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mcat biochemistry > Chapter 5: Lipid Structure and Function > Flashcards

Chapter 5: Lipid Structure and Function Flashcards

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MCAT flashcards
1
Q

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

A

amphipathic

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2
Q

Phospholipids contain what elements?

A
  1. Polar head group
  2. Fatty acid tail
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3
Q

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

A
  1. Phosphate
  2. Alcohol
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4
Q

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

A

backbone

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5
Q

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

A

Phosphodiester linkages

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6
Q

What do all lipids share in common?

A

A tail composed of long-chain fatty acids

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7
Q

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

A

separation; length

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8
Q

Fully ____________ fatty acid tails will ahve only single bonds.

A

saturated

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9
Q

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

A

four; pi

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10
Q

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

A

van der Waals; stable

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11
Q

Saturated fatty acids tend to form ________ at room temperature.

A

solids

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12
Q

An ____________ fatty acid includes one or more double bonds.

A

unsaturated

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13
Q

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

A

For them to stack and solidify

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14
Q

Unsaturated fats tend to be ____________ at room temperature.

A

liquids

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15
Q

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

A

fluid

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16
Q

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.

A

glycerol; ester

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17
Q

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

A

head

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18
Q

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

A

phosphatidylcholine

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19
Q

____________________ is one with an ethanol-amine head group.

A

phosphatidylethanolamine

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20
Q

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

A

positively, negatively, neutral

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21
Q

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

A

sphingolipids

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22
Q

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

A

sphingosine, sphingoid

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23
Q

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

A

phosphodiester

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24
Q

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

A

glycosidic; glycolipid

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25
Q

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

A
  1. Ceramide
  2. Sphingomyelins
  3. Glycosphingolipids (glycolipids)
  4. Gangliosides
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26
Q

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

A

ceramide

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27
Q

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

A

sphingomyelins

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28
Q

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

A

phosphocholine, phosphoethanolamine; phosphodiester

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29
Q

What is the charge of sphingomyeline head groups?

A

No net charge

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30
Q

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

A

myelin

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31
Q

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

A

glycolipids; glycosphingolipids

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32
Q

Sphingolipids are not phospholipids because they contain no ________________ linkage.

A

phosphodiester

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33
Q

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

A
  1. cerebrosides
  2. globosides
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34
Q

Glycosphinglipids

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

A

cerebrosides; globosides

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35
Q

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.

A

N-acetylneuraminic

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36
Q

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

A

glycolipids

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37
Q

What roles do gangliosides play?

A

Cell interaction, recognition, and signal transduction

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38
Q

What do gangliosides look like?

A

They are gangly sphingolipids, with complex structure and functional groups

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39
Q

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

A

esters; alcohols

40
Q

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

A

coenzymes

41
Q

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

A

terpenes

42
Q

How are terprenes grouped?

A

Based on the number of isoprene units present

43
Q

A single terpene unit contains how many isoprene units?

A

two

44
Q

____________ contain two isoprene units.

A

Monoterpenes

45
Q

________________ contain three isoprene units.

A

Sesquiterpenes

sesqui- meaning “one and a half”

46
Q

____________ contain four isoprene units.

A

diterpenes

47
Q

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

A

triterpenes; cholesterol

48
Q

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

A

carotenoids; tetraterpenes

49
Q

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

A

terpenoids; oxygenation

50
Q

____________ are metabolic derivatives of terpenes.

A

steroids

51
Q

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

A

cycloalkane; cyclohexane, cyclopentane

52
Q

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

A

oxidation status

53
Q

The larger number of carbons and hydrogens make steroids ____________.

A

nonpolar

54
Q

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

A

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

55
Q

What do steroid hormones do?

A

They regulate gene expression and metabolism

56
Q

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

A

Cholesterol

57
Q

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

A

amphipathic

58
Q

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

A

Steroid hormones, bile acids, vitamin D

59
Q

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

A

prostaglandins

60
Q

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

A

arachidonic acid; five

61
Q

Prostaglandins act as ____________ or ____________ signaling molecules.

A

paracrine, autocrine

62
Q

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.

A

cAMP

63
Q

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

A

vitamin

64
Q

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

A

water, lipid

65
Q

What are the fat-soluble vitamins?

A

A, D, E, and K

66
Q

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

A

A; carotene

67
Q

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.

A

retinal

68
Q

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

A

retinol; retinoic acid

69
Q

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

A

D, cholecalciferol

70
Q

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

A

calcitriol

71
Q

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

A

calcium and phosphate

72
Q

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.

A

rickets

73
Q

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

A

tocopherols and tocotrienols

74
Q

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

A

substituted; isoprenoid

75
Q

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

A

antioxidants; free radicals

76
Q

When tocopherols destroy free radicals, it prevents ________ ________.

A

oxidative damage

77
Q

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

A

K; phylloquinone and menaquinones

78
Q

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

A

prothrombin

79
Q

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.

A

calcium

80
Q

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

A

triacylglycerols

81
Q

Why are lipids a good way to store energy?

A
  1. Carbon atoms of fatty acids are more reduced than those of sugars
  2. Triacylglycerols are hydrophobic
82
Q

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.

A

twice

83
Q

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.

A

hydration; weight

84
Q

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

A

triglycerides; ester, glycerol

85
Q

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.

A

nonpolar, hydrophobic; polar hydroxyl, polar carboxylates

86
Q

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.

A

adipocytes

87
Q

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

A

bidirectionally

88
Q

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

A

saturation, unsaturation

89
Q

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

A

unesterified, carboxylate

90
Q

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

A

serum albumin

91
Q

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

A

Saponification

92
Q

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

A

lye

93
Q

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.

A

cleavage

94
Q

Soaps can act as surfactants. A surfactant lowers what?

A

surface tension at the surface of a liquid

95
Q

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 ____________.

A

colloid

mcat biochemistry (13 decks)

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