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Organic Molecules Chapter 3 2- Carbon: The Central Atom Carbon is the central atom in all organic molecules. Carbon has unique bonding properties. – – 3- Can combine with other carbon atoms in long chains Can form ring structures Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Carbon: The Central Atom Carbon atoms participate in four covalent bonds. – – – 3- Has four electrons in the outer energy level Can double bond with oxygen Can triple bond with other carbon atoms Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Organic Molecules Organic Molecules – – – Some Inorganic molecules are incorporated as well – 3- Composed of Carbon and Hydrogen Elements Nitrogen, Oxygen, Phosphate, Sulfur also included in small amounts as trace elements These six elements compose 98.5% of body weight (Saladin, 5th ed.) The Heme group in Hemoglobin contains Fe, for example Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Biochemistry The study of the chemistry of living things 4 Classes of Biological Molecules 1. Carbohydrates 2. Nucleic Acids 3. Proteins 4. Lipids 3- The Classes are determined by the proportions of C, H, O in the molecule Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Organic Molecules Organic molecules are composed of: 1. A Central Carbon or Carbon Chain 2. Functional Groups 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Carbon Skeleton All organic molecules have a carbon skeleton. – This determines the overall shape of the molecule. Organic molecules differ in these ways: – – – The length and arrangement of the carbon skeleton The kinds and location of atoms attached to it How the attached atoms are combined together 3- These combinations are called functional groups. Functional groups determine the chemical nature of the molecule. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Organic Molecules The carbon chain backbone of a molecule or Carbon Skeleton: –CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH3 3- Recall: Carbon makes 4 covalent bonds Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Functional Groups 3- Functional Groups are specific combinations of bonded atoms attached to a Carbon Skeleton The Functional Groups determine the chemistry of the molecule Functional groups behave in chemically predictable ways Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Functional Groups 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Isomers Several factors determine the properties of an organic molecule. – – The types of atoms in the molecule The 3-D arrangement of atoms within the molecule Organic molecules can have the same number and composition of atoms, but can have different arrangements. – These are called isomers. 3- Molecules with the same empirical formula but different structural formulas Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Isomers Pentose C5H10O5 empirical formula Hexose C6H12O6 empirical formula 67 Hexose Isomers 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Macromolecules of Life Macromolecules are very large organic molecules. Most important organic compounds found in living things are large macromolecules – – – – 3- Carbohydrates Proteins Nucleic acids Lipids Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Macromolecules Biological molecules are typically Marcomolecules Very large molecules with high molecular weights – Macromolecules are Polymers assembled from smaller Monomers – – 3- DNA over a meter long Monomers - small, identical or similar subunits Polymers - covalently bonded monomers Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Polymers • Proteins - amino acid monomers polymerize to form proteins • Nucleic acids - nucleotide monomers polymerize to form DNA and RNA Macromolecules • Carbohydrates: •Simple sugar monomers polymerize to form complex sugars •Monosaccharides polymerize to form disaccharides, polysaccharides 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Polymerization 3- The joining monomers to form a polymer Dehydration Synthesis - the chemical reaction for how living cells form polymers A bond is formed between monomers and water is produced as a product of the reaction As the name implies, water is lost during the reaction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dehydration Synthesis 3- A hydroxyl (-OH) group is removed from one monomer, and a hydrogen (H+) from another A new covalent bond is formed between the monomers Water is released as a by-product Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dehydration Synthesis 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hydrolysis The reaction for the separation of joined monomers – Opposite of dehydration synthesis – – – 3- “Splitting with water” a water molecule ionizes into –OH and H+ the covalent bond linking one monomer to the other is broken the –OH is returned to one monomer, the H+ is returned to the other Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hydrolysis 