell Organelles. The Nucleus. Most functions of a cell are controlled by the nucleus. The nucleus is surrounded by a double membrane called the nuclear envelope or nuclear membrane .

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Biology 3.3 Cell Organelles

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  1. Biology 3.3 Cell Organelles Cell Organelles

  2. The Nucleus • Most functions of a cell are controlled by the nucleus. • The nucleus is surrounded by a double membrane called the nuclear envelope or nuclear membrane. • The nuclear envelope is made of two lipid bilayers that separate the nucleus from the protoplasm.

  3. The Nucleus Nuclear pores • Scattered over the surface of the envelope are many small channels called nuclear pores. • Substances that are made in the nucleus, including RNA, move into the cytoplasm by passing through these nuclear pores. • Ribosomes are partially assembled in a region called the nucleolus.

  4. The Nucleus • The hereditary information of a cell is coded in the cell’s DNA, most of which is stored in the nucleus. • Most of the time DNA is long thin strands but when it is about to divide it appears as tightly wound. • These DNA strands are called chromosomes. • The human body cells contain 46 chromosomes.

  5. Ribosomes • Eukaryotic cells have a system of internal membranes that play an essential role in the processing of proteins. • Cells make proteins on ribosomes. • A ribosome is a cell organelle composed of RNA and protein, the site of protein synthesis. • Each ribosome is made of dozens of different proteins as well as RNA.

  6. Production of Proteins • Proteins that are exported from a cell are made of ribosomes that lie on the surface of the endoplasmic reticulum. (ER) • The endoplasmic reticulum (ER) is an extensive system of internal membranes that move proteins and other substances through the cell.

  7. Production of Proteins • The part of the ER with attached ribosomes is called rough ER because it has a rough appearance when viewed in the electron microscope. As each protein is made, it crosses the ER membrane and enters the ER.

  8. Production of Proteins • The rest of the ER is called smooth ER because it lacks ribosomes and thus appears smooth when viewed in an electron microscope. • The portion of the ER that contains completed protein pinches off to form a vesicle. • A vesicle is a small, membrane -bound sac that transports substances in cells.

  9. 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.

  10. Packaging and Distribution of Proteins • The Golgi Apparatusis a set of flattened, membrane-bound sacs that serve as the packaging and distribution centers of the cell.

  11. Packaging and Distribution of Proteins • Enzymes inside the Golgi Apparatus modify the proteins that are received in vesicles from the ER. • The modified proteins are than enclosed in new vesicles that bud from the surface of the Golgi Apparatus.

  12. Packaging and Distribution of Proteins • Other vesicles include lysosomes which are small spherical organelles that contain the cell’s digestive enzymes. • The ER, the Golgi Apparatus, and lysosomes work together in the production, packaging and distribution of proteins.

  13. Mitochondria • Nearly all eukaryotic cells contain many mitochondria. • A mitochondria is an organelle that harvests energy from organic compounds to make ATP, the main energy currency of cells. • Although some ATP is made in the cytosol, most of the cell’s ATP is made inside mitochondria. mitochondria

  14. Mitochondria DNA • The nucleus is not the only organelle in the cell that contains nucleic acids. • Mitochondria also have DNA and ribosomes, and mitochondria make some of their own proteins. • Mitochondria DNA is separate from nuclear DNA and similar to the circular DNA of prokaryotic cells.

  15. Structure of Plant cells • The organelles described here are found in both plant cells and animal cells. • However, plant cells have three additional structures not found in animal cells. • Cell Walls • Chloroplasts • Central Vacuole

  16. Cell Wall & membrane Cell Wall: cell membrane • The cell membrane of a plant is surrounded by a thick cell wall, composed of proteins and carbohydrates. • The cell wall • helps support and maintain the shape of the cell • protects the cell from damage • and connects it with adjacent cells

  17. Chloroplasts • Plants cells contain one or more chloroplasts. • Chloroplasts are organelles that use energy from sunlight to make carbohydrates from carbon dioxide and water. • Carbon dioxide + water  carbohydrates • Chloroplasts, along with mitochondria, supply much of the energy needed to power the energy of plant cells.

  18. Central Vacuole • Much of a plant cell’s volume is taken up by a large membrane-bound space called the central vacuole. • The central vacuole stores water and may contain many substances, including ions, nutrients, and wastes. • When the central vacuole is full, it makes the plant rigid. • This rigidity enables a plant to stand upright.

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