Chapter 5: Lipid Structure and Function

Question 1

Each lipid membrane component is an ____________ molecule, meaning it has both hydrophilic and hydrophobic regions.

Answer 1

amphipathic

Question 2

Phospholipids contain what elements?

Answer 2

1. Polar head group
2. Fatty acid tail

Question 3

What is the polar head group of a phospholipid made of?

Answer 3

1. Phosphate
2. Alcohol

Question 4

Phospholipids can be further classified according to the ________ on which the molecule is built.

Answer 4

backbone

Question 5

What joins the polar head group to the fatty acid tail?

Answer 5

Phosphodiester linkages

Question 6

What do all lipids share in common?

Answer 6

A tail composed of long-chain fatty acids

Question 7

The hydrocarbon chains of lipids vary by their degree of ____________ and ________.

Answer 7

separation; length

Question 8

Fully ____________ fatty acid tails will ahve only single bonds.

Answer 8

saturated

Question 9

The carbon atom is considered “saturated” when it is bonded to ____ other atoms, with no ____ bonds.

Answer 9

four; pi

Question 10

Saturated fatty acids have greater____________ forces and a more ________ overall structure.

Answer 10

van der Waals; stable

Question 11

Saturated fatty acids tend to form ________ at room temperature.

Answer 11

solids

Question 12

An ____________ fatty acid includes one or more double bonds.

Answer 12

unsaturated

Question 13

Double bonds introduce kinks into the fatty acid chain, which makes it difficult for what?

Answer 13

For them to stack and solidify

Question 14

Unsaturated fats tend to be ____________ at room temperature.

Answer 14

liquids

Question 15

Phospholipids with unsaturated fatty acid tails make up more ________ regions of the phospholipid bilayer.

Answer 15

fluid

Question 16

Glycerophospholipids (or phosphoglycerides) are specifically those phospholipids that contain a ____________ backbone bonded by ________ linkages to 2 fatty acids and by a phosphodiester linkage to a highly polar head group.

Answer 16

glycerol; ester

Question 17

Because the ________ group determines membrane surface properties, glycerophosphipids are named according to this.

Answer 17

head

Question 18

________________ is the name of a glycerophospholipid with a choline head group.

Answer 18

phosphatidylcholine

Question 19

____________________ is one with an ethanol-amine head group.

Answer 19

phosphatidylethanolamine

Question 20

The head group of a glycerophospholipid can be ____________ charged, ____________ charged, or ________.

Answer 20

positively, negatively, neutral

Question 21

The ABO blood typing system is based on cell-surface antigens on RBCs. These cell-surface antigens are some of the most well-known ________________.

Answer 21

sphingolipids

Question 22

Sphingolipids have a ____________ or ________ backbone, as opposed to the glycerol backbone of glycerophospholipids.

Answer 22

sphingosine, sphingoid

Question 23

Sphingolipids have long-chain, nonpolar fatty acid tails and polar head groups. Many sphingolipids are also phospholipids because they contain a ________________ linkage.

Answer 23

phosphodiester

Question 24

Other sphingolipids contain ____________ linkages to sugars; any lipid linked to a sugar can be termed a ____________.

Answer 24

glycosidic; glycolipid

Question 25

What are the four major subclasses of sphingolipids, as divided by their head group?

Answer 25

1. Ceramide 2. Sphingomyelins 3. Glycosphingolipids (glycolipids) 4. Gangliosides

Question 26

The simplest sphingolipid is ____________, which has a single hydrogen atom as its head group.

Answer 26

ceramide

Question 27

____________ are the major class of sphingolipids that are also phospholipids.

Answer 27

sphingomyelins

Question 28

Sphingomyelins have either ____________ or ____________________ as a head group, and thus contain a ________________ bond.

Answer 28

phosphocholine, phosphoethanolamine; phosphodiester

Question 29

What is the charge of sphingomyeline head groups?

Answer 29

No net charge

Question 30

Sphingomyelins are major componenets in the plasma membranes of cells producing ____________, the insulating sheath for axons.

Answer 30

myelin

Question 31

Sphingolipids with head groups composed of sugars bonded by glycosidic linkages are considered ____________, or more specifically, ________________.

Answer 31

glycolipids; glycosphingolipids

Question 32

Sphingolipids are not phospholipids because they contain no ________________ linkage.

Answer 32

phosphodiester

Question 33

Glycosphingolipids are found mainly on the outer surface of the plasma membrane and can be further classified as what two groups?

