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Biochemistry > Lipids (2) > Flashcards

Lipids (2) Flashcards

1
Q

What is the meaning of the term hydrophobic?
Why is the hydrophobic nature of lipids important?

A

Hydrophobic means “water-hating.” If the body did not have such molecules, there could be no structure because the water would dissolve everything.

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2
Q

Oleic acid has a melting point of 16°C. If you converted the cis double bond into a trans double bond, what would happen to the melting point? Explain.

A

The melting point would increase. The trans double bonds would fit more in the packing of the long hydrophobic tails, creating more order and therefore more interaction between chains. This would require more energy to disrupt, and hence a higher melting point.

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3
Q

Which has the higher melting point: (a) a triglyceride containing only lauric acid and glycerol or (b) a triglyceride containing only stearic acid and glycerol?

A

(b), because its molecular weight is higher.

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4
Q

Predict the order of the melting points of triglycerides containing fatty acids, as follows:

(a) Palmitic, palmitic, stearic
(b) Oleic, stearic, palmitic
(c) Oleic, linoleic, oleic

A

lowest (c); then (b); highest (a)

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5
Q

Rank the following in order of increasing solubility in water (assuming that all are made with the same fatty acids): Explain your answer.
(a) triglycerides
(b) diglycerides
(c) monoglycerides

A

The more long-chain groups, the lower the solubility;
lowest (a); then (b); highest (c).

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6
Q

What are the main types of complex lipids, and what are the main characteristics of their structures?

A

Complex lipids can be classified into two groups: phospholipids and glycolipids. Phospholipids contain alcohol, two fatty acids, and a phosphate group. There are two types: glycerophospholipids and sphingolipids. In glycerophospholipids, the alcohol is glycerol. In sphingolipids, the alcohol is sphingosine. Glycolipids are complex lipids that contain carbohydrates.

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7
Q

How do the unsaturated fatty acids of the complex lipids contribute to the fluidity of a membrane?

A

The presence of cis double bonds in fatty acids produces greater fluidity because they cannot pack together as closely as saturated fatty acids.

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8
Q

What is the difference between an integral and
a peripheral membrane protein?

A

Integral membrane proteins are embedded in the membrane. Peripheral membrane proteins are found on membrane surfaces.

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9
Q

Name all the groups of complex lipids that contain ceramides.

A

21.25 Complex lipids that contain ceramides include sphingomyelin, sphingolipids, and the cerebroside glycolipids.

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10
Q

■ Enumerate the functional groups that contribute to the hydrophilic character of (a) glucocerebroside and (b) sphingomyelin.

A

The hydrophilic functional groups of (a) glucocerebroside: carbohydrate; hydroxyl and amide groups of the cerebroside. (b) Sphingomyelin: phosphate group; choline; hydroxyl and amide of ceramide.

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11
Q

Where can pure cholesterol crystals be found in the body?

A

Cholesterol crystals may be found in (1) gallstones, which are sometimes pure cholesterol, and (2) joints of people suffering from bursitis.

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12
Q

How does LDL deliver its cholesterol to the cells?

A

LDL from the bloodstream enters the cells by binding to LDL receptor proteins on the surface. After binding, the LDL is transported inside the cells, where cholesterol is released by enzymatic degradation of the LDL.

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13
Q

How does VLDL become LDL?

A

Removing lipids from the triglyceride cores of VLDL particles increases the density of the particles and converts them from VLDL to LDL particles.

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14
Q

How does the serum cholesterol level control both cholesterol synthesis in the liver and LDL uptake?

A

When serum cholesterol concentration is high, the synthesis of cholesterol in the liver is inhibited and the synthesis of LDL receptors in the cell is increased. Serum cholesterol levels control the formation of cholesterol in the
liver by regulating enzymes that synthesize cholesterol.

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15
Q
A

Estradiol (E) is synthesized from progesterone (P) through the intermediate testosterone (T). First, the D-ring acetyl group of P is converted to a hydroxyl group and T is produced. The methyl group in T, at the junction of rings A and B, is removed, and ring A becomes aromatic. The keto group in P and T is converted to a hydroxyl group in E.

