Lipids

Question 1

What makes up a lipid?

Answer 1

A high number of carbon and hydrogen atoms and a low number of oxygen atoms

Question 2

What common features do lipids have?

Answer 2

• Insoluble in water
• soluble in alcohol
• not polymers, they are macromolecules as no repeating units

Question 3

What is the structure of a triglyceride?

Answer 3

3 hydrocarbon chains derived from fatty acids that are ester bonded to one molecule of glycerol

Question 4

What is an unsaturated fatty acid? How is it arranged?

Answer 4

• has one or more carbon carbon double bonds
• causes kinks in the chains so they cant pack tightly together
• this means more unsaturated fatty acids cause weak IMF / Van der Waals

Question 5

What is a saturated fatty acid? How is it arranged?

Answer 5

• has no carbon carbon double bonds
• so chains pack tightly
• so strong IMF/ Van der Waals

Question 6

What makes up the ester bond?

Answer 6

the carbon of the glycerol bonded to an oxygen bonded to a carbon, double bonded to an oxygen

Question 7

What is the function of a triglyceride?

Answer 7

• Great energy source due to high ratio of c-h bonds
• great energy store as its insoluble, doesn’t affect water potential
• provides heat and electrical insulation
• waterproofing
• protects organs

Question 8

What is the structure of a phospholipid?

Answer 8

2 hydrocarbon chains derived from fatty acids that are ester bonded to one molecule of glycerol which is ester bonded to a phosphate group

Question 9

What properties does a phospholipid have?

Answer 9

• it is amphipathic which means it has a hydrophobic tail and a hydrophilic head
• this causes it to form phospholipid bilayers and micelles in water
• it can form a fluid mosaic
• bacteria have more proteins in the membrane
• it is selectively permeable, only small non polar molecules can pass through it

Question 10

What is cholesterol? Why is important?

Answer 10

• A steroid and a lipid
• contains no fatty acid or glycerol
• made of 4 isoprene units
• small and hydrophobic
• can sit in the hydrophobic layer of the phospholipid bilayer
• regulates fluidity
• made in the liver
• can make testosterone, oestrogen and vitamin D which can also pass through PBL

Question 11

what is the test for lipids?

Answer 11

• shake sample with alcohol
• combine with water
• if it turns cloudy white then its positive

Question 12

Why does the emulsion test produce a cloudy white substance?

Answer 12

• lipids are insoluble in water and soluble in ethanol
• After lipids have been dissolved in ethanol and then added to H2O, they will form tiny dispersed droplets in the water. This is called an emulsion.
• These droplets scatter light as it passes through the water so it appears white and cloudy.