save my exams lipids

Question 1

what are lipids

Answer 1

Macromolecules which contain carbon, hydrogen and oxygen atoms
contain lower o2 than carbs
Non-polar and hydrophobic
insoluble in water

Question 2

two types of lipids

Answer 2

1)phospholipids
2)triglycerides

Question 3

non polar

Answer 3

when electrons are shared equally so aren’t charged

Question 4

triglycerides

Answer 4

non-polar, hydrophobic molecules
glycerol and fatty acids
contain a methyl group at one end of a hydrocarbon chain known as the R group
other is a carboxyl group
RCOOH

Question 5

how do fatty acids vary

Answer 5

Length of the hydrocarbon chain (R group)

(R group) may be saturated
or unsaturated

Question 6

polyunsaturated

Answer 6

more than one double carbon

Question 7

how triglycerides are formed

Answer 7

-formed by esterfication
-An H from glycerol combines with an OH from the fatty acid to make water
-The formation of an ester bond is a condensation reaction
-For each ester bond formed a water molecule is released
-Three fatty acids join to one glycerol molecule to form a triglyceride
-Therefore for one triglyceride to form, three water molecules are released

Question 8

why triglycerides are energy reserves

Answer 8

they store more energy per gram due to their hydrocarbon chains

Question 9

triglyceride functions

Answer 9

Energy storage
Insulation
Buoyancy
Protection

Question 10

Energy storage

Answer 10

-when triglycerides are oxidised during cellular respiration this causes these bonds to break releasing energy used to produce ATP
- therefore store more energy per gram than carbohydrates and proteins

Question 11

hydrophobic

Answer 11

-do not cause osmotic water uptake in cells so more can be stored

Question 12

The oxidation of the carbon-hydrogen bonds

Answer 12

-releases large numbers of water molecules (metabolic water) during cellular respiration
-Desert animals retain this water if there is no liquid water to drink
Bird and reptile embryos in their shells also use this water

Question 13

Insulation

Answer 13

myelin sheath
provides insulation which increases the speed of transmission of nerve impulses

Question 14

Buoyancy

Answer 14

low density of fat tissue increases the ability of animals to float more easily

Question 15

Protection

Answer 15

tissue in mammals contains stored triglycerides and this tissue helps protect organs from the risk of damage

Question 16

structure of phospholipids

Answer 16

-two fatty acids bonded to a glycerol molecule in a phospholipid as one has been replaced by a phosphate ion
-phosphate is polar it is soluble in water
-fatty acid ‘tails’ are non-polar and therefore insoluble in water

Question 17

presence of hydrophobic fatty acid tails

Answer 17

-hydrophobic core is created when a phospholipid bilayer forms
This acts as a barrier to water-soluble molecules
-

Question 18

hydrophilic phosphate heads

Answer 18

-forms h bonds
-This enables the cells to organise specific roles into organelles helping with efficiency

Question 19

saturated fatty acids

Answer 19

-each carbon atom in the hydrocarbon tail (except for the final carbon atom) is bonded to two hydrogen atoms
-carbon atoms in the hydrocarbon tail are all single bonds

Question 20

unsaturated fatty acids

Answer 20

at least one carbon-carbon double bond
cause the hydrocarbon tail of unsaturated fatty acids to kink
not as straight as saturated fatty acids
does not contain the maximum number of hydrogen atoms possible
each carbon atom in a carbon-carbon double bond can only bond to one hydrogen atom

Question 21

properties of triglycerides

Answer 21

energy storage molecules
insoluble

Question 22

peroperties of phospholipids

Answer 22

phosphate group is hydrophilic
centre of the phospholipid bilayer is hydrophobic

Question 23

energy storage

Answer 23

hydrocarbon tails of the fatty acids in triglycerides contain large amounts of chemical energy, which can be released when the fatty acids are broken down

Question 24

insoluble

Answer 24

they don’t affect the water potential inside the cell

Question 25

phosphate group is hydrophilic

Answer 25

makes phospholipids suitable for making up the bilayer of cell membranes, with the fatty acids facing inwards and the phosphate groups facing outwards

Question 26

centre of the phospholipid bilayer is hydrophobic

Answer 26

meaning water-soluble substances cannot easily pass through
This allows the cell membrane to act as a barrier, controlling what substances enter and leave the cell