H2 biology: lipids

Question 1

What is a key characteristic of lipids?

Answer 1

Lipids are insoluble in water and highly soluble in non-polar solvents.

Question 2

What is the molecular formula of glycerol?

Answer 2

C3H8O3

Question 3

Describe the structure of fatty acids.

Answer 3

Fatty acids are carboxylic acids with an acidic carboxyl (COOH) group and a hydrocarbon chain.

Question 4

What differentiates saturated and unsaturated fatty acids?

Answer 4

• Saturated fatty acids have no double bonds
• Unsaturated fatty acids have one or more double bonds

Question 5

Fill in the blank: A glyceride is formed when glycerol is linked to one or more fatty acids via _______.

Answer 5

[ester linkage]

Question 6

What is the process called when a glyceride is formed?

Answer 6

Condensation reaction (dehydration synthesis)

Question 7

What type of bond is formed between glycerol and fatty acids?

Answer 7

Ester bond

Question 8

How do the chain length and saturation of fatty acids affect triglyceride properties?

Answer 8

• Longer chains increase melting point
• More unsaturation decreases melting point

Question 9

True or False: Triglycerides are efficient energy stores compared to carbohydrates.

Answer 9

True

Question 10

What is the significance of triglycerides being hydrophobic?

Answer 10

They do not affect water potential of cells and do not carry water of hydration.

Question 11

What role do triglycerides play in animals’ bodies?

Answer 11

• Energy storage
• Insulation
• Protection of organs
• Buoyancy in aquatic animals

Question 12

What are compound lipids?

Answer 12

Esters of fatty acids and alcohol plus other chemical groups, such as phosphate and sugar.

Question 13

What is the primary function of phospholipids?

Answer 13

Construction of cell membranes.

Question 14

Describe the structure of phospholipids.

Answer 14

Phospholipids consist of one glycerol, two fatty acids, and a phosphate group.

Question 15

Fill in the blank: Phospholipids are described as _______ due to their hydrophobic and hydrophilic regions.

Answer 15

[amphipathic]

Question 16

What types of aggregates can phospholipids form in aqueous environments?

Answer 16

Lipid bilayers, micelles, and liposomes.

Question 17

What is the role of the phosphate group in phospholipids?

Answer 17

Forms a polar/charged hydrophilic head that has an affinity for water.

Question 18

What is metabolic water and why is it important?

Answer 18

Water released during the oxidation of triglycerides, important for desert animals.

Question 19

What are carbon tails described as?

Answer 19

Non-polar and hydrophobic

Carbon tails can form bonds with hydrophobic molecules or among themselves.

Question 20

What type of head do phospholipids have?

Answer 20

Polar / charged hydrophilic head

This head has an affinity for water.

Question 21

What term describes molecules like phospholipids that have both hydrophobic and hydrophilic regions?

Answer 21

Amphipathic

Question 22

What is a micelle?

Answer 22

A small, spherical droplet consisting of a phospholipid monolayer

The phosphate heads are on the outside, in contact with the aqueous environment.

Question 23

What is a bilayer?

Answer 23

Two lipid monolayers forming a two-dimensional sheet

The hydrophilic heads are exposed to the polar exterior while the hydrophobic tails are in contact with those of neighboring molecules.

Question 24

What is a liposome?

Answer 24

A hollow sphere formed when a lipid bilayer folds back on itself

Liposomes enclose aqueous solutions, creating a separate aqueous compartment.

Question 25

What is the function of phospholipids in cell membranes?

Answer 25

Form a selectively permeable barrier ## Footnote Hydrophilic heads are exposed to the aqueous medium while hydrophobic tails are excluded from the aqueous medium.

Question 26

What is the role of liposomes in cells?

Answer 26

Storage and transport of cellular products ## Footnote They are also involved in the digestion of waste and drug delivery.

Question 27

How do phospholipids facilitate fat transport in the body?

Answer 27

Form micelles for transport between the gut and body tissues

Question 28

What type of interactions exist between fatty acid tails?

Answer 28

Hydrophobic interactions

Question 29

What do most phospholipids contain?

Answer 29

Choline

Question 30

What is the structure of glycolipids?

Answer 30

Composed of two hydrophobic hydrocarbon tails and a polar carbohydrate chain ## Footnote The carbohydrate chain has less than 15 sugar residues and no phosphate.

Question 31

How is the carbohydrate chain in glycolipids formed?

Answer 31

Joined to glycerol's –OH group by a glycosidic bond

Question 32

What is one function of the carbohydrate chain in glycolipids?

Answer 32

Serves as a marker for cell-cell recognition

Question 33

What is the function of hydrophobic interactions in glycolipids?

Answer 33

Anchor the entire glycolipids at the cell surface membrane

Question 34

What are derived lipids?

Answer 34

Include steroid hormones, ketone bodies, fatty alcohols, terpenes, and carotenoids

Question 35

What is the structure of cholesterol?

Answer 35

Made up of three fused six-membered rings and one five-membered ring

Question 36

What is a key role of cholesterol in cell membranes?

Answer 36

Regulates membrane fluidity

Question 37

What is the principle of the emulsion test?

Answer 37

Lipids are soluble in organic solvents but not in water

Question 38

What happens if lipid is present during the emulsion test?

Answer 38

Forms a clear solution in ethanol that creates an emulsion with water

Question 39

What observation indicates that lipid is absent in the emulsion test?

Answer 39

A clear solution remains clear when added to water