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CHAPTER 1: CARBOHYDRATES CHM 102: BIOCHEMISTRY - LECTURE The Study of Living Things...

CHAPTER 1: CARBOHYDRATES CHM 102: BIOCHEMISTRY - LECTURE The Study of Living Things meansa Oligosaccharides - Contains 2-10 monosaccharide units covalently bonded to each other Biochemistry Disaccharides (contain 2 monosaccharide units) more common Study of the chemical substances found in living organisms and the crystalline water soluble substances g lucose + fructose glucose galactose + chemical interactions of these substances with each other. Table sugar (sucrose) and milk sugar (lactose) are common Biochemical Substance disaccharides non-reducing sugar La hydrolysis monosaccharide A chemical substance found within a living organism. Upon hydrolysis they produce monosaccharide Two types of biochemical substances In human body associated with proteins and lipids for structural and oligosaccharides regulatory functions Fructo R affi nose Bioinorganic substances water inorganic containsgalactose,aandfructosealucose plants Loccur in smaller - salts I Bioorganic substances. , & composed of linear chain of & olanine-potato bigger toxin fructose units unit and B D fructor organic compound nucleic acid carbohydrates proteins lipids one - · , , , Bioinorganic substances Polysaccharides mean, Water and inorganic salts. Contains many monosaccharide units covalently bonded Bioorganic substances mostly living organism - found on Polymers: May contain 100s of 1000s of monosaccharide units Carbohydrates, lipids, proteins, and nucleic acids Examples: ○ Cellulose: Paper, cotton, wood purposes - for industrial ○ Starch: Bread, pasta, potatoes, rice, corn, beans, peas, etc. Biochemistry – An Overview I primarystorage losare Chirality: Handedness in Molecules As isolated compounds, bioinorganic and bioorganic substances have Most monosaccharides exist in two forms: a “left handed” and “right no life in and of themselves. Yet when these substances are gathered handed” form - same as two hands together in a cell, their chemical interactions are able to sustain life. Two types of objects: It is estimated that more than half of all organic carbon atoms are ○ Superimposable on their mirror images: images that coincide found in the carbohydrate materials of plants. at all points when the images are laid upon each other, a dinner Human uses for carbohydrates of the plant kingdom extend beyond plate with no design features, Achiral possess right - do not handedness the and left food. Carbohydrates in the form of cotton and linen are used as ○ Non-superimposable on their mirror images: Chiral possess handedness clothing. Carbohydrates in the form of wood are used for shelter and (handedness) Limages upon that do not conside when laid each other heating and in making paper. ~ leftandrighthanda L industrial function The property of handedness is not restricted to carbohydrates. It is a Occurrence and Functions of Carbohydrates general phenomenon found in all classes of organic compounds. Photosynthesis Chirality 75% of dry plant material: Produced by photosynthesis Cellulose: - structural element S Starch/glycogen animals ~ be stored in liver and ia muscle formsa did plants energy reservoir small amount in human body Plant products are source of carbohydrates average human diet contains 2/3 of carbohydrates Most of the matter in plants, except water, is carbohydrate material. Functions of Carbohydrates in the Human Body Chiral Center: C atom attached to 4 different groups bonded to it A Carbohydrate oxidation molecule with chiral center is a chiral molecule Provides energy ○ Best way to visualize - look at all C atoms and see if there are at Carbohydrate storage, in the form of glycogen, provides a least two H atoms then that can’t be a chiral center short-term energy reserve ○ C atoms with less than one H atom are worth looking at for their Carbohydrates supply carbon atoms for the synthesis of other chirality. biochemical substances (proteins, lipids, and nucleic acids) An achiral molecule is a molecule whose mirror images are Carbohydrates form part of the structural framework of DNA and RNA superimposable. molecules Achiral molecules do not possess handedness. Carbohydrates linked to lipids (Chapter 19) are structural components Be careful as a C atom may apparently look similar but may not have of cell membranes four DIFFERENT groups. Carbohydrates linked to proteins (Chapter 