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16
Q

What are Lipids?

A
  • found in living organisms
  • insoluble in water
  • soluble in nonpolar or low-polar solvents
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17
Q
  • found in living organisms
  • insoluble in water
  • soluble in nonpolar or low-polar solvents
A

Lipids

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18
Q

3 major roles of lipids in human biochemistry

A
  • store energy within the fat cells
  • part of the membrane that separates compartments of aqueous solution from each other
  • serves as chemical messenger
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19
Q

Classification of Lipids

A
  • Simple lipids
  • Compound lipids
  • Terpenes and Steroids
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20
Q

are physiologically potent regulatory
molecules such as prostaglandins,
thromboxanes and leukotrienes

A

Eicosanoids

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21
Q

– solid at room temperature
– obtained from animal sources
– contain a greater proportion of saturated fatty acids

A

fats

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22
Q
  • liquid at room temperature
  • of plant origin
  • contain a greater percentage of unsaturated fatty acids
A

oils

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23
Q

are esters composed of three fatty acids joined to the trihydroxy alcohol, glycerol.

A

Triglycerides or triacylglycerols (TAG)

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24
Q
  • are long-chain monocarboxylic acids
  • contains even number of carbon atoms (the consequence of their biosynthesis)
  • most common: 12–18 C
A

Fatty Acids

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25
Q

melting points of saturated fatty acids decrease with decreasing carbon number.

A

TRUE. melting points of saturated fatty acids increase with increasing carbon number.

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26
Q

saturated fatty acids containing ten or more carbons are LIQUID at room temperature.

A

FALSE. saturated fatty acids containing ten or more carbons are SOLID at room temperature.

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27
Q

melting point of a saturated fatty acid is greater than that of an unsaturated fatty acid of the same chain length.

A

TRUE. melting point of a saturated fatty acid is greater than that of an unsaturated fatty acid of the same chain length.

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28
Q
  • a precursor for the synthesis of prostacyclin
  • inhibits the clumping of platelets
  • reduces clot formation.
A

EPA

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29
Q
  • one of the major fatty acids in the phospholipids of sperm and brain cells and retina
  • reduce triglyceride levels (although the mechanism is not understood).
A

DHA

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30
Q
  • reduce the incidence of cardiovascular disease
  • not clear whether it acts alone or because it is the precursor of DHA and EPA.
A

ALA

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31
Q

essential fatty acid, required for the synthesis of arachidonic acid, the precursor for many prostaglandins.

A

Linoleic acid

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32
Q
  • precursors of prostaglandins
  • anti-inflammatory effects
A

Omega-3 fatty acids

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33
Q
  • precursors to prostaglandins
  • inflammatory effects.
A

Omega-6 fatty acids

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34
Q
  • colorless, tasteless, and odorless
  • characteristic colors, odors, and flavors associated with lipids are imparted to them by foreign substances that have been absorbed by the lipid and are soluble in them.
A

Pure fats & Oils

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35
Q

– addition of H2 to double bonds of unsaturated fatty acids in lipids, converting them to single bonds of saturated fatty acids.

A

Hydrogenation

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36
Q

best way to convert unsaturated liquid oils to solids

A

Hydrogenation

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37
Q

Complete hydrogenation gives a very SOFT product

A

FALSE. BRITTLE

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38
Q

partial hydrogenation of a liquid vegetable oil changes it to a SOFT, semisolid fat.

A

TRUE

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39
Q

addition of water to ester bonds of lipids in the
presence of strong acids or digestive enzymes called lipases.

A

Hydrolysis

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40
Q

the reaction of lipids with a strong base (alkaline
hydrolysis) to give glycerol and salts of the fatty acids

A

Saponification

41
Q

sulfates of fatty acids or sulfonate salts of hydrocarbons

A

Anionic detergents

42
Q

referred to as inverted soap because their water-soluble end carries a positive, rather than negative charge; widely used in hospitals, good cleansing agents, have germicidal properties

A

Cationic detergents

43
Q

contain polar covalent structures that provide the required water solubility; used extensively in dishwashing liquid and on all occasions that call for the absence of inorganic ions.

