01_CHAPTER 1 MACROMOLECULES 20242025 (1).pdf

CHAPTER 1 MACROMOLECULES BIO091 Semester 1 2024 / 2025  SUB-TOPICS 1.1 Functional groups 1.2 Water 1.3 Introduction to macromolecules 1.4 Amino acids, peptides and proteins 1.5 Structures and functions of carbohydrates...

CHAPTER 1 MACROMOLECULES BIO091 Semester 1 2024 / 2025  SUB-TOPICS 1.1 Functional groups 1.2 Water 1.3 Introduction to macromolecules 1.4 Amino acids, peptides and proteins 1.5 Structures and functions of carbohydrates 1.6 Structures and functions of lipids 1.7 Structures and functions of nucleic acids 2  LEARNING OUTCOMES 1.1 Discuss some biologically important functional groups. 1.2 Explain the structure of water and describe the properties of water and its importance. 1.3 Formation of macromolecules from monomers. 1.4 Describe the general structure of amino acids and group them based on their side chains. 1.4 Describe the formation of dipeptide and polypeptide. 1.4 Discuss the classification of protein in term of levels of organization, structure, composition and functions. 3  1.5 Describe the four groups of carbohydrates. 1.5 Describe the synthesis of disaccharides and polysaccharides. 1.5 Describe the structure and function of starch, glycogen and cellulose. 1.6 State the types of lipids. 1.6 Describe the synthesis and structure of fat/triglycerides. 1.6 State the functions of lipids. 1.7 Describe the structures and components of nucleic acids. 1.7 State the types and functions of DNA and RNA. 4  INTRODUCTION Proteins, DNA, carbohydrates, and lipids contain C atom/elements; H, O, N, S, P. Atoms are held together by chemical bonds.  CHEMICAL BONDS Types of chemical bonds: 1. Covalent bond 2. Ionic bond 3. Hydrogen bond 4. Hydrophobic interaction 5. Van der Waals interaction  ELECTRONEGATIVITY Is an atom’s affinity or attraction for electrons. The more electronegative an atom is, the more strongly it pulls shared electrons toward itself. 7  1. COVALENT BOND Is the sharing of a pair of electrons by two atoms. No unpaired electrons. Strength depends on the number of shared electrons. Maybe single, double, or triple (with 1, 2, or 3 shared pairs of electrons respectively). 8 Two (2) types of covalent bonds: 1) Nonpolar covalent bond A covalent bond between 2 atoms of the same element, where the electrons are shared equally because the 2 atoms have the same electronegativity. Eg: Two hydrogen atoms share one pair of electrons: H – H 2) Polar covalent bond When an atom is bonded to a more electronegative atom, the electrons of the bond are not shared equally. Such bonds vary in their polarity. E.g.: The bonds between the oxygen and two hydrogen atoms of H2O molecule are quite polar. ✓ The oxygen atom is more electronegative. Therefore, it attracts shared electrons more strongly than the H atom.  POLAR & NON POLAR MOLECULE 1) Water Molecule 2) Ethane Molecule Electrons of hydrogen atoms have a negative The individual bonds of ethane are much less polar charge and are pulled toward the oxygen atom in a because the electronegativities of carbon and water molecule. hydrogen are similar The O atom has a partial negative charge, Each H atom has a partial positive charge.  2. IONIC BOND The chemical attraction between a cation and an anion. ⮚ Na atom loses an electron to become Na+ ⮚ Cl atom gains an electron to become Cl– ⮚ Opposite charges of Na+ and Cl– is linked by ionic bond to form an ionic compound. 12  3. HYDROGEN BOND ⮚A weak attractive force exists between a hydrogen atom with a partial positive charge, δ− δ+ and an electronegative atom (N, O, F). Water (H2O) ⮚ Hydrogen bond is formed between two δ+ Hydrogen bond Hydrogen bond molecules. δ− ⮚ Hydrogen bonds are collectively strong when δ+ δ+ present in large numbers. δ+ Ammonia (NH3) H has partial positive charge. O and N with partial negative charge.  4. HYDROPHOBIC INTERACTION The interaction between the non-polar/ hydrophobic molecules in a polar solvent (usually water). E.g: The mixing of fats (non-polar) in water (polar).  