Cell Organelles

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Cell Membrane

STRUCTURE

  • Cell surface membrane is made of two layers of phospholipids
  • It is embedded with proteins, such as recptors on the outer surface

FUNCTION

  • Separates the contents of the cell from its external environment
  • Regulates the movement of substances in to and out of the cell
  • Most organelles inside the cell are surrounded by their own membrane which enable separate compartments to be formed where specialist reactions take place
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Nucleus

STRUCTURE

  • The nucleus is a large, round organelle
  • It is surrounded by a double membrane called the nuclear envelope
  • The nuclear envelope contains nuclear pores to allow exchange of materials between nucleus and cytoplasm
  • DNA is found in the nucleus
  • It contains a dark staining region called nucleolus which produces ribosomes

FUNCTION

  • Contains the cells DNA
  • Controls activities of the cell
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Mitrochondrion

STRUCTURE

  • They are an oval shape
  • They have a double membrane
  • Inner membrane is highly folded in to cristae - increase surface ares
  • Matrix is a viscous liquid that contains enzymes

FUNCTION

  • Some reactions of aerobic respiration occur
  • They are the "power houses" of the cell - producing energy in the form of ATP
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Ribosomes

STRUCTURE

  • Consist of two subunits; one large and one small
  • Subunits made up of protein and ribosomal RNA
  • Can be found floating free or attached to endoplasmic reticulum

FUNCTION

  • The site of protein synthesis
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Endoplasmic Reticulum (ER)

STRUCTURE

  • Large network of membranes
  • There are two types
    • Rough endoplasmic reticulum (RER) - covered with ribosomes
    • Smooth endoplasmic reticulum (SER) - does not have ribosomes

FUNCTION

  • Rough endoplasmic reticulum - transports the proteins synthesised at the ribosomes
  • Smooth enodplasmic reticulum - produces and transports lipids
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Golgi Apparatus (also known as Golgi body)

STRUCTURE

  • Stack of flattened, membrane bound sacks
  • Smaller vesicles around it

FUNCTION

  • Transports and chemically modifes the substances in it
  • Produces lysosomes
  • Cells involved with secretion contain large amounts of Golgi apparatus e.g. cells of the pancreas which secrete digestive enzymes
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Lysosome

STRUCTURE

  • Sac consisting of a single membrane which contains digestive membranes
  • Enzymes have to be kept apart from rest of cell or they would destroy it
  • Contents are acidic and enzymes have a low optimum pH

FUNCTION

  • Breaks down unwanted molecules and structures inside the cell
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