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Lipids and Biological Membranes > Lipids final -- 2019 > Flashcards

Lipids final -- 2019 Flashcards

1
Q

Lipids are the most disparate molecules and share a common physical property rather than what?

A

Lipids are the most disparate molecules and share a common physical property rather than a common structural aspect :

THEY ARE HYDROPHOBIC, NON POLAR MOLECULES

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2
Q

LIPIDS ARE A CLASS OF BIOLOGICAL MOLECULES DEFINED BY what?

A
  1. LOW SOULUBILITY IN WATER

2. HIGH SOLUBILITY IN NON POLAR SOLVENTS

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3
Q

What are the three major functions of LIPIDS?

A

LIPIDS, with physiological relevance for humans, have 3 major functions :

  1. They serve as structural components of biological membranes.
  2. They provide energy reserves : LIPIDS represent a highly reduced form of carbons that are oxidated in the specific metabolic process, giving great amount of energy.
  3. Lipids and lipid derivatives are biologically active molecules exerting a wide range of functions.
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4
Q

Describe more specifically about the functions of LIPIDS.

A
  1. Energy Stores
    - Triglycerides act as energy reserves. the majority of triglycerides are stored in adipose tissue, in adipocytes. (fat cells)
  2. Sources of Energy
    - Fatty acids are released from triglycerides are broken down in the mitochondria and used in the production of energy.
  3. Insulation
    - Subcutaneous adipose tissue is important in the maintenance of body temperature.
  4. Protection against Shock
    - Visceral fat protects organs like the kidneys
  5. Absorption
    - Phospholipids help to emulsify fats and increase absorption of fats and fat-soluble nutrients (e.g. sterols, vitamis)
  6. Local Hormones
    - Membrane phospholipids can be converted into hormone-like substances called ‘eicosanoids’ which control smooth muscle contraction, blood clotting and immune cell stimulation.
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5
Q

Why LIPIDIC STEROID CHOLESTEROL is important?

A

It is important itself but also for its derivatives; they are biologically active molecules and in particular.

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6
Q

Cholesterol is metabolised to what? (5 types)

A
  1. Sex Hormones - reproduction
  2. Corticosteroids - stress response
  3. Mineralcorticoids - blood pressure regulation
  4. Bile Acids - digestive health
  5. Vitamin D - immune modulation, cellular growth
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7
Q

Describe about the LIPIDS.

A
  1. Simple : FATTY ACIDS, OILS, WAXES, STEROIDS.
  2. Complex : TRIGLYCERIDES, GLYCEROPHOSPHOLIPIDS and SPHINGOPHOSPHOLIPIDS (or SPHINGOLIPIDS), GLYCOLIPIDS.
  3. Derivatives : HORMONES , FAT SOLUBLE VITAMINS, BILE SALTS, ETC.
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8
Q

Describe the structure of these LIPIDS.

  1. FATTY ACIDS
  2. WAXES
  3. TRIGLYCERIDES or TRIACYLGLYCEROLS
  4. GLYCEROPHOSPHOLIPIDS & SPHINGOPHOSPHOLIPIDS (or SPHINGOLIPIDS)
  5. GLYCOLIPIDS
  6. STEROIDS
  7. EICOSANOIDS
A
  1. FATTY ACIDS
    - Acylic chain + Carboxylic Acid
  2. WAXES
    - Fatty Acids + Alcohols
  3. TRIGLYCERIDES or TRIACYLGLYCEROLS
    - 3 Fatty Acids + Glycerol
  4. GLYCEROPHOSPHOLIPIDS & SPHINGOPHOSPHOLIPIDS (or SPHINGOLIPIDS)
    - 2 or 1 Fatty Acids + Glycerol or Sphingosine + Phosphate + X Compound
  5. GLYCOLIPIDS
    - 1 Fatty Acid + Sphingosine + X Compound
  6. STEROIDS
    - Derivatives of Cholesterol
  7. EICOSANOIDS
    - Derivatives of the Fatty Acid ARACHIDONIC ACID
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9
Q

What are the three roles in the organism of Fatty Acids?

A
  1. Fatty Acids are components of the structural lipids forming biological membranes.
  2. Fatty Acids are the main components of stored fats (Tyiglycerides).
  3. Fatty Acids are the precursors for the synthesis of bioactive lipids.
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10
Q

Fatty Acids are long-chain Hydrocarbon - Molecules containing what?