5. Van der Waals INTERACTION ⮚ Weak attractive forces between atoms caused by interaction among fluctuating charges. ⮚ Individually weak & occur when atoms & molecules are very close together. ⮚ But when many such interactions occur simultaneously → they can be powerful. 15  BONDS & INTERACTIONS Name Basis of interaction (1) Covalent bond Sharing of electron pairs. Between atom in a molecule. (A) Ionic bond Attraction of opposite charges. (B) Hydrogen bond Between partially positive hydrogen Between atom of different atom and partially negative atom in molecule. polar covalent bonds. (2)Non covalent bonds (C) Hydrophobic interaction / Forcing of hydrophobic portion of hydrophobic exclusion molecules together when placed in water. (D) Van der Waals Weak attraction between atoms due to interaction opposite polarized electron clouds.  ISOMERS “Compounds with the same molecular formula but different structures and properties.”  ISOMERS Structural Isomers have different covalent arrangements of their atoms.  ISOMERS Cis-trans Isomers have the same covalent arrangements but differ in spatial arrangements.  ISOMERS Enantiomers are isomers that are mirror images of each other. 20 FUNCTIONAL GROUPS  CHEMICAL GROUPS (Functional groups) A functional group is a group of atoms that give distinctive properties of an organic molecule to which it is attached. Involved in chemical reactions. 1. Hydroxyl group 2. Carbonyl group 3. Carboxyl group 4. Amino group 5. Sulfhydryl group 6. Phosphate group 7. Methyl group 23 24 25 26 27 28 29 WATER  WATER MOLECULE Water is a polar molecule: ⮚ One end of each molecule have a partial positive charge (H) and a partial negative charge (O).  Each water molecule can form hydrogen bonds with as many as 4 neighboring water molecules. Hydrogen bonds between water molecules  THREE FORMS OF WATER The degree of Hydrogen bonding between water molecules are different for the three different forms of water: 1. Gas (vapor) 2. Liquid 3. Ice (a crystalline solid) Hydrogen bonds are formed or broken as water changes from one state to another.  As water boils – loose H bonds break → steam forms, containing minuscule water droplets. Water molecules move freely as water vapor (gas). In a liquid state → hydrogen bonds continually form, break, and re-form between water molecules. In ice, each water molecule form 4 H bonds with adjacent molecules. Forms a regular & evenly distanced crystalline lattice structure.  1. High specific heat capacity. 2. High heat 7. Cohesion of & Adhesion vaporization PROPERTIES OF WATER 3. Good 6. Reactivity solvent 5. 4. High Transparency density  PROPERTIES OF WATER 1. Water has a high specific heat capacity: ⮚ A large amount of heat energy is required to raise the temperature of the water. ⮚ The specific heat of water is 1 calorie / g of water per degree Celsius. ⮚Therefore, water temperature is fairly stable when air temperature changes rapidly. ⮚Essential for: ✔ enzymes activities, ✔ aquatic organisms living in oceans and lakes (these large bodies of water have relatively constant temperatures) ✔ Stabilizes temperatures on Earth’s surface.  PROPERTIES OF WATER 2. High heat of vaporization: ⮚ Heat of vaporization is the amount of heat energy a liquid must absorb for 1 g to be converted to gas (vapor). ⮚ Water has a high heat of vaporization because much heat energy is absorbed to cause water molecules to move faster → to break H bonds between water molecules and evaporate from the water body surface ⮚.: As a liquid evaporates (taking heat along with it), its remaining surface cools, a process called evaporative cooling. ⮚ Evaporative cooling of water helps stabilize temperatures in organisms and bodies of water. ⮚ Examples: Sweating, panting, and transpiration are effective ways of cooling.  PROPERTIES OF WATER 3. Good/universal solvent: ⮚ A solvent is the dissolving agent of a solution. ⮚ Water is a polar molecule, so large polar molecules such as proteins can dissolve in water if they have ionic and polar regions. ⮚ Metabolic reactions take place between substances in solution. PROPERTIES OF WATER ⮚ When an ionic / polar compound is dissolved in water, ✓ each ion / molecule is surrounded by a sphere of water molecules called a hydration shell.  