Chapter 10: Lipids

Question 1

1. What do Storage Lipids contain and what are they built to do?
2. What do Structural Lipids contain and what are they built to do?
3. What do Other Lipids contain and what are they built to do?

Answer 1

1. Contain fatty acids and oils. Built to make them stable and easy to disassemble.
2. Contain phospholipids and sterols. Built to provide stability and mobility for membrane components.
3. Contain cofactors, electron carriers, pigments, hydrophobic anchors, hormones, intracellular messengers. Built for specialized functions.

Question 2

1. What makes up the backbone?
2. What are fatty acids made of?
3. What moleules complex rings?

Answer 2

1. Sphingosine and Glycerol
2. Hydrocarbons
3. Cholesterol and derivatives, Cofactors, Signaling molecules, and vitamins.

Question 3

1. Which molecules are storage lipids?
2. What is the structure of fatty acids? What may they be? What may they contain?
3. What do biological fatty acids not contain?
4. What are the double bonds usually separated by?

Answer 3

1. Fatty Acids and Glycerol
2. Hydrocarbon Derivatives, Carboxylic Acids with hydrocarbon chains (4-36 carbons). May be fully or partly saturated. Branched or unbranched. May contain three-carbon rings and R-groups: methyl and hydroxyl.
3. Do not usually contain conjugated double bonds.
   
   1. -CH=CH-CH=CH-
4. Usually separated by a methylene group (enzymes recognize this).
   
   1. -CH=CH-CH2-CH=CH-

Question 4

1. What is the basic setup of Fatty Acid nomenclature?
2. How many double bonds do monounsaturated fatty acids contain?
3. How many double bonds do polyunsaturated fatty acids contain?
4. How many carbons do common fatty acids contain? Do they contain an even number of carbons? How are they build?

Answer 4

1. Based on chain length : double bond character (Palmitic acid 16:0, Oleic acid 18:1)
2. one double bond
3. more than one double bond
4. 12-24 carbons, unbranched chains
   
   1. Even number of carbons
   2. Acetate condensation (two carbons) = even number.

Question 5

1. Are the chains of storage lipids polar or non-polar? Are they water-soluble?
2. What are storage lipids physical properties at room temperature?
3. What form do saturated chains take?
4. What form do unsaturated chains take?

Answer 5

1. Chain is non-polar.
   
   1. Fatty acids tend to be poorly water-soluble.
   2. Slight solubility in water is due to carboxyl groups.
2. At room temperature saturated fatty acids are waxy solids. Unsaturated fatty acids are more liquid, oily
3. Saturated chains are linear.
4. Unsaturated chains contain bends.

Question 6

1. What are Triacylglycerols?
2. What do they contain?
3. What kinds of bonds do they contain?
4. What are their properties?
5. What are Triacylglycerols the storage form of?
6. What are they cleaved by?
7. What are some advantages of using Triacylglycerols as fuels?

Answer 6

1. Glycerol and Fatty Acids
2. Glycerol + 3 fatty acids
3. Ester bonds
4. Hydrophobic, nonpolar Nearly insoluble in water
5. The storage form of both glycerol and fatty acids
6. Cleaved by Lipases: hydrolyze ester linkages
7. Hydrophobic: No solvation layer for each molecule. One layer around many molecules, saves energy!
   1. Carbon atoms are highly reduced: Yield more energy than carbohydrates through oxidation (that is, catabolic pathways)
   2. Example: 15 mg of triacylglycerols = ~1,350 mg of glycogen

Question 7

1. What are waxes?
2. Are their melting points higher than Triacylglycerols?
3. What are they derived from?

Answer 7

1. Esters of Long chain (14-36 carbon) saturated/unsaturated fatty acids + Long chain (16-30 carbon) alcohols
2. Melting points are higher than triacylglycerols
   
   1. Waterproofers for feathers
   2. Prevent evaporation from holly, rhododendron, poison ivy
   3. Polishes and lotions
3. Derived from palm, lanolin (sheep’s wool), beeswax

Question 8

1. What make up Glycerophospholipids?
2. What make up Spingolipids?
3. What make up Sterols?
4. What are the above three classes examples of?
5. What makes up Phospholipids?
6. What makes up Glycolipids?

Answer 8

1. Glycerophospholipids: Two fatty acids joined to glycerol
2. Spingolipids: One fatty acid + one fatty amine (sphingosine)
3. Sterols: Rigid core of four fused hydrocarbon rings
4. Above three are membrane lipid classes
5. Phospholipids: Some glycerophospholipids and sphingolipids with a polar head group + fatty acid
6. Glycolipids: Some sphingolipids with a simple sugar instead of phosphate

Question 9

1. What is the general structure of Glycerophospholipids?
2. What part of the molecule is chiral and which is not?

Answer 9

1. General Structure Glycerol:
   
   1. C1 fatty acid
   2. C2 fatty acid
   3. C3 phosphate + polar head group (alcohol)
2. Glycerol is not chiral BUT Glycerol + phosphate is chiral

Question 10

1. What are Ether Lipids?
2. What is their functional significance?
3. What my they function in?

Answer 10

1. Phospholipids with fatty acids in ether linkages. About 50% of heart phospholipids are plasmalogens
2. Functional significance of ether, rather than ester, linkage not known.
3. MAY function in membrane trafficking, anti-tumor agents
   
   1. No strong evidence supports positive roles in health

Question 11

1. What is the structure of Sphingolipids?
2. What are they derived from?
3. What is the structure of Ceramide?
4. What are their functions?