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. Carbohydrates Sugars 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Carbohydrates Organic molecules composed of carbon, hydrogen and oxygen All follow the general formula CH2O Names end in –ose Serve as the primary energy source for most living things Also serve as structural support – Important components of nucleic acids – 3- Plant cell walls DNA and RNA Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Carbohydrates Sugars, Starches, Fibers Names of carbohydrates often built from: – – – 3- word root ‘sacchar-’ the suffix ’-ose’ both mean ‘sugar’ or ‘sweet’ Monosaccharide or Glucose Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Carbohydrates Carbohydrates are composed of carbon backbones with Hydroxyl Groups and a Carboxyl Group – – 3- R-OH R-COOH The carbon backbone may be a in straight line or a closed ring of carbon atoms Polar and therefore Hydrophilic Molecules Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Carbohydrates 60 Carbohydrates The Proportions of C, H, and O for Carbohydrates follow the General Formula: – – 3- CnH2nOn n = number of carbon atoms For glucose, n = 6, so formula is C6H12O6 2:1 ratio of hydrogen to oxygen Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Simple Sugars Simple sugars are described by the number of carbons in the molecule. – – – Common names of simple sugars: – – – 3- Triose-3 carbons Pentose-5 carbons Hexose-6 carbons Glucose Fructose Galactose Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Simple Sugars Numbering the C’s – For Example: – 3- Carbohydrates are classified by the number of Carbon atoms they contain Ribose is a pentose sugar because it contains 5 carbon atoms. Glucose is a hexose sugar because it contains 6 carbon atoms Many Carbohydrates have informal names that do not provide information about the molecule Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Simple Sugars Numbering the Carbons – The Carbons of Carbohydrates are numbered For Example: – – 3- Numbering System allows the molecules to be described efficiently Describing locations of covalent bonds Ribose vs 2’ Deoxy-ribose Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Carbohydrate Structure Numbering the Carbons Ribose vs. 2 Deoxyribose • Ribose • 2’ Deoxyribose 7 Simple Sugars 32 Simple Sugars There are over 200 different monosaccharides Monosaccharides differ in the number of carbon atoms they contain in the C-C backbone (Ex. hexose vs. pentose) Monosaccharides also differ in their 3-D shape – 3- Isomers Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Isomers of Monosaccharides Pentose C5H10O5 empirical formula Hexose C6H12O6 empirical formula 67 Functions of Monosaccharides Energy Source – – – efficiently oxidized for energy the C-H bonds are high in energy the C-H bonds are oxidized Most Important example: – Glucose in Cellular Respiration C6H12O6 + 6O2 Glucose Oxygen 3- 6H2O + 6CO2 +Energy Water Carbon Dioxide Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Complex Carbohydrates When two or more simple sugars are combined, they form complex carbohydrates. – Formed via dehydration synthesis Disaccharides – Two simple sugars 3- Sucrose Lactose Maltose Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Polysaccharides Structure – Functions – – – 3- Multiple Monosaccharides linked together 1. Structural Molecules 2. Signaling Molecules 3. Energy Storage Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Polysaccharides Contain many simple sugars Examples of polysaccharides: – Starch and glycogen – Used for energy storage in plants (starch) and animals (glycogen) Cellulose Important component of plant cell walls Humans cannot digest cellulose; it is the fiber in our diet. – Helps facilitate movement of food through the digestive tract – 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Complex Carbohydrates 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycogen Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. CH2OH O O O O CH2OH O CH2OH O CH2 O (a) CH2OH O O CH2OH O O O O O (b) Figure 2.18 2-73 Glycogen Stryer's Biochemistry Fig. 23-2 82 Complex Carbohydrates Starch: energy storage polysaccharide in plants Cellulose: structural molecule of plant cell walls – 3- fiber in our diet Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Complex Carbohydrates Conjugated carbohydrates – covalently bound to lipid or protein – glycolipids – glycoproteins 3- external surface of cell membrane external surface of cell membrane mucus of respiratory and digestive tracts Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Viral Bioinformatics Resource Center athena.bioc.uvic.ca/.../copy9_of_sample/surface 24 2. Amino Acids Proteins 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Amino Acids Protein - a polymer of amino acids – 3- Amino acids - the monomers of proteins 20 Amino acids are used to construct proteins Peptide Bonds are the covalent bonds between adjacent amino