PROPERTIES OF WATER 4. High density: ⮚ Water is a dense liquid that enables it to support organisms by the upthrust it exerts. ⮚ Example: A whale could not support its body weight in the air. ⮚ Maximum density at 4°C and expand upon freezing (more H-bond form lattice in ice crystals). ⮚ Ice floats on water and lakes freeze at the top, protecting organisms below.  PROPERTIES OF WATER 5. Transparency: ⮚ Light sources can penetrate through the water medium. ⮚ Essential for photosynthesis in aquatic organisms like brown algae (phytoplankton).  PROPERTIES OF WATER 6. Reactivity: ⮚ Water can take part in chemical reactions in body metabolism. ⮚ Essential reactant in hydrolysis reactions and photosynthesis.  PROPERTIES OF WATER 7. Cohesion: ⮚ Linking together of water molecules by hydrogen bonds. ⮚ Cohesion helps the transport of water against gravity in plants. ⮚ Water has an unusually high surface tension due to hydrogen bonding between the water molecules at the air-water interface (meet/interact) and the water molecule below. Adhesion: ⮚ The ability to stick to many other kinds of substances such as charged group of atoms or molecules on their surfaces. ⮚ This explains how water makes things wet.   Adhesion of the water to cell walls by hydrogen bonds → helps resists the downward pull of gravity. Cohesion due to hydrogen bonds between water molecules, → helps hold together the column of water within the cell. Water transport in a plant. Evaporation from leaves pulls water upward from the roots through water-conducting cells45(xylem wall). ⮚ Surface tension is an attraction that molecules at the surface of a liquid may have for one another. ⮚ Due to the cohesion of water. For example, the collective strength of hydrogen bonding between water molecules allows this raft spider to walk on the surface of a pond. MACROMOLECULES  MACROMOLECULES ARE POLYMERS Four classes of large biological molecules: Carbohydrates, lipids, proteins, and nucleic acids. Polymer = long molecule consisting of many similar building blocks. Monomers = the small building blocks. Three of the four classes of macromolecules are polymers: ❑ Proteins ❑ Carbohydrates ❑ Nucleic acids  MONOMERS Components Examples Functions Enzymes Catalyze chemical reactions Defensive proteins Protect against disease Storage proteins Store amino acids Transport proteins Transport substances Hormones Coordinate organismal responses Receptor proteins Receive signals from outside cell Amino acid monomer Motor proteins Function in cell movement (20 types) Structural proteins Provide structural support Components Examples Functions Monosaccharides: glucose, Fuel; carbon sources that can be fructose converted to other molecules or combined into polymers Disaccharides: lactose, sucrose Polysaccharides: Cellulose (plants) Strengthens plant cell walls Monosaccharide Starch (plants) Stores glucose for energy monomer Glycogen (animals) Stores glucose for energy Chitin (animals and fungi) Strengthens exoskeletons and fungal cell walls 50  Components Examples Functions Glycerol Triacylglycerols (fats or oils): Important energy source glycerol + three fatty acids 3 fatty acids Head Phospholipids: glycerol + Lipid bilayers of membranes with P phosphate group + two fatty Hydrophobic acids tails 2 fatty acids Hydrophilic heads Steroids: four fused rings with Component of cell membranes attached chemical groups (cholesterol) Signaling molecules that travel through the body (hormones) Steroid backbone 51  Components Examples Functions Nitrogenous base DNA: Stores hereditary information Phosphate Sugar = deoxyribose group Nitrogenous bases = C, G, A, T P Usually double-stranded Sugar RNA: Various functions in gene Sugar = ribose expression, including carrying Nucleotide (monomer instructions from DNA to Nitrogenous bases = C, G, A, U of a polynucleotide) ribosomes Usually single-stranded SYNTHESIS AND BREAKDOWN OF POLYMERS PROTEIN PROTEINS Consists of one or more polypeptides. Monomer = amino acids. Feature of each amino acid:  α-carbon  carboxyl group  amino group  H atom  Side chain (R group) Each amino acid has different side chain [R group].  