Chapters 25-7 Biomolecules.

Chapters 25-7 Biomolecules Importance of Carbohydrates
Widely distributed in nature Key intermediates of metabolism (sugars) Found in the structural components of plants (cellulose) Important in manufacturing materials of industrial products: Paper, lumber, fibers Key component in food sources Sugars, flour, vegetable fiber Chemical Formula and Name
Term carbohydrate comes from the historical belief that glucose was a hydrate of carbon Carbohydrate generally refers to polyhydroxylated aldehydes and ketones Classification of Carbohydrates
Simple sugars(monosaccharides) cannot be converted into smaller sugars by hydrolysis Complex carbohydrates consist of two or more simple sugars connected by acetal bonds Classification of carbohydrates Naturally Occurring D Sugars
D sugars occur naturally and have the hydroxyl group at the bottom of the chirality center pointing to the right L sugars are the mirror image of corresponding D sugars and have the opposite configuration from the D sugar at all chirality centers D, L sugars Anomers Anomers are produced when an open-chain monosacchride cyclizes to a pyranose form Cyclization of the open-chain monosacchride results in generation of a new chirality center at the former carbonyl atom The hemiacetal carbon is called the anomeric center Cyclic structures of monosaccharides: Anomers Glucose in its Cyclic Pyranose Forms
Cyclic structures of monosaccharides: Anomers Glycoprotein Formation
Reactions of monosaccharides The Eight Essential Monosaccharides
Cells need eight monosaccharides for proper functioning It is more energetically efficient to obtain these from environment than through biosynthesis They include L-fucose, D-galactose, D-glucose, D-mannose, N-acetyl-D-glucosamine, N-acetyl-D-galactosamine, D-xylose, and N-acetyl-D-neuraminic acid The eight essential monosaccharides The Eight Essential Monosaccharides Maltose and Cellobiose
Disaccharides Lactose Disaccharide that occurs naturally in milk
Contains two different monosaccharides joined by a -glycosidic bond Disaccharides Sucrose Also known as table sugar
Yields 1 equivalent of glucose and 1 equivalent of fructose on hydrolysis Disaccharides Polysaccharides and Their Synthesis
Polysacchrides are complex carbohydrates in which many simple sugars are linked Cellulose and starch are the two most widely occurring polysaccharides Polysaccharides and their synthesis Cellulose Comprises thousands of D-glucopyranosyl 14--glucopyranosides as in cellobiose Cellulose molecules form a large aggregate structures held together by hydrogen bonds Main component of wood and plant fiber Polysaccharides and their synthesis Starch and Glycogen Digested into glucose Components of starch
Starch comprises monosaccharide units linked by 14--glycoside bonds Digested into glucose Components of starch Amylose, which comprises 20% of starch Polysaccharides and their synthesis Starch and Glycogen Amylopectin, which comprises 80% of starch
Polysaccharides and their synthesis Glycogen Polysaccharide that serves the same energy storage function in animals that starch serves in plants Highly branched and larger than amylopectin-up to 100,000 glucose units Polysaccharides and their synthesis Biomolecules Amino acids contain a basic amino group and an acidic carboxyl group They are joined as amides between the NH2 of one amino acid and the CO2H to the next amino acid Chains with fewer than 50 units are called peptides A protein comprises of large chains that have structural or catalytic functions in biology Structures of Amino Acids
Amino acids occur primarily in the form of a dipolar ion, orzwitterion, in an aqueous solution Since amino acid zwitterions are internal salts, most properties are associated with salts Amino acids are amphiprotic Structures of amino acids Common Amino Acids 20 amino acids form amides in proteins
All are -amino acids - Amino and carboxyl are connected to the same C They differ by the other substituent attached to the carbon, called the side chain Structures of amino acids The 20 Common Amino Acids in Proteins
Structures of amino acids The 20 Common Amino Acids in Proteins
Structures of amino acids The 20 Common Amino Acids in Proteins
Structures of amino acids The 20 Common Amino Acids in Proteins
Structures of amino acids Chirality of Amino Acids
The carbons of the amino acids are centers of chirality Glycine is achiral The stereochemical attributes of naturally occurring -amino acids are similar to that of L sugars -amino acids are also called L amino acids Structures of amino acids Classification Based on Side Chains
Common amino acids can be classified as: Neutral - Fifteen amino acids Acidic - Two amino acids Aspartic and glutamic acid Basic - Three amino acids Lysine, arginine, and histidine Cysteine and tyrosine possess weakly acidic chains that can be protonated in a basic solution Classified as neutral amino acids Structures of amino acids Essential Amino Acids Humans can synthesize only 11 of the 20 amino acids Called non-essential amino acids Rest are obtained from food Found in plants and microorganisms Called essential amino acids Structures of amino acids Isoelectric Point (pI) of Amino Acids
It is the pH at which the amino acid is balanced between anionic and cationic forms Exists primarily as the neutral, dipolar zwitterion Amino acids and the Henderson-Hasselbalch equation: Isoelectric points Peptides and Proteins Proteins and peptides are amino acid polymers in which the individual amino acid units, called residues, are linked together by amide bonds or peptide bonds Peptides and proteins Peptides and Proteins The long repetitive sequence of NCHCO atoms that make up a continuous chain is called the proteins backbone Peptides are always written with the N-terminal amino acid (the one with the free NH2 group) on the left and the C-terminal amino acid (the one with the free CO2H group) on the right Alanylserine is abbreviated Ala-Ser or A-S, and serylalanine is abbreviated Ser-Ala or S-A Peptides and proteins Peptide Linkages Amino acids in peptides are linked together by amide bonds Amide nitrogen interacts with the carbonyl group, causing delocalization of its unshared electron pair Peptides and proteins Peptide Linkages Disulfide linkages in peptides occur between two cysteine residues Peptides and proteins Protein Structure Classified as fibrous or globular
