membranes

Question 1

what are the roles of membranes within cells and at the surface of cells?

Answer 1

-site of chemical reactions
-site of cell communication/ signalling
-partially permeable barrier between cell and environment or organelle and cytoplasm (compartmentalising)

Question 2

what are the different components of the membrane structure?

Answer 2

-phospholipids
-cholesterol
-glycolipids
-glycoproteins
-receptors

Question 3

explain the phospholipid bilayer

Answer 3

-hydrophilic phosphate heads
-hydrophobic tails
-allows lipid soluble substances in and out

Question 4

explain the role of cholesterol in the membrane

Answer 4

-adds mechanical strength and flexibility, helps protect against temp changes
-controls fluidity

Question 5

explain the role of glycolipids in the membrane

Answer 5

-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

Question 6

explain the role of glycoproteins in membranes

Answer 6

-carbohydrates attached to protein

-allow cells to attach to eachother to make tissues
-act as receptors

Question 7

explain the role of proteins in a cell membrane

Answer 7

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

Question 8

what is the role of membrane bound receptors in the membrane

Answer 8

site where hormones and drugs can bind

Question 9

why are membranes described as having a fluid mosaic structure

Answer 9

-phospholipid bilayer
-proteins are randomly scattered throughout the membrane
-phospholipid molecules can move making the membrane flexible