20) function in a variety of ○ E. g. 3-bromopentane - C has two CH2-CH3 groups – so it is cell–cell and cell–molecule recognition processes achiral. A chiral C is usually denoted by iodo methane carbon atoms with at least two hydrogen atomy bromo chloro L cannot be chiral centers with less than carbon atoms one hydrogen atomy Classification of Carbohydrates L worth examing for chirality Carbohydrates Carbohydrates are polyhydroxy aldehydes or ketones or compounds that produce such substances upon hydrolysis Responses of Left and Right Handed Forms of a Molecule in a Human Body double bond Both may be active, one may be more active or one may be active and other non-active epi /nephr Kidney (nephron) line hormone = into : = Example: Right handed hormone epinephrine is 20 times more active than left handed form gland I released by adrenal Almost all monosaccharides are right handed Amino acids are almost always left handed Stereoisomerism: Enantiomers and Diastereoisomers Stereoisomers Monosaccharide Stereoisomers are isomers that have the same molecular and Contain single polyhydroxy aldehyde or ketone unit structural formulas but differ in the orientation of atoms in space. They can’t be broken down into simpler substances by hydrolysis Two types: positionof hydroxyl group on one or more o thera (reaction with water) reactions Enantiomers are stereoisomers whose molecules are Contains 3-7 C atoms mirrorImaare nonsuperimposable mirror images of each other. Molecules with a 5 and 6 carbon species are more common chiral center. Water soluble white crystalline solids Diastereomers are stereoisomers whose molecules are not mirror not mirror imagetoc images of each other. a other DI : hindl mirror images of each  CARBOHYDRATES Properties of Enantiomers Constitutional Isomers and Diastereomers Constitutional isomers differ in most chemical and physical properties. For example, constitutional isomers have different boiling points and melting points. Diastereomers also differ in most chemical and physical properties. They also have different boiling points and freezing points. In contrast, nearly all the properties of a pair of enantiomers are the same Two differences 1. Their interaction with plane polarized light L mirror other image of each Inot mirror imagea 2. Their interaction with other chiral substances Designating Handedness Using Fischer Projection Formulas Interaction of Enantiomers with Plane-Polarized Light The German chemist Hermann Emil Fischer (1852-1919) developed Properties of light the two-dimensional system for specifying chirality. He was one of the ○ Ordinary Light: Move in all directions early greats in organic chemistry. In 1902, he was awarded the second unpolarized Nobel Prize in chemistry. Fischer Project Formulas Fischer projection formulas - a method for giving molecular chirality specifications in two dimensions. A Fischer projection formula is a two-dimensional structural notation for showing the spatial arrangement of groups about chiral centers in molecules. rotated clockwise In a Fischer projection formula a chiral center (Carbon) is represented ○ Plane polarized light move only in one direction (see Figure on as the intersection of vertical and horizontal lines OIt C right side) chiral center Functional groups of high priority will be written at top - CHO D and L system used to designate the handedness of glyceraldehyde right and enantiomers left Tetrahedral Arrangements The four groups attached to the atom at the chiral center assume a tetrahedral geometry and it is governed by the following conventions Plane polarized light is rotated clockwise Vertical lines from the chiral center represent bonds to groups directed (to right) or counterclockwise (to left) when passed through into the printed page. enantiomers -mirrorimage of a each Horizontal lines from the chiral center represent bonds to groups Direction and extent of rotation will depend upon the enantiomer directed out of the printed page Same concentration of two enantiomers rotate light to same extent verticalline a b but in opposite direction & directed out of printed page Dextrorotatory and Levorotatory Compounds Enantiomers are optically active: Compounds that rotates the plane polarized light Two Types: ○ Dextrorotatory: ➔ Chiral compound that rotates light towards right Fischer Project Formulas (clockwise; +) D and L system used to designate the handedness of glyceraldehyde ○ Levorotatory: dextro ➔ Chiral