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Chapter 3-3: Cell Organelles
Objectives
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Describe the role of the nucleus in cell activities.
Analyze the role of internal membranes in protein production.
Summarize the importance of mitochondria in eukaryotic cells.
Identify three structure in plant cells that are absent from animal cells.
The Nucleus
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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.
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The nucleus is surrounded by a double membrane called the nuclear envelope.
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Scattered over the surface of the nuclear envelope are many small channels called
nuclear pores.
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Ribosomal proteins and RNA are made in the nucleus.
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Ribosomes are partially assembled in a region of the nucleus called the nucleolus.
Ribosomes and the Endoplasmic Reticulum
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Ribosomes are the cellular structures on which
proteins are made.
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The Endoplasmic Reticulum or ER is an
extensive system of internal membranes that move
proteins and other substances through the cell.
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The part of the ER with attached ribosomes is
called the rough ER.
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The rough ER helps transport proteins that are
made by the attached ribosomes.
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New proteins enter the ER.
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The portion of the ER that contains the completed protein pinches off to form a vesicle.
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A vesicle is a small, membrane-bound sac that transports substances in cells.
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The ER moves proteins and other substances within eukaryotic cells.
Packaging and Distribution of Proteins
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Vesicles that contain newly made proteins move through the cytoplasm from the ER to
an organelle called the Golgi apparatus.
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The Golgi apparatus is a set of flattened, membrane-bound sacs that serve as the
packaging and distribution center of the cell.
Lysosome
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Function: allows the cell to digest food and recycle organelles.
Mitochondria
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Mitochondria are organelles that harvest energy from organic compounds to make
ATP.
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ATP is the main energy currency of cells. Most ATP is made inside the mitochondria.
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Mitochondria have two membranes. The outer membrane is smooth. The inner
membrane is greatly folded, and has a large surface area.
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Mitochondria have their own DNA. Mitochondria reproduce independently of the cell.
Mitochondrial DNA is similar to the DNA of prokaryotic cells.
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Mitochondria are thought to be descendents of primitive prokaryotes.
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Mitochondria have an inner and an outer membrane.
Structures of Plant Cells
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Plants have three unique structures that are not found in animal cells:
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Cell Wall
o
Chloroplasts
o Central Vacuole
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The cell membrane of plant cells is surrounded by a thick cell wall, composed of
proteins and carbohydrates.
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The cell wall
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helps support and maintain the shape of the
cell
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protects the cell from damage
o connects the cell with adjacent cells
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Chloroplasts are organelles that use light energy to make carbohydrates from carbon
dioxide and water.
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Chloroplasts, along with mitochondria, supply
much of the energy needed to power the
activities of plant cells.
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Chloroplasts, like mitochondria, have their own
DNA and reproduce independently of the plant
cell.
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Chloroplasts, like mitochondria, are thought to be
descendents of ancient prokaryotes.
Central Vacuole:
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Most of a plant cell’s volume is taken up by a large, membrane-bound space called the
central vacuole.
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The central vacuole stores water and may contain ions, nutrients, and wastes.
Found in plant and animal cells:
Found only in plant cells:
1. Cell membrane
1. Cell wall
2. Ribosome
2. Chloroplast
3. Endoplasmic reticulum
3. Large vacuole
4. Lysosome
5. Golgi complex
6. Mitochondrion
Summary of Organelles