Cell Structure and Function

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Chapter 4

• Cell Structure and Function

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Cell Theory

• Every organism is made of one or more cells.
• A cell is the smallest unit of life.
• Cells come from preexisting cells.

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Cells are highly organized

• They have a plasma membrane surrounding them made
  of a phospholipid bilayer.
• This membrane determines what substances may
  enter and leave the cell.

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• They have a DNA containing region.
• In a prokaryote cell, it is simply a circular
  piece of DNA called a plasmid.
• In eukaryote cells, the genetic material is
  contained in a nucleus.

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• They have cytoplasm. Cytoplasm is the substance
  between the cell membrane and the DNA region. It
  is a fluid substance that contains the organelles.

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Fluid Mosaic Model

• Cells are surrounded by fluids, inside the cell
  itself and around it.
• The membrane is a flexible substance that allows
  the cell to move around in this fluid
  environment.

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• The membrane is made up of various substances
  phospholipids, sterols, proteins, and
  glycolipids.
• All of these components are working together for
  the membrane to function properly. It is not a
  rigid barrier, but a flexible one

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Cell Membrane

• Made of a phospholipid bilayer.
• Responsible for controlling what enters and
  leaves the cell.

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Cell Wall

• Found in plant cells and prokaryotic cells.
• More rigid than a cell membrane.

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Prokaryote

• Simpler cells
• Lack a membrane bound nucleus.
• Domains Archaea and Bacteria consist of
  prokaryotic cells.
• Do have ribosomes

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Eukaryote

• Structurally very complex.
• Distinguishing feature is the presence of a
  nucleus.
• Have a variety of organelles.

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• Cells contain subcellular particles called
  organelles.
• These organelles have a specific function in the
  cell.
• All of them must work together to keep the cell
  functioning properly.

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The Nucleus

• Stores genetic information
• Governs the characteristics of the cell
• Regulates cellular activities
• Sometimes considered the brain of the cell

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Nucleolus

• Small body found within the nucleus
• Responsible for ribosome production, RNA
  production, and some protein production

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Endoplasmic Reticulum

• Rough covered in ribosomes. Responsible for
  synthesis, processing, and modification of
  protein. Continuous with nuclear membrane.

Smooth no ribosomes. Makes phospholipids
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Ribosomes

• Can be free in cytoplasm or attached to the rough
  endoplasmic reticulum
• Responsible for protein synthesis within a cell.

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Golgi Apparatus

• Collects, sorts, packages, and distributes
  materials such as proteins and lipids

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Vesicle

• Branch off of the Golgi (or sometimes the
  membrane)
• Responsible for the transportation of products
  made in the cell

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Lysosomes

• Contain digestive enzymes.
• Responsible for breaking down worn out organelles
  and other cellular debris

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Vacuoles

• Larger than vesicles.
• Store substances
• In plant cells, they are responsible for water
  storage that maintains a plants rigidity

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Chloroplast

• Found in plant cells
• Allows plants and algae cells to perform
  photosynthesis

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Mitochondria

• Energy center for the cell.
• Converts glucose (sugar) to ATP, which is the
  cells energy source.

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Cytoskeleton

• Maintain cell shape and allow the cell and its
  organelles to move
• Consists of microtubules and microfilaments

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Centrioles

• Responsible for cell division.
• Helps direct chromosomes
• Usually found near the nucleus.
• During division, they move to opposite poles of
  the cell

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Cilia

• Hair-like projections that help in cell movement
• Can either move the cell itself
• Or it can move something along the surface of the
  cell

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Flagella

• Tail like structure
• Moves in a whip-like motion to propel the cell
• Found on many bacterial cells