The R group of amino acids can vary in: structure charge (positive, negative, or neutral) affinity with water and the reactivity with other molecules There are 20 amino acids which commonly found in proteins, each identified by variable R groups. Amino acids are grouped by the properties of the side chain. R groups can be polar, nonpolar, acidic, and basic. 56 GROUPS OF AMINO ACIDS GROUPS OF AMINO ACIDS GROUPS OF AMINO ACIDS  Amino acids are amphoteric molecules ✓ have both basic and acidic groups. When dissolves in water, amino acids ionized to form zwitterions (bipolar): i. Basic amino group (a proton acceptor) is ionised into NH3+ , ii. Acidic carboxyl group (a proton donor) is ionised into COO-. Molecules with amphoteric properties can function as buffers - resist any change in pH and try to maintain the pH. 60  AMINO ACIDS POLYMERS Amino acids are linked by peptide bonds. A polypeptide is a polymer of amino acids.  CLASSIFICATION OF PROTEIN Proteins can also be classified based on: 1. Levels of organization 2. Structure 3. Composition 4. Functions 1) FOUR LEVELS OF ORGANIZATION IN PROTEIN I. Primary structure ✓ linear sequence of amino acids. II. Secondary structure ✓ results from hydrogen bonding involving the backbone. III. Tertiary structure ✓ interaction among various side chains (R groups). IV. Quaternary structure ✓ interaction among multiple polypeptide chains. Primary structure Simple, linear sequence of amino acids, joined by peptide bonds. Genetic code in DNA molecule determine the amino acid sequence of the polypeptide. Secondary structure Segments of a polypeptide chain that coiled or folded led to the protein’s overall shape. ⮚ coils & folds are the result of hydrogen bonds between the carboxyl and the amino groups of the polypeptide backbone. 2 types of secondary structures: i. α helix: coiled form ii. β pleated sheet: folded form i) α helix structure: The polypeptide chain is coiled to form a helical structure. The helical shape is maintained by hydrogen bonds between an oxygen of carboxyl group of one amino acid & a hydrogen of an amino group of the fourth amino acids down the chain. ii) β pleated sheet : 2 or more segments of a single polypeptide chain are arranged parallel to each other & held together by hydrogen bonds. Hydrogen bonds hold neighboring strands in different regions of a polypeptide chain. The polypeptide chains become folded. Has high resistance to stretching. It is strong and flexible.  Tertiary structure ✓ is the overall 3-D shape of a polypeptide chain that results from interactions between R groups of the amino acids. These interactions between R groups include hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals interactions. Strong covalent bonds called disulfide bridges may reinforce the protein’s structure. Quaternary structure ✓ The overall conformation of a protein produced by the interaction of two or more polypeptide chains. Collagen is a fibrous protein consisting of three polypeptides coiled like a rope. Hemoglobin is a globular protein consisting of four polypeptides: two alpha and two beta chains.  2) STRUCTURE Fibrous protein Globular protein Long strands of polypeptide chains. Polypeptide chains coiled and folded into globular shape. Composed of primary and secondary structure. Composed of secondary and tertiary structure. Polypeptide chains held by hydrogen bonds, form helical Polypeptide chains held by hydrogen bonds, ionic bonds, structure or pleated sheets. hydrophobic interactions, disulfide linkages and Van der Waals interaction. Repetitive amino acid sequences. Irregular amino acid sequences. Generally, insoluble in water. Generally soluble in water (can form colloidal suspension). Important function as structural and supporting protein. Important function in metabolic reactions. Examples: keratin, collagen, elastin, fibroin (silk protein). Examples: hemoglobin, myoglobin, antibodies, enzymes.  