Chapter 5 - Biological Membranes Flashcards
What is the role of a membrane?
Partially permeable barriers between the cell and its environment, between organelles and the cytoplasm
Sites of chemical reactions
Site of cell communications (cell signalling)
What is compartmentalisation?
Allows different reactions to kept separate within the same cell
What is the fluid mosaic model?
Phospholipid layer is not a fixed structure and although the bilayer remains in a similar structure (like a mosaic) the phospholipids are able to move (fluid)
What are the structures of a membrane?
Phospholipid bilayer
Cholesterol
Proteins
Glycoproteins
Glycolipids
Channel/carrier proteins
What are intrinsic proteins?
Go through both layers of the membrane
Have hydrophobic r-groups on the external surface that interact with the hydrophobic core of the membrane
What are channel proteins?
Allows passive movement of polar molecules and ions via diffusion in a hydrophilic channel
What are carrier proteins?
Used in both diffusion and active transport
Shape of the protein can change to move molecules across
What are extrinsic proteins?
Present in one side of the bilayer
Hydrophilic R-groups interact with the polar heads of the phospholipids
Can be on either side and move through the bilayer
Can be enzymes
What are glycoproteins?
Protein and carbohydrates
Allows cells to stick to each other
Acts as a receptor for chemical signals (neurotransmitters in a synapse and hormones such as insulin and glucagon)
What are glycolipids?
Lipid and carbohydrate
Cell markers/antigens
Identify the cell to the immune system as self or non-self
What is cholesterol in the membrane?
Lipid with a hydrophobic end and hydrophilic end
Regulates the fluidity of the membrane
Positioned between phospholipids
Adds stability without making them too rigid by preventing the phospholipids getting too close to each other and crystallising
