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Cell Structure Notes

General Biology

Mr. Walker

 

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Objective 4: Describe the characteristics of a prokaryotic and eukaryotic cell.

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  1. Compare and contrast prokaryotic and eukaryotic cells (presence or absence of a nucleus, size, organelles, complexity).
  2. Know which organelles may be found in each type of cell.
  3. Identify examples of each type of cell.

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Two Types of Cells

  • Prokaryotic cells (No membrane bound structures) NO NUCLEUS
    • Single celled organisms (Bacteria)
    • Much smaller in size than eukaryotic cells
  • Eukaryotic cells (With membrane bound structures) HAS NUCLEUS
    • Can be single or multicellular. Examples:
      • Protists
      • Fungi
      • Plants
      • Animals
    • Larger in size than prokaryotic cells

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Prokaryotic Cells

  • Have a nucleoid region which has DNA but is not membrane bound
  • Structures in a prokaryotic cell:
    • Cell wall
    • Cell membrane
    • Ribosomes
    • DNA
  • Can have cilia or flagellum
    • Cilia are short hair like structures outside of the cell wall which can help the bacteria move
    • Flagellum are long whip like structures which can help the bacteria move
  • Always unicellular
  • Examples:

Bacteria

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Eukaryotic cells have organelles

  • What is an organelle?
    • In the cytoplasm of eukaryotic cells are organized structures called organelles.
      • Examples include: nucleus, mitochondria, ribosomes..etc.
  • Organelles (little organs) have membranes around them and specific functions.
  • Found in Eukaryotic cells. Prokaryotic cells don’t have membrane bound organelles.

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Eukaryotic Cells Examples

Animal Cell

Plant Cell

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Cell Membrane �

  • Structure: Made/composed of proteins and lipid (fat) molecules.
    • Phospholipid Bilayer
    • Fluid Mosaic Model
  • Function:
    • 1) acts as a boundary layer to contain the cytoplasm (fluid in cell) � 2) Regulates interactions between the cell and the environment.

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Cytoplasm

  • Structure: a gelatin-like substance which flows inside the cell membrane. Within the cytoplasm is a framework called the cytoskeleton.
  • Function: Keeps balance of organelles and cell membrane.

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Cell Wall �

  • Structure: Made of a carbohydrate called cellulose.
  • Function: Protect the cell and give it shape.

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Not every cell has a cell wall. Cells of plants, algae, fungi, and most bacterial have a cell wall.

Animal cells do not have a cell wall!

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Nucleus

Structure: Surrounded by a membrane. Materials enter and leave the nucleus through openings in the membrane.

Function: Directs all cell activities. It contains all instructions for everything that the cell does. The instructions are found on long, threadlike, hereditary material made of DNA.

-DNA is the chemical that contains the code for the cell’s structure and activities.

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Chloroplasts

  • Structure: Green organelles in cytoplasm. They contain the pigment chlorophyll.
  • Function: Make food for the cell. Chlorophyll captures light energy that is used to make a sugar called glucose. It is the site of photosynthesis.

                                         

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  • Chlorophyll �  Carbon Dioxide + Water ---------------> Glucose + Oxygen (food)
  • Animals cells do not have chloroplasts!

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Mitochondria (THE POWERHOUSE)

  • Structure: Made/composed of double unit membrane (protein, lipid).
    • inner membrane infolded to form cristae

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  • Function: Site of cellular respiration ie. the release of chemical energy from food
    • Glucose  +  Oxygen  ------> Carbon dioxide +  Water  + Energy (ATP)

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Ribosomes

  • Structure: Not membrane bound. Spherical bodies composed of RNA (ribonucleic acid) and protein enzymes
  • Function: Produce proteins and other small structures.

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Endoplasmic Reticulum (ER)

  • Structure: A series of folded membrane.
  • Function: Allows materials to be processed and moved around inside the cell.

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Two types of ER:

-Smooth and Rough

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Smooth ER has no attached ribosomes. Smooth ER processes other cellular substances such as lipids (fat). Rough ER is bumpy because it has ribosomes. Ribosomes make proteins.

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Golgi Bodies

  • Structure: Stacked, flattened membranes

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  • Function: Sorts proteins and other cellular substances and package them into membrane-bound structures called vesicles.

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Lysosome

  • Structure: Spherical, membrane bound organelles.
  • Function: Contain digestive chemicals that help break down food molecules, cell wastes, and worn-out cell parts.

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Vacuole

  • Structure: a single layer of unit membrane enclosing fluid in a sack
  • Function:  produces pressure against cell wall for support �   - stores water and various chemicals �   - may store insoluble wastes