3) COMPOSITION 1. Simple proteins Consists only of amino acids. Do not contain any other substances. Examples: - Albumins : egg albumin, serum albumin. - Globulins : antibodies, fibrinogen. - Histones : protein associated with DNA. - Scleroprotein : keratin, collagen in connective tissues. 2. Conjugated proteins Contain protein & non-protein material (prosthetic group) Prosthetic group: required in protein function. 4) FUNCTION  DENATURATION OF PROTEIN Protein on Denaturation: Loss of a protein’s original structure/3D shape. Due to changes in pH, salt concentration, temperature. A denatured protein sometimes can return to its functional shape when: I. the denaturing agents are removed, II. the chemical and physical aspects of its environment are restored to normal. CARBOHYDRATES  CARBOHYDRATES Four groups of carbohydrates are: 1. Monosaccharides ✓ The simplest carbohydrates (simple sugars). 2. Disaccharides ✓ Consists of 2 monosaccharides joined by a covalent bond. 3. Oligosaccharides ✓ Consists of 3 – 14 monosaccharides. 4. Polysaccharides ✓ Polymers composed of many sugar monomers.  MONOSACCHARIDES Monosaccharides have molecular formulas that are usually multiples of CH2O. Glucose (C6H12O6) is the most common monosaccharide. Monosaccharides are classified by I. The location of the carbonyl group (as aldose or ketose). II. The number of carbons in the carbon skeleton.  MONOSACCHARIDES ⮚ Monosaccharide properties; have a sweet taste. can be crystallized. are polar due to the hydroxyl group attached to C atoms, forming H bonds with water. molecules - dissolve easily in water. have reducing properties.  MONOSACCHARIDES ⮚ The ring form of glucose can exist as α or β. α glucose β glucose The position of –OH at C1 is below The position of –OH at C1 is above the plane of the ring. the plane of the ring.  MONOSACCHARIDES ⮚ Monosaccharides are usually drawn as linear skeletons. ⮚ However, in aqueous solutions, monosaccharides form ring structures, which are more stable. linear skeletons ring structures The carbons of the sugars carbon 1 bonds to the oxygen are numbered from 1 – 6 to attached to carbon 5. form the glucose ring. 81  DISACCHARIDES A disaccharide is formed when a dehydration/condensation reaction joins two monosaccharides. This covalent bond is called a glycosidic linkage. Characteristics:  Water soluble  Sweet tasting  Can be crystallized (a) Dehydration reaction in the synthesis of maltose (b) Dehydration reaction in the synthesis of sucrose (c) Dehydration reaction in the synthesis of lactose  OLIGOSACCHARIDES Monosaccharides can be linked together to form small chains termed oligosaccharides. Each oligosaccharide may contain 3 to 14 monosaccharides. Oligosaccharides may be found attached to: I. Proteins → forming glycoproteins II. Lipids → forming glycolipids  POLYSACCHARIDES Polymer of monosaccharides, have storage and structural roles. The structure and function of a polysaccharide are determined by its sugar monomers and the positions of glycosidic linkages. Insoluble in water and not sweet in taste. Important as food storage and building materials for the cell or the whole organism. Example: starch, glycogen and cellulose, chitin and murein.  I) STARCH Starch, a storage polysaccharide of plants, consists entirely of α–glucose monomers. Plants cells store starch mainly as granules within specialized organelles called amyloplast. ✔Potatoes cells are very rich in amyloplasts. Plants hydrolyze the starch, releasing the glucose subunit. Glucose serves as cellular fuel to generate the energy needed for cell work. Starch is made up of 2 components: I) Amylose II) Amylopectin  2. Amylopectin: 1. AMYLOSE: ⮚ A highly branched polymer. ⮚ A linear unbranched polymer of α-glucose subunits linked together by α 1-4 glycosidic bonds. ⮚ Each branch of amylopectin is a short chain made up of many α-glucose subunits that are linked ⮚ The amylose chains are coiled into a helix held by together through α 1-4 glycosidic bonds. hydrogen bonds formed between hydroxyl groups of glucose subunits. ⮚ Branches are linked together through α 1-6 glycosidic bonds. Structure of amylose Structure of amylopectin 88 89  2) GLYCOGEN Glycogen is a storage polysaccharide in animals. Humans and other vertebrates store glycogen mainly in liver and muscle cells. The structure is similar to amylopectin, but it is a larger macromolecule made from α–glucose, with more branches and more water-soluble.  