Lipids 1: Triglycerides

Question 1

What is a lipid?

Answer 1

• Group of soluble substances in alcohol rather than water
• Include triglycerides, phospholipids, glycolipids and cholesterol

Question 2

What is a macromolecule?

Answer 2

Very large, organic molecule

Question 3

What is a phospholipid?

Answer 3

Molecule consisting of glycerol, two fatty acids and one phosphate group

Question 4

What do lipids contain?

Answer 4

Lots of carbon and hydrogen, and smaller amounts of oxygen

Question 5

Why are lipids insoluble in water?

Answer 5

Not polar

Question 6

What are the three most important lipids in living things?

Answer 6

• Triglycerides
• Phospholipids
• Steroids

Question 7

What are the three most important lipids examples of?

Answer 7

Macromolecules, as they aren’t polymers but have different components bonded together

Question 8

How are triglycerides structured?

Answer 8

Made of glycerol and fatty acids (many different types)

Question 9

What are essential fatty acids?

Answer 9

Fatty acids that we must ingest to get into our bodies, not made in our bodies

Question 10

How is glycerol structured and what is it?

Answer 10

• Has 3 carbon atoms
• An alcohol (free –OH groups)

Question 11

How are fatty acids structured?

Answer 11

Have carboxylic group on one end, attached to hydrocarbon tail

Question 12

How long can a fatty acid hydrocarbon tail be?

Answer 12

2-20 carbons long

Question 13

How are fatty acids acidic?

Answer 13

Carboxylic group ionises into H⁺ and –COO⁻ group

Question 14

What does it mean if a fatty acid is saturated?

Answer 14

Has no C=C bonds in molecule

Question 15

What does it mean if a fatty acid is unsaturated?

Answer 15

Has C=C bond, meaning fewer hydrogen atoms can bond to molecule

Question 16

What does mono- and polyunsaturated mean?

Answer 16

• Monounsaturated is a single C=C bond
• Polyunsaturated is more than one C=C bond

Question 17

What are the effects of more C=C bonds in a fatty acid hydrocarbon chain?

Answer 17

• Has kinks, pushing it apart slightly
• Makes it more fluid
• Lowers melting point (normally 20°C with less unsaturated)

Question 18

What is an ester bond?

Answer 18

Condensation reaction between carboxilic fatty acid group and hydroxyl-glycerol group

Question 19

What are waxes?

Answer 19

Type of lipid formed by combining fatty acids with alcohol molecules much larger than glycerol

Question 20

How are triglycerides an energy source?

Answer 20

• Can be broken down in respiration to release energy, generating ATP
• Starts by hydrolysing ester bonds, then both glycerol and fatty acids can be broken down completely to carbon dioxide and water

Question 21

How are triglycerides an energy store?

Answer 21

• As they’re insoluble in water, can be stored without affecting water potential of cell
• Mammals store fat in adipose cells under skin

Question 22

How much energy does one gram of fat release?

Answer 22

Twice as much as one gram of glucose

Question 23

Why does fat release twice as much energy as glucose?

Answer 23

Lipids have higher hydrogen atom proportions than carbohydrates, and almost no oxygen atoms

Question 24

How are triglycerides good for insulation?

Answer 24

• Adipose tissue is storage location for lipids, acting as heat insulator
• Lipid in nerve cells acts as electrical insulator
• Animals preparing for hibernation store extra fat

Question 25

How are triglycerides good for buoyancy?

Answer 25

Fat is less dense than water

Question 26

How are triglycerides good for protection?

Answer 26

Act as shock absorber