Answer 33

1. cerebrosides 2. globosides

Question 34

# Glycosphinglipids ____________ have a single sugar, whereas ____________ have two or more.

Answer 34

cerebrosides; globosides

Question 35

Gangliosides are glycolipids that have polar head groups composed of oligosaccharides with one or more ________________________ acid (NANA) molecules at the terminus and a negative charge.

Answer 35

N-acetylneuraminic

Question 36

Gangliosides are also considered ____________ because they have a glycosidic linkage and no phosphate group.

Answer 36

glycolipids

Question 37

What roles do gangliosides play?

Answer 37

Cell interaction, recognition, and signal transduction

Question 38

What do gangliosides look like?

Answer 38

They are gangly sphingolipids, with complex structure and functional groups

Question 39

Waxes are ________ of long-chain fatty acids with long-chain ____________.

Answer 39

esters; alcohols

Question 40

Lipids serve as ____________ in the electron transport chain and in glycosylation reactions.

Answer 40

coenzymes

Question 41

________ are a class of lipids built from *isoprene* moieties and share a common structural pattern with carbons grouped in multiples of five.

Answer 41

terpenes

Question 42

How are terprenes grouped?

Answer 42

Based on the number of isoprene units present

Question 43

A single terpene unit contains how many isoprene units?

Answer 43

two

Question 44

____________ contain two isoprene units.

Answer 44

Monoterpenes

Question 45

________________ contain three isoprene units.

Answer 45

Sesquiterpenes | sesqui- meaning "one and a half"

Question 46

____________ contain four isoprene units.

Answer 46

diterpenes

Question 47

____________ with six isoprene units, can be converted to ____________ and various steroids.

Answer 47

triterpenes; cholesterol

Question 48

____________, like beta-carotene and lutein, are ____________ and have eight isoprene units.

Answer 48

carotenoids; tetraterpenes

Question 49

____________, also sometimes referred to as isoprenoids, are derivatives of terpenes that have undergone ____________ or rearrangement of the carbon skeleton.

Answer 49

terpenoids; oxygenation

Question 50

____________ are metabolic derivatives of terpenes.

Answer 50

steroids

Question 51

Steroids are characterized by having four ____________ rings fused together: three ____________ and one ________________.

Answer 51

cycloalkane; cyclohexane, cyclopentane

Question 52

Steroid functionality is determined by the ____________ ________ of these rings, as well as the functional groups they carry.

Answer 52

oxidation status

Question 53

The larger number of carbons and hydrogens make steroids ____________.

Answer 53

nonpolar

Question 54

Steroid refers to a group defined by a particular chemical structure, but steroid hormones are what?

Answer 54

steroids that *act* as hormones, meaning they are secreted by endorcine glands into the bloodstream and then travel on protein carriers to distant sites

Question 55

What do steroid hormones do?

Answer 55

They regulate gene expression and metabolism

Question 56

____________ is a steroid of primary importance. It is a major component of the phospholipid bilayer and is responsible for mediating membrane fluidity.

Answer 56

Cholesterol

Question 57

Cholesterol, like a phospholipid, is an ____________ molecule, which allows it to maintain relatively constant fluidity in cell membranes.

Answer 57

amphipathic

Question 58

Cholesterol also serves as a precursor to many important molecules like?

Answer 58

Steroid hormones, bile acids, vitamin D

Question 59

____________ are 20-carbon molecules that are unsaturated carboxylic acids.

Answer 59

prostaglandins

Question 60

Prostaglandins are derived from ________________ ________ and contain one ____-carbon ring.

Answer 60

arachidonic acid; five

Question 61

Prostaglandins act as ____________ or ____________ signaling molecules.

Answer 61

paracrine, autocrine

Question 62

The biological function of prostaglandins is to regulate the synthesis of ____________, which is a ubiquitous intracellular messenger, and in turn, mediates the actions of many other hormones.

Answer 62

cAMP

Question 63

A ____________ is an essential nutrient that cannot be adequately synthesized by the body and therefore must be consumed in the diet.

Answer 63

vitamin

Question 64

Vitaimins are commonly divided into ________-soluble and ________-soluble categories.

Answer 64

water, lipid

Question 65

What are the fat-soluble vitamins?

Answer 65

A, D, E, and K

Question 66

Vitamin ____, or ____________, is an unsaturated hydrocarbon that is important in vision, growth and development, and immune function.

Answer 66

A; carotene

Question 67

The most significant metabolite of vitamin A is the aldehyde form, ____________, which is a component of the light-sending molecular system in the human eye.

