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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

What is an amphiphatic molecule?

A

Contains hydrophilic and hydrophobic regions

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2
Q

What are the three types of structures membrane lipids can form in aqueous solutions?

A
  • Liposome
  • Micelle
  • Phospholipid bilayer
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3
Q

What do phospholipids contain?

A
  • Polar head group: phosphate and alcohol

- Hydrophobic tail: fatty acid

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4
Q

What is the linkage that joins the polar head group to the fatty acid tail in phospholipids?

A

Phosphodiester linkage

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5
Q

If a phospholipid has a glycerol backbone, what is its name?

A

Phosphoglyceride or glycerophospholipid

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6
Q

If a phospholipid has a sphingosine backbone, what is its name?

A

Sphingolipids

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7
Q

Can all sphingolipids be defined as phospholipids?

A

No

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8
Q

Differentiate saturated and unsaturated fatty acids.

A

Saturated: only single bonds
Unsaturated: one or more double bonds

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9
Q

When is a carbon atom considered to be saturated?

A

When it is bonded to four other atoms, with no pi bonds

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10
Q

Which type of fatty acid has greater Van der Waals force? Which type of fatty acid has kinks? Which type of fatty acid is liquid at room temperature?

A
  • Van der Waals: saturated
  • Kinks: unsaturated
  • Liquid: unsaturated
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11
Q

Are all glycerophospholipids phospholipids?

A

Yes

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12
Q

What is the structure of glycerophospholipids?

A
  • Glycerol backbone bound by ester linkages to two fatty acids
  • Glycerol backbone bound by a phosphodiester linkage to a highly polar head group
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13
Q

How are glycerophospholipids named?

A

According to their head group since they determine the membrane’s surface properties

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14
Q

What is phosphatidylcholine?

A

Glycerophospholipid with a choline head group

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15
Q

Are all sphingolipids phospholipids?

A
  • Many, but not all (sphingophospholipids containing a phosphodiester bond)
  • Can also be glycolipids (glycosidic linkages to sugars)
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16
Q

What is the simplest sphingolipid? What is its head group?

A
  • Ceramide

- Single hydrogen atom at its head group

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17
Q

Which sphingolipid is a major component of myelin sheaths?

A

Sphingomyelin

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18
Q

What are sphingomyelins? What are their head groups? What is their linkage? What is the charge of the head group?

A
  • Major class of sphingophospholipids
  • Phosphatidylcholine or phosphatidylethanolamine head group
  • Phosphodiester bond
  • Head group has no net charge
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19
Q

What are glycosphingolipids? What are their head groups? What is their linkage?

A
  • Glycolipids
  • Sugars
  • Glycosidic linkage
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20
Q

Where are glycosphingolipids mainly found in terms of the plasma membrane?

A

Outer surface of the plasma membrane

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21
Q

What are the two classification of glycosphingolipids?

A
  • Cerebrosides

- Globosides

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22
Q

Differentiate cerebrosides and globosides.

A

Cerebrosides: one sugar connected to sphingosine
Globosides: two or more sugars connected to sphingosine

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23
Q

Why can cerebrosides and globosides be referred to as neutral glycolipids?

A

They have no net charge at physiological pH

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24
Q

What are gangliosides? What is their head group composed of? What is the charge of the head group?

A
  • Glycolipids
  • Polar head groups composed of oligosaccharides with one or more NANA molecules at the terminus
  • Negative charge
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25
Q

Do gangliosides possess a glycosidic linkage or a phosphodiester linkage?

A

Glycosidic

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26
Q

Which sphingolipid is the most complex?

A

Gangliosides

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27
Q

What does NANA mean? What is it also called?

A

N-acetylneuraminic acid (sialic acid)

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28
Q

ABO blood typing system is based on cell-surface antigens on red blood cells, which are examples of which lipid?

A

Sphingolipids

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29
Q

What are the major roles of gangliosides?

A

Major role in cell interaction, recognition, and signal transduction

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30
Q

What are waxes?

A

Long-chain fatty acids esterified to long-chain alcohols

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31
Q

What is the major role of waxes?

A

Used as protection against evaporation and parasites in plants and animals

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32
Q

What components of membrane lipids contribute to their function?

A
  • Polar head group

- Degree of unsaturation of fatty acid tails

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33
Q

What is the difference between a sphingolipid that is also a phospholipid and one that is NOT?