3) CELLULOSE Cellulose is a major component of the tough wall of plant cells. Cellulose is a polymer of β glucose, with β glycosidic linkages. α 1-4 glycosidic bonds In starch, all α- glucose monomers are in the same orientation (helical). β 1-4 glycosidic bonds In cellulose, all β-glucose monomers are upside down (straight) with respect to its neighbours.  In straight structures, H atoms on one strand can bond with OH groups on other strands. Parallel cellulose molecules held together this way are grouped into microfibrils, which form strong building materials for plants. Some hydroxyl groups on its glucose monomers are free to hydrogen-bond with the hydroxyls of other cellulose molecules lying parallel to it.  4) CHITIN Chitin structural polysaccharide found in the exoskeleton of insects, crayfish and other arthropods. provides structural support for the cell walls of many fungi.  5) MUREIN (PEPTIDOGLYCAN) A polysaccharide. Component of bacterial cell wall. Consists of polysaccharides cross- linked with amino acids. 95 LIPID  LIPID Lipids are the one class of large biological molecules that do not form polymers. Contain carbon, hydrogen and oxygen. 3 important groups of lipids are: i. fats (triglycerides) ii. phospholipids iii. steroids Other group of lipid is waxes.  The unifying feature of lipids is having little to no affinity for water. Lipids are hydrophobic because they consist mostly of hydrocarbons, which form non-polar covalent bonds. Soluble in organic or nonpolar solvents such as acetone, ether, chloroform, benzene, and toluene. 98  1. FATS (TRIGLYCERIDES) Fats and oils are esters produced from condensation of one molecule of glycerol and 3 molecules of fatty acids by an ester linkage. Also known as esterification (involving alcohol and acids). Glycerol + 3 fatty acids = Triglycerides/ Triacylglycerol Glycerol is a three-carbon alcohol with a hydroxyl group attached to each carbon. A fatty acid consists of a carboxyl group attached to a long carbon skeleton. 99  One water molecule is removed for each fatty acid joined to the glycerol. Therefore, to form one molecule of triglyceride, three molecules of water are removed. Hydrocarbon tails  Fats separate from water, because water molecules form hydrogen bonds with each other and exclude the fats. Oil layer (nonpolar molecule) Water (polar molecule) 102  FATTY ACIDS Fatty acids vary in: length (number of carbons), and in the number and locations of double bonds. Two type of fatty acids: 1. Saturated fatty acids 2. Unsaturated fatty acids 103  1) SATURATED FATTY ACIDS Saturated fatty acids  have the maximum number of hydrogen atoms possible  have no double bonds Example: palmitic acid and stearic acid. Straight molecules. 104  2) UNSATURATED FATTY ACIDS Unsaturated fatty acids  have one or more double bonds. Examples: oleic acid and linolenic acid. Bent molecule (due to one or more double bonds). Therefore, it still can accept hydrogen atoms. 105  SATURATED FATS UNSATURATED FATS Fats made from saturated fatty acids Fats made from unsaturated fatty acids are called saturated fats. are called unsaturated fats. Saturated fats are solid at room Unsaturated fats are liquid at room temperature. temperature. ⮚ Example: Most animal fats. ⮚ Example: Plant fats and fish fats. 106  A diet rich in saturated fats may contribute to cardiovascular disease through plaque deposits. Hydrogenation is the process of converting unsaturated fatty acids to saturated fatty acids by adding hydrogen. Hydrogenating vegetable oils also create unsaturated fats with trans double bonds. These trans fats may contribute more than saturated fats to cardiovascular disease due to their configuration does not produce bend at the site of the double bond. Trans fatty acids are more solid at room temperature than cis fatty acids. 