2.5 Protiens In Membranes Flashcards
How much of a cell membrane do proteins make up?
45% by mass (can vary from 25% to 75%)
What are intergral proteins?
Proteins that span the whole width of the membrane
What are other names for intergral proteins?
Intrinsic
Transmembrane
What are peripheral proteins?
Proteins confined to the inner or outer membrane surface
What is another name for peripheral proteins?
Extrinsic
What are many intergral proteins?
Carrier molecules of channels
What do intergral carrier molecules or channels help do?
Transport may substances such as ions, sugars and amino acids that cannot diffuse across the membrane but are still vital to a cells functioning
What are other intergral proteins that are not channel or carrier molecules?
Receptors for hormones and neurotransmitters
Or
Enzymes for catalysing reactions
Where are intergral proteins found?
Embedded through both layers of the membrane
How are intrinsic proteins kept in place?
They have amino acids with hydrophobic R groups in their external surfaces which interact with the hydrophobic core of the membrane, keeping them in place
What do channel proteins do?
They provide a hydrophilic channel allowing passive movement of polar molecules and ions down a concentration gradient through membranes
What do carrier proteins play an important role in?
Passive and active transport into cells
Where are peripheral proteins found?
Free on the membrane surface or bound to intergral proteins
What do peripheral proteins on the extra cellular side of the membrane act as?
Receptors for hormones and neurotransmitters or are involved in cell recognition
What are many peripheral proteins on the extra cellular side of the membrane?
Glycoproteins (conjugated)
What are peripheral proteins on the cytosolic side of the membrane involved in?
Cell signalling or chemical reactions
What can peripheral proteins on the cytosolic side of the membrane do?
Dissociate from the membrane and move into the cytoplasm
Give an example of a peripheral protein that is an enzyme:
ATPase in the mitochondria
Where are extrinsic/peripheral proteins present?
In only one side of the bilayer, they are able to move between layers
What do peripheral proteins have on their outer surfaces and what do they do?
Hydrophilic r groups on their outer surfaces that interact with the polar heads of the phospholipids or with intrinsic proteins
What is ATPase and where is it found?
An enzyme involved in the production of ATP it is found in the inner membrane of the mitochondria
What are glycoproteins?
Intrinsic proteins embedded in the cell surface membrane with a carbohydrate chain attached
What are recognition proteins?
Proteins on the extra cellular side of the cell acting as receptors for hormones or neurotransmitters approaching the cell