acids Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Protein Functions Structure – – Communication – – 3- keratin – tough structural protein gives strength to hair, nails, and skin surface collagen – durable protein contained in deeper layers of skin, bones, cartilage, and teeth some hormones and other cell-to-cell signals receptors to which signal molecules bind Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Protein Functions Membrane Transport – 3- channels in cell membranes carrier proteins – transports solute particles to other side of membrane turn nerve and muscle activity on and off Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Protein Functions Catalysis – Recognition and Protection – – – 3- enzymes immune recognition antibodies clotting proteins Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Protein Functions Movement – 3- motor proteins - molecules with the ability to change shape repeatedly Cell adhesion proteins bind cells together immune cells to bind to cancer cells keeps tissues from falling apart Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Amino Acid Structure A Central carbon with 4 attachments: 1. amino group (NH2) 2. carboxyl group (COOH) 3. radical group (R group) 4. hydrogen 3- Properties of amino acid determined by the -R group Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Amino Acid Structure 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Amino Acid Structure 3- By definition, all amino acids have the amine and carboxyl functional groups in common Amino differ in the side chains Different side chains (-R Groups) give amino acids different chemical properties (for example, some amino acids are hydrophobic, some are hydrophilic) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Representative Amino Acids Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Some nonpolar amino acids Some polar amino acids Methionine H Cysteine H H N N C H CH2 CH2 S C H CH3 O OH O Tyrosine H SH H H C OH Arginine N H N CH2 OH H C O CH2 C C H H C NH2+ (CH2)3 O C NH2 C OH NH Figure 2.23a OH (a) • Note: they differ only in the R group 2-86 Amino Acid Structure The structure of the R group dictates the chemical properties of the amino acid. Amino acids can be classified as: – – – – – 3- 1. nonpolar 2. polar 3. charged 4. aromatic 5. special functions (acidic, basic) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 3.20 Peptides Peptide – any molecule composed of two or more amino acids joined by peptide bonds – – Peptides – – – 3- Peptide Bond – joins the amino group of one amino acid to the carboxyl group of the next formed by dehydration synthesis – dipeptides have 2 oligopeptides have fewer than 10 to 15 polypeptides have more than 15 proteins have more than 50 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Peptide Bonds 3- Amino acids are joined together into polypeptide chains through a DEHYDRATION REACTION Similarly, Polypeptide chains are cleaved apart through a HYDROLYSIS REACTION Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Amino Acid Polymerization 59 Amino Acid Polymerization 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Formation of a Peptide Bond Dehydration Reaction: The loss of water Hydrolysis Reaction Hydrolysis Reaction: The Bond is Cleaved with water H2O Find the Peptide Bond Peptide Bond Terminal Animo Group Side Chain Carboxyl Group Peptide Bond Amino Group Side Chain Protein Structure and Shape Protein properties and functions depend on Protein Conformation – 3- Conformation – unique three dimensional shape of protein crucial to function Because of unique conformations, proteins are very specific to their functions Protein conformation depends on the environment Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Protein Structure and Shape Four Level of Protein Structure 1. Primary structure 2. Secondary structure 3. Tertiary structure 4. Quaternary structure 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. Primary Structure 3- The sequence of amino acids in a polypeptide constitutes the primary structure of the protein. This sequence is dictated by information in genes (DNA). All levels of protein structure depend on the primary sequence. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2. Secondary Structure Polypeptides twist and fold into their secondary structure. – Some sequences of amino acids twist into a helix. – Some sequences of amino acids remain straight and fold back on themselves. 3- This is called an alpha helix. This is called a beta-pleated sheet. Held in place by bonds between Rgroups within the polypeptide chain Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 3.21a Fig. 3.22-2 Fig. 3.22-3 3. Tertiary Structure 3- 3-D shape of protein The various alpha helices and beta pleated sheets interact to form a globular structure. This globular structure is unique for each polypeptide. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 3.22-4 4. Quaternary Structure Some proteins contain more than one polypeptide chain. Each of these polypeptides has its own unique tertiary structure. – 3- These polypeptides interact to form a more complex globular structure. Quaternary structure can be stabilized by disulfide bonds. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 3.22 Form and Function The protein’s overall shape determines its job. If a protein is not shaped properly, it likely will not work properly. Example: – – – Denaturation: – 3- Sickle cell anemia A mutation in the gene causes the protein to have a different shape. This shape change results in a change in function. When heat or other environmental conditions break the bonds that stabilize tertiary structure. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Types of Proteins Structural proteins – – Regulatory proteins – – Determine what activities will occur in a protein Enzymes and hormones Carrier proteins – 3- Important in maintaining the shape of cells and organisms Collagen – Transport molecules from one place to another Lipoproteins Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Enzymes Enzymes - special class of proteins that functions as biological catalysts – facilitate chemical reactions The Rules to be an Enzyme 1. It is a protein molecule that speeds up a chemical reaction 2. Enzymes are not changed during the reaction 3. Enzymes can be re-used many times 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3. Nucleic Acids DNA 3- and RNA Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucleic Acids The largest biological molecules Store and transfer information within a cell Include DNA and RNA Are made of nucleotides – – – 3- 5-carbon sugar Phosphate group Nitrogenous group Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucleotides 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucleic Acids DNA = Deoxyribonucleic Acid – RNA = Ribonucleic Acid – – 3- Function to store, transport, and control hereditary information carries out genetic instruction for synthesizing proteins assembles amino acids in the right order to produce proteins Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucleic Acids 3- Nucleic Acids are composed of Carbon, Hydrogen, Oxygen, Nitrogen and Phosphorous atoms Nucleotides are the building blocks of nucleic acids (DNA and RNA) and ATP Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucleotides 3 components of nucleotides 1. Nitrogenous base 2. Ribose Sugar (monosaccharide) 3. Phosphate groups 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucleotides 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucleotides - Nitrogenous Base 3- There are 5 different Nitrogenous Bases to choose from when building Nucleic Acids: Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucleotides - Nitrogenous Base 87 Nucleotides - Nitrogenous Base 3- • DNA is composed • RNA is composed of of the Nitrogenous Bases: Thymine, Cytosine, Adenine, and Guanine the Nitrogenous Bases: Uracil, Cytosine, Adenine, and Guanine Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucleotides - Ribose Sugar The Nucleotides of DNA – – 3- The name, Deoxyribonucleic Acid, tells us the structure of the ribose sugar in the Nucleotides of DNA It lacks a hydroxyl group at C2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucleotides - Ribose Sugar The Nucleotides of RNA – 3- The name, Ribonucleic acid, tells us the structure of the ribose sugar in the RNA Nucleotides Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucleotides - Phosphate Group 3- Both The Phosphate Group and the Nitrogenous Base attach to the central Ribose Sugar The Phosphate Group is important in forming the “Backbone” of the Nucleic Acid Molecule Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Phosphate Group of Nucleotides 158 Polymerization of Nucleotides to Make Nucleic Acids 3- Nucleotides are covalently bound together into long strands through a Dehydration Reaction The Phosphate of one Nucleotide is bound to the Ribose Sugar of an adjacent nucleotide These Phosphate-Ribose bonds form the backbones of the Nucleic Acid Molecules Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Backbone is formed by multiple C3C5 phospho-ribose linkages 160 The Backbone is formed by multiple C3C5 phospho-ribose linkages 161 DNA Molecular Structure Two DNA strands are united by hydrogen bonds to form the doublehelix DNA base pairing – – Law of Complementary Base Pairing – 3- A – T with 2 hydrogen bonds C – G with 3 hydrogen bonds One strand serves as the template for the complementary strand Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Structure of DNA 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Complementary Base Pairing 164 Fig. 3.16-1 Nucleic Acids 100 DNA DNA stores the genetic code for constructing proteins – Genes – 3- the code is stored in the order of nitrogenous bases along a single stand Each segment of DNA that codes for a protein is known as a gene. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. DNA and Chromosomes 3- Each DNA strand has many genes. Each DNA strand (molecule) is called a chromosome. Human cells have 46 chromosomes in each cell Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Functions of DNA DNA is able to: – – – – 3- Replicate itself Store information and transmit it to offspring Direct synthesis of proteins Mutate (change chemically) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. RNA RNA is a single-stranded molecule. Base pairs with itself and DNA – – RNA is found in three different forms: – – – 3- A-U G-C mRNA (messenger RNA) rRNA (ribosomal RNA) tRNA (transfer RNA) RNA functions in the decoding of DNA and the construction of proteins Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Functions of DNA 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. DNA vs. RNA 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Other Nucleotide Molecules ATP: Adenosine triphosphate – NAD+ and FAD – 3- primary energy currency of the cell electron carriers for many cellular reactions Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4. Lipids Fats 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lipids Commonly called fats Large and nonpolar – – Composed of C, H, O – Do not dissolve in water Dissolve in other nonpolar molecules like acetone Contain fewer oxygen atoms than carbohydrates There are three main types of lipids: 1. True fats (Triglycerides) 2. Phospholipids 3. Steroids 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. True Fats (Triglycerides) Function: – energy source Structure: 1. A glycerol molecule 2. Three fatty acids 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. True Fats (Triglycerides) Composed of 2 Parts: 1. Glycerol Molecule 2. Three Fatty Acids (tri) 3 fatty acids covalently bonded to a glycerol molecule – – 3- each bond formed by dehydration synthesis broken down by hydrolysis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. True Fats (Triglycerides) Glycerol is a 3 carbon molecule with 3 hydroxyl groups – 3- One, two, or three fatty acids can bind at the locations of the Hydroxyl Groups to form a lipid Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. True Fats (Triglycerides) Fatty Acids are chains of 4 to 24 carbon atoms – There is a carboxyl group on one end of the chain – There is a methyl group on the other end of the chain – 3- -COOH -CH3 Hydrogen atoms bonded along the side Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fatty Acids • Chain of 4 to 24 carbon atoms – carboxyl group on one end, methyl group on the other and hydrogen bonded along the side H H H H H H H H H H H H H H H C C C C C C C C C C C C C C C H H H H H H H H H H H H H H H O C H HO Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 2.19 2-77 Triglyceride Synthesis Glycerol + 3 Fatty Acids A Triglyceride + 3H2O A Dehydration Rxn. 96 Fatty Acids Classes of Fatty Acids 1. Saturated - carbon chains are saturated with hydrogen 2. Unsaturated - carbon chains contain C=C bonds 3. Polyunsaturated – contains many C=C bonds 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Saturated and Unsaturated Fatty Acids 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Saturated and Unsaturated Fatty Acids 87 Saturated and Unsaturated Fatty Acids 3- The Saturation or Unsaturation of the Fatty Acids affects the properties of the lipid Unsaturations put “kinks” in the fatty acids Kinks in the fatty acids prevent them from stacking together, making them less stable solids Unsaturated Fats are usually liquids at room temperature – plant fats Copyright (oils)© The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Saturated and Unsaturated Fatty Acids 3- Saturated fats are not kinked They stack together making the lipid more stable solids Saturated Fats are usually solid at room temperature – animal fats and waxes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Saturation • Saturated Fatty Acids • Unsaturated Fatty Acids 94 2. Phospholipids 3- Similar to triglycerides except that one fatty acid is replaced by a phosphate group on the glycerol Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3. Phospholipids • Phospholipids are Amphiphilic molecules – fatty acid “tails” are hydrophobic – phosphate “head” is hydrophilic Polar Head Group Nonpolar Hydrocarbon Tail 101 2. Phospholipids 3- Phospholipids form droplets or lipid bilayers in water The hydrophobic tail regions of the phospholipid move toward the inside of the droplets The hydrophilic head regions are exposed to the water environment Phospholipids form cell membranes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Phospholipid droplet in water 125 Phospholipid bilayer in water 126 4. Steroids Composed of 4 carbon rings Steroids are important components of cell membranes. – Steroids often serve as hormones and serve in regulation of body processes. – 3- Cholesterol Testosterone, estrogen Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Overview 3- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.