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BIOCHEM CHAP 19
Lipids
| Question | Answer |
|---|---|
| What is a lipid? | a lipid is an organic compound found in living organisms that is insoluble ( or only sparingly soluble) in water but soluble in NONPOLAR ORGANIC SOLVENTS. |
| How is a lipid characterized? | a lipid is characterized based on solubility characteristics. |
| Lipids include | Fatty acids, triglycerides, sphingolipids, phosphoacylglycerols, and glycolipids. Lipid-soluble vitamins. Prostaglandins, leukotrienes, and thromboxanes. Cholesterol, steroid hormones, and bile acids. |
| What is saponification? | a hydrolysis reaction that occurs in basic solution. |
| Based on biochemical function, lipids are divided into 5 categories | 1) Energy-storage lipids (triacylglycerols). 2) Membrane lipids (phospholipids, sphingoglycolipids,cholesterol). 3) Emulsification lipids (bile acids). 4. Messenger lipids (steroid hormones and eicosanoids) 5. Protective-coating lipids (biological waxes). |
| Based on whether or not saponification occurs when a lipid is placed in basic aqueous solution, lipids are divided into 2 categories | 1) Saponifiable lipids (triacylglycerols, phospholipids, sphingoglycolipids, and biological waxes). 2. Nonsaponifiable lipids (cholesterol, steroid hormones, bile acids, and eicosanoids). |
| Membrane lipids are used for what? | are used to hold the contents of the cell. Have membrane lipids like phospholipids, sphingoglygolipids, cholesterol (must have cholesterol embedded in the membranes so that it will be fluid.) |
| What is emulsion? | emulsion is the lipids suspended in a liquid. |
| Emulsification lipids | emulsion is the lipids suspended in a liquid. We need this in the body for bile acids secreted by the liver emulsifying the fats. It helps us digest fat soluble vitamins. |
| Messinger lipids | the steroid hormones (like sex the sex hormones or eicosanoids). |
| Lipids as Protective coating | biological waxes such as found in the plant world. Water repellant- Hydrophobic nature- keeps surface of the organism dry. Prevents excessive wetting (birds). Prevents loss of water via evaporation |
| Lipids learning objectives | Storage lipids (Fats). Fatty acids and health, Waxes, Membrane lipids, Steroids, Lipids as signals; hormones, intracellular messengers, Enzyme cofactors, Pigments. |
| Fats and oils are comparable to fossil fuels | chemically reduced, efficient storage, respiration and combustion yield CO2 + H2O. |
| What are Triglycerides? | they are storage lipids composed of 3 fatty acids in ester linkages to glycerol. Triglycerides are fats and oils. |
| Fatty acids are carboxylic acids with what kind of chian? | an R chain 4 to 36 carbons long. If R is an alkane, the fatty acid is saturated (SFAs). If R is an alkene, the fatty acid is unsaturated- A single double bond is monounsaturated (MUFAs). More than one double bond is polyunsaturated (PUFAs). |
| Triglyceride | A triester of glycerol with three fatty acids. In most triglycerides, two or three different fatty acid components are present. The hydrophobic character is caused by the long hydrocarbon chains. The triglycerides are insoluble in water. |
| What are fatty acids? | a fatty acid is a naturally occurring monocarboxylic acid. contain an even # of carbon atoms and have a carbon chain that is unbranched. Fatty acids are rarely found free in nature but rather occur as part of the structure of more complex lipid molecules. |
| How are fatty acids characterized? | they are characterized as long-chain fatty acids (C12-C26), medium-chain fatty acids (C8-C10) or short chain fatty acids (C4 and C6). |
| How are fatty acids classified? | they are classified as saturated fatty acids and unsaturated fatty acids. |
| What is a saturated fatty acid? | no double bonds between carbons in the chain. All single bonds |
| Most natural fatty acids are branched or unbranched? | unbranched. They have an even amount of carbons and have double bonds that are –cis. |
| Monounsaturated | one double bond between carbons in the alkyl chain. |
| Polyunsaturated | more than one double bond in the alkyl chain. |
| Nomenclature for fatty acids. Consider palmitic acid 16 | 0 |
| Nomenclature for fatty acids. Consider a-linolenic acid | 18 |
| The shape of saturated fatty acids (FA) | the 109.5 C-C bond angle creates a zigzag pattern. They are packed together and so have a high melting point. |
| What is the bond angle of C-C double bonds in a saturated fatty acid? | it is 180 degree angle. |
