Cell ultrastructure

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The structure and function of the nucleus:

The structure  and function of the nucleus:

  • Found in all eukaryotic cells at some pointContains DNA arranged as chromosomesThe chromosomes are made of coiled DNA held together by protein (Histones)Uncoiled DNA is called Chromatin
    • (example: red blood cells do not contain nucleus)
  • Enclosed by a double membrane-Nuclear envelope
  • The nuclear envelope is perforated by Nuclear pores
  • These pores allow the movement of molecules such as RNA and nucleotides to move between the nucleus and the cytoplasm
  • Contains one or more dark stains- Nucleolous-Site of ribosomal RNA synthesis
  • Functions of nucleus:

    • Controls the activities of the cell and hold the genetic material
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The structure and function of the mitochandria

The structure  and function of the mitochandria

  • They are rod like in shape
  • Surrounded by two layers of membrane
  • The inner membrane is folded into cristae
  • Contains a fluid called the matrix
  • Site of aerobic respiration-process for creating ATP which is the source of energy for the cell
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Structure and function of endoplasmic reticulum

The structure and function of the endoplasmic reticulum

  • Found throught the cytoplasm
  • A network of flattened membrane bound sacs and tubes
  • There are two types:
    • Rough- has ribosomes on the surface and its function is to transport proteins through the cisternae
    • Smooth- no ribososmes on the surface and its function is the site of lipid synthesis
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The structure and function of Ribosomes

The structure and function of the ribosomes:

  • The smallest organelle (about 20nm)
  • Found throughout the cytoplasm and some are associated with the rough endoplasmic reticulum
  • The function is the site of protein synthesis
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The structure and function of the Golgi apparatus

The structure  and function of the Golgi apparatus

  • A stack of flattened sacs surrounded by membrane
  • Small vesicles bud off the edge
  • Functions:
    • Store and chemically modify chemicals formed in the cell
    • They are packaged into vesicles and then secreted out of the cell
    • Also make lysosomes
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The structure and function of the Lysosomes

The structure  and function of the Lysosomes

  • A small sphere of liquid surrounded by a membrane
  • Contain protein digesting enzymes
  • Function:
    • To digest protein 
  • An example is:
    • To digest a cell after its death
    • White blood cells use them to dgest protein
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The structure and function of the Centrioles

The structure  and function of the Centrioles

  • Produces spindle fibres during cell division to allow the separation of chromosomes
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