A

Fatty Acids are long-chain Hydrocarbon Molecules containing a CARBOXYLIC ACID GROUP.

  • The fatty acids have usually AN EVEN NUMBER of carbon atoms (with an odd number are more frequently in plants).
  • Fatty acids in general contain 12 at up to 20 carbon atoms.
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11
Q

At physiological PH value, the carboxyl group is readily ionized, and confers what on fatty acids?

A

At physiological PH value, the carboxyl group is readily ionized, and confers a NEGATIVE CHARGE on fatty acids.

  • The non polar tails interact with not covalent forces.
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12
Q

Fatty Acids containing carbon-carbon single bonds are named what?

A

SATURATED FATTY ACIDS.

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13
Q

Those containing double bonds at Fatty Acids are what?

A

UNSATURATED FATTY ACIDS.

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14
Q

Fatty Acids with multiple sites of unsaturation are the what?

A

POLYUNNSATURATED FATTY ACIDS (PUFAs).

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15
Q

What is SATURATED FATS?

A

Animal fats present in milk, butter and meat Vegetable oil like coconut and palm oils.

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16
Q

What is MONOSATURATED FATS?

A

Plant products such as : olive, avocado and peanut oils

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17
Q

What is POLYUNSATURATED FATS?

A

Plant products such as : corn, cottonseed, sunflower and soybean oils

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18
Q

The numeric description used for fatty acids starts with the number of what?

A

Starts with the number of carbon atoms, followed by the number of sites of unsaturation.

  • If they are no present, the number is ZERO (e.g., Palmitic acid is a 16-carbon fatty acid with NO UNSATURATION and is designated by 16:0).
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19
Q

Describe the features about Fatty Acid Nomenclature.

A
  1. Nomenclature reflects location of double bonds.
  2. Also used are common names (e.g., oleic stearic, palmitic)
  3. Linoleic Acid is also known as 18:2 n-6
    - i.e. FA is 18 carbons in length, has 2 double bonds, the first of which is on the 6th carbon, from the omega or methyl group end so it is known as an omega 6 fatty acid
  4. Arachidonic Acid = 20:4 n-6
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20
Q

What is Palmitic Acid?

A

Palmitic acid, or hexadecanoic acid in IUPAC nomenclature, is the most common saturated fatty acid found in animals, plants and microorganisms.

*Its chemical formula is CH3(CH2)14COOH, and its C:D is 16:0.

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21
Q

What are the type of Fatty Acid Structure?

A
  1. Carboxylic Acid (COOH is C1)
  2. Hydrocarbon Tails (C2 - C36)
  3. Saturated Fatty Acids (N:0)
  4. Unsaturated Fatty Acids (N:1,2,3,…)
  5. Double bonds specified by (delta times to the n)
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22
Q

There is free rotation about Carbon-Carbon bonds in the hydrocarbon chain, except for what?

A

Except for where there is a double bond, that is in CIS configuration.

  • The CIS double bonds produce a sort of elbow in the chain, which disturbs the not covalent forces by preventing the tails to package close to one another.
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23
Q

Double bonds in Fatty Acid prevents the free rotation around the bond, creating two configurations : what are these?

A
  1. CIS configuration
  2. TRANS configuration
    * These are geometrical isomers.
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24
Q

In CIS-form the hydrogen atoms of double bonded carbon atom oriented on which side?

A

It oriented on SAME SIDE.

  • The differences in geometry play an important role in biological processes.
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25
Q

In TRANS-form they oriented in which direction?

A

They oriented in OPPOSITE DIRECTION.

  • The differences in geometry play an important role in biological processes.
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26
Q

Thanks to the presence of the (what), the UNSATURATED FATTY ACIDS are more flexible and they can pack less closely with each other with respect to the SATURATED FATTY ACIDS.

A

Thanks to the presence of the CIS DOUBLE BONDS, the UNSATURATED FATTY ACIDS are more flexible and they can pack less closely with each other with respect to the SATURATED FATTY ACIDS.

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27
Q

The Negative Charge makes what?

A

The Negative Charge makes THE POLAR HEAD PROTION of the Fatty Acid even MORE POLAR AND HYDROPHILIC.

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28
Q

The salts of fatty acids are also called what?

A

The salts of fatty acids are also called SOAPS, and are con sidered AMPHIPATHIC, meaning they have a part that is very hydrophobic along with a part that is very hydrophilic.