A

Nonionic detergents

44
Q
  • a fat or oil becomes rancid when its double bonds are oxidized by oxygen and microorganisms.
  • the oxidation products are short – chain fatty acids and aldehydes that have very disagreeable odors.
A

Oxidation

45
Q

fat and oil develop a disagreeable odor caused by hydrolysis and oxidation.

A

Rancidity

46
Q

Under moist and warm conditions, ______
of the ester linkages occurs, liberating the volatile acids. Microorganisms present in the air furnish the enzyme (lipases) that catalyze the process. Rancidity can easily be prevented by storing butter covered in a refrigerator.

A

Hydrolytic rancidity

47
Q

Rancidity occurs in triglycerides containing unsaturated fatty acids.

A

Oxidative rancidity

48
Q

are compounds added to foods in very small amounts (0.01–0.001%) to suppress rancidity.

A

Antioxidants

49
Q

is an ester of a saturated fatty acid and a
long-chain alcohol, each containing from 14 to 30 carbon atoms.

A

wax

50
Q

found in the surfaces of leaves and stems and
serve to protect the plant from dehydration and from invasion by harmful organisms.

A

Plant waxes

51
Q

also serve as protective coatings; found on the
the surface of feathers, skin, and hair and help keep these surfaces soft and pliable

A

Animal waxes

52
Q

similar to soap and detergents because of hydrophobic tails and hydrophilic heads but differs in having two tails instead of one.

A

membrane lipids

53
Q

are the primary components in the cellular membrane (lipid bilayer)

A

Phospholipids

54
Q

substances that can coat droplets of nonpolar liquids and hold them in water. suspension in water.

A

Emulsifying agents

55
Q

contains the important quaternary ammonium
salt, choline, joined to the phosphoric acid residue.

A

Lecithin

56
Q

ethanolamine or serine, is linked to the phosphate moiety

A

Cephalins

57
Q

characterized by the presence of a single monosaccharide head group;

A

Cerebrosides

58
Q

the coating of nerve axons, conataining a different kind of complex lipid

A

Myelin

59
Q
  • most important lipids in the myelin sheaths of nerve cells
  • associated with diseases such as multiple sclerosis
A

Sphingomyelins

60
Q

found in the membranes of macrophages (cells that protect the body by ingesting and destroying foreign microorganisms)

A

glucocerebroside

61
Q

found almost exclusively in the membranes of brain cells

A

galactocerebroside

62
Q
  • possess oligosaccharide groups, including one or more molecules of N -acetylneuraminic acid (sialic acid)
  • found in most tissues in the body.
A

Gangliosides

63
Q

The important feature of biological membranes

A
  1. Membrane fluidity
  2. Selective permeability
  3. Self-sealing capability
  4. Asymmetry
64
Q

Transport wherein there is no direct energy input.

A

Passive transport

65
Q

– molecules move through a membrane down
a concentration gradient (towards lower concentration)

A

simple diffusion

66
Q

molecules move through protein channels in membrane; permease,
- a membrane protein assists in diffusion.

A

facilitated diffusion

67
Q

Transport that requires energy.

A

Active transport

68
Q

– energy is provided by ATP (e.g., Na+ - K+ pump system)

A

primary

69
Q

concentration gradients generated by the primary active transport are used to move substances across membranes (e.g., Na+
gradient from Na+- K+the pump system is used to transport glucose in kidney tubules).

A

secondary

70
Q
  • The most common and important complex lipids
  • which are responsible for the transport of other lipids in the body.
A

plasma lipoproteins

71
Q

4 major classes of human plasma lipoproteins

A
  • Chylomicrons
  • Very low density lipoproteins (VLDL)
  • Low-density lipoproteins (LDL)
  • High-density lipoproteins (HDL)
72
Q

– carry dietary triglycerides from the intestine to other tissues.