compound that rotates light towards left levo left enantiomers (see figure below) D-glyceraldehyde (counterclockwise; -) 1 glyceraldehyde CHO CHO There is no correlation between D, L and +, - H H OH ○ In D and L you need to look at the structure #0 ○ + and - are determined by using a polarimeter & measures polarization of light CHeOH CHeOH Enantiomers levo 2) ex+ro left right We now consider Fischer projection formulas for the compound Ordinarya in all direction 2,3,4-trihydroxybutanal + etrose ○ a monosaccharide with four carbons and two chiral centers planepola as There are four stereoisomers for this compound—two pairs of at one direction enantiomers chiralars Interactions Between Chiral Compounds Right and Left handed baseball players can’t use same glove (chiral) but can use same hat (achiral) ○ Two members of enantiomer pair (chiral) react differently with other chiral molecules Enantiomeric pairs have same solubility in achiral solvents like The D,L system used to designate the handedness of glyceraldehyde ethanol and have different solubility in chiral solvent like D-2-butanol enantiomers can be extended to other monosaccharides with more Enantiomers have same boiling points, melting points and densities - than one chiral center all these are dependent upon intermolecular forces and chirality The carbon chain is numbered starting at the carbonyl group end of doesn’t depend on them the molecule, and the highest-numbered chiral center is used to Our body responds differently to different enantiomers: determine D or L configuration One may give higher rate or one may be inactive ~ aka adrenaline Epimers are diastereomers whose molecules differ only in the ○ Example: Body response to D form of hormone epinephrine is configuration at one chiral center 20 times greater than its L isomer clifferintheposition hydroxyl group of at only one It H Br i to iniculate no. of stereoisomers. 2 LLOYD TUBILLARA l BSN 1-F  CARBOHYDRATES Classification of Monosaccharides Cyclic Forms of Monosaccharides Monosaccharides Cyclic Hemiacetal Forms of D-Glucose Triose TRI : three Dominant form of monosaccharides with 5 or more C atoms is cyclic - ○ 3 carbon atoms cyclic forms are in equilibrium with open chain form Tetrose Cyclic forms are formed by the reaction of carbonyl group (C=O) with ○ 4 carbon atoms hydroxyl (-OH) group on carbon 5 Pentoses Playb) ~ : five 2 forms of D-glucose: ○ 5 carbon atoms ○ Alpha-form: -OH of C1 and CH2OH of C5 are on opposite sides Hexoses HEX : Sex ○ Beta-form: -OH of C1 and CH2OH of C5 are on same sides ○ 6 carbon atoms Intramolecular cyclic hemiacetal formation and the equilibrium between Aldoses CHO ↑ various forms are not restricted to glucose. ○ Monosaccharides with one aldehyde group All aldoses with five or more carbon atoms establish similar equilibria, Ketoses has bond - double C - = 0 but with different percentages of the alpha, beta, and open-chain ○ Monosaccharides with one ketone group forms. Combined # of C atoms and functional group: Fructose and other ketoses with a sufficient number of carbon atoms ○ Example: Aldohexose: Monosaccharide with aldehyde group and also cyclize. 6 C atoms aldehyde 16cara one 5 - furanose Pyranose and Furanose 6-pyranose Most Common Monosaccharides A cyclic monosaccharide containing a six-atom ring is called a Example: pyranose, and one containing a five-atom ring is called furanose Aldohexose because their ring structures resemble the ring structures in the cyclic ○ Monosaccharide with aldehyde group and 6 C atoms – ethers pyran and furan respectively. D-glucose Ketohexose ○ Monosaccharide with ketone group and 6 C atoms – D-fructose Walter Norman Haworth (188301950), the developer of Haworth projection formulas, was a British carbohydrate chemist. 1937 co Biochemically Important Monosaccharides recipient of the Nobel Peace Prize in Chemistry. D-Glucose (aldohexose) Haworth Projection Formulas 1. Most abundant in nature A Haworth projection formula is a two-dimensional structural notation 2. Nutritionally most important glucose supply energy body -due to to that specifies the three-dimensional structure of a cyclic form of a 3. Grapefruit good source of glucose (20 - 30% by mass) -- also named monosaccharide. grape sugar, dextrose and blood sugar (70 - 100 mg/100 mL of blood) L 4. Six membered cyclic form insulin plays role Alpha and Beta Configuration found in fruits Alpha or Beta configuration is determined by the position of the —OH D-Fructose (ketohexose) group on C1 relative to the CH2OH group that determines D or L 1. Ketohexose series. 