A
  • The bond between the sphingosine backbone and the head group
  • Phospholipid: phosphodiester bond
  • Glycolipids: glycosidic bond
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34
Q

What would happen if an amphiphatic molecule were placed in a nonpolar solvent rather than an aqueous solution?

A

The opposite of what would happen in water: polar part of molecules on the inside, nonpolar part on the outside

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35
Q

In what way do lipids serve as coenzymes?

A

In the electron transport chain and in glycosylation reactions

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36
Q

What kind of special lipids can absorb light?

A

Lipids with conjugated double bonds

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37
Q

Terpenes are a class of lipids build from ______ moieties and share a common structural pattern with carbons grouped in multiples of ____

A
  • isoprene (C5H8)

- 5

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38
Q

Which odiferous chemicals are the metabolic precursors to steroids and other lipid signaling molecules?

A

Terpenes

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39
Q

What does odiferous mean? Give an example of an odiferous compound.

A
  • Something that carries a smell

- Terpenes

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40
Q

What is one terpene unit called? How many isoprene units does it contain?

A
  • Monoterpene

- 2 isoprene units

41
Q

How are terpenoids derived from terpenes?

A
  • Via oxygenation or backbone rearragement

- Similar odorous characteristics

42
Q

What are terpenes mainly produced by?

A
  • Plants and some insects

- In some cases, pungent chemicals are part of the plant or insect’s protective mechanism

43
Q

How many isoprene units do sesquiterpenes, diterpenes and triterpenes?

A

Sesquiterpenes: 3
Diterpenes: 4
Triterpenes: 6

44
Q

Vitamin A is a ______ from which retinal is derived

A

diterpene

45
Q

Carotenoids are _______ and have eight isoprene units

A

tetraterpenes

46
Q

Terpenes get their name from their original discovery in what?

A

Turpentine

47
Q

What is the general structure of a steroid? What are they derivates of?

A
  • Derivatives of terpenes

- Three cyclohexane rings and one cyclopentane ring

48
Q

What is steroid functionality determined by? (2)

A
  • The oxidation status of the rings

- The functional groups that the rings carry

49
Q

What are steroid hormones? Give examples.

A
  • High-affinity receptors, work at low concentrations, and affect gene expression and metabolism
  • Testosterone, various estrogens, cortisol, aldosterone
50
Q

What is cholesterol a major component of? What is its role?

A
  • Major component of the phospholipid bilayer

- Responsible for mediating membrane fluidity

51
Q

Is cholesterol a hydrophilic or hydrophobic molecule?

A

Neither, it is amphiphatic

52
Q

What allows cholesterol to maintain relatively constant fluidity in cell membranes?

A

Interactions with both the hydrophobic tails and hydrophilic heads of phospholipids

53
Q

What does cholesterol do at low temperatures? What does it do at high temperatures? With this in mind, what is it also referred as?

A
  • Fluidity buffer
  • Low temperature: keeps the cell membrane from solidifying
  • High temperature: holds the membrane intact and prevents it from becoming too permeable
54
Q

Steroid hormones, bile acids, and vitamin D are derived from which precursor?

A

Cholesterol

55
Q

How did prostaglandins acquire their name?

A

They were first thought to be produced by the prostate gland

56
Q

Where are prostaglandins produced from?

A

Produced by almost all cells in the body

57
Q

How many carbons do prostaglandins contain? What are they derived from?

A
  • 20 carbons

- Arachidonic acid

58
Q

What is the general structure of prostaglandins?

A
  • Unsaturated carboxylic acids

- Contain one five-carbon ring

59
Q

Prostaglandins act as ____ or _____ hormones

A

paracrine or autocrine

60
Q

What is the biological function of prostaglandins? What does it regulate?

A

Regulates the synthesis of cyclic adenosine monophosphate (cAMP)

61
Q

What is cAMP? What is its role?

A

Ubiquitous intracellular messenger that mediates the actions of many other hormones

62
Q

What is the relationship between aspirin and prostaglandins?

A

Aspirin inhibits the enzyme cyclooxygenase (COX), which aids in the production of prostaglandins

63
Q

Which lipid has powerful effects on muscle contraction, body temperature, the sleep-wake cycle, and pain?

A

Prostaglandins

64
Q

What are the fat-soluble vitamins? Where do they accumulate?

A
  • A, D, E, K

- Accumulate in stored fat

65
Q

What is vitamin A important in? What is its other name?

A
  • Carotene

- Important in vision, growth and development, and immune function

66
Q

What is the most significant metabolite of vitamin A? What form is it in?

