1.4 - Lipids

Question 1

What are lipids?

Answer 1

A diverse group of compounds that are insoluble in water but soluble in organic solvents e.g ethanol

Question 2

Name four important lipids

Answer 2

• Triglycerides a.k.a fats (most common)
• Waxes
• Steroids
• Cholesterol

Question 3

Explain the difference between the C, H & O ratio in carbohydrates & lipids

Answer 3

Lipids have a higher proportion of H & a lower proportion of O than carbohydrates

Question 4

What is the main role of lipids? How does this role compare the carbohydrates?

Answer 4

• Main role of lipids is as an energy source

- Provides more than twice the amount of energy as carbohydrates

Question 5

Where are lipids stored?

Answer 5

In adipose tissue (body fat)

Question 6

Describe the two other roles of lipids (apart from as an energy source)

Answer 6

Heat insulation - adipose tissue (underneath skin of mammals) helps reduce heat loss

Protection - Adipose tissue around delicate organs e.g kidneys acts as cushion against impacts

Question 7

Name the two smaller molecules that make up lipids

Answer 7

Glycerol & fatty acids

Question 8

What is glycerol?

Answer 8

3C alcohol w/ -OH (hydroxyl) group attached to each C

Question 9

What is a fatty acid?

Answer 9

Consists of -COOH (carboxyl) group attached to a long C skeleton

Question 10

What is a saturated fatty acid?

Answer 10

• It has the max. no. of H atoms possible

- No double bonds

Question 11

What is a unsaturated fatty acid?

Answer 11

Have one or more double bonds

Question 12

What does polyunsaturated mean?

Answer 12

Has 2 or more double bonds

Question 13

What does monounsaturated mean?

Answer 13

Has one double bond

Question 14

Describe the structure of a phospholipid

Answer 14

• Has 2 fatty acids & glycerol attached to phosphate group
• Fatty acid tails are hydrophobic
• Phosphate head (w/ glycerol) is hydrophilic

Question 15

Why do fats separate from water?

Answer 15

Water molecules H bond to each other & exclude the fats

Question 16

Describe what happens to phospholipids in water and how this applies in the body

Answer 16

• They self-assemble into double-layered structures called bilayers
• Hydrophobic tails point toward the interior
• The bilayer arrangement made is found in cell membranes
  (Existence of cells depends on phospholipids)

Question 17

What are the components of the cell membrane?

Answer 17

• Phospholipids
• Proteins
• Transport protein
• Carbohydrates

Question 18

What are triglycerides?

Answer 18

3 fatty acids joined to glycerol (by an ester linkage)

Question 19

What are the roles of triglycerides?

Answer 19

• Main component of blood
• Makes up most of adipose tissue
• Covers internal organs & protects them from physical ‘trauma’ or ‘shock’

Question 20

Triglycerides can be saturated or unsaturated. True or false?

Answer 20

True

Question 21

What is the most abundant steroid in the body?

Answer 21

Cholesterol

Question 22

Describe the general structure of cholesterol

Answer 22

• Methyl (-CH3) groups
• Alkyl chain (-CH2-CH2-)
• Hydroxyl (-OH) groups
• These groups are attached to a steroid nucleus

Question 23

Name the parts that a steroid nucleus consists of

Answer 23

• 3 cyclohexane rings
• 1 cyclopentane ring attached
• No fatty acids

Question 24

What is cholesterol?

Answer 24

• A type of steroid
• Component in animal cell membranes
  (& a precursor from which other steroids are synthesised)

Question 25

From which foods is cholesterol obtained?

Answer 25

Meats, milk & eggs

Question 26

Where is cholesterol made?

Answer 26

Cholesterol is synthesised in the liver

Question 27

What is the importance of cholesterol?

Answer 27

Needed in:

• Cell membranes
• Brain & nerve tissue
• Steroid hormones
• Vitamin D

Question 28

How can a high level of cholesterol be damaging to the body?

Answer 28

High levels of cholesterol in the blood clogs arteries (does so by forming plaques) and may contribute to cardiovascular disease