Answer 11

1. 3-carbon backbone: Sphingosine + long chain FA + Polar Head Group. Head group joined by phosphodiester or glycosidic linkage.
2. Derived from Sphingosine.
3. Ceramide: FA is attached to an amide at C2 = The Parent sphingolipid
4. Function:
   
   1. Cell recognition molecules, especially in neurons.
   2. Blood group determinants (A, B, O System)

Question 12

1. How do the three classes of Sphingomyelins differ?
2. Class 1: Sphingomyelins
   
   1. What is their head group?
   2. What are they similar to?
3. Class 2: Glycosphingolipids.
   
   1. Where are they contained?
   2. What do their head groups consist of?
   3. What are Cerebrosides?
   4. What are Globosides?
   5. What separates Blood Group Antigens?
4. Class 3: Gangliosides
   
   1. What are their head groups?
   2. What does the carbohydrate portion contain?

Answer 12

1. Differ in head groups.
2. Class 1: Sphingomyelins
   
   1. Head group = phosphocholine or phosphoethanolamine.
   2. Therefore, they are phospholipids similar to phosphatidylcholine: No net charge on the head group at physiological pH.
3. Class 2: Glycosphingolipids.
   1. Mostly on the outer face of the plasma membrane.
   2. Head groups have one or more sugars on C1 of ceramid.
   3. Cerebrosides: one sugar on ceramide.
   4. Globosides: more than one sugar on ceramide. No net charge at pH 7.0 = Neutral Glycolipids
4. Class 3. Gangliosides:
   
   1. Polar head groups = Oligosaccharides
   2. Carbohydrate portion has one or more N-acetylneuraminic acids (a sialic acid).

Question 13

1. How are Galactolipids different from other molecules?
2. Where are they located?
3. How numerous are they?

Answer 13

1. No nitrogen: Different from Glycosphingolipids. No phosphate: Plants conserve phosphate
2. Located in the thylakoid membranes of chloroplast.
3. The most abundant membrane lipids on earth.

Question 14

1. Metabolism of Phospholipids and Sphingolipids: What are signaling products a result of?
2. What do membrane lipids become?
3. What do Phospholipases cleave?
4. What is the product? How is the function of this newly formed molecule?
5. How are different signaling molecules made?

Answer 14

1. Results from a cleavage of certain lipid bonds by specific enzymes.
2. Membrane lipids become signaling molecules.
3. Cleave phospholipids.
4. Product is a Lysophospholipid. Functions in signaling, one secondary product is a fatty acid
5. Different signaling products result from cleavage of certain bonds by specific enzymes. Such as Diacylglycerol.

Question 15

1. What kind of cells do not synthesized Sterols?
2. What is the Sterol nucleus composed of?
3. What is it produced from?

Answer 15

1. Bacterial cells
2. Nucleus:
   
   1. Three 6-carbon rings.
   2. One 5-carbon ring.
   3. Nearly planar
3. Produced from acetate: CH₃-COO- (Two carbons)

Question 16

1. Functions of Sterols: Passive Role: Structural Lipids: What kind of kind molecule is Cholesterol?
2. What does Cholesterol alter?
3. What does addition of cholesterol do at low temperatures?
4. What does addition of cholesterol do at high temperatures?
5. Active Roles: What are steroid hormones involved in?
6. What do bile acids do?
7. What are they precursors for?

Answer 16

1. Cholesterol is amphipathic, polar head group + nonpolar tail.
2. Alters membrane fluidity and assist in lipid transport.
3. Prevents hydrocarbon crystalization
4. Decreases overall fluidity.
5. They are potent signals for gene expression.
6. Emulsify fats to make them more accessible for degradation.
7. Vitamins and hormones

Question 17

1. What are the functions of second messengers?
2. What can happen to Phosphatidylinsitol?
   
   1. Where do they reside?
   2. What are their derivitives?
3. Where is Phosphatidylinositol 4,5-biophosphate (PIP2) located?
4. What are PIP2s fuctions?
5. What is PIP2 converted into?
6. What is this new molecule cause?
7. What is unique about calcium?
8. What is Diacylglycerol?
9. What does Protein Kinase C do after it is activiated?

Answer 17

1. A “signal” induces the activation of reactions that produce other molecules and amplify the initial signal.
   
   1. The “other molecules” are second messengers.
   2. The amplification may be in several steps and is part of a Signal Transduction Pathway.
2. Can become phosphorylated in several places.
   