A
  • Retinal

- Aldehyde form

67
Q

What is the role of retinal?

A

Component of the light-sensing molecular system of the human eye (vision)

68
Q

What are the two metabolites of vitamin A?

A
  • Retinal

- Retinoic acid

69
Q

What is the storage form of vitamin A?

A

Retinol

70
Q

How is retinoic acid derived?

A

Retinol is oxidized to retinoic acid

71
Q

What is the function of retinoic acid?

A

Hormone that regulates gene expression during epithelial development

72
Q

What is vitamin D also called? How can it be acquired?

A
  • Cholecalciferol

- Consumed or formed in a UV-driven reaction in the skin

73
Q

How is vitamin D converted to calcitriol?

A

The liver and kidneys convert vitamin D to calcitriol, the biologically active form of vitamin D

74
Q

What is the role of calcitriol?

A

Increases calcium and phosphate uptake in the intestines, which promotes bone production

75
Q

What does a lack of vitamin D result in?

A

Rickets, seen in children and characterized by underdeveloped, curved long bones as well as impeded growth

76
Q

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

A

tocopherols and tocotrienols

77
Q

What are tocopherols and tocotrienols characterized by in terms of structure? Are they hydrophilic or hydrophobic?

A

Substituted aromatic ring with a long isoprenoid side chain and are usually hydrophobic

78
Q

What is the role of tocopherols?

A
  • Biological antioxidants
  • Aromatic ring reacts with free radicals, destroying them
  • Prevents oxidative damage (contributor to the development of cancer and aging)
79
Q

Vitamin K is a group of compounds. Which compounds are included in this group?

A
  • Phylloquinone (K1)

- Menaquinone (K2)

80
Q

What is the major function of vitamin K?

A
  • Vital to the posttranslational modifications required to form prothrombin; important factor in blood clotting
  • Aromatic ring of vitamin K undergoes a cycle of redox reactions during the formation of prothrombin
81
Q

What is vitamin K’s role in bone health?

A

Required to introduce calcium-binding sites on several calcium-dependent proteins

82
Q

How many carbons are in diterpene?

A

20 carbons

83
Q

Why are lipids a fantastic way to store energy, from the body’s point of view? (2)

A

1) Carbon atoms of FA are more reduced than those of sugars, which contain numerous alcohol groups (2x as much energy per gram) - dense energy store
2) Triacylglycerols are hydrophobic; decrease their weight
* Also serves as insulation for animals living in colder temperature

84
Q

Which lipid is the preferred method of storing energy for long-term use?

A

Triacylglycerols

85
Q

What is the general structure of triacylglycerols? What linkages are used?

A

One glycerol attached to three fatty acids by ester bonds

86
Q

Animal cells specifically used for storage of large triacylglycerol deposits are called _______

A

adipocytes

87
Q

Where are triacylglycerol deposits found in plants?

A

In seeds as oils

88
Q

Triacylglycerols travel bidirectionally in the bloodstream between the ______ and _______

A

liver and adipose tissue

89
Q

What are free fatty acids?

A

Unesterified fatty acids with a free carboxylate group

90
Q

How do free fatty acids circulate in the body?

A

In the blood bound noncovalently to serum albumin

91
Q

Which lipid make up soap?

A

Fatty acid salt

92
Q

What is saponification? What is the compound that is used?

A
  • The ester hydrolysis of triacylglycerols using a strong base
  • Lye (sodium or potassium hydroxide)
93
Q

What can act as surfactants?

A

Soap

94
Q

What are surfactants? What do they form to do so?

A
  • They lower the surface tension at the surface of a liquid, serving as a detergent or emulsifier
  • Forming micelles
95
Q

What can micelles dissolve? Why does it wash away?

A
  • Can dissolve a lipid-soluble molecule in its fatty acid core
  • Washes away with water because of its shell of carboxylate head groups
96
Q

What is a micelle in terms of soap?

A

Tiny aggregates of soap with the hydrophobic tails turned inward and the hydrophilic heads turned outward, thereby shielding the hydrophobic lipid tails and allowing for overall solvation

97
Q

How does the human body store energy?

A

As glycogen and triacylglycerols

98
Q

If you are washing dishes with soap, where do fat-soluble particles dissolve? Where do water-soluble compounds dissolve?

A
  • Fat-soluble: dissolve inside micelles in the soap-water solution and wash away
  • Water-soluble: freely dissolve in water

MCAT: Biochemistry (12 decks)

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