Lipids

Question 1

What are the different types of lipids?

Answer 1

• Triglycerides
• Phosphlipids
• Cholesterol
• Steroid hormones
• Lipid-based hormones e.g. vitamiin A, E, D, K

Question 2

What are the 3 catergories of lipids?

Answer 2

• Triglycerides
• Phospholipids
• Steroids

Question 3

What is a surfactant and what do they do?

Answer 3

• It is short for surface active agents
• A substance that, when added to liquid, reduces its surface tension increasing its spreading and wetting properties
• An example of this is a detergent

Question 4

What are the functions of triglycerides in living organisms?

Answer 4

• Source of energy => can be used in respiration to provide twice as much energy per gram than carbohydrates or proteins
• Energy storage => for the equivalent amount of energy, lipids have half the mass of carbohydrates and proteins which facilitates movment in animals and seed dispersal in plants. lipids are hydrophobic so not affect water potential meaning large amounts can be stored
• Buoyancy => lipids are less dense than water and aquatic animals have large amounts of subcutaneous fat
• Thermal insulation => bad conductor of heat. lipids also provide electrical insulation in the form of the myelin sheath around axons of nerve cells
• Protection => vital organs have fat pudding which cushions and absorbs impact
• Reduces water loss

Question 5

What are triglycerides formed of?

Answer 5

It formed from glycerol and 3 fatty acids through 3 condensation reactions

Question 6

Draw glycerol

Answer 6

Answer on revision card

Question 7

Draw a fatty acid

Answer 7

Answer on revision card

Question 8

What is a saturated fatty acid?

Answer 8

• Every carbon in the hydrocarbon chain hs the maximum number of hydrogens
• All C-C bonds are single bonds
• They are solid at room temperature

Question 9

What is the general formula of saturated fatty acids?

Answer 9

C_{nH2n+1 COOH}

Question 10

What is the general formular for unsaturated fatty acids?

Answer 10

C_nH2n-1COOH

Question 11

What is an unsaturated fatty acid?

Answer 11

• They are C=C double bonds so fewer hydrogens in the hydrocarbon chain
• They are liquid at room temperature as the double bonds cause them to kink, prevemtomg them from packing closely together

Question 12

What is a polunsaturated fatty acid?

Answer 12

It is an unsaturated acid with more than one C=C double bond

Question 13

What is a phospholipid formed of?

Answer 13

• 2 fatty acids, 1 glycerol and a phosphate group
• They have a hydrophilic head and a hydrophobic tail

Question 14

Draw a phospholipid

Answer 14

Answer on revision card

Question 15

Draw a triglyceride

Answer 15

Answer on revision card

Question 16

Where is cholesterol primarily manafactured?

Answer 16

In the liver and intestines

Question 17

What molecules are manafactured using cholesterol?

Answer 17

• Steroid hormones (fat soluble) => lipid soluble hormones e.g. testosterone, cortisol, progesterone etc
• Fat soluble vitamins and vitamin D
• Bile

Question 18

Draw cholesterol

Answer 18

Answer on revision card

Question 19

What is cholesterol’s contribution to the plasma membrane?

Answer 19

• Cholesterole is found in the phospholipid bilayer of the membrane
• It is positioned between the phospholipids with the hydroxyl group at the periphery (phosphate head) and the hydrophobic side bound to the fatty acid tails
• This adds stability to cell membranes and regulates the fluidity by keeping membranes fluid (hinders solidification) at low temperatures by disrupting the regular packaging of phospholipids
• It stops them from becoming too fluid at high temperatures

Question 20

How do you test for lipids?

Answer 20

• Add ethanol to the sample and mix well
• Mix the resulting solution with water and shake gently
• If a white emulsion forms, this indicates the prescence of a lipid