| How does each double bond have an effect on the boiling point? | It is introduced as a kink in the straight zigzag pattern. With increasing double bonds, the molecule attraction goes down. Therefore, the melting point goes down and decreases with increasing number of C-C double bonds. |
| Unsaturated fatty acids | have ONE carbon-carbon double bond. |
| What are the physical properties of fatty acids (FA) and lipids influenced by? | determined by the length and degree of unsaturation of the fatty acid carbon. |
| Water solubility for fatty acids is a direction function of what? | of carbon chain length. Solubility decreases as carbon chain length increase. Short chain fatty acids have a slight solubility in water. Long chain fatty acids are essentially insoluble in water. |
| Melting points for fatty acids are strongly influenced by both | carbon chain length and degree of unsaturation (number of double bonds). As the carbon chain length increases, melting point increases. This is because of the greater surface area associated with a longer carbon chain. |
| Do saturated FA have higher or lower melting points than unsaturated FA with the same number of carbon atoms? | saturated FA have higher melting points. The greater the degree of unsaturation, the greater the reduction in melting point. |
| Unsaturated vs saturated fatty acids melting points | Because of the bends the double bonds create in the fatty acid structure, it prevents the atoms from packing as close together. So the increase of double bonds will cause unsaturated fatty acids to have lower melting points. |
| More nomenclature for fatty acids. How you number the structure | The carbonyl carbon is carbon #1. Carbon #2 is the a-carbon. Carbon #3 is the b-carbon. Carbon # 4 is the g-carbon. Carbon # 5 is the e-carbon. The methyl-terminal (last) carbon is w. |
| PUFAs polyunsaturated fatty acids. Examples of this | Linoleic and linolenic are essential fatty acids. Vertebrates cannot introduce a point of unsaturation at the omega-3 or the omega-6 position. |
| What are essential fatty acids? | the body cannot make this on its own. You must eat it. |
| What are the sources of Linoleic Acid | safflower oil, soybean oil, |
| What are the sources of Linolenic Acid | flax seed oil (linseed oil). Goes rancid easily. |
| Linoleic acid | is an essential fatty acid. Must have this in your diet or you cannot survive. |
| How can you tell Linoleic from linolenic acid? | linoleic acid had 2 C-C double bonds at 9 and 12 and has omega 6 fatty acid. You figure out the omega 6 by counting down from the opposite end of the carbonyl group. |
| Fatty acids you need to know= Palmitic, stearic, linoleic, linolenic, eicosapentaenoic acid, docosahexaenoic acid | (- replaces the colans) Palmitic 16-0. Stearic 18-0. Linoleic 18-2D9,12 . Linolenic 18-3 D9,12,15. Eicosapentaenoic acid (EPA) 20-5 D5,8,11,14,17 .Docosahexaenoic acid (DHA) 22-6 D4,7,10,13,16,19 |
| Fats are naturally occurring mixtures of what? | mixtures of triacylglycerol molecules in which many different kinds of triacylglycerol molecules are present. |
| Fats are composed largely of what kind of fatty acids? And what effect does this have on its melting points? | are composed largely of triacylgylcerols in which saturated fatty acids predominate, although some unsaturated fatty acids are present. Such traicylglycerols can pack closely together thus causing the higher melting points associated with fats. |
| Oils contain triacylglycerols with…. And what effect does this have on its melting point | larger amounts of mono- and polyunsaturated fatty acids than those in fats. They cannot pack as tightly together because of bends in their fatty acids and HAVE A LOWER MELTING POINT. |
| What are the characteristics of PURE fats and oils? Like do they have a smell, what color are they? | they are colorless and odorless. The warmer body temperatures in living animals keeps the fats somewhat liquid and so they are able to move around. |
| Coconut oil is highly | saturated. It is a liquid. |
| Oils are naturally occurring mixtures of | triacylglycerol molecules in which there are many different kinds of triacylglycerol molevules present. |
| Where are fat and oils taken from? | fat is taken from animals. Oils are usually taken from plants. |
| What are energy-storage lipids called? | triacylglycerols. Human cells store small amounts of energy providing materials for use when energy demand is high. The most widespread energy storage material within cells is the carbohydrate glycogen. Triacylglycerols also store energy. |
| Define triacylglycerol | is a lipid formed by esterification of three fatty acids to a glycerol molecule. |