Answer 67

retinal

Question 68

____________ , the storage form of Vitamin A, is also oxidized to ________ ________, a hormone that regulates gene expression during epithelial development.

Answer 68

retinol; retinoic acid

Question 69

Vitamin ____, or ____________, can be consumed or formed in a UV light-driven reaction in the skin.

Answer 69

D, cholecalciferol

Question 70

In the liver and kidneys, vitamin D is converted to ____________, the biologically active form of vitamin D.

Answer 70

calcitriol

Question 71

Calcitriol increases ________ and ________ uptake in the intestines, which promotes bone production.

Answer 71

calcium and phosphate

Question 72

A lack of vitamin D can result in ________, a condition seen in children and characterized by underdeveloped, curved long bones as well as impeded growth.

Answer 72

rickets

Question 73

Vitamin E characterizes a group of closely related lipids called ____________ and ____________.

Answer 73

tocopherols and tocotrienols

Question 74

Vitamin E lipids are characterized by a ____________ aromatic ring with a long ____________ side chain and are characteristically hydrophobic.

Answer 74

substituted; isoprenoid

Question 75

Tocopherols are biological ____________. The aromatic ring reacts with ________ ____________, destroying them.

Answer 75

antioxidants; free radicals

Question 76

When tocopherols destroy free radicals, it prevents ________ ________.

Answer 76

oxidative damage

Question 77

Vitamin ____ is actually a group of compounds, including ____________ and the ________________

Answer 77

K; phylloquinone and menaquinones

Question 78

Vitamin K is vital to the posttranslational modifications required to form ____________, an important clotting factor in the blood.

Answer 78

prothrombin

Question 79

The aromatic ring of vitamin K underoges a cycle of redox during the formation of prothrombin. Vitamin K is also required to introduce ________-binding sites on several calcium-dependent proteins.

Answer 79

calcium

Question 80

________________ are a class of lipids specifically used for energy storage.

Answer 80

triacylglycerols

Question 81

Why are lipids a good way to store energy?

Answer 81

1. Carbon atoms of fatty acids are more reduced than those of sugars 2. Triacylglycerols are hydrophobic

Question 82

Because fatty acids are more reduced than those of sugars, the oxidation of triacylglycerols yields ________ the amount of energy per gram as carbohydrates, making them very energy dense.

Answer 82

twice

Question 83

Because triacylglycerols are hydrophobic, they do not draw in water and do not require ____________ for stability. This helps decrease their ________, especially in comparison to hydrophilic polysaccharides.

Answer 83

hydration; weight

Question 84

Triacylglycerols, also called ____________, are composed of three fatty acids bonded by ________ linkages to ____________.

Answer 84

triglycerides; ester, glycerol

Question 85

Overall, triacylglycerols are ________ and ________, which contributes to their insolubility in water, as the ________ ____________ groups of the glycerol component and the ________ ____________ of fatty acids are bonded together, decreasing their polarity.

Answer 85

nonpolar, hydrophobic; polar hydroxyl, polar carboxylates

Question 86

Special cells in animals, known as ____________, store large amounts of fat and are found primarily under the skin, around mammary glands, and in the abdominal cavity.

Answer 86

adipocytes

Question 87

Triacylglycerols travel ____________ in the bloodstream between the liver and adipose tissue.

Answer 87

bidirectionally

Question 88

The physical characteristics of triacylglycerols are primarily determined by the ____________ (or ____________) of the fatty acid chains that make them up, much like phospholipids.

Answer 88

saturation, unsaturation

Question 89

Free fatty acids are ____________ fatty acids with a free ____________ group.

Answer 89

unesterified, carboxylate

Question 90

In the blood, free fatty acids circulate in the blood bonded noncovalently to ________ ____________.

Answer 90

serum albumin

Question 91

____________ is the ester hydrolysis of triacylglycerols using a strong base.

Answer 91

Saponification

Question 92

Traditionally, the base that is used is ____, the common name for sodium or potassium hydroxide.

Answer 92

lye

Question 93

The result of saponification is the basic ____________ of the fatty acid, leaving the sodium salt of the fatty acid and glycerol. This salt is known as soap.

Answer 93

cleavage

Question 94

Soaps can act as surfactants. A surfactant lowers what?

Answer 94

surface tension at the surface of a liquid

Question 95

IF we were to add a soap between the two phases in a mixture of vinegar and olive oil, the two phases would combine into a single phase, forming a ____________.

Answer 95

colloid