1.3 membrane structure

Question 1

amphipathic

Answer 1

having both hydrophilic and hydrophobic parts

Question 2

structure of phospholipids

Answer 2

• Consist of a polar head (hydrophilic) composed of a glycerol and a phosphate molecule
• Consist of two non-polar tails (hydrophobic) composed of fatty acid (hydrocarbon) chains

Question 3

phospholipid arrangement in membranes

Answer 3

Phospholipids spontaneously arrange into a bilayer
The hydrophobic tail regions face inwards and are shielded from the surrounding polar fluids, while the two hydrophilic head regions associate with the cytosolic and extracellular fluids respectively

Question 4

2 types of proteins in phospholipid bilayer

Answer 4

integral and peripheral

Question 5

integral proteins

Answer 5

permanently attached to the membrane

Question 6

polytopic

Answer 6

go through the entire membrane (integral)

Question 7

monotopic

Answer 7

attached to only one side of the membrane (integral)

Question 8

peripheral proteins

Answer 8

temporarily attached to the membrane

Question 9

glycoproteins

Answer 9

contains an oligosaccharide (simple sugar chain).
Important in cell-cell recognition and act as hormone/drug receptors

Question 10

functions of membrane proteins

Answer 10

A - attachment to the cytoskeleton and extracellular matrix (ECM)
R - receptors
C - catalysts - enzymatic activity
T - transport
I - intercellular joining
C - cell-cell recognition

Question 11

mnemonic for functions of membrane proteins

Answer 11

ARCTIC

Question 12

cholesterol

Answer 12

• a component of animal cell membranes
• makes the membrane less fluid by restricting movement of phospholipids
• makes the membrane more flexible by preventing hydrophobic tails from packing
• makes the membrane less permeable to hydrophilic substances

Question 13

how does temperature increase affect membrane fluidity?

Answer 13

Cholesterol reduces fluidity as it prevents phospholipids from moving apart. (Holds phospholipids together)

Question 14

how does temperature decrease affect membrane fluidity?

Answer 14

Cholesterol increases fluidity as it prevents phospholipids from packing. (Creates space between phospholipids)

Question 15

The fluid membrane allows the cell to:

Answer 15

move
transport biological molecules across it (endocytosis, )
If the membrane is too fluid, it cannot restrict the movement of substances across it.

Question 16

freeze fracture technique

Answer 16

was used to split open the membrane and revealed irregular rough surfaces within the membrane

These rough surfaces were interpreted as being transmembrane proteins, demonstrating that proteins were not solely localised to the outside of the membrane structure

Question 17

draw a fluid mosaic model

Answer 17

see ipad

Question 18

Cholesterol has a role in making sure which type of protein is anchored to the membrane?

Answer 18

peripheral proteins

Question 19

What techniques allowed scientists to falsify the Davson–Danielli model? (2)

Answer 19

freeze-etched electron micrographs and fluorescent markers