Cell structure

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Cell structure
R. C. Gupta Professor and Head Dept. of
Biochemistry National Institute of Medical
Sciences Jaipur, India
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A typical prokaryotic cell
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A typical eukaryotic cell
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A eukaryotic cell
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Functions of different organelles can be
studied in vitro by
Disrupting the cell
Subjecting it to differential centrifugation
Isolating the organelles
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Differential centrifugation for isolation of cell
organelles
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Plasma (cell) membrane
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Nucleus
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Ribosomes
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Eukaryotic ribosome
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Endoplasmic reticulum
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When the cell is disrupted, the membranes of
endoplasmic reticulum are broken
They are spontaneously resealed to form vesicles
known as microsomes
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Golgi apparatus
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The modified proteins enter the vesicles, and are
secreted
Golgi apparatus is the site of synthesis of
mucopolysaccharides
Golgi apparatus and endoplasmic reti-culum also
form some other subcellular organelles e.g.
lysosomes and peroxisomes
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Mitochondria
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Mitochondrial DNA
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Lysosomes
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The extracellular substrates to be digested,
e.g. components of micro-organisms, enter the
cell by endocytosis
A portion of the plasma membrane invaginates and
surrounds the extracellular material
This membrane fuses with the lysosomal membrane,
and the lysosomal hydrolases digest the foreign
material
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Peroxisomes
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Cytoskeleton
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Cytosol
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Transport across membranes
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An example of P-type ATPase
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Ligand-gated channel
Ligand ?
Channel ?
The ligand is like a key that opens the gate
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Voltage-gated channel
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Methods of bulk transport
Required for large molecules and particles
Include endocytosis and exocytosis
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Endocytosis
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Endocytosis
Endocytosis
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Phagocytosis
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Pinocytosis

• Literally means drinking by the cell
• Molecules, including water, are taken up from
  extracellular fluid
• Vesicles formed are small
• Vesicles need not fuse with lysosomes

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Receptor-mediated endocytosis
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Exocytosis
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Thank you