Fibrous proteins comprise polypeptide chains arranged side by side in long filaments Tough and insoluble in water Globular proteins are coiled into compact, roughly spherical shapes Soluble in water and are capable of motion within the cells Protein structure Protein Structure The primary structure of a protein is simply the amino acid sequence. The secondary structure of a protein describes how segments of the peptide backbone orient into a regular pattern. The tertiary structure describes how the entire protein molecule coils into an overall three-dimensional shape. The quaternary structure describes how different protein molecules come together to yield large aggregate structures Protein structure -Helix Right-handed coil of the protein backbone
Each spiral contains 3.6 amino acid residues Protein structure -Pleated Sheet -pleated sheet contains a fully extended peptide chain Protein structure Tertiary Proteins Structure of tertiary proteins is influenced by
Hydrophilic interactions of the polar side chains Hydrophobic interactions of the nonpolar side chains Formation of disulphide bridges between cysteine residues Formation of hydrogen bonds between nearby amino acid residues Salt bridges Protein structure Denaturation of Proteins
The tertiary structure of a globular protein is the result of weak intramolecular attractions that can be disrupted by a change in temperature or pH, causing the protein to become denatured Protein structure Enzymes and Coenzymes An enzyme is a protein that acts as a catalyst for a biological reaction. Increases the rate of reaction by decreasing the activation energy Most enzymes are specific for substrates while enzymes involved in digestion, such as papain, attack many substrates Enzymes and coenzymes Enzymes and Coenzymes Factors that contribute to the accelerating action of enzymes: Ability to adjust their shape Wrapping action Ability to lower the rate-limiting transition state Enzymes and coenzymes Energy Diagrams for Uncatalyzed and Enzyme-Catalyzed Processes
Enzymes and coenzymes Classification of Enzymes
Enzymes and coenzymes Enzymes and Coenzymes Most enzymes contain a non-protein component called a cofactor It is either an inorganic ion or a small organic molecule called a coenzyme Coenzymes are reactants that undergo a chemical change during the reaction and require an additional step to revert to their initial state Derived from vitamins Enzymes and coenzymes Lipids Natural molecules that can be preferentially extracted using nonpolar organic solvents Includes fats, oils, waxes, vitamins and hormones, some components of membrane Classified based on hydrolysis Fats and waxes Waxes, Fats, and Oils Waxes contain various esters formed from long-chain (C16-C36) carboxylic acids and long-chain alcohols (C24-C36) Triacontyl hexadecanoate is found in beeswax Waxes, Fats, and Oils Triacylglycerol Triesters of glycerol with three long-chain carboxylic acids called fatty acids Waxes, Fats, and Oils Structures of Some Common Fatty Acids
Waxes, Fats, and Oils Fatty Acids When hydrolysed with NaOH, a fat or oil yields glycerol and three fatty acids Fatty acids contain an even number of carbon atoms and are unbranched Of the 100 different known fatty acids, 40 are common Palmitic acid (C16) and stearic acid (C18) are the most common saturated fatty acids Oleic (C18) and linoleic (C18) acids are the most common unsaturated fatty acids Waxes, Fats, and Oils Fatty Acids Monosaturated fatty acids have one double bond
Oleic acid Polyunsaturated fatty acids have more than one double bond Linoleic, linolenic, and arachinodic acid Humans require linoleic and linolenic acid Deprivation leads to stunted growth and skin lesions in infants Linolenic acid has shown to lower blood tryglyceride levels Waxes, Fats, and Oils Unsaturated and Polyunsaturated Fatty Acids
Waxes, Fats, and Oils Double Bonds in Fatty Acids
Melting points of unsaturated fatty acids are generally lower than those of saturated fatty acids Number of double bonds influences the melting point of oil Catalytic hydrogenation reduces the number of double bonds Reaction is carried at a high temperature using a nickel catalyst Remaining double bonds undergo cis-trans isomerization, resulting in trans unsaturated fatty acids Waxes, Fats, and Oils Soap Mixture of sodium or potassium salts of long-chain fatty acids produced by alkaline hydrolysis (saponification) of animal fat with alkali Soap Cleansing Action of Soap
Carboxylate end of the long-chain molecule is ionic and therefore is hydrophilic Hydrocarbon tail is nonpolar and dissolves in grease and oil Soaps enable grease to be dissolved into water Soap Phospholipids Phospholipids are diesters of H3PO4, phosphoric acid
Classified into glycerophospholipids and sphingomyelins Glycerophospholipids
Based on phosphatidic acid, which contains a glycerol backbone linked by ester bonds to two fatty acids and phosphoric acid Phospholipids Phosphoglyceride Membranes
Phosphoglycerides are the major lipid component of cell membranes Their nonpolar tails aggregate in the center of a lipid bilayer Phospholipids Steroids Molecules derived from the triterpenoid lanosterol
Has four fused rings A, B, C, and D, beginning at the lower left Steroids Steroids Two cyclohexane rings can be joined in either a cis or trans manner Steroids Steroid Conformations
Steroids Male Sex Hormones Testosterone and androsterone are the two most important male sex hormones, or androgens Have a significant influence on the development of secondary sex characteristics and muscle growth Steroids Female Sex Hormones Estrone and estradiol are two most important female sex hormones, or estrogens Progesterone is the most important progestin; it that functions during pregnancy Steroids