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29
Q

What is the AMIPHIPATHIC?

A

An amphipathic molecule is a molecule that has both polar and non-polar parts.

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30
Q

What is the WAXES?

A

A WAX is a MONOESTER deriving from the reactionof a LONG-CHAIN MONOHYDROXYL ALCOHOL with A FATTY ACID MOLECULE.

31
Q

What is the different between ESTER with ETHER?

A

The main difference between ether and ester lies in their structure. An ester group requires two oxygen atoms and two carbon atoms to complete its characteristic structure, while an ether group only needs one oxygen atom and two carbon atoms for its structure.

32
Q

What is the biological role of WAXES?

A

WAXES are very HYDROPHOBIC molecules; they serve as protective water-proof coatings on leaves and fruit of plants and the skin, features and fur of animals.

  • E.G. water birds produce waxes in glands located under the wings.
33
Q

What is the GLANDS?

A

A gland is a group of cells in an animal’s body that synthesizes substances (such as hormones) for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland).

34
Q

What is the TRIGLYCERIDES?

A

TRIGLYCERIDES are the storage form of fatty acids in mammals.
- High triglyceride levels in the blood are a risk indicator for ARTHROSCLEROSIS

35
Q

(TRIGLYCERIDES)

GLYCEROL (glyceraldehyde derivative, it is also called glycerin) is a what?

A

It is a polyalcohol with three carbon atoms and 3 hydroxyl groups.
- The fatty acid chains c an react with the hydroxyl groups to form ESTERS.

36
Q

What is the ESTER?

A

Esters are a functional group commonly encountered in organic chemistry.

They are characterized by a carbon bound to three other atoms: a single bond to a carbon, a double bond to an oxygen, and a single bond to an oxygen.

Ester names are derived from the parent alcohol and the parent acid.

37
Q

(TRIGLYCERIDES)

In TRIGLYCERIDES, all of the 3 glycerol hydroxyl groups have what?

A

In triglycerides, all of the 3 glycerol hydroxyl groups have a FATTY ACID RESIDUE linked by 3 ester bonds.

  • They are known also as TRIACYLGLYCEROLS, NEUTRAL LIPIDS, or STORAGE LIPIDS.
38
Q

(TRIGLYCERIDES)

It is possible to distinguish these molecules in :

A
  1. SIMPLE
    TRIACYLGLYCEROLS with the same fatty acid in all of the 3 positions (e.g. 3 chains of Palmitic Acid)
  2. MIXED
    There are 2 or 3 different Hydrocarbon Chains linked to the glycerol structure (e.g. 1 oleic acid and 2 linoleic acids)
39
Q

(TRIGLYCERIDES)

The presence of CIS DOUBLE BONDS lowers the what?

A

The presence of CIS DOUBLE BONDS lowers the MELTING POINT
- Triglycerides with UNSATURATED FAs(FATTY ACIDS) have lower melting points than those having SATURATED FAs.

  • Melting Point is depending also on the chain length.
40
Q

TRIGLYCERIDES FROM ANIMALS TEND TO HAVE A HIGHER NUMBER OF WHAT??

A
  • TRIGLYCERIDES FROM ANIMALS TEND TO HAVE A HIGHER NUMBER OF SATURATED FATTY ACIDS.
  • MOST ARE SOLIDS AT ROOM TEMPERATURE (butter).
41
Q

(TRIGLYCERIDES)

DIFFERENTLY, TRIGLYCERIDES FROM PLANTS TEND TO HAVE WHAT??

A

It tend to have A HIGHER NUMBER OF UNSATURATED FATTY ACIDS.

  • MOST ARE LIQUID AT ROOM TEMPERATURE (olive oil)
42
Q

(TRIGLYCERIDES)
Oxidationof TRIGLYCERIDES

Unaturated and Saturated TRIGLYCERIDES can react with what?

A

Unsaturated and Saturated TRIGLYCERIDES can react with OXYGEN to produce small changes in fatty acids.

  • These often do not smell very good, and it is what happens when butter goes rancid and yellow.
43
Q

TRIGLYCERIDES are used by cells as a form of what?

A

TRYGLYCERIDES are used by cells as a form of STORED ENERGY.

  • In mammals the fats are stored in the adipocytes of adipose tissue.
44
Q

What is Phospholipids?

