Molecules (lipids)- topic 1

Question 1

what are the elements that lipids contain?

Answer 1

-carbon
-hydrogen
-oxygen

Question 2

what makes lipids and carbohydrates different if they consist of the same elements?

Answer 2

-the proportion of hydrogen relative to oxygen is much greater than carbohydrates where the ratio is 2:1

Question 3

are lipids polymers?

Answer 3

-they do form large molecules known as macromolecules however they are not polymers

Question 4

what substances are lipids soluble in?

Answer 4

-they are not soluble in water (hydrophobic) but are soluble in organic solvents such as ethanol

Question 5

what are the 4 types of lipids?

Answer 5

-triglycerides
-phospholipids
-waxes
-steroids

Question 6

how are triglycerides formed?

Answer 6

-through a combination of glycerol and fatty acids
-each triglyceride contains one glycerol molecule which is joined with three fatty acid molecules

Question 7

what are fatty acids and how are they formed ?

Answer 7

-organic acids that form long hydrocarbon tails linked to a carboxyl group at one end of the chain
-different fatty acids have different lengths of hydrocarbons

Question 8

what is a carboxyl group?

Answer 8

-a group linked to the end of a fatty acid molecule
-COOH

Question 9

how can different triglycerides be formed and why is this?

Answer 9

-there are over 70 types of fatty acids which can be the same or a range of different types in one triglyceride

Question 10

in triglycerides where does the condensation reaction occur ?

Answer 10

-it occurs between the OH hydroxyl group of the glycerol and the COOH carboxyl group of each fatty acid

Question 11

following a condensation reaction what is the bond called between the fatty acids and the glycerol?

Answer 11

-an ester bond holds the two in place

Question 12

how does the hydrolysis of a triglyceride occur? when does this occur ?

Answer 12

-it uses three molecules of water and produces three fatty acids and one molecule of glycerol
-happens during lipid digestion

Question 13

what are saturated fatty acids and why are they called this?

Answer 13

-they contain the maximum amount of hydrogen molecules along the length of hydrocarbon chain i.e. each carbon atom is linked with two hydrogen atoms
-all the carbons are saturated

Question 14

how are the carbon atoms linked in saturated fatty acids?

Answer 14

-by single carbon to carbon bonds

Question 15

how are the carbon atoms linked in unsaturated fatty acids?

Answer 15

-they have at least one carbon to carbon double bond (monounsaturated fatty acids) or contain more that one double bond (polyunsaturated fatty acids)

Question 16

are fats and oils triglycerides?

Answer 16

-yes and they are both chemically very similar

Question 17

how does the condition of fats and oils differ at room temperature ? how else do fats and oils differ?

Answer 17

-fats are usually solid at room temp whereas oils are liquid
-fats are animal sources and oils are made from plant sources
-fats are formed form saturated fatty acids whereas oils are formed from unsaturated hydrocarbon chains

Question 18

what are triglycerides used for?

Answer 18

-they are an excellent energy store as they release more energy per unit mass than carbohydrate
-fats are used for insulation and are stored in a layer just below the skin
-fat also protects organs of the body

Question 19

how do phospholipids differ from triglycerides?

Answer 19

-they are similar however one of the fatty acid molecules is replaced by a phosphate group

Question 20

what is the effect of fatty acids in a phospholipid molecule?

Answer 20

-they repel water by forming hydrophobic tails

Question 21

what is the effect of a phosphate group attached to the glycerol in a phospholipid molecule?

Answer 21

-it attracts water by forming hydrophilic heads
-it makes the phospholipid soluble in water

Question 22

what type of molecule are phospholipids and why is this important?

Answer 22

-they are polar which helps determine their orientation and function in cell membranes