Protein definition:

A molecule composed of polymers of amino acids joined together by peptide bonds. It can be distinguished from fats and carbohydrates by containing nitrogen. Other components include carbon, hydrogen, oxygen,sulphur, and sometimes phosphorus

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Job:

Transport materials that cannot be diffused (e.g. ions)

Proteins in membranes

Membrane proteins are two types of protein one is called extrinsic protein , is loosely attached to ionic bonds or calcium bridges to the electrically charged phosphoryl surface of the bilayer. They can also attach to the second type of protein , called intrinsic proteins. Which are firmly embedded within the phospholipids bilayer. Almost all intrinsic proteins contain special amino acidsequences , generally about 20- 24 amino acids long, that extend through the internal regions of cell membrane.


  • The integral and peripheral proteins:
Peripheral proteins are under the phospholipid bilayer, while integral proteins are inscribed in the bilayer.
  • Integral proteins pass entirely through the lipid bilayer of the plasma membrane and have domains that go from the outside of the cell to the cytoplasm inside the cell. While peripheral proteins are only on the one side of the lipid bilayer, either the outside of the cell of the cytoplasmic side inside the cell, but not both.
  • Proteins within the membrane are key to the functioning of the overall membrane. These proteins mainly transport chemicals and information across the membrane. Every membrane has a varying degree of protein content. Proteins can be in the form of peripheral or integr

  • Membrane proteins:

  1. Type
Description
2.Integral proteins
Span the membrane and have a hydrophilic cytosolic domain, which interacts with internal molecules.
3.Lipid anchored proteins
Covalently bound to single or multiple lipid molecules; hydrophobically insert into the cell membrane and anchor the protein.
4.Peripheral proteins
Attached to integral membrane proteins, or associated with peripheral regions of the lipid bilayr. These proteins tend to have only temporary interactions with biological membranes, and, once reacted the molecule, dissociates to carry on its work in the cytoplasm.

protein video




Protein Pump


Protein pump is a type of an active transport. It is capable of pumping out compounds that are likely to pose a threat to the cell. It pump out/in solutes or ions from a low concentration region to high concentration region, exploiting the energy from ATP. A good example is AcrB, a bacterial protein complex which repels a wide range of antibiotics through its ability to capture and pump out structurally diverse compounds.









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The image above is a diagram of a MDR protein. It has got its name from the place it was originally discovered roughly a decade ago: in the membranes of cancer cells. MDR is a huge, snake-like protein which pump threads through a membrane like a needle through a piece of cloth, back and forth across the membrane 12 times. To force out the toxic, the pump uses the energy from ATP, made from the cell.















Work Cited