A

Phospholipids = STRUCTURAL LIPIDS ; there are two types of phospholipids

  1. Glycerophospholipids
  2. Sphingophospholipids
45
Q

What is the feature of GLYCEROPHOSPHOLIPIDS?

A

The common glycerophospholipids are lipids linked to head-group alcohols through a PHOSPHOESTER BOND.

The glycerophospholipids contain a large variety of fatty acids combined with the various alcoholic heads.

  • The two fatty acids tend to be non identical : They may differ in length and/or the presence or absence of double bonds.
  • Their distribution is very different not only in different organisms, but also in different tissued of the same organism.
46
Q

(GLYCEROPHOSPHOLIPIDS)

The polar head linked to phosphate can be which kind of charged?

A
  1. POSITIVELY CHARGED
    - Phosphatidylcholine
    - Phosphatidylethanolamine
  2. NEGATIVELY CHARGED
    - Phosphatidylinositol-4,5-bisphosphate
  3. NEUTRAL CHARGED
    - Phosphatidylserine
47
Q

What are the features of Phospholipid Structure?

A
  1. A glycerol esterified to 2 fatty acids (nonpolar).
    - The two fatty acids tend to be non-identical. They may differ in length and/or the presence or absence of double bonds.
  2. The third alcohol group on the glycerol is bonded to phosphoric acid through a phosphate ester bond (oxygen-phosphorus double bond oxygen)
  3. There is usually a complex amino alcohol also attached to the phosphate through a second phosphate ester bond. The complex amino alcohols include choline, ethanolamine, and the amino acid - serine (polar)
48
Q

Phospholipids are used commercially as what?

A

They are used commercially as emulsifying agents.

  • An emulsifying agent stabilizes and emulsion.
  • An emulsion is a colloidal suspension of one liquid in another.
  • An example is mayonnaise, which is a colloidal suspension of oil and water.
  • Lecithin, (or phosphatidylcholine) is used as an emulsifying agent in mayonnaise and other prepared foods.
49
Q

Are they similar functions between the sphingophospholipids with glycerophospholipids?

A

Yes , but structurally they are different.

  • There is NOT the GLYCEROL BACKBONE.
  • The glycerol and one of the fatty acids found in glycerophospholipids is replaced by SPHINGOSINE.
50
Q

SPINGOMYELIN has a what as head group?

A

It has a PHOSPHOCHOLINE or PHOSPHOETHANOLAMINE as head group.

51
Q

Sphingomyelins are common constituent of what?

A

Sphingomyelins are common constituent of plasma membranes and are important structural components of the myelin cover, the protective and insulating coating that surrounds nerves.

52
Q

Sphingomyelin, with a phosphocholine head group, is similar in size and shape to the what?

A

It is similar in size and shape to the glycerophospholipid phosphatidyl choline.

53
Q

Some sphingolipids have (what) as constituents of the polar head with no phosphate group.

A

Some spingolipids have SACCHARIDES as constituents of the polar head with no phosphate group.

  • These are called GLYCOSPHINGOLIPIDS = polar head consisting of one or more saccharides directly linked to the (-OH) of C1 without the phosphate bridge.
  • They have no net charge at pH 7.0
54
Q

Glycosphingolipids are distinguished as what?

A
  1. CEREBROSIDES
    = a single saccharide such as GLUCOSE or GALACTOSE as polar head.
  2. GLOBOSIDES
    = Polar head with 2 or slightly more saccharides, usually simple neutral Oligosaccharides with D-Glucose, D-Galactose, N-Acetylgalactosamine.
  3. GANGLIOSIDES
    = Polar head is formed by more complicated anionic more complicated anionic OLIGOSACCHARIDES, at up to 7-10 monosaccharide units are present; sometimes ending in one or more residues of sialic acid.
    * At pH 7.0 have a negative charge.
55
Q

What is Galactose?

A

It is a component of membranes of nervous tissue.

56
Q

What is Glucose?

A

In membranes of tissues, other than nervous.

57
Q

Glycosphingolipids specify what?

A

It specify cell identity.

  • Blood groups
  • O
  • A (+GalNac)
  • B (+Gal)
58
Q

What is the category of STEROIDS?

A

Steroids are a category of LIPID that is not derived from a FATTY ACID.
- They are based instead on a system of four cycloalkane rings that are fused together.

59
Q

What are the features of Steroid Structure?

