2.4.1~ The structure of cell membranes

Question 1

what does the cell surface membrane create

Answer 1

an enclosed space separating the internal cell environment from the external environment

Question 2

what does the cell surface membrane create inside the cell

Answer 2

intracellular membranes form compartments within the cell such as the nucleus, mitochondria and RER

Question 3

how do membranes act as an interface for communication

Answer 3

-they are partially permeable
-substances can cross the membranes by diffusion, osmosis and active transport

Question 4

what is the bilayer in cellular membranes formed from

Answer 4

phospholipids

Question 5

how wide is phospholipd bilayer

Answer 5

roughly 7nm

Question 6

what can the phospholipid bilayer be seen under

Answer 6

an electron microscope at very high magnifications

Question 7

when was the fluid mosaic model first outlined

Answer 7

1972

Question 8

what does fluid mosaic model do

Answer 8

explains how biological molecules are arranged to form cell membranes

Question 9

what can the fluid mosaic model help to explain

Answer 9

-passive and active movement between cells and their surroundings
-cell-to-cell interactions
-cell signaling

Question 10

what 2 distinct regions do phospholipds contain

Answer 10

-a polar head (hydrophillic) which is soluble in water
-a non-polar tale (hydrophobic) which is insoluble in water

Question 11

how is the phospholipd monolayer arranged

Answer 11

a single layer with the hydropillic phosphate heads in the water and hydrophobic tails sticking up away from the water

Question 12

what happens if phospholipds are mixed/shaken with water (micelle)

Answer 12

they from spheres with the hydrophilic phosphate heads facing out towards the water and the hydrophobic fatty acid tails facing towards each other–> this is called a micelle

Question 13

what happens if phospholipds are mixed/shaken with water (sheet)

Answer 13

alternatively, two-layered structures may form in sheets, these are called phospholipd bilayers which is the basic structure if the cell membrane

Question 14

what happens the phospholpid bilayer forms compartments

Answer 14

the bilayer forming the cell surface membrane establishing the boundary of each cell

Question 15

what do internally, membrane-bound compartments provide

Answer 15

internally, membrane bound compartments formed from phospholipd bilayers provide the basic structures of organelles, allowing for specialisation of processes within the cell

Question 16

why is the lysosome a membrane bound organelle

Answer 16

contains hydrolytic enzymes that need to be compartmentalised to prevent breakdown of most cellular components

Question 17

are proteins in the phospholipd bilayer

Answer 17

yes

Question 18

what types of proteins are in phospholipd bilayer

Answer 18

-intrinsic (integral)
-extrinsic (peripheral)

Question 19

how are intrinsic proteins embedded in the membrane

Answer 19

arrangment determined by hydrophilic and hydrophobic regions

Question 20

where are extrinsic proteins found

Answer 20

on the inner or outer surface of the membrane

Question 21

why is the fluid mosaic model described as fluid

Answer 21

-phosophlipds and proteins can move around via diffusion
-the phospholipods mainly move sideways within their own layers
-the may different types of proteins interspersed throughout the bilayer move about within it (although some may be in a fixed position)

Question 22

why is the fluid mosaic model described as mosaic

Answer 22

the scattered pattern produced by the proteins within the phospholipid bilayer look like a mosaic when viewed above