2.5.1 the structure of cell membranes

Question 1

fluid mosaic model

Answer 1

theory of cell membrane structure with proteins embedded in sea of phospholipids

Question 2

glycolipid

Answer 2

lipid/phospholipid with chain of carbohydrate molecules attached to

Question 3

glycoprotein

Answer 3

protein with chain of carbohydrate molecules attached to

Question 4

plasma membrane

Answer 4

cell surface membrane

Question 5

role of membranes at surface of cells

Answer 5

• separates cell components from external environment
• regulate transport of materials into/out of cell
• may contain enzymes used in specific metabolic pathways
• has antigens (recognised by immune system)
• release chemicals to signal to other cells
• site for cell signalling (communication) as contain receptors
• site of chemical reactions

Question 6

history of fluid mosaic model

Answer 6

1972 - singer & nicolson

Question 7

what did fluid mosaic model propose

Answer 7

• fabric of membrane consisted of phospholipid bilayer (double layer) with proteins floating in it
• lipid molecules can change places & some proteins may move = fluidity

Question 8

describe the lipid bilayer

Answer 8

• 2 layers of phospholipid molecules
• hydrophilic heads in contact with watery exterior/interior (cytoplasm)
• hydrophobic tail regions in centre of membrane (away from water)

Question 9

role of cholesterol in phospholipid bilayer (eukaryotic cells)

Answer 9

• helps regulate fluidity of membrane
• maintains mechanical stability
• resist effects of temperature changes on structure

Question 10

describe the different types of proteins in a phospholipid bilayer

Answer 10

1. some have pores & act as channels to allow ions (with electrical charge & surrounded by water molecules) to pass through
2. some are carrier & change shape to carry specific molecules across
3. other proteins attached to carrie proteins & act as enzymes, antigens or receptor sites for complementary shaped signalling chemicals

Question 11

integral proteins

Answer 11

= channel & carrier proteins

• span whole membrane
• membrane-spanning regions interact with hydrophobic region of phospholipid bilayer

Question 12

glycocalyx (carbohydrate molecules)

Answer 12

• on outside of membrane
• formed by carbohydrate chains attached to lipids (glycolipids) or proteins (glycoproteins)
• very hydrophilic
• attract water with dissolved solutes
• helps cell interact with watery environment & obtain dissolved substances