A

Chylomicrons

73
Q

– bind triglycerides synthesized in the liver and carry them to adipose and other tissues for storage.

A

Very low density lipoproteins (VLDL)

74
Q

– carries cholesterol to peripheral tissues and help regulate cholesterol levels in those tissues; richest in cholesterol, frequently carrying 40% of the plasma cholesterol; allows accumulation.

A

Low-density lipoproteins (LDL)

75
Q

– bound to plasma cholesterol; however, they transport cholesterol from peripheral tissues to the liver for removal.

A

High-density lipoproteins (HDL)

76
Q

2 Important function of cholesterol

A
  1. Regulator of membrane fluidity
  2. Cholesterol serves as the body’s starting material for the synthesis of all other steroids (e.g. steroid hormones and bile salts).
77
Q

2 major classes of steroid hormone

A
  1. Sex hormones
  2. Adrenocortical hormones
78
Q

Sex hormones essential for preparing the uterus for implantation of a fertilized ovum during pregnancy.

A

progestin e.g. progesterone

79
Q

regulate a variety of metabolic processes

A

Adrenocortical hormones

80
Q

Aldosterone controls tissue swelling by regulating the delicate cellular salt balance between Na+ and K

A

mineralocorticoids

81
Q

Involved in the regulation of glucose metabolism and in the control of inflammation (e.g. used in the treatment of rheumatoid arthritis, asthma, GI disorder, many skin conditions and a variety of other diseases).

A

glucocorticoids e.g. hydrocortisone and cortisone

82
Q
  • oral contraceptives and anabolic agents.
A

Synthetic Steroids

83
Q

produced by the liver (from cholesterol), stored in the gall bladder and secreted into the intestine.

A

Bile Salts

84
Q

play a major role in the regulation of calcium and phosphorus metabolism.

A

Vitamin D

85
Q

ergocalciferol (vegetable origin)

A

Vitamin D2

86
Q

cholecalciferol (animal origin);

A

Vitamin D3

87
Q

One of the most important of these compounds vitamins is formed from cholesterol by the action of ultraviolet radiation from the sun.

A

vitamin D

88
Q

These lipids are found in the oils of some plants and flowers that give them their characteristic odors and colors.

A

Terpenes

89
Q

Terpenes are composed of two or more sections containing five-carbon conjugated structure called _______.

A

isoprene

90
Q

Vitamins required for the formation of the visual a pigment found in the retina of the eye.

A

Vitamin A

91
Q
  • Vitamins found in the plant world in the form of carotenes.
A

Provitamin A

92
Q

(α-tocopherol) prevents oxidation of unsaturated fatty acids in cellular membranes
(antioxidant).

A

Vitamin E

93
Q
  • antihemorrhagic vitamin
    – needed in the formation of prothrombin for blood clotting (phylloquinone)
  • synthesized by intestinal bacteria.
A

Vitamin K

94
Q
  • are hormone-like molecules.
  • not transported in the bloodstream to their site of action but exert their effects in the tissues where they are synthesized.
  • The name ______is derived from the Greek word ____, meaning twenty, because they are all derivatives of 20 carbon fatty acids, arachidonic acid.
A

Eicosanoids:eikos

95
Q

is the precursor for the different
prostaglandins, leukotrienes and thromboxanes.

A

Arachidonic acid

96
Q

unsaturated carboxylic acids consisting of a
20–carbon skeleton that contains a cyclopentane ring; extremely potent biological molecules with hormone-like activity.

A

Prostaglandins

97
Q

– contain three conjugated double bonds and
differ from prostaglandins by the absence of the ring.

A

Leukotrienes

98
Q

– differ from the other eicosanoids in that their
structures have a cyclic ether; thromboxane A2
- the most prominent member of this group, is primarily produced by platelets; ____ -promotes platelet aggregation and smooth muscle contraction.

A

Thromboxanes

Biochemistry (10 decks)

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