108 Source of Fats  2. PHOSPHOLIPIDS In a phospholipid, two fatty acids and a phosphate group are attached to glycerol. The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head.  When phospholipids are added to water, they self- assemble into a bilayer, with the hydrophobic tails pointing toward the interior. The structure of phospholipids results in a bilayer arrangement found in cell membranes. Phospholipids are the major component of all cell membranes. 112  3. STEROIDS Steroids are lipids characterized by a carbon skeleton consisting of four fused rings. Steroids are classified as lipids due to their insolubility in water and solubility in non-polar solvents. Cholesterol, ⮚ an important steroid, is a component in animal cell membranes. ⮚ Cholesterol belongs in the family of steroids because it shares a similar chemical structure ⮚ It is a precursor to Vit D and for steroid hormones such as testosterone, progesterone, estrogen, and cortisol. 113  Cholesterol in animal cell Steroid Hormones membranes NUCLEIC ACIDS  NUCLEIC ACIDS Nucleic acids are polymers called polynucleotides. Each polynucleotide is made of monomers called nucleotides. Each nucleotide consists of a nitrogenous base, a pentose sugar, and a phosphate group. The portion of a nucleotide without the phosphate group is called a nucleoside. Nucleoside = nitrogenous base + sugar Phosphodiester bond A type of covalent bond between adjacent nucleotides. Formed between the –OH group on the 3′ carbon of one nucleotide and the phosphate on the 5′ carbon on the next. The chain of nucleotides has a 5′-to-3′ orientation. The backbone is negatively charged due to a negative charge on each phosphate. NITROGENOUS BASES Two families of nitrogenous bases: 1. Pyrimidines (C, T, U) ⮚Single six-membered ring. 2. Purines (A, G) ⮚ Six-membered ring fused to a five-membered ring.  NUCLEIC ACIDS There are two types of nucleic acids: 1. Deoxyribonucleic acid (DNA) 2. Ribonucleic acid (RNA) DNA provides directions for its own replication. Genes in DNA direct the synthesis of messenger RNA (mRNA) and, through mRNA, control protein synthesis.  In DNA, In RNA, the the pentose sugar is pentose sugar is deoxyribose ribose DNA DOUBLE HELIX Has two polynucleotide strands spiraling (coiled together) around an imaginary axis, forming a double helix structure. The two backbones in DNA double helix run in opposite 5′ → 3′ directions from each other, an arrangement referred to as antiparallel. ⮚ (the 2 strands are anti-parallel) 122 DNA DOUBLE HELIX One DNA molecule includes many genes. The nitrogenous bases in DNA pair up and form hydrogen bonds: i. adenine (A) always with thymine (T), ii. guanine (G) always with cytosine (C). ⮚This is called COMPLEMENTARY BASE PAIRING. 123 Pyrimidines Purines  Uracil replaces thymine  DIFFERENCES OF RNA & DNA RNA DNA Consists of single strand only – much shorter than DNA. Consists of double strands arranged in anti-parallel manner & coiled around. The pentose sugar unit is ribose. The pentose sugar unit is deoxyribose. Uracil replaces thymine. It also contains adenine, guanine & Contains the bases adenine, guanine, thymine & cytosine. cytosine. Produced in the nucleus but found anywhere within the cell. Found almost entirely in chromosomes within the nucleus. A small amounts is also found in mitochondria & chloroplast. 3 basic types of RNA : messenger RNA (mRNA), transfer There is only 1 type of DNA. RNA (tRNA) & ribosomal RNA (rRNA). Smaller nuclear mass (20 000 – 2 000 000) Larger molecular mass (100 000 – 150 000 000). Does not act as a gene. Nucleotide sequences may encode genes. Each genes in DNA is - important in the production of proteins a unit of genetic information. 126 TASK: Protein DO A MIND MAP ON: Carbohydrates 1) Functional groups Macromolecules 2) Chemical bonds 3) Properties of Water 4) Macromolecules Lipids Amino Nucleic Acids Carbonyl Hydroxyl Functional Groups Carboxyl Sulfhydryl THANK YOU