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Biology
Biology
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7-2 Eukaryotic Cell Structure
Photo Credit: © Quest/Science Photo Library/Photo Researchers, Inc.
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3. Comparing the Cell to a Factory
Eukaryotic Cell Structures
Structures within a eukaryotic cell that perform important cellular functions are known as organelles.
Cell biologists divide the eukaryotic cell into two major parts: the nucleus and the cytoplasm.
The cytoplasm is the portion of the cell outside the nucleus.
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Nucleus
What is the function of the nucleus?
The nucleus is the control center of the cell.
The nucleus contains all the cell's DNA and coded instructions for making proteins and other important molecules.
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Nucleus
The Nucleus
Chromatin
Nuclear envelope
Nucleolus
The nucleus controls most cell processes and contains the hereditary information of DNA. The DNA combines with protein to form chromatin, which is found throughout the nucleus. The small, dense region in the nucleus is the nucleolus.
Nuclear pores
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Nucleus
The nucleus is surrounded by a nuclear envelope composed of two membranes.
The envelope is dotted with nuclear pores, which allow material to move in and out of the nucleus.
Nuclear envelope
Nuclear pores
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Nucleus
The granular material in the nucleus is called chromatin.
Chromatin consists of DNA bound to protein.
Chromatin
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Nucleus
When a cell divides, chromatin condenses to form chromosomes.
Chromosomes contain the genetic information that is passed from one generation of cells to the next.
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Nucleus
Most nuclei also contain a nucleolus.
The nucleolus is where the assembly of ribosomes begins.
Nucleolus
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Ribosomes
What is the function of the ribosomes?
Proteins are assembled on ribosomes.
One of the most important jobs carried out in the cell is making proteins.
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Ribosomes
Ribosomes produce proteins by following coded instructions that come from the nucleus.
Cells that are active in protein synthesis are often packed with ribosomes.
Instructions from nucleus…
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12. Endoplasmic Reticulum
What is the function of the endoplasmic reticulum?
The ER is where lipid (fat) components of the cell membrane are assembled, along with proteins.
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13. Endoplasmic Reticulum
Ribosomes
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14. Endoplasmic Reticulum
There are two types of ER—rough and smooth.
The portion of the ER involved in protein synthesis is called rough endoplasmic reticulum, or rough ER.
Ribosomes are found on the surface of rough ER.
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15. Endoplasmic Reticulum
Smooth ER does not have ribosomes on its surface.
Smooth ER contains collections of enzymes that perform specialized tasks, such as synthesis of membrane lipids and detoxification of drugs.
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Golgi Apparatus
What is the function of the Golgi apparatus?
The Golgi apparatus sorts and packages proteins and other materials from the endoplasmic reticulum for storage in the cell or secretion outside the cell.
From the Golgi apparatus, proteins are then “shipped” to their final destinations throughout the cell or outside of the cell.
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Golgi Apparatus
The Golgi apparatus appears as a stack of closely apposed membranes.
The Golgi apparatus modifies, sorts, and packages proteins. Notice the stacklike membranes that make up the Golgi apparatus.
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Lysosomes
What is the function of lysosomes?
Lysosomes are small organelles filled with enzymes.
Lysosomes break down lipids, carbohydrates, and proteins into small molecules that can be used by the rest of the cell.
Lysosomes also break down organelles that have outlived their usefulness.
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Vacuoles
What is the function of vacuoles?
Saclike structures that store materials such as water, salts, proteins, and carbohydrates.
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Vacuoles
In many plant cells there is a single, large central vacuole filled with liquid.
The pressure of the central vacuole allows plants to support heavy structures such as leaves and flowers.
Vacuole
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Vacuoles
Contractile vacuole
Vacuoles are also found in some unicellular organisms and in some animals.
The paramecium contains a contractile vacuole that pumps excess water out of the cell.
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22. Mitochondria and Chloroplasts
What is the function of the mitochondria?
“Powerhouse” of the cell
Mitochondria convert chemical energy stored in food into materials that the cell can use.
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23. Mitochondria and Chloroplasts
Mitochondria are enclosed by two membranes—an outer membrane and an inner membrane.
The inner membrane is folded up inside the organelle.
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24. Mitochondria and Chloroplasts
What is the function of chloroplasts?
Chloroplasts capture energy from sunlight and convert it into chemical energy in a process called photosynthesis.
Chloroplasts are ONLY found in plant cells and contain a pigment called chlorophyll!
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Cytoskeleton
What are the functions of the cytoskeleton?
Network of protein filaments that helps the cell to maintain its shape. The cytoskeleton is also involved in movement.
The cytoskeleton is made up of:
microfilaments
microtubules
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Cytoskeleton
Cytoskeleton
Cell membrane
Endoplasmic reticulum
Microtubule
The cytoskeleton is a network of protein filaments that helps the cell to maintain its shape and is involved in many forms of cell movement. Microtubules are part of the cytoskeleton that help maintain cell shape.
Microfilament
Ribosomes
Mitochondrion
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Cytoskeleton
Microfilaments:
are threadlike structures made up of the protein actin.
produce a tough, flexible framework that supports the cell.
Microtubules
hollow structures which maintain cell shape.
are important in cell division.
Centrioles help to organize cell division.
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7-2
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7-2
In the nucleus of a cell, the DNA is usually visible as
a dense region called the nucleolus.
the nuclear envelope.
granular material called chromatin.
condensed bodies called chloroplasts.
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7-2
Two functions of vacuoles are storing materials and helping to
break down organelles.
assemble proteins.
maintain homeostasis.
make new organelles.
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7-2
Chloroplasts are found in the cells of
plants only.
plants and some other organisms.
all eukaryotes.
most prokaryotes.
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7-2
Which of the following is NOT a function of the Golgi apparatus?
synthesize proteins
modify proteins
sort proteins
package proteins
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7-2
Which of the following is a function of the cytoskeleton?
manufactures new cell organelles
assists in movement of some cells from one place to another
releases energy in cells
modifies, sorts, and packages proteins
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34. Comparing the Cell to a Factory
Plant Cell
Nucleolus
Nucleus
Smooth endoplasmic reticulum
Nuclear envelope
Ribosome (free)
Rough endoplasmic reticulum
Ribosome (attached)
Cell wall
Golgi apparatus
Cell membrane
Chloroplast
Mitochondrion
Vacuole
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35. Comparing the Cell to a Factory
Animal Cell
Smooth endoplasmic reticulum
Nucleolus
Nucleus
Ribosome (free)
Nuclear envelope
Cell membrane
Rough endoplasmic reticulum
Ribosome (attached)
Centrioles
Golgi apparatus
Mitochondrion
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36. END OF SECTION