Biochem - lipid structure and function

Question 1

What are lipids characterized by?

Answer 1

Insolubility in water and solubility in nonpolar organic solvents

Question 2

What is the major component of the phospholipid bilayer?

Answer 2

Lipids

Question 3

Define amphipathic molecule.

Answer 3

A molecule with both hydrophilic and hydrophobic regions

Question 4

What are the two regions of membrane lipids?

Answer 4

• Polar head (hydrophilic region)
• Fatty acid tails (hydrophobic region)

Question 5

What structures do lipids form in aqueous solutions?

Answer 5

• Liposomes
• Micelles
• Phospholipid bilayer

Question 6

What determines the behavior of lipids?

Answer 6

The degree of saturation and length of the long-chain fatty acids

Question 7

What are saturated fatty acids characterized by?

Answer 7

Single bonds connected to four other atoms and no pi bonds

Question 8

What is the effect of unsaturated bonds in fatty acids?

Answer 8

They introduce kinks which make it hard to stack

Question 9

What elements do phospholipids contain?

Answer 9

• Phosphate
• Alcohol (polar head group)
• Hydrophobic fatty acid tail

Question 10

What is a glycerophospholipid?

Answer 10

Phospholipids with a glycerol backbone bonded to two fatty acids

Question 11

What is phosphatidylcholine?

Answer 11

A glycerophospholipid with a choline head group

Question 12

What distinguishes sphingolipids from glycerophospholipids?

Answer 12

Sphingolipids have a sphingosine backbone

Question 13

What is the simplest sphingolipid?

Answer 13

Ceramide

Question 14

What are sphingomyelins?

Answer 14

Sphingolipids that are also phospholipids with either phosphocholine or phosphoethanolamine as a head group

Question 15

What are glycolipids?

Answer 15

Sphingolipids with head groups composed of sugars bonded by glycosidic linkages

Question 16

What are cerebrosides?

Answer 16

Glycosphingolipids with a single sugar

Question 17

What are gangliosides?

Answer 17

Glycolipids with polar head groups composed of oligosaccharides and a negative charge

Question 18

What are waxes?

Answer 18

Esters of long-chain fatty acids with long-chain alcohols

Question 19

What role do waxes play in plants?

Answer 19

Prevent excessive evaporation and protect against parasites

Question 20

What are terpenes?

Answer 20

Lipids built from isoprene moieties with carbon groups in multiples of five

Question 21

What is the structural characteristic of steroids?

Answer 21

Four fused cycloalkane rings: three cyclohexane and one cyclopentane

Question 22

What is the role of cholesterol in membranes?

Answer 22

Mediates membrane fluidity and serves as a precursor to many important molecules

Question 23

What are prostaglandins derived from?

Answer 23

Arachidonic acid

Question 24

What are the two classes of vitamins?

Answer 24

• Water-soluble vitamins
• Fat-soluble vitamins

Question 25

What is Vitamin A important for?

Answer 25

* Vision * Growth and development * Immune function

Question 26

What is the biologically active form of Vitamin D?

Answer 26

Calcitriol (1,25-(OH)2D3)

Question 27

What is the function of Vitamin E?

Answer 27

Biological antioxidant preventing oxidative damage

Question 28

What is the role of Vitamin K?

Answer 28

Vital for posttranslational modifications required to form prothrombin

Question 29

What are triacylglycerols used for?

Answer 29

Energy storage

Question 30

Why are lipids effective for energy storage?

Answer 30

* More reduced carbon atoms than sugars * Hydrophobic and do not require hydration for stability

Question 31

What is the relationship between triacylglycerols and carbohydrates in terms of energy yield?

Answer 31

Triacylglycerols yield twice the amount of energy per gram as carbohydrates

Question 32

What is the primary storage mechanism of triacylglycerols compared to polysaccharides?

Answer 32

Triacylglycerols are a more efficient storage mechanism than polysaccharides like glycogen.

Question 33

How do triacylglycerols affect weight compared to hydrophilic polysaccharides?

Answer 33

Triacylglycerols are hydrophobic and do not require hydration for stability, decreasing their weight.

Question 34

What contributes to the insolubility of triacylglycerols in water?

Answer 34

Their nonpolar and hydrophobic nature, which decreases polarity due to bonded polar groups.

Question 35

What role do triacylglycerols serve in the body?

Answer 35

They serve as depots of metabolic fuel for energy during cell division or low fuel supplies.

Question 36

Where are adipocytes primarily located in animals?

Answer 36

Under the skin, around mammary glands, and in the abdominal cavity.

Question 37

In plants, where are triacylglycerol deposits commonly found?

Answer 37

In seeds as oils.

Question 38

How do triacylglycerols travel in the bloodstream?

Answer 38

Bidirectionally between the liver and adipose tissue.

Question 39

What primarily determines the physical characteristics of triacylglycerols?

Answer 39

The saturation or unsaturation of the fatty acid chains.

Question 40

Define free fatty acids.

Answer 40

Unesterified fatty acids with a free carboxylate group.

Question 41

How do free fatty acids circulate in the body?

Answer 41

Bonded noncovalently to serum albumin.

Question 42

What is saponification?

Answer 42

The ester hydrolysis of triacylglycerols using a strong base.

Question 43

What traditional base is used in saponification?

Answer 43

Lye, which is sodium or potassium hydroxide.

Question 44

What are the products of saponification?

Answer 44

The sodium salt of the fatty acid and glycerol.

Question 45

What is adipocere?

Answer 45

The result of natural saponification occurring in corpses, known as grave wax.

Question 46

What function do soaps serve as surfactants?

Answer 46

They lower the surface tension at the surface of a liquid.

Question 47

What happens when soap is added to an aqueous solution and oil?

Answer 47

The two phases appear to combine into a single phase, forming a colloid.

Question 48

What are micelles?

Answer 48

Tiny aggregates of soap with hydrophobic tails inward and hydrophilic heads outward.

Question 49

What is the role of micelles in cleaning?

Answer 49

They allow cleaning agents to dissolve both water-soluble and water-insoluble messes.

Question 50

What vitamins are absorbed with the help of micelles?

Answer 50

Fat-soluble vitamins A, D, E, and K.

Question 51

What forms micelles in the body for fat absorption?

Answer 51

Fatty acids and bile salts secreted by the gallbladder.

Question 52

True or False: Triacylglycerols are polar compounds.

Answer 52

False