Lipids - phospholipids

Question 1

what is a phospholipid

Answer 1

modified triglycerides and contains elements phosphorous along with carbon, hydrogen and oxygen

Question 2

where are inorganic phosphate ions found

Answer 2

in the cytoplasm of every cell. the phosphate ions have extra electrons and are negatively charged, making them soluble in water

Question 3

what is the structure of a phospholipid

Answer 3

they have the same structures as triglycerides but one of the fatty acids is replaced by a phosphate group

Question 4

how do phospholipids form

Answer 4

a condensation reaction between an OH group and a phosphoric acid molecule and one of the three -OH groups on the glycerol forms an ester bond

Question 5

how many carbon atoms do the fatty acids in phospholipids have

Answer 5

an even number of carbon atoms (often 16 or 18)

Question 6

what do phospholipids have due to their length

Answer 6

a non polar end or tail and a charged end or head

Question 7

are the fatty acid chains in phospholipids saturated or unsaturated

Answer 7

commonly one of the chains is unsaturated and the other is saturated

Question 8

which part of the phospholipid is polar

Answer 8

the phosphate group/head

Question 9

which part of the phospholipid is nonpolar

Answer 9

the fatty acids/tails

Question 10

why are the tails hydrophobic

Answer 10

they are repelled by water

Question 11

why is the phosphate head hydrophillic

Answer 11

the charged head will interact with water

Question 12

why is the phospholipid molecule amphipathic

Answer 12

it has both hydrophilic and hydrophobic parts

Question 13

which lipids tend to be amphipathic and which do not

Answer 13

membrane lipids tend to be amphipathic whereas those involved in storage are not

Question 14

what properties for amphipathic phospholipids have

Answer 14

they may form a layer on the surface of the water with heads in the water and tails sticking out of the water

Question 15

what do amphipathic phospholipids form

Answer 15

micelles which are tiny balls with the tails tucked away inside and the heads pointing outwards into the water. this is why they are called surfactants/surface active agents

Question 16

what is the phospholipid bilayer

Answer 16

amphipathic phospholipids are excellent at forming membranes around cells and organelles. inside and outside a cell membrane is an aqueous solution
the phospholipids form a bilayer with two rows of phospholipids tails pointing inwards and heads pointing outwards into the solution

Question 17

how many % of membranes in plant and animal cells are made of phospholipids

Answer 17

between 20-80%

Question 18

which membranes tend to contain a greater propertion of proteins

Answer 18

bacterial membranes

Question 19

why are membranes considered to have stability

Answer 19

the individual phospholipids are free to move around in their layer but will not move in any position where their hydrophobic tails are exposed to water. the tails are protected from the water by the hydrophillic heads.

Question 20

what can phospholipids do to aqueous environments

Answer 20

they can separate an aqueous environment in which cells usually exist from the aqueous cytosol within cells

Question 21

why is membrane selectively permeable

Answer 21

it is only possible for small and non polar molecules such as oxygen and carbon dioxide to move through the tails in the bilayer. it lets the membrane control what goes in and out of the cell so it functions properly