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Cells

Cells. A Comparison of Eukaryotes and Prokaryotes. What is a Eukaryote Cell?. Eukaryotic cells differ from prokaryotic cells in many ways They are usually larger Cytoplasm houses a variety of membrane bound organelles

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Cells

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  1. Cells A Comparison of Eukaryotes and Prokaryotes

  2. What is a Eukaryote Cell? • Eukaryotic cells differ from prokaryotic cells in many ways • They are usually larger • Cytoplasm houses a variety of membrane bound organelles • A network of protein fibers, the cytoskeleton gives shape and organization to eukaryotic cells and is a place for organelle attachment

  3. A Eukaryotic Cell • As there are differences in Prokaryotic cells there are major differences in Eukaryotic cells, these cells are classified as Animal Cells and Plant Cells • Your hand out illustrates the differences between Prokaryote, Eukaryote (Animal) and Eukaryote (Plant)

  4. Eukaryotic Cell Organelles • We will discuss the following organelles and their function • Nucleus - Vacuoles • Nucleolus - Chloroplasts • Nuclear Membrane - Plastids • Plasma Membrane - Centrioles • Cell Wall - Cytoskeleton • Endoplasmic Reticulum - Cilia and Flagella • Smooth/Rough • Golgi Complex - Mitochondria

  5. Eukaryote: Nucleus • The nucleus is an organelle, usually the largest in the cell • It consists of three readily distinguishable parts • Nuclear envelope • Chromatin • Nucleolus

  6. Eukaryote: Nucleus • The nuclear envelope separates the nuclear material from the cytoplasm. • The granular region is the chromatin • The dark region is the nucleolus

  7. Eukaryote: Nucleus, Nuclear Envelope • The Nucleus is isolated from the rest of the cell by a nuclear envelope that consists of a double membrane. • The membrane is perforated with tiny membrane-lined channels called pores.

  8. Eukaryote: Nucleus, Nuclear Envelope • Water, ions, and small molecules can pass freely through the pores, but the passage of larger molecules, particularly proteins, pieces of ribosomes, and RNA, is regulated by specialized “gatekeeper proteins” that lineeach nuclear pore • Ribosomes stud the outer nuclear membrane which is continuous with the rough endoplasmic reticulum.

  9. Eukaryote: Nucleus, Nuclear Envelope

  10. Eukaryote: Nucleus, Chomatin • Due to the stains used to look at cells early in biology the dense nuclear material was named Chromatin or “colored substance” • Since this discovery we have come to realize that this chromatin consists of DNA associated with proteins (histones)

  11. Eukaryote: Nucleus, Chromatin • Because the DNA stays in the nucleus, whereas most of the chemical reactions that it controls occur in the cytoplasm, information molecules must be exchanged between the nucleus and the cytoplasm. • These molecules are called RNA

  12. Eukaryote: Nucleus, Chromatin • Eukaryoteic DNA and its associated proteins form long strands called chromosomes (“colored bodies”) • When cells divideThe chromosomes uncoil and is read, then recoils.

  13. Eukaryote: Nucleus, Chromatin • Genetic information is copied from DNA into molecules of RNA, which move through the pores of the nuclear envelope into the cytoplasm. • From here the RNA directs the synthesis of cellular proteins, including enzymes, membrane proteins, and a variety of structural proteins.

  14. Eukaryote: Nucleus, Nucleolus • Most eukaryotic nuclei have one or more darkly stained regions called nucleoli (“little nuclei”)

  15. Eukaryote: Nucleus, Nucleolus • The nucleolus consists of ribosomeal RNA, proteins, ribosomes in various stages of synthesis, and DNA (bearing genes that specify the blueprint for ribosomal RNA) • Nucleoli are the sites of ribosome synthesis • Ribosomes are RNA and proteins in combination to form a “workbench” for making proteins.

  16. Eukaryote: Nucleus, Nucleolus • Ribosomes are located in cytoplasm or as metioned on the nuclear envelope. • They can make any of thousands of different proteins.

  17. Eukaryotic Cells have an elaborate system of membranes that enclose the cell and create internal compartments that allow a huge variety of processes to occur within the cytoplasm. This complex system includes: Plasma membrane Endoplasmic reticulum Nuclear envelope Golgi complex Lysosomes Eukaryotic Membranes

  18. Eukaryotic Membranes: Plasma Membrane • The plasma membrane forms the outer boundary of the living part of a cell, enclosing the cytoplasm.

  19. Eukaryotic Membranes: Plasma Membrane • The plasma regulates what comes into and what goes out of the cell. To do this it must perform three general functions.

  20. Eukaryotic Membranes: Plasma Membrane • Selectively isolate the cell’s contents from the external environment. • Regulate the exchange of essential substances between the cell’s contents and the external environment. • Communicate with other cells

  21. Eukaryotic Membranes: Plasma Membrane • This task seems simple but if you consider the width of the plasma membrane it might not. • If you stacked 10,000 plasma membranes on top of each other how thick do you think it would be? • The answer is the thickness of one page of paper.

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