membranes Flashcards
what are the roles of membranes within cells and at the surface of cells?
-site of chemical reactions
-site of cell communication/ signalling
-partially permeable barrier between cell and environment or organelle and cytoplasm (compartmentalising)
what are the different components of the membrane structure?
-phospholipids
-cholesterol
-glycolipids
-glycoproteins
-receptors
explain the phospholipid bilayer
-hydrophilic phosphate heads
-hydrophobic tails
-allows lipid soluble substances in and out
explain the role of cholesterol in the membrane
-adds mechanical strength and flexibility, helps protect against temp changes
-controls fluidity Cholesterol molecules consist of a hydrophilic and hydrophobic region. The hydrophobic regions bind to phospholipid fatty acid tails, causing them to pack more closely together.
explain the role of glycolipids in the membrane
-carbohydrates attached to phospholipid molecules
-acts as a receptor molecule
-cell signalling
-cell recognition, acts as an antigen
-stabilise cell- carbohydrate part can hydrogen bond with water
explain the role of glycoproteins in membranes
-carbohydrates attached to protein
-allow cells to attach to eachother to make tissues
-act as receptors
explain the role of proteins in a cell membrane
intrinsic protein- channel and carrier proteins span the whole bilayer
extrinsic- give mechanical strength and act as cell receptors for e.g hormones
channel proteins- allow ions and polar molecules to travel through membrane
carrier protein- change shape to transport substances across membrane
what is the role of membrane bound receptors in the membrane
site where hormones and drugs can bind
why are membranes described as having a fluid mosaic structure
-phospholipid bilayer
-proteins are randomly scattered throughout the membrane
-phospholipid molecules can move making the membrane flexible