| Is triacylglycerols better at storing energy than glycerol? | triacylglycerols are much more efficient at storing energy than is glycogen because large quantities of them can be packed into a very small volume. These are the most abundant energy storage lipid in the body. |
| In terms of functional groups, triacylglycerols are | triesters. Three ester functional groups are present. There are three fatty acids attached to glycerol and the esters attached the fatty acids to glycerol. |
| How is an ester produced? | from the reaction of an alcohol with a carboxylic acid. |
| Where can triacylglycerols be found? | in special cells called adipocytes. |
| Fats are in what state at room temperature? | solid |
| Oils are in what state at room temperature? | liquid. Only difference here is the presence of C-C double bond. |
| Define acyl group | is the portion of a carboxylic acid that remains after the –OH group is removed from the carboxylic carbon atom. R-Cdouble bonded to an O. |
| What is the basic definition of triacylcylerols? What are they made up of in other words? | fats and oils. |
| Fatty acids are amphipathic | possessing both polar and nonpolar groups; that is, hydrophilic and hydrophobic substituents. |
| Dietary consideration and triacylglycrols. In general, nations whose citizens have high dietary intakes of triacylglycerols(fats and oils) tend to have higher incidences of what kind of diseases? | heart disease and certain types of cancers. |
| What is a healthy diet? What is the limit of fat to the total of colories in food? | 30% |
| Plant oil is high in omega-_____ | high in omega-6 fatty acids.5 |
| How are oils useful? What can they be used for in the body? | 1) important in membranes (it helps them build the membranes). 2) building blocks for longer fatty acids. |
| In dietary discussions, the term FAT is used as a substitute for ________ | triacylglycerol. Thus a dietary fat can be either a fat or an oil. |
| What are considered “bad fats?” | saturated fats. Can increase the risk of heart disease. |
| What are considered “good fats?” | monounsaturated fats. Polyunsaturated fats can both be a “good fat” and a “bad fat”. Monounsaturated fats can decrease the risk of heart disease and breast cancer. Polyunsaturated may be a risk of certain types of cancers. |
| Inuit people have a diet high in fat, but they have a low heart disease risk in the population. The American diet is high in fat too but they have a high risk of heart diseases. Why is this? | because their diet consists in omega-3 fatty acids (from fish!). These are cold fish, also called fatty fish. Examples are tuna, salmon, and mackerel. The US diet is high in omega-6 fatty acids (from plant oils). |
| Nuts contain what kind of fat? | good fat! |
| What are examples of two fatty acids? | linolEIC and linolenic acid. |
| LinolEIC acid is the primary member of _______? | (18-2) (-replaces the colan) is the primary member of the omega-6 acid family. |
| LinolENIC acid is the primary member of _________? | (18-3) is the primary member of the omega-3 acid family. |
| Linoleic acid(18-4) is the starting material for the biosynthesis of _______? | arachidonic acid. (20-4) |
| Arachidonic acid is the major starting material for ____? | eicosanoid substances that help regulate blood pressure, clotting, and several other important body functions. |
| Linolenic acids is the starting material for the biosynthesis of two additional _____ | two additional omega-3. EPA (20-5) and DHA (22-6) |
| EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are important constituents of the communication membranes of the brain and are necessary for | normal brain development. They are also active in the retina of the eye. |
| What are four important triacylglycerol reactions? | hydrolysis, saponification, hydrogenation, and oxidation. |
| Hydrolysis of a triacylglycerol is | the reverse of the esterification reaction by which it was formed. (see figure 19.5) |
| Triacylglyercol hydrolysis when carried out in a laboratory setting requires the presence of _____ or a ____ | an acid or a base. |
| Under basic conditions, the hydrolysis products are | glycerols and fatty acids salts. |
| Within the human body, triacylglycerol hydrolysis occurs during the process of _____? | digestion. The fatty acids are removed from the glycerol. |
| What is complete hydrolysis | In situations where all three fatty acids are removed, the hydrolysis process if referred to as complete hydrolysis. |
| What is partial hydrolysis? | if one or more of the fatty acid residues remain attached to the glycerol. |