A
  1. Steroid have a four ring structure consisting of 3 cyclohexane rings and 1 cyclopentane ring.
  2. Sterols are steroid alcohols, the most common is cholesterol.
60
Q

What are the characteristics of Cholesterol?

A
  1. Cholesterol, an important constituent of cell membranes, has a rigid ring system and a short branched hydrocarbon tail.
  2. Cholesterol is largely hydrophobic. But it has one polar group, a hydroxyl, making it amphipathic.
61
Q

Cholesterol is only found in where?

A

Only found in ANIMALS.

  • CHOLESTEROL is the steroid that used as the starting point for the synthesis of all other steroids, including the sex hormones, etc.
62
Q

Cholesterol is a minor but very important component of where?

A

It is minor but very important component of cell membranes, where it helps to maintain the fluidity of membranes.

63
Q

Cholesterol is largely (HYDROPHOBIC or HYDROPHILIC)?

A

It is largely HYDROPHOBIC due to a short branched hydrocarbon chain linked to the rigid ring system.

  • But it has one polar group, (little polar head) a HYDROXYL, that making it AMPHIPATHIC.
64
Q

CHOLESTEROL, is the most abundant WHICH STEROID?

A

It is the most abundant ANIMAL STEROID.

  • It has been estimated that a 60KG person has a total of about 175g of cholesterol distributed throughout the body.
  • Much part of this cholesterol is bonded through ESTER LINKS to fatty acids and are mainly present in LIPOPROTEINS, but it is also present as the FREE STEROID.
65
Q

CHOLESTEROL inserts into where?

A

It inserts into BILAYER MEMBRANES with its HYDROXYL GROUP oriented toward the aqueous phase and its HYDROPHOBIC RING SYSTEM ADJACENT to FATTY ACID CHAINS of PHOSPHOLIPIDS.

66
Q

The OH group of CHOLESTEROL forms what?

A

It forms hydrogen bonds with polar phospholipidic head groups.

67
Q

What does the liver produces?

A

The BILE ACIDS which is a clear, golden-yellow and viscous fluid.

  • It is stored in the gall bladder and is mainly useful for digestive system.
68
Q

What are the 3 features of STEROID HORMONES?

A
  1. Low solubility in water.
  2. Transported by proteins.
  3. Can pass through membranes.
69
Q

(About FAT-SOLUBLE VITAMINS)

What is the features of FAT-SOLUBLE VITAMINS?

A
  1. These are oily substances, not readily soluble in water and their biochemical functions are not well understood. They contain only carbon, hydrogen and oxygen.
    - Their examples are Vitamin A, D, E and K.
  2. They, however, play more specialized roles in certain group of animals and in particular type of activities.
70
Q

(About FAT-SOLUBLE VITAMINS)

What are the functions?

A
  1. The formation of a visual pigment (VITAMIN A).
  2. In the absorption of calcium and phosphorus from the vertebrate intestine (VITAMIN D).
  3. In protecting mitochondrial system from INACTIVATION (VITAMIN E).
  4. In formation of a blood clotting factor in vertebrates (VITAMIN K).
71
Q

(About FAT-SOLUBLE VITAMINS)

VITAMIN E is the collective name for a group of closely related lipids called what?

A

TOCOPHEROLS.

  • The various tocopherols differ from each other in substituents on carbon 5,7 and 8.
  • The tocopherols are excellent antioxidants. They prevent other vitamins presents in food (E.G., Vitamin A) from oxidative damage.
72
Q

On account of its preventive action on rickets, VITAMIN D is often called as what?

A

It is often called as ANTIRACHITIC FACTOR.

  • It is also known as ‘sunshine vitamine’ as its provitamin form present in human skin is easily converted.
  • At least 10 different compounds are known to have antirachitic properties and are designated as D2, D3 etc, but the two, 2 3 namely, VITAMIN D2 (ERGOCALCIFEROL) and VITAMIN D3 (CHOLECALCIFEROL) are more important.
73
Q

What are derived from ARACHIDONIC ACID 20:4(delta times to the 5,8,11,14)?

A

EICOSANOIDS

  1. PROSTAGLANDINS
    - C8-C12 bond generates 5 membered ring.
  2. THROMBOXANES
    - C8-C12 bond + Oxygen in heterocyclic ring.
  3. LEUKOTRIENES
    - Involved in asthma and other pathological processes.

Lipids and Biological Membranes (2 decks)

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