2. Sweetest tasting of all sugars In a Beta configuration, both of these groups point in the same 3. Found in many fruits and in honey direction 4. Good dietary sugar-- due to higher sweetness In an Alpha configuration, the two groups point in opposite directions. 5. Five membered cyclic form - OH Group Ketose if double bond occurs - The specific identity of a monosaccharide is determined by the - positioning of the other —OH groups in the Haworth projection - - - Ohis totheright of a formula. - ofistothe left of ! Any —OH group at a chiral center that is to the right in a Fischer - - projection formula points down in the Haworth projection formula and - - any —OH group to the left in a Fischer projection formula points up in the Haworth projection formula. - - 15 carbon atoms L6 Catoms Reactions of Monosaccharides Five important reactions of monosaccharides ORGPA A 5% (m/v) glucose solution is often used in hospitals as an ○ Oxidation to acidic sugars intravenous source of nourishment for patients who cannot take food ○ Reduction to sugar alcohols by mouth. The body can use it as an energy source without digesting ○ Glycoside formation it. ○ Phosphate ester formation brain ○ Amino sugar formation sugar D-Galactose (aldohexose) These reactions will be considered with respect to glucose. Other aldoses, as well as ketoses, undergo similar reactions. 1. Milk sugar 2. Synthesize in human Oxidation 3. Also called brain sugar-- part of brain and 4. nerve tissue Oxidation to acidic sugars: The redox chemistry of monosaccharides is 5. Used to differentiate between blood types closely linked to the alcohol and aldehyde functional groups present in 6. Six membered cyclic form them. Oxidation can yield three different types of acidic sugars depending on D-Ribose (aldopentose) the type of oxidizing agent used: ○ Weak oxidizing agents such as Tollens and Benedict’s solutions 1. Part of RNA oxidize the aldehyde end to give an aldonic acid. 2. Part of ATP ○ Reducing sugar is a carbohydrate that gives a positive test with 3. Part of DNA Tollens and Benedict’s solutions. 4. Five membered cyclic form Oxidizing Agents Strong oxidizing agents can oxidize both ends of a monosaccharide at the same time (the carbonyl group and the terminal primary alcohol group) to produce a dicarboxylic acid: ○ Such polyhydroxy dicarboxylic acids are known as aldaric acids. Oxidization In biochemical systems enzymes can oxidize the primary alcohol end of an aldose such as glucose, without oxidation of the aldehyde group, to produce an aldonic acid. LLOYD TUBILLARA l BSN 1-F  CARBOHYDRATES The glucose to a color chart that indicates glucose concentration ○ Cellobiose contains two β - D-glucose monosaccharide units content of urine can be determined by dipping plastic strip treated linked through a β (1—4) glycosidic linkage. with oxidizing agents into the urine sample and comparing the color change of the strip linkedais Sugar Alcohols Reduction to sugar alcohols: The carbonyl group in a monosaccharide (either an aldose or a ketose) is reduced to a hydroxyl group using hydrogen as the reducing agent. ○ The product is the corresponding polyhydroxy alcohol - sugar alcohol. glucose + glucose ○ Sorbitol - used as moisturizing agents in foods and cosmetics and Maltose enzyme maltase digested by humans : as a sweetening agent in chewing gum Maltose is digested easily by humans because we have enzymes that Glycoside can break α (1-4) linkages but not β (1-4) linkages of cellobiose. Glycoside formation: Cyclic forms of monosaccharides are hemiacetals, Therefore cellobiose cannot be digested by humans. they react with alcohols to form acetals: - ○ Monosaccharide acetals are called glycoside A glycoside is an acetal formed from a cyclic monosaccharide by replacement of the hemiacetal carbon —OH group with an —OR group: ○ A glycoside produced from glucose - glucoside ○ A glycoside produced from galactose – galactoside ○ Glycosides exist in both Alpha and Beta forms Blood Types and Monosaccharides Three Forms of Maltose Blood Types and Monosaccharides: Human blood is classified into four types: A, B, AB, and O: ○ Blood of one type cannot be given to a recipient with blood of another type. ○ A transfusion of wrong blood type can cause the blood cells to form clumps ➔ a potentially fatal reaction. ○ People with type O blood are universal donors, and