| What is saponification? | is a reaction carried out in an alkaline (basic) solution. |
| For fats and oils, the products of saponification are | glycerol and fatty acid salts. |
| What does alkaline mean? | it means it is a basic solution. |
| Saponification of animal fat is how what is made? | soap. |
| What is a micelle? | is a spherical cluster of molecules in which the polar portions of the molecules are on the surface and the nonpolar potions are located in the interior. |
| Hydrogenation is a chemical reaction that involves what? And what effect does this have on the melting point? | hydrogen addition across the C-C multiple bonds which increases the degree of saturation as some double bonds are converted to single bonds. There is an increase in the melting point of the substance. |
| What is an example of carboxyloic acid salt? | soap |
| What is a food produced by partial hydrogenation? | peanut butter. Stick of margarine. |
| Oxidation reaction | is the C-C double bonds present in the fatty acid residues of a triacylglycerol are subject to oxidation with molecular oxygen (from air) as the odixizing agent. Such oxidation breaks these bonds, producing both aldehyde and carboxylic acid products. |
| What are the three common types of membrane lipids? | phospholipids, sphingoglycolipids, and cholesterol. |
| CHART ON PG 676! | IT IS VERY HELPFUL With FATS!!! |
| What is the most abundant type of membrane lipid? | a phospholipid. |
| What is a phospholipid? | is a lipid that contains one or more fatty acids, a phosphate group, a platform molecule to which the acid(s) and the phosphate group are attached, and an alcohol that is attached to the phosphate group. |
| What is the most abundant type of membrane lipid? | a phospholipid. |
| What is a phospholipid? | is a lipid that contains one or more fatty acids, a phosphate group, a platform molecule to which the acid(s) and the phosphate group are attached, and an alcohol that is attached to the phosphate group. |
| When a triacylglycerol undergoes complete hydrolysis, there are four organic products. What are they? | glycerol and three fatty acids. |
| When a triacylglycerol undergoes complete saponification, there are four organic products produced What are they? | glycerol and three fatty acids. The base is NaOH. |
| Complete hydrogenation will change the given triacylglycerol into a triacylglycerol in which | all three fatty acid residues are 18-0 fatty acid residues. That is, all of the fatty acid residues are completely saturated (there are no C-C double bonds!!). |
| Glycerophospholipid consists of what? Is made up of what? | 2 fatty acids esterified to a glycerol molecule and an alcohol esterified to a phosphate group. All bonds between groups are ESTER LINKAGES (just like triacylglycerols). It has FOUR ester linkages. |
| Sphingosine consists of what? Is made up of what? | one fatty acid, a phosphate, and an alcohol. |
| Ethanolamine or serine are | these are cephalins. Cephalins in high amounts in brain, nerve, and blood clotting membranes. |
| Choline | these are lecithins. Lecithins are in high amounts in egg yolk and soybean, nerve and brain membranes. |
| What is the second most abundant group of naturally occurring lipids? | Glycerophospholipids, also called phosphoglycerides are the second most abundant group of naturally occurring lipids. |
| Glycerophospholipids are Found almost exclusively in | plant and animal membranes, which typically consist of 40% -50% phosphoacylglycerols and 50% - 60% proteins. |
| The three most abundant fatty acids in phosphatidic acids are | palmitic (16-0), stearic (18-0), and oleic (18-1). |
| A Sphingophospholipid is a | is a lipid that contains one fatty acid and one phosphate group attached to a sphingosine molecule and an alcohol attached to the phosphate group. |
| What kind of reactions does sphingophospholipids participate in? | hydrolysis and saponification reactions. |
| Sphingophospholipids contain | one fatty acid and one phosphate group attached to a sphingosine molecule and an alcohol attached to the phosphate group |
| The backbone of sphingolipids is a | long-chain amino alcohol sphingosine. |
| Sphingoglycolipids | Contains both a fatty acid and carbohydrate |
| Simple sphingoglycolipids are called cerebrosides, they are lipids that contain | that contains both a fatty acid and a carbohydrate component attached to a sphingosine molecule. |
| What two reactions can Sphingoglycolipids undergo? | hydrolysis and saponification. |
| PG 565 CHART IS REALLY GREAT | for looking up lipids. |
