4.1 Introduction to the Cell

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4.1 Introduction to the Cell

• Cell
• Smallest unit of matter that can carry on
  all processes of life

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Robert Hooke (1635)

• Examined slice of cork under a microscope
  and saw things that reminded him of small rooms
  in which Monks lived so he called them cells.
• Development of the microscope lead to the
  discovery of the cell

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Cell Theory

• All living things are composed of 1 or more
  cells
• Cells are the basic unit of structure and
  function in an organism
• Cells come only from the reproduction of
  existing cells

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3 Characteristics of Cells

• 1. Size
• 2. Shape
• 3. Internal organization

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1. Size

• Not all cells are alike, they have a
  different structure to fit their function
• Body has 200- different types of cells
• Most cells are only visible to microscope

• Most plant and animal cells measure only
  0.002 inches in diameter
• They are limited in size by the ratio of
  their surface area to their volume. The larger
  this ratio then the better the cell can survive
  which means the smaller the cell the better for
  survival.

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2. Cell Shape

• Shape relates to its function
• Nerve cells have long extensions to pick up
  impulses

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2. Cell Shape

• Skin cells are flat shape to help in covering
  body surface

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2. Cell Shape

•  White blood cells can change form which
  allows them to leave the blood and go to areas
  where infection is, engulf the infection
  (bacteria) and destroy it.

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3. Internal organization

• Organelles are cell components which perform
  specific functions.

• Organs in a multicellular organism carry on
  functions of life just like organelles carry on
  life within a cell.

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2 Types of Cells

• 1. Eukaryotic cells
• 2. Prokaryotic cells

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1. Eukaryotic Cells

• First discovered about 1.5 billion years ago
• Has membrane bound nucleus which contains the
  genetic information and directs most of cells
  activities

• Has membrane bound organelles
• Has cell membrane
• Has cytoplasm (liquid portion inside cell that
  nourishes the organelles)

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Eukaryotic Cells
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2. Prokaryotic Cells

•    First discovered about 3.5 billion years
  ago
• Does not have a membrane bound nucleus
• Does not have membrane bound organelles

• First cells on earth which did not make their
  own food
•   Has cell membrane
• Examples are bacteria and all unicellular
  (one-celled) organisms.

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Prokaryotic Cells