those with means that the two convertible/reversible/2-way reactions are type AB blood are universal recipients. Blood Types In the United States type O blood is the most common and type A the second most common. glucose + galactose The biochemical basis for the various blood types involves Lactose monosaccharides present on plasma membranes of red blood cells. Lactose is made up of β-D-galactose unit and a β-D- glucose unit The monosaccharides responsible for blood groups are D-galactose joined by a β(1-4) glycosidic linkage and its derivatives. Differences Between Blood Types Principal carbohydrate in milk. Human - 7%–8% lactose Cow’s milk - 4%–5% lactose Lactose intolerance ○ a condition in which people lack the enzyme lactase needed to hydrolyze lactose to galactose and glucose. Lactase hydrolyzes β(1-4) glycosidic linkages hydrolize are 1actosetogalact Deficiency of lactase can be caused by a genetic defect, physiological decline with age, or by injuries to intestinal mucosa. When lactose is undigested it attracts water causing fullness, discomfort, cramping, nausea, and diarrhea. Bacterial fermentation of the lactose further along the intestinal tract produces acid (lactic acid) Phosphate Ester Formation and gas, adding to the discomfort. 7 8% 4- 5 % Phosphate ester formation: The hydroxyl groups of a monosaccharide - can react with inorganic oxyacids to form inorganic esters. Human milk contains more lactose than does cow’s milk. Lactose Phosphate esters of various monosaccharides are stable in aqueous intolerance is a condition in which people lack the enzyme lactase, solution and play important roles in the metabolism of carbohydrates. which is needed to hydrolyze lactose to galactose and glucose. fructose glucose + ~ Sucrose reducing sugar- not a Amino Sugar Formation Sucrose (table sugar): The most abundant of all disaccharides and Amino sugar formation: An amino sugar - one of the hydroxyl groups of found in plants. commonlyu day day ↳ in to basic a monosaccharide is replaced with an amino group It is produced commercially from the juice of sugar cane and sugar In naturally occurring amino sugars the carbon 2 hydroxyl group is beets. replaced by an amino group ○ Sugar cane contains up to 20% by mass sucrose Amino sugars and their N-acetyl derivatives are important building ○ Sugar beets contain up to 17% by mass sucrose blocks of polysaccharides such as chitin canbefoundonexoskele I a Disaccharides Two monosaccharides can react to form disaccharide One monosaccharide act as a hemiacetal and other as alcohol hydrolysis nemiacetal + alcohol Cellobiose Cellobiose is produced as an intermediate in the hydrolysis of the polysaccharide cellulose: LLOYD TUBILLARA l BSN 1-F  CARBOHYDRATES Honeybees and many other insects possess an enzyme called invertase that hydrolyzes sucrose to invert sugar. Thus honey is ○ 20 - 35 g of dietary fiber is desired everyday predominantly a mixture of D- glucose and D-fructose with some unhydrolyzed sucrose General Characteristics of Polysaccharides The Polymer Chain Polymers Many monosaccharide units bonded with glycosidic linkages Two types: ○ Linear and branched, homo and hetero-polysaccharides Chitin Similar to cellulose in both function and structure Linear polymer with all b (14) glycosidic linkages - it has a N- acetyl amino derivative of glucose Function is to give rigidity to the exoskeletons of crabs, lobsters, shrimp, insects, and other arthropods Polysaccharides are not sweet and don’t show positive tests with Tollens and Benedict’s solutions whereas monosaccharides are sweet and show positive tests Limited water solubility Examples: plant's provides rigidity ~ cell wall ○ Cellulose, starch in plants – Glycogen in animals storedinlivees ↳ e ○ Chitin in arthropod Icanbefouna Storage Polysaccharides Starch in plants - A storage polysaccharide is a polysaccharide that is a storage form for monosaccharides and is used as an energy source in cells. Starch: Chitin, a linear β (1-4) polysaccharide, produces the rigidity in the ○ Glucose is the monomeric unit exoskeletons of crabs and other arthropods. ○ Storage polysaccharide in plants ○ Two types of polysaccharides isolated from starch: Acidic Polysaccharide ○ Amylose: Straight chain polymer - 15 - 20% of the starch and has ↓ linear 50, α (14) glycosidic bonds 000 Acidic Polysaccharides joints - can be found on ○ Molecular Mass: 50,000 (up to 1000 glucose units) Polysaccharides with a repeating disaccharide