| What are the two ways that cholesterol’s structure differs from other membrane lipids? | 1) there are NO fatty acid residues present and 2) neither glycerol nor sphingosine is present as the platform molecule. |
| What is cholesterol? | cholesterol is a steroid. |
| What is a steroid? | a steroid is a lipid whose structure is based on a fused ring system that involves three 6-membered rings and one 5 membered ring. |
| Within the human body, where is cholesterol found? | it is found in cell membranes, in nerve tissue, in brain tissue, and in virtually all fluids. |
| Cholesterol has how many carbon atoms? | 27 carbon atoms. |
| Although a portion of the body’s cholesterol is obtained from dietary intake, most of it is biosynthesized by the | liver and (to a lesser extent) the intestine. |
| Typically how mg of cholesterol is synthesized by the body per day? | 800-100 mg. 1.5 to 2.0 grams |
| How is cholesterol carried throughout the body? | it travels via the blood stream and are carried by lipoproteins. |
| Major function of lipoproteins | help suspend lipids and transport them through the bloodstream |
| Four major classes of plasma lipoproteins | Chylomicrons, Very-low-density lipoproteins (VLDL), Low-density lipoproteins (VLDL). |
| Chylomicrons | Transport dietary triacylglycerols from intestine to liver and to adipose tissue. **from notes definition- chylomicrons are synthesized in your intestine in response to a meal. This gets it across the cell membrane. |
| Very-low-density lipoproteins (VLDL) | Transport triacylglycerols synthesized in the liver to adipose tissue. |
| Low-density lipoproteins (LDL) | takes cholesterol to the tissues. |
| What makes LDL and HDL? What does lipids and proteins have to do with it? | the proteins are much more dense than lipids. If there is more proteins, then it is more dense. If more lipids, then less dense. |
| High-density lipoproteins (HDL) | takes cholesterol to the liver to make bile acids. |
| People who have Familial Hypercholesterolemia have what wrong with them? | their LDL-receptors are absent or defective. They have extremely high cholesterol levels. They will die of CVD at an early age. |
| **What should the cholesterol levels be for a person?? | want less than 200 for cholesterol for the average person. |
| What are some drugs that are taken for high cholesterol? | STATINS, Zocor, Mevacor, Pravachol, Lipitor. |
| What is the function of bile? | Aid in the digestion of lipids and absorption of vitamins A,E,K, and D vitamins. Use it in excretion of hemoglobin catabolism. Important in excreting in some toxins including drugs and heavy metals. |
| How can we lower total cholesterol (other than statins)? | Exercise and weight control. Very moderate amounts of red wine. EPA and DHA |
| What is the most abundant steroid in the membrane? | cholesterol. |
| What does high cholesterol cause? | CVD cardiovascular disease and dementia. |
| How does one lower their cholesterol? | due to the drugs called STATINS. |
| How are the prostaglandins important in the body? | prostaglandins are important in inhibiting inflammation . They influence ion transport, participates in uterus contractions in child birth, mediate pain. |
| What are thromboxanes? | blood plates, blood clots, leukotriene. They are cyclic ethers. |
| Define a cell membrane, what does it do? | is a lipid-based structure that separates a cell’s aqueous based interior from the aqueous environment surrounding the cell. It separates! The cell membrane also controls the movement of substances into and out of the cell. |
| What is the three types of membrane lipids usually found in cell membranes? | phospholipids, glycolipid, and cholesterol. |
| Are the cell membranes soluble in water? What is their structure? | they are NOT soluble in water. They are insoluble in water. They have one head and two tails. Polar head (hydrophilic) and nonpolar (hydrophobic tails). |
| What is a lipid bilayer? | is a two-layer-thick structure of phospholipids and glycolipids where the nonpolar tails are in the middle and the polar head are on the outside surface. |
| What is the purpose of cholesterol molecules in the cell membrane? | they regulate membrane rigidity. |
| Proteins are present in the phospholipid bilayer. What is their purpose? | the proteins are responsible for moving substances such as nutrients and electrolytes across the membrane. |
| There are two types of proteins in the phospholipid bilayer | integral membrane protein-penetrates the cell membrane. and peripheral membrane protein-is a nonpenetrating membrane protein located on the surface of the cell membrane. |
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