Cells

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Cells

• A Comparison of Eukaryotes and Prokaryotes

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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

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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)

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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

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Eukaryote Nucleus

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

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Eukaryote Nucleus

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

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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.

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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.

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Eukaryote Nucleus, Nuclear Envelope
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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)

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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

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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.

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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.

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Eukaryote Nucleus, Nucleolus

• Most eukaryotic nuclei have one or more darkly
  stained regions called nucleoli (little nuclei)

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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.

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Eukaryote Nucleus, Nucleolus

• Ribosomes are located in cytoplasm or as metioned
  on the nuclear envelope.
• They can make any of thousands of different
  proteins.

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Eukaryotic Membranes

• 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

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Eukaryotic Membranes Plasma Membrane

• The plasma membrane forms the outer boundary of
  the living part of a cell, enclosing the
  cytoplasm.

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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.

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Eukaryotic Membranes Plasma Membrane

1. Selectively isolate the cells contents from the
   external environment.
2. Regulate the exchange of essential substances
   between the cells contents and the external
   environment.
3. Communicate with other cells

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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.