   1. Phosphatidylinositol resides in the plasma membrane.
   2. Derivatives are Second Messengers
3. A lipid on the inner surface of plasma membrane,
4. Functions to…
   
   1. Bind cytoskeletal proteins
   2. Bind specific soluble proteins to promote membrane fusion.
   3. Bind second messengers after receptor-ligand interactions
5. Inositol 1,4,5-trisphosphate (IP3) + diacylglycerol Phospholipase C
6. IP3 is a second messenger: Causes release of intracellular calcium.
7. Calcium is a second messenger and cofactor for Protein Kinase C.
8. Diacylglycerol is a second messenger and cofactor for Protein Kinase C. Protein kinase C becomes active.
9. Phosphorylates proteins.

Question 18

1. Where do Paracrine Hormones act?
2. What are some functions?
3. What are they derivitives of?
4. What are the three classes?

Answer 18

1. Act near where they are released
2. Diverse Functions: Inflammation (Fever), Pain response (Regulation of blood pressure), Blood clot formation (Gastric acid release).
3. Derivatives of Arachidonic acid (20 carbons).
4. Prostaglandins, Thromboxanes, and Leukotrienes.

Question 19

1. What do Prostaglandins (Eicosanoids) consist up?
2. What are the two types of groups?
3. How do they regulate cAMP?
4. What is cAMP?
5. What do Thromboxanes consist up?
6. What are they produced by?
7. What activities are they involved in?
8. How is synthesis inhibited?
9. What do Leukotrienes contain?
10. What type of struture do they have?
11. What are their function?
12. What does an overproduction of this molecule cause?

Answer 19

1. One 5-carbon ring
2. Two groups with many subtypes:
   
   1. PG E = ether-soluble
   2. PG F = phosphate (water) soluble
3. Regulate cAMP synthesis through Adenylate Cyclase.
4. cAMP is a second messenger and a co-factor.
5. One 6-carbon ring
6. Produced by platelets
7. Involved in platelet-derived activities like clotting.
8. Synthesis is inhibited by non-steroidal anti-inflammatory drugs.
9. Contains 3 conjugated double bonds.
10. Open structure
11. Serve as signaling molecules.
12. Overproduction causes asthma attacks and contributes to anaphyllactic shock.

Question 20

1. Where do steroid hormones opperate?
2. What are they derivatives of?
3. How are they transported?
   
   1. Do they have specificity?
   2. Do they have a high binding affinity?
   3. What do they induce?
4. What are their functions?

Answer 20

1. Act as messengers between tissues.
2. Oxidative derivatives of sterol. Sterol nucleus but no alkyl side chain.
3. Move through the blood stream as a complex with proteins.
   
   1. Bind to specific receptors.
   2. Bind with high affinity (Low concentrations have maximal effects)
   3. Induce gene expression and changes in metabolism.
4. Functions: Gender hormones, Anti-inflammatory drugs, Treat asthma and arthritis.

Question 21

1. What are vitamines A (Retinol) and D and example of?
2. What are the functions of its derivatives? What does Retinoic acid do?
3. What is Retinal? What does it produce?
4. What can deficiencies lead to?

Answer 21

1. Example of Lipids that are Hormone Precursors
2. Derivatives are metabolic and cell regulators. Retinoic acid regulates epithelial cell gene expression through nuclear receptors
3. Retinal: a photosensitive pigment in rod and cone cells.
   
   1. Produces a neuronal response
   2. Precursor is β-carotene.
4. Deficiencies lead to skin and eyes disorders (wrinkles and night blindness).

Question 22

1. What does separation of lipids utilize?
2. During lipid extraction what organic solvent is used for natural lipids, and which are used for membrane lipids?
3. What is the method?

Answer 22

1. Differences in polarity, differences in solubility in non-polar solvents.
2. Natural lipids use: Ethyl ether, chloroform or benzene. Membrane lipids use: polar organic solvents (ethanol or methanol).
3. Phase extraction using 1(Chloroform):2(methanol):0.8(water). Solvents reduce weak interactions.
   
   1. This one phase extracts all lipids.
   2. Addition of more water and it separates into two phases. Water/methanol phase on top with proteins and sugars (organic phase) on bottom with lipids.

Question 23

1. What does absoption chromatography separate lipids based on?
2. What is the column packed with?
3. Where do polar lipids bind? Where do neutral lipids bind?
4. Which lipids will elute first?
   
   1. How are left over lipids eluted?
   2. What are very polar lipids eluted with?

Answer 23

1. Separation based on polarity.
2. Insoluble polar material (silica).
3. Polar lipids bind to the column, neutral lipids do not bind to the column.
4. Neutral lipids will elute after the first wash with chloroform.
   
   1. By using solvents with increased polarity.
   2. Alcohol

Question 24

1. What Gas-Liquid Chromatography used for?
2. How are lipids separated?
3. How does this method work?
4. What does order of elution depend on?

Answer 24

1. Separates charged lipids best.
2. By solubility and volatility in solvent.
3. Goes from liquid to gas states with increased temperature. Many lipids are naturally volatile, those that are not have to be derivatized in order to separate them.
4. Nature of the solid column support, boiling point of the lipid.