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Biochem Ch. 11
Lipids
| Question | Answer |
|---|---|
| Lipids | molecules that are not soluble in water, but are soluble in organic solvents. |
| What are five classes of lipids we will examine? | free fatty acids, triacylglycerols, phospholipids, glycolipids, and steroids |
| Free fatty acids | a common fuel |
| Triacylglycerols | Storage form of fatty acids. |
| Phospholipids | Membrane lipids. |
| Glycolipids | Membrane lipids composed in part of carbohydrates. |
| Steroids | Polycyclic hydrocarbons with a variety of functions. |
| Fatty acids are a main source of _____ | fuel |
| fatty acids hydrocarbon chains that have a __________ _____ at one end a and a _______ group at the other end | carboxylic acid, methyl group |
| fatty acids may be ________ or __________ | saturated or unsaturated |
| What are two key roles of fatty acids? | they act as fuels and as building blocks for membrane lipids |
| Fats are better fuels than carbohydrates. Why? | their carbons are bonded to hydrogens and other carbons, rather than oxygen (greater reduction) |
| a fatty acid's systematic name is derived from what? | the name of its parent hydrocarbon by the substitution of oic for the final e |
| Systematic name of fatty acids: ex) the C18 saturated fatty acid is systematically called what? | octadecanoic acid (parent hydrocarbon is octadecane) |
| Fatty acids composed of single bonds only are called __________ fatty acids | saturated (every carbon atom is attached to 4 other atoms |
| Fatty acids with double or triple bonds are called _________ fatty acids | unsaturated |
| Systematic name of fatty acids: ex) the C18 saturated fatty acid that contains a double bond is systematically called what? | octadecenoic acid (18:1) |
| Systematic name of fatty acids: ex) the C18 saturated fatty acid that contains two double bonds is systematically called what? | octadecadienoic acid (18:2) |
| Systematic name of fatty acids: ex) the C18 saturated fatty acid that contains three double bonds is systematically called what? | octadecatrienoic acid (18:3) |
| How are the carbon atoms in fatty acids numbered? | beginning with the carboxyl terminal carbon atom |
| Carbon atoms 2 and 3 are often referred to as __ and __, respectively | α and β |
| Fatty acids can also be numbered from the methyl carbon atom, which is called the __- carbon. | omega (ω) |
| How are the positions of double bonds indicated? | with the symbol Δ, with the first atom of the double bond indicated by superscript number. (ex: Δ9 indicates a double bond between carbon atoms 9 and 10.) |
| ___ and ___ designate the relative positions of substituents on either side of the double bond | cis and trans |
| Just like amino acids, fatty acids are _________ at physiological pH and so it is preferable to refer to them according to their carboxylate form. | ionized |
| The carboxyl group has a low pKa (2-4). Thus, at physiological pH, the COOH is ____________ | deprotonated (COO-) |
| Fatty acids in biological systems usually contain an ____ number of carbon atoms with the 16 and 18 carbon atom chains the most common. | even |
| When double bonds are present, they are most commonly found in the ____ configuration | cis |
| In polyunsaturated fatty acids, the double bonds are separated by at least one ______ group. | methylene group (-CH2-) |
| The properties of fatty acids and of lipids derived from them are dependent on what two things? | chain length and degree of saturation |
| Unsaturated fatty acids have ________ melting points than those of saturated fatty acids of the same length | lower (the shorter the chain, the less interactions = more fluid) |
| What does the presence of a cis double bond do? | introduces a kink in the fatty acid, making tight packing between the chains impossible. This limits the van der Waals interactions between chains, LOWERING the melting point |
| Therefor, a short chain length and the presence of a cis double bond _______ the fluidity of fatty acids | enhances |
| Although fat are crucial biochemicals, too much _________ and ____-________ fats in a diet are correlated with high blood levels of cholesterol and cardiovascular disease. | saturated, trans-saturated |
| Cis polyunsaturated fatty acids are essential components of our diets. Why? | we cannot synthesize them |
| ω-3 oils are also called the supersaturated oils due to the presence of _#_ double bonds, i.e., Δ9, 12, 15. | 3 (ω-6 oils have two double bonds, i.e., Δ9, 12) |
| What are the important ω-3 fatty acids? | α-linolenate (foudn in vegetable oils), and eicosapentaenoate (EPA) and docosahexaenoate (DHA) both of which are found in fatty fish and shellfish |
| these fatty acids are __________ to important hormones and appear to offer some protection from coronary heart disease. | precursors |
| Although fatty acids are our principle energy source, free fatty acid concentration in cells or blood is low. why? | because free fatty acids are strong acids that would disrupt the pH balance of cells |
| Fatty acids are stored as ____________ in which three fatty acids are esterified (linked with ester-linkages) to one molecule of glycerol. | triacylglycerols |
| In mammals, the major site for triacylglycerol storage is ________ tissue. | adipose |
| Each adipocyte (adipose cell or fat cell) contains a large ______ droplet, in which the triacylglycerols are housed. | lipid |
| Triacylglycerols are energy rich. why? | they are hydrophobic and are stored in a nearly anhydrous form (containing NO water) |
| Because triacylglycerols are hydrophobic and reduced, a gram of anhydrous fat stores more than _#_ times the energy of a gram of hydrated glycogen. | six (glycogen is a polymer of glucose-typically water soluble) |
| What are the three common lipids found in membranes? | Phospholipids, Glycolipids, and Cholesterol |
| Phospholipids: Composed of four components. What are they? | fatty acids (2 or more), a glycerol backbone, a phosphate, and an alcohol. |
| Phospholipids: The platform on which phospholipids are built may be glycerol, or sphingosine. Phospholipids with a glycerol backbone are called ________________ or ________________. | phosphoglycerides or phosphoglycerols. |
| Phospholipids: The platform on which phospholipids are built may be glycerol, or sphingosine. Phospholipids with a sphingosine backbone are called ________________ | sphingo- or glycolipids |
| Phospholipids: Phosphoglycerides, the hydroxyl groups at C# and C# of glycerol are esterified to the carboxyl groups of the two fatty acid chains. | C1 and C2 |
| Phospholipids: The major phospholipids are derived from ____________ | phosphatidate |
| Phospholipids: What is the general structure for phospholipids? | two fatty acids = glycerol - phosphate - alchohol |
| Membrane lipids can include _____________ | carbohydrates |
| Glycolipids, as their name implies, are _______-containing lipids | sugar |
| Glycolipids are ubiquitous in all cell membranes, where they play role in what? | cell to cell interaction |
| How do glycolipids differ from sphingolipids? | the unit that is linked to the primary hydroxyl group of the sphingosine backbone |
| Glycolipids: | |
| Glycolipids: | |
| Glycolipids: |
Created by:
cmccartney2