Lipids

Question 1

What are the molecules that make up lipids and what does it lead to them being called?

Answer 1

1 glycerol
3 fatty acid
Known as triglycerides

Question 2

Where do fatty acids join to glycerol?

Answer 2

OH groupsu

Question 3

What is the general formula of glycerol?

Answer 3

C3H8O3

Question 4

What elements do lipids contain?

Answer 4

Carbon
Hydrogen
Oxygen

Question 5

What do fatty acids consist of?

Answer 5

• A carboxyl group COOH.
• a variable length hydrocarbon chain (CH2)n. There is always an even number of hydrogens between 14 and 22.
• a methyl group (CH3)

Question 6

What is the general fatty acid formula?

Answer 6

CH3(CH2)nCOOH

Question 7

Where can saturated fats generally be found?

Answer 7

In animals

Question 8

Where can unsaturated generally be found?

Answer 8

Oils in plants

Question 9

How is a saturated fat’s hydrocarbon chain structured?

Answer 9

Single bonds between carbons with all other bonds having hydrogen so it is ‘saturated’ with hydrogen.

Question 10

What state is a saturated fat at room temperature and why?

Answer 10

Solid due to high melting point

Question 11

What effect does high sat fat intake have?

Answer 11

Artheroma (fat) patches developing withing artery lining which can reduce/block blood flow or be taken in blood stream. Contributory factor in heart disease, strokes, etc

Question 12

How are unsaturated fatty acids’ hydrocarbon chains different from sat?

Answer 12

One or more double bond.

Question 13

What is the difference between mono and polyunsatured?

Answer 13

1 carbon-carbon double bond in mono.

2 or more in poly

Question 14

What effect do the double bonds have?

Answer 14

Gives molecules a kink and they tend not to pack together well, giving a more open and therefore oily nature

Question 15

What is unsaturated’s state at room temp?

Answer 15

Liquid

Question 16

What are the bonds between glycerol and the fatty acids in a triglyceride called and how are they formed?

Answer 16

Three ester bonds formed by condensation reactions (releasing 3 water molecules).

Question 17

What are the 2 key properties of Triglycerides?

Answer 17

Non-polar so don’t attract water (called hydrophobic molecules).

Insoluble in water (but soluble in some solvents e.g. Acetone and ethanol

Question 18

What is the structural difference of a phospholipid?

Answer 18

One fatty acid is replaced by a phosphate group (PO4)3-

on the opposite site of the glycerol.

Question 19

What is the effect of the phosphate group being ionised?

Answer 19

It is polar so it attracts water molecules, making the phosphate part of the phospholipid hydrophilic whereas the fatty acid tails are hydrophobic (repel water)

Question 20

What is the phospholipids’ structure important in?

Answer 20

Formation of cell membranes

Question 21

What is the test for Lipids/triglycerides?

Answer 21

Emulsion Test:-

• mix the ‘lipid’ with ethanol
• pour/decant mixture into water
• white emulsion shows that lipid is present. Stays clear= negative result

Question 22

Use of lipids as an energy store:-

Answer 22

Store twice as much as same mass of carbohydrates- very efficient. However, can’t be broken down as quickly to be used in respiration so are only used for medium/long term storage.

Question 23

What the 5 uses of lipids beyond as an energy store?

Answer 23

• thermal insulation
• protect vital organs like kidneys against physical damage
• provide buoyancy in aquatic animals
• provide water-proofing layers. e.g. waxy cuticles on leaves.
• provide metabolic water source from respiration in organisms in dry environments. E.g. Camels