Lipids - triglycerides

Question 1

what are lipids

Answer 1

commonly known as fats and oils. these contain the elements hydrogen, oxygen and carbon

Question 2

what is the difference between fats and oils

Answer 2

lipids that are solid at room temperature are fats
lipids that are liquid at room temperature are liquids

Question 3

are lipids soluble or insoluble in water

Answer 3

insoluble

Question 4

why are lipids insoluble

Answer 4

they are non polar molecules as the electrons in the outer orbitals that form the bonds are more evenly distributed than in polar molecules. this means there are no positive or negative areas within the molecules so do not attract water molecules

Question 5

what substance does lipid dissolve in

Answer 5

alcohol

Question 6

are lipids polymers

Answer 6

no. they are large, complex molecules called macromolecules

Question 7

why don’t lipids form polymers

Answer 7

lipids aren’t built from repeating units or monomers

Question 8

what is a triglyceride

Answer 8

made by combining one glycerol molecule with three fatty acids.

Question 9

what group of chemicals does glycerol belong to

Answer 9

alcohols.

Question 10

what group of acids do fatty acids belong to

Answer 10

carboxylic acids

Question 11

what do fatty acids consist of

Answer 11

a carboxyl group (COOH) with a hydrocarbon chain attached.

Question 12

describe glycerol

Answer 12

has 3 carbon atoms. it is an alcohol so has free -OH groups. it has 3 -OH groups which are important to the structure of triglycerides

Question 13

describe a fatty acid

Answer 13

have a carboxyl on one end, attached to a hydrocarbon tail, made of only carbon and hydrogen atoms.

Question 14

how many carbons can fatty acids have

Answer 14

anything from 2 to 20 carbons long

Question 15

why is the fatty acid an acid

Answer 15

the carboxyl group ionises into H+ and -COO group. this structure is therefore an acid because it produces free H+ ions

Question 16

what are saturated fatty acids

Answer 16

fatty acid chains that have no double bonds present between the carbon atoms. they are saturated because all the carbon atoms form the maximum number of bonds with hydrogen atoms

Question 17

what are unsaturated fatty acids

Answer 17

a fatty acid with double bonds between some of the carbon atoms

Question 18

if there is one double bond present it means..

Answer 18

it is a monounsaturated fatty acid

Question 19

if there is two or more double bonds it means..

Answer 19

it is a polyunsaturated fatty acid

Question 20

what does the presence of the double bond in the fatty acid do

Answer 20

causes the molecule to kink or bend and they therefore cannot pack closely together. this makes them liquid at room temperature

Question 21

why are plants more healthier

Answer 21

they contain unsaturated triglycerides which normally occur as oils and tend to be more healthy than the triglycerides in fats (solids).

Question 22

what can excess saturated fats cause

Answer 22

coronary heart disease. an excess of any type of fat can lead to obesity

Question 23

what does a triglyceride consist of

Answer 23

one glycerol molecule bonded to three fatty acids

Question 24

what do both fatty acids and glycerol molecules have

Answer 24

hydroxyl groups

Question 25

how do triglycerides form

Answer 25

both fatty acids and a glycerol molecule have hydroxyl group. when these groups react it leads to the formation of three water molecules and bonds between the fatty acids and glycerol molecules

Question 26

what bond form when glycerol and fatty acids react

Answer 26

ester bonds

Question 27

what type of bond is an ester bond

Answer 27

covalent

Question 28

what type of reaction occurs when a triglyceride is formed

Answer 28

esterification/condensation

Question 29

what needs to be supplied to break down triglycerides

Answer 29

three water molecules

Question 30

what type of reaction occurs when triglycerides are broken down

Answer 30

hydrolysis

Question 31

what are the functions of triglycerides

Answer 31

• energy source
• energy store
• insulation
• buoyancy
• protection
• steroid hormones
• cell structure

Question 32

how are triglycerides used as a source of energy

Answer 32

triglycerides can be broken in respiration to release energy and generate ATP. the ester bonds are hydrolysed and then the glycerol and fatty acids can be broken down completely to carbon dioxide and water. respiration of a lipid produces more water than respiration of sugar

Question 33

how are triglycerides used as an energy store

Answer 33

insoluble in water so can be stored without affecting the water potential of cells. one g of fat releases twice as much energy as 1g of glucose. this is because lipids have a higher proportion of hydrogen atoms than carbohydrates and almost no oxygen atoms.

Question 34

how are triglycerides used as a form of insulation

Answer 34

adipose tissue is a storage location for lipids in whales acting as a heat insulator. lipids in nerve cells act as electrical insulators

Question 35

how are triglycerides used to provide buoyancy

Answer 35

fat is less dense than water so is used by aquatic animals to help them stay afloat

Question 36

how do triglycerides provide protection

Answer 36

humans have fat around delicate organs as the kidneys