lipids

Question 1

what is a lipid?

Answer 1

a triglyceride; it is made up of one glyercol bonded to three fatty acid chains via ester bonds

Question 2

why are lipids not polymers?

Answer 2

they are made up of chemical units not monomers (no repeated units)

Question 3

what is a monoglyceride?

Answer 3

a glycerol attached to one fatty acid chain via an ester bond

Question 4

what is the structural formula for glycerol?

Answer 4

H
I
H – C – OH
I
H – C – O H
I
H – C – OH
I
H

Question 5

what is the hydroxyl functional group in glycerol?

Answer 5

-OH

Question 6

what are fatty acids made of?

Answer 6

a carboxyl group (-COOH) and a hydrocarbon

Question 7

what is a hydrocarbon?

Answer 7

a compound only made of hydrogen and carbon

Question 8

what does R represent in the fatty acid structural formula?

Answer 8

hydrocarbon

Question 9

what can vary about the R group of fatty acids?

Answer 9

they can be saturated or unsaturated

Question 10

what is teh difference between saturated and unsaturated hydrocarbons?

Answer 10

saturated means single bonds and unsaturated are double bonds

Question 11

what does polyunsaturated mean?

Answer 11

more than one double bond in the chain

Question 12

why can’t triglycerides dissolve in water?

Answer 12

they are non-polar

Question 13

what can lipids be dissolved in?

Answer 13

ethanol

Question 14

write a description of a condensation reaction to form a monoglyceride from a glycerol and fatty fatty acid?

Answer 14

the hydroxyl group of glycerol reacts with the carboxyl group of the fatty acid

water is removed to form an ester bond between the glycerol and fatty acid

a monoglyceride has been produced and one molecule of water

Question 15

what is the test for lipds?

Answer 15

emulsion test

Question 16

how does the emulsion test work?

Answer 16

add ethanol, shake , add water , shake

reagents are ethanol and water

Question 17

what is the positive result in the lipids test?

Answer 17

milky white emulsion

Question 18

what is a phospholipid?

Answer 18

glycerol bonded to two fatty acid chains and a phosphate ion (negative charge)

Question 19

why can phospholipids be dissolved in water?

Answer 19

a phosphate ion has a negatice charge (polar)

Question 20

how are phospholipids structured?

Answer 20

head and two tails

Question 21

what is the head of a phospholipid made up of and what are its properties?

Answer 21

a phosphate ion and glycerol
negative charge

HYDROPHILIC (love water) face outward towards the intracellular and extracellular fluid

Question 22

what are the tails of phospholipids made of and what are the properties?

Answer 22

fatty acid chains
no charge
not water soluble

HYDROPHOBIC (don’t dissolve in water)

Question 23

what are cell membranes and organelle membranes made from?

Answer 23

phospholipid bilayer

Question 24

what is the phospholipid bilayer?

Answer 24

two layers of phospholipids that make up the cell or plasma membrane.

Question 25

what is a significant point about the phospholipid bilayer?

Answer 25

no charge- so charged ions cannot pass through

Question 26

what can/ can't get across a phospholipid bilayer?

Answer 26

small non-polar molecules that are lipid soluble not polar molecules that can dissolve in water

Question 27

what are the roles of lipids?

Answer 27

-cell membranes -source of energy (when oxidised they provide more than twice the energy as the same mass of carbohydrate and release valuable water) -waterproofing (since they are insoluble) -insulation (slow conductors of heat and help retain body heat) -protection

Question 28

why are triglycerides such a good source of energy?

Answer 28

high ratio of energy- storing carbon-hydrogen bonds to carbon atoms

Question 29

why are triglycerides good storage molecules?

Answer 29

have low mass to energy ratio, making them good storage molecules because much energy can be stored in a small volume- beneficial to animals as it reduces the mass they have to carry as they move around

Question 30

what is the benefit of triglycerides being insoluble in water?

Answer 30

being large, non-polar molecules makes them insoluble in water so their storage does not affect osmosis in cells or the water potential of them

Question 31

how are triglycerides an important source of water?

Answer 31

as they have high ratio of hydrogen to oxygen atoms, triglycerides release water when oxidised