The Cell

1
The Cell

• 7th Grade Science
• Mrs. Christopherson
• Mrs. Goede

2
History of Cells

• 1665 Robert Hooke used a compound microscope to
  look at cork.
• 1674 Anton von Leeuwenhoek observes
  microorganisms in pond water
• 1838 Matthias Schleiden concludes all plants are
  made up of cells.
• 1839 Theodor Schwann concludes all animals are
  made up of cells.
• 1855 Rudolph Virchow proposes that all cells
  come from existing cells, completing the cell
  theory.

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Cell Theory

• All organisms are composed of one or more cells
• Organisms can be unicellular or multicellular
• The cell is the basic unit of organization of
  organisms
• All cells come from pre-existing cells
• Cells reproduce to make exact copies of themselves

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Two Types of Cells

• Prokaryotic Cells
• No nucleus
• No organelles
• Mostly unicellular organisms
• Cell wall or membrane

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Two Types of Cells

• Eukaryotic Cells
• Nucleus
• Organelles surrounded by membranes
• Mostly multicellular
• organisms
• Cell wall or membrane

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• Prokaryotes
• No Nucleus
• Single celled
• Little or no organization within cell wall and
  membrane

• Both
• Cell wall
• Cell membrane

• Eukaryotes
• Have a nucleus
• Contain membrane-bound organelles that have
  specialized tasks
• Single-celled or multicellular

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Cell Specialization

• Multicellular organisms have cells that do many
  different jobs.
• For example, there are blood cells, muscle cells,
  nerve cells, etc. These cells are said to be
  specialized.
• Specialized cells perform only their specific
  functions and cannot live on their own.

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Levels of Organization Within Organisms

• In multicellular organisms, cells are grouped
  together in tissues.
• A tissue is a group of similar cells that do a
  specific job.
• An example is our skin.
• Tissues that work together form organs.
• An example of an organ is the heart.
• Organs and tissues working together from organ
  systems. Example the digestive system
• The largest level of organization is the organism
  itself.

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Levels of Organization Within Organisms
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Cell Organelles

• Cell wall a tough outer covering that protects
  the cell and provides support.
• Only plant cells have cell walls. Can you guess
  why?

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Cell Organelles

• Cell membrane a protective covering that
  surrounds the cell.
• Materials entering the cell must pass thru the
  cell membrane. Some materials can easily enter
  while others cannot cross at all.
• Selectively permeable.
• Both plant and animal cells have cell membranes

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Cell Organelles

• Cytoplasm gel-like material found inside the
  cell, contains the organelles.
• Nucleus genetic material is stored here in the
  form of chromosomes, which are made of DNA.
• The nucleus is usually the largest organelle
  found in the cell!
• Nuclear membrane surrounds and protects the
  nucleus.

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Cell Organelles

• Endoplasmic Reticulum is responsible for
  transporting materials in the cell.
• Smooth ER does not contain ribosomes, makes
  lipids and membrane proteins
• Rough ER contains ribosomes, makes proteins
• Ribosomes produce proteins and are attached to
  the endoplasmic reticulum.

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Cell Organelles

• Mitochondria transform the energy in food to
  energy the cell can use to drive chemical
  reactions.
• The powerhouse of the cell
• Vacuoles store substances in the cell.
• Lysosomes involved in digestion of old cell
  organelles as well as breaking large molecules
  into smaller ones.

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Cell Organelles

• Golgi Body packages products from the ER and
  distribute them around or outside of the cell.

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Cell Organelles
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Cell Growth and Division

• Multicellular organisms grow because cell
  division increases the number of cells in them.
• Cells become specialized during the development
  of an organism.
• Cells that are damaged or worn out are replaced
  by cell division.

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Cell Growth and Division The Cell Cycle

• Interphase The part of the cell cycle when the
  cell is not dividing.
• This is the longest phase in the cell cycle.
• Cells grow and go about their daily routines in
  this part of the cycle.
• DNA (genetic material) replicates.

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Cell Growth and Division The Cell Cycle

• Mitosis the part of the cell cycle where the
  nucleus divides. Occurs in non-reproductive
  cells and produces exact copies of the parent
  cell.
• Prophase The chromosomes condense
• Metaphase The chromosomes line up in the middle
  of the cell.
• Anaphase The chromosomes separate and are
  pulled to either end of the cell.
• Telophase The new nuclear membrane forms.
• Cytokinesis The cell splits in half.

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Cell Growth and Division The Cell Cycle