Chapter 5: Lipid Structure and Function Flashcards Preview

MCAT: Biochemistry > Chapter 5: Lipid Structure and Function > Flashcards

Flashcards in Chapter 5: Lipid Structure and Function Deck (98):
1

What is an amphiphatic molecule?

Contains hydrophilic and hydrophobic regions

2

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

- Liposome
- Micelle
- Phospholipid bilayer

3

What do phospholipids contain?

- Polar head group: phosphate and alcohol
- Hydrophobic tail: fatty acid

4

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

Phosphodiester linkage

5

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

Phosphoglyceride or glycerophospholipid

6

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

Sphingolipids

7

Can all sphingolipids be defined as phospholipids?

No

8

Differentiate saturated and unsaturated fatty acids.

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

9

When is a carbon atom considered to be saturated?

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

10

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?

- Van der Waals: saturated
- Kinks: unsaturated
- Liquid: unsaturated

11

Are all glycerophospholipids phospholipids?

Yes

12

What is the structure of glycerophospholipids?

- Glycerol backbone bound by ester linkages to two fatty acids
- Glycerol backbone bound by a phosphodiester linkage to a highly polar head group

13

How are glycerophospholipids named?

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

14

What is phosphatidylcholine?

Glycerophospholipid with a choline head group

15

Are all sphingolipids phospholipids?

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

16

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

- Ceramide
- Single hydrogen atom at its head group

17

Which sphingolipid is a major component of myelin sheaths?

Sphingomyelin

18

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

- Major class of sphingophospholipids
- Phosphatidylcholine or phosphatidylethanolamine head group
- Phosphodiester bond
- Head group has no net charge

19

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

- Glycolipids
- Sugars
- Glycosidic linkage

20

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

Outer surface of the plasma membrane

21

What are the two classification of glycosphingolipids?

- Cerebrosides
- Globosides

22

Differentiate cerebrosides and globosides.

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

23

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

They have no net charge at physiological pH

24

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

- Glycolipids
- Polar head groups composed of oligosaccharides with one or more NANA molecules at the terminus
- Negative charge

25

Do gangliosides possess a glycosidic linkage or a phosphodiester linkage?

Glycosidic

26

Which sphingolipid is the most complex?

Gangliosides

27

What does NANA mean? What is it also called?

N-acetylneuraminic acid (sialic acid)

28

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

Sphingolipids

29

What are the major roles of gangliosides?

Major role in cell interaction, recognition, and signal transduction

30

What are waxes?

Long-chain fatty acids esterified to long-chain alcohols

31

What is the major role of waxes?

Used as protection against evaporation and parasites in plants and animals

32

What components of membrane lipids contribute to their function?

- Polar head group
- Degree of unsaturation of fatty acid tails

33

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

- The bond between the sphingosine backbone and the head group
- Phospholipid: phosphodiester bond
- Glycolipids: glycosidic bond

34

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

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

35

In what way do lipids serve as coenzymes?

In the electron transport chain and in glycosylation reactions

36

What kind of special lipids can absorb light?

Lipids with conjugated double bonds

37

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

- isoprene (C5H8)
- 5

38

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

Terpenes

39

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

- Something that carries a smell
- Terpenes

40

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

- Monoterpene
- 2 isoprene units

41

How are terpenoids derived from terpenes?

- Via oxygenation or backbone rearragement
- Similar odorous characteristics

42

What are terpenes mainly produced by?

- Plants and some insects
- In some cases, pungent chemicals are part of the plant or insect's protective mechanism

43

How many isoprene units do sesquiterpenes, diterpenes and triterpenes?

Sesquiterpenes: 3
Diterpenes: 4
Triterpenes: 6

44

Vitamin A is a ______ from which retinal is derived

diterpene

45

Carotenoids are _______ and have eight isoprene units

tetraterpenes

46

Terpenes get their name from their original discovery in what?

Turpentine

47

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

- Derivatives of terpenes
- Three cyclohexane rings and one cyclopentane ring

48

What is steroid functionality determined by? (2)

- The oxidation status of the rings
- The functional groups that the rings carry

49

What are steroid hormones? Give examples.

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

50

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

- Major component of the phospholipid bilayer
- Responsible for mediating membrane fluidity

51

Is cholesterol a hydrophilic or hydrophobic molecule?

Neither, it is amphiphatic

52

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

Interactions with both the hydrophobic tails and hydrophilic heads of phospholipids

53

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

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

54

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

Cholesterol

55

How did prostaglandins acquire their name?

They were first thought to be produced by the prostate gland

56

Where are prostaglandins produced from?

Produced by almost all cells in the body

57

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

- 20 carbons
- Arachidonic acid

58

What is the general structure of prostaglandins?

- Unsaturated carboxylic acids
- Contain one five-carbon ring

59

Prostaglandins act as ____ or _____ hormones

paracrine or autocrine

60

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

Regulates the synthesis of cyclic adenosine monophosphate (cAMP)

61

What is cAMP? What is its role?

Ubiquitous intracellular messenger that mediates the actions of many other hormones

62

What is the relationship between aspirin and prostaglandins?

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

63

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

Prostaglandins

64

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

- A, D, E, K
- Accumulate in stored fat

65

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

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

66

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

- Retinal
- Aldehyde form

67

What is the role of retinal?

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

68

What are the two metabolites of vitamin A?

- Retinal
- Retinoic acid

69

What is the storage form of vitamin A?

Retinol

70

How is retinoic acid derived?

Retinol is oxidized to retinoic acid

71

What is the function of retinoic acid?

Hormone that regulates gene expression during epithelial development

72

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

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

73

How is vitamin D converted to calcitriol?

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

74

What is the role of calcitriol?

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

75

What does a lack of vitamin D result in?

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

76

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

tocopherols and tocotrienols

77

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

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

78

What is the role of tocopherols?

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

79

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

- Phylloquinone (K1)
- Menaquinone (K2)

80

What is the major function of vitamin K?

- 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

What is vitamin K's role in bone health?

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

82

How many carbons are in diterpene?

20 carbons

83

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

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

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

Triacylglycerols

85

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

One glycerol attached to three fatty acids by ester bonds

86

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

adipocytes

87

Where are triacylglycerol deposits found in plants?

In seeds as oils

88

Triacylglycerols travel bidirectionally in the bloodstream between the ______ and _______

liver and adipose tissue

89

What are free fatty acids?

Unesterified fatty acids with a free carboxylate group

90

How do free fatty acids circulate in the body?

In the blood bound noncovalently to serum albumin

91

Which lipid make up soap?

Fatty acid salt

92

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

- The ester hydrolysis of triacylglycerols using a strong base
- Lye (sodium or potassium hydroxide)

93

What can act as surfactants?

Soap

94

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

- They lower the surface tension at the surface of a liquid, serving as a detergent or emulsifier
- Forming micelles

95

What can micelles dissolve? Why does it wash away?

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

96

What is a micelle in terms of soap?

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

How does the human body store energy?

As glycogen and triacylglycerols

98

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

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