Eukaryotic cell components

Here are basic cell components of eukaryotes:

 

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All cells have: (also found in Prokaryotes)

  • Cell Wall (not found in animal cell)
    • This is rigid strong outer layer that protects cell from osmosis (bursting) and supports the cell by maintaining the shape.
    • In prokaryotes, it is often made out of peptidoglycan
    • In eukaryotes, (fungi, plants) it is often made out of cellulose
  • Cytoplasmic membrane/plasma membrane/cell membrane
    • This is a barrier that separates the inside of the cell from the outside of the cell.
    • Function is to control what nutrients can enter/exit the cell. This can serve to protect cell from harmful substances like antibiotics.
  • Cytoplasm
    • This is aqueous mixture containing macromolecules, ions, proteins, ribosomes etc. that fills the dead space inside the cell.
    • Molecules found in cytoplasm are essential for efficient metabolism.
  • Ribosomes (free forms in cytoplasm)

    • These are found within cytoplasm, and is the site of protein synthesis.
  • Flagellum (exception, found in protozoan)
    • This is long microtubule structure that allows cell to move.
    • Also note that sperm tail is called flagellum, but this is not typical cell structure.

 

Components only specific to eukaryotes (Lodish et al, 2000)

  • Nucleus (Nuclear membrane)
    • This is the largest organelle in eukaryotic cells.
    • Contains DNA, and site of mRNA synthesis
    • Two nuclear membrane both made out of phospholipid bilayer. Inner membrane and outer membrane that is connected to RER.
    • The dense DNA region = nucleoplasm
    • Fibrous proteins = lamins are the ones giving nucleus its shape and allow DNA to be bound.
  • Nucleolus
    • This is suborganelle of the nucleus, found inside nucleus
    • Site of synthesis for rRNA and ribosomal subunit
  • Mitochondria
    • Can occupy up to 25% of cytoplasmic space
    • Small organelle which is a site of electron transport chain to produce ATP during aerobic metabolism.
    • Contains intermembrane space between outer membrane and inner membrane. This structure is very similar to gram negative bacteria (endosymbiosis theory)
    • To increase surface area for efficient ATP production, inner membrane is folded, also known as cristae.
    • TCA cycle occurs inside the mitochondria at the matrix
    • Contains own DNA
  • Chloroplast
    • Similar to mitochondria, have two membranes: inner membrane and outer membrane.
    • Inside of chloroplast is filled with thylakoid sacs (disk-like), often held in matrix (stroma) in grana stacks.
    • The green pigments chlorophylls in thylakoid membranes, other pigments and enzymes are used for ATP synthesis during photosynthesis by absorbing light.
    • Contains own DNA
  • Rough Endoplasmic reticulum (RER)
    • This is a closed, interconnected membrane vesicles.
    • This is Rough because of ribosomes bound to endoplasmic reticulum.
    • Site of synthesis for membrane, organelle proteins an proteins to be exported (secreted)
  • Smooth Endoplasmic reticulum (SER)
    • No ribosome bound, hence smooth
    • Site of fatty acid and phospholipid synthesis (abundant in hepatocytes)
    • In liver, enzymes in SER can modify or detoxify hydrophobic chemicals (carcinogens, pesticides) by making them more water-soluble and into something that is familiar in our body
  • Golgi complex/golgi apparatus
    • Processes protein synthesized in RER
    • Have 3 parts of region of flattened sac: cis, medial and trans
    • Transfer vesicle from RER first bind to cis region, fuse. Then proteins move to medial and to the trans region.
    • In these regions, protein is modified according to their needs. If secretory or membrane protein.
    • Then modified protein are transported out in vesicle from trans region. Some are fused with plasma membrane or secreted out of the cell.
  • Vacuoles (only in plant)
    • Site of storage for ions and nutrients
  • Granules (only in plant)
    • Site of extra starch storage

 

Reference

Cell Functions. Cell Functions. (http://www.biologyjunction.com/cell_functions.htm) (accessed Feb. 2, 2017).

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