unit containing an amino Amylopectin Structure sugar and a sugar with a negative charge due to a sulfate or a carboxyl group. Amylopectin: Structural polysaccharide present in connective tissue associated with 300 , ○ Branched chain polymer - 80 - 85 % of the starch α (14) glycosidic 000 joints, cartilage, synovial fluids in animals and humans bond for straight chain and α (16) for branch ○ Primary function is lubrication necessary for joint movement ○ Molecular Mass: 300,000 (up to 100,000 glucose units) - higher ○ These are heteropolysaccharides - have more than one type of than amylose monosaccharide monomer present. ○ Human can hydrolyze alpha linkage but not beta linkage Examples: - 3 , 000 000 , ○ Hyaluronic Acid Glycogen ○ Heparin Humans and animals storage polysaccharide essential for athletes Contains only glucose units Acidic polysaccharides, associated with the connective tissue of Branched chain polymer – a (14) glycosidic bonds in straight chains joints give hurdlers the flexibility needed to accomplish their task. and a (16) in branches Molecular Mass:3,000,000(upto1,000,000glucose units) Hyaluronic Acid and Heparin Three times more highly branched than amylopectin in starch Excess glucose in blood stored in the form of glycogen Hyaluronic acid - locks in moisture or water ○ Alternating residues of N- acetyl-b-D-glucosamine and D-glucuronic acid. ○ Highly viscous - serve as lubricants in the fluid of joints and part sticky vitreous humor of the eye. I provide shape The small, dense particles within this electron micrograph of a liver cell are glycogen granules dietary Cellulose super branched - Linear homopolysaccharide with b (1 4) glycosidic bond Up to 5000 glucose units with molecular mass of 900,000 amu ○ Cotton ~95% cellulose and wood ~50% cellulose ○ Humans don’t have enzymes that hydrolyze b (1 4) - so humans cellulase cenzyme can not digest cellulose -- animals also lack these enzymes but they can digest cellulose because they have bacteria in their guts in exampletermites to hydrolyze cellulose Lenglina (protozoa) symbiotic relationship ○ It serves as dietary fiber in food-- readily absorbs water and results in softer stools LLOYD TUBILLARA l BSN 1-F  CARBOHYDRATES Heparin ○ An anticoagulant-prevents blood clots. ○ Polysaccharide with 15–90 disaccharide residues per chain. Glycolipids and Glycoproteins: Cell Recognition A glycolipid is a lipid molecule that has one or more carbohydrate (or carbohydrate derivative) units covalently bonded to it. A glycoprotein is a protein molecule that has one or more carbohydrate (or carbohydrate derivative) units covalently bonded to it. Dietary Considerations and Carbohydrates Nutrition Foods high in carbs content constitute over 50% of the diet of most people of the world -- a balanced dietary food should contain about 60% of carbohydrate: ○ Corn in South America ○ Rice in Asia ○ Starchy root vegetables in parts of Africa ○ Potato and wheat in North America Nutritionist divide dietary carbs into two classes: ○ Simple carb: dietary monosaccharides or disaccharides - sweet to mono or di taste commonly referred to as sugars - 20 % of the energy in the US die ○ Complex carbs: Dietary polysaccharides -- starch and cellulose - poly normally not sweet to taste Glycemic Foods A developing concern about intake of carbohydrates involves how fast the given dietary carbs are broken down to glucose within the human body Glycemic effect refers to: ○ how quickly carbs are digested ○ how high blood glucose rise ○ how quickly blood glucose levels return to normal Glycemic index (GI) has been developed for rating foods LLOYD TUBILLARA l BSN 1-F  CHAPTER 2: LIPIDS CHM 102: BIOCHEMISTRY - LECTURE Structure and Classification of Lipids Omega (ω)-6 fatty acid ~ can be coverted to prostaglanding Unsaturated fatty acid with its endmost double bond six carbon Lipids atoms away from its methyl end An organic compound found in living organisms that is insoluble (or only sparingly soluble) in water but soluble in non-polar organic Physical Properties of Fatty Acids solvents Water Solubility Unlike other biomolecules, lipids do not have a common structural Short-chain fatty acids have some solubility, whereas long-chain fatty feature that serves as the basis for defining such compounds acids are insoluble Classification is based on two methods Short-chain fatty acids are sparingly soluble because of the presence ○ Biochemical function of carboxylic group ○ Saponification Melting Point Classification based on Biochemical Function Depends upon the following: Divided into five categories based on their biochemical function: ○ Length of carbon chain ○ Energy-storage lipids (triacylglycerols) ○ Degree of unsaturation (number of double bonds in a ○ Membrane lipids (phospholipids, sphingoglycolipids and molecule) cholesterol) Number of “bends” in a fatty acid chain increases as the number of ○ Emulsification lipids (bile acids) chemical messenger double bonds increase ○ Messenger lipids (steroid hormones and eicosanoids) ○ Less packing occurs ○ Protective-coating lipids (biological waxes) ○ Melting point is lower runsaturated ○ Tend to be liquid at room temperature Classification Based on Saponification Energy-Storage Lipids: Triacylglycerols Saponification reaction Hydrolysis reaction that occurs in a basic solution Energy-Storage Materials Based on saponification reactions, lipids are divided into two With the notable exception of nerve cells, human cells store small categories: soap by ~ turn into reaction with an alkali amounts of energy-providing materials ○ Saponifiable lipids (triacylglycerols, phospholipids, ○ Carbohydrate glycogen sphingoglycolipids, cholesterol, and biological waxes) ➔ Most widespread energy storage material present in small ○ Nonsaponifiable lipids (bile acids, steroid hormones, and amounts eicosanoids) Major energy-storage material is triacylglycerol ○ Concentrated primarily in special cells (adipocytes) which are Structural Diversity of Lipids nearly filled with triacylglycerols Lipids exhibit structural diversity Some are esters, some are amides, and some are alcohols (acyclic, Two Types of Triacylglycerols cyclic, and polycyclic) Simple triacylglycerol Types of Fatty Acids Triester formed from the esterification of glycerol with three identical fatty acid molecules Fatty Acids ○ Naturally occurring simple triacylglycerols are rare Naturally occurring monocarboxylic acids with linear (unbranched) Mixed triacylglycerol carbon chain Triester formed from the esterification of glycerol with more than one ○ Have even number of carbon atoms kind of fatty acid molecule ○ Long-chain fatty acids (C12 to C26) ○ Medium-chain fatty acids (C8-C10) Fats and Oils ○ Short-chain fatty acids (C4-C6) Two types: packs ~ well Fats 2 2 C ○ Saturated temperature - solid carbons at room... connected C Predominantly Saturated all are ↓ ➔ All C–C bonds are single bonds Omega-9 doesn't pack well C Solids or semi solids at room temperature ○ Unsaturated liquid S C temperature methyl at room end C Lomega end C Sources ➔ Monounsaturated double bond cComega-6 · one double bond kink in molecula ○ Animals L C ➔ Polyunsaturated (omega-3) - two or more double bond c Oils Saturated Fatty Acids Predominantly unsaturated Fatty acids with a carbon chain in which all C–C bonds are single Liquids at room temperature bonds Sources Numbering starts from the end of –COOH group ○ Plants and fish oil Consider the structural notations for palmitic acid: Dietary Considerations and Triacylglycerols Unsaturated Fatty Acids Monounsaturated fatty acid: Fatty acid with a carbon chain in which Studies Concerning Role of Dietary Factors as a Cause of Disease one carbon–carbon double bond is present Nations whose citizens have high dietary intakes of fats and oils tend There are different ways of depicting the structure to have higher incidences of heart disease and certain types of cancers Polyunsaturated Fatty Acids (PUFAs) Typical American diet contains too much fat Fatty acids with a carbon chain in which two or more carbon–carbon ○ Americans are being asked to reduce their total dietary fat double bonds are present intake Up to six double bonds are found in biochemically important PUFAs Other studies show that risk factors involve more than simply the total amount of triacylglycerols consumed Double-Bond Position in Unsaturated Fatty Acids Numbering starts from the other end of –COOH “Good Fats” Versus “Bad Fats” Structural notation indicates number of C atoms Studies indicate that type of dietary fat and amount of dietary fat are Example: important to determine body responses to dietary fat ○ 18:2 signifies that a fatty acid has 18 carbons with 2 double bonds Current recommended amount for total fat intake in calories: no of carbon no · of bonds ○ 15% - Monounsaturated fat Types of Unsaturated Fatty Acids ○ 10% - Polyunsaturated contains alpha-linolenic acid found on peanuts ○