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1 Chapter 3: Chemistry of Water 1. Polar covalent bonds within water -Between slightly positive hydrogen atoms and slightly negative oxygen atom 2. Hydrogen bonds between water molecules -Hydrogen bonds are electrical attractions between the hydrogen atom of one water molecule and the oxygen atom of a nearby water molecule -they create a structural organization of water that leads to its emergent properties -weaker than polar covalent bonds *One water molecule can form 4 hydrogen bonds 3. “Bent” geometry O H H 4. Polar molecules -Water molecules have a partial charge -Oxygen has a partially negative charge (δ—) and hydrogen has a partially positive charge (δ+) because oxygen is more electronegative (which means it attracts electrons more) δ+ INTER-molecular INTRA-molecular attractions δ— attractions Polar Covalent bond Hydrogen bond -between hydrogen and oxygen of the same atom -between hydrogen and oxygen of different atoms δ+ δ δ+ — = oxygen = hydrogen δ+ 5. An attraction may exist between water molecules – depending on temperature -At higher temperatures, molecules are farther apart -When temperature decreases, kinetic energy and speed decrease, so entropy decreases (which means molecules are more organized and closer together) -As this happens, water goes from a gas to a liquid to a solid Properties of Water 1) Cohesion/ Adhesion 2) Specific heat 3) Heat of vaporization 4) Less dense as a solid 5) Universal solvent 6) Neutral pH *Explain each property of water and relate to its importance in biology ©SarahStudyGuides 2 Cohesion and Adhesion Cohesion- water molecules stick to each other -They stick to each other due to the constant of forming and reforming of hydrogen bonds that hold the molecules close together. Adhesion- water molecules stick to other things Capillary tubes: -they have a tiny diameter: water molecules are smushed together in a small space they stick to each other better -xylem = water conducting tissue Importance in Biology: Cohesion and adhesion help transport water upward through plants (to the leaves) -Water hits the ground and moves to the roots by diffusion -Water moves up the roots and is pulled up through the stems to the leaves because of their attractions to each other and the stem walls. This is called capillary action. -This allows plants to produce glucose and oxygen in a process called photosynthesis. Transpiration pull is the main way water travels to the leaves though. -This process is: As water is lost in the stem, it’s pulled up through the roots. This allows there to be a constant flow of water. Cohesion and adhesion are the reason for water’s high surface tension -benefits organisms who can walk on the surface of water -soap breaks surface tension Specific Heat and Heat of Vaporization Heat is a measure of the total amount of kinetic energy Temperature measures the average amount of kinetic energy -Temperature is measured using a Celsius scale -Water boils at 100ºC and freezes at 0ºC -A calorie (cal) is the amount of heat energy it takes to raise 1 g of water 1ºC -1 Joule = .239 cal ; 1 cal = 4.184 J -A kilocalorie (kcal) is 1,000 calories, the amount of heat energy it takes to raise 1 kg of water 1ºC Specific heat – amount of heat required to change the temperature of 1 gram of water by 1ºC **Involves change in temperature -It takes a lot of energy to change the temperature of water (exactly 1 cal) Because a lot of energy must be absorbed to break hydrogen bonds, and a lot of energy is released when forming hydrogen bonds -Water’s specific heat is very HIGH water is resistant to temperature change Vaporization or evaporation occurs when molecules of a liquid with sufficient kinetic overcome their attraction to other molecules and escape into the air as gas ©SarahStudyGuides 3 Heat of vaporization – amount of energy required to convert 1 gram of water to 1 gram of water vapor **Involves change in phase -Takes a lot of energy to change phase (exactly 4.18 J/g/ ºC or 580 cal/g/ºC) Because a lot of heat must be absorbed to break hydrogen bonds, allowing water molecules to escape into the gas phase -Water’s heat of vaporization is very HIGH it’s very resistant to phase change Importance in Biology: Specific heat moderates temperature: -In coastal areas, water and land temperatures are more moderate and mild than inland areas For aquatic organisms, water temperature is usually constant: -they don’t have to adapt to wildly changing temperatures (like terrestrial animals do) -they have less coping mechanisms Evaporative cooling helps protect terrestrial organisms from overheating and contributes to the stability of temperatures in lakes and ponds -As a liquid vaporizes, the surface left behind loses the kinetic energy of the escaping molecules, cooling it down Water takes a long time to evaporate because of its high heat of vaporization **Water-based organisms are resistant to evaporation -Large bodies of water like the ocean do not evaporate -When water finally does evaporate, it takes away heat from its surroundings; conversely, when water condenses and it rains, it releases heat to its surroundings Less Dense as a Solid As water freezes it expands Hydrogen bonds pushed apart, creating a fixed crystalline structure. The INTER-molecular attractions are stronger and more stable, creating more space. So ice floats. Importance in Biology Floating ice insulates the liquid water below, preventing it from freezing and allowing life to exist under the frozen surface. COLD AIR November WARM AIR Ice insulates the pond, allowing life to exist under the surface. COOL AIR colder warmer October Ice melts Colder water sinks and warmer water rises colder warmer March -This is called SPRING OVERTURN. It recirculates nutrients. The warm water at the surface becomes colder and the bottom warms up Colder water sinks and warmer water rises -This is called FALL OVERTURN. It also re-circulates nutrients. ©SarahStudyGuides 4 Change in phase Temperature Change in phase ΔT Change in temperature = increases the average kinetic energy of molecules (increases speed) Change in phase = disrupts hydrogen bonds But the structure of water never changes because covalent bonds are very strong ΔT ΔT Time Cellular Respiration: C6H12C6 + O2 CO2 + H2O + ATP (energy) -Fish get oxygen from underwater plants, not by breaking down water molecules. Universal Solvent Water is the solvent in an aqueous solution -A solution is a liquid homogeneous mixture of 2 or more substances -The solvent is the dissolving agent and the solute is the substance that is dissolved Hydration shell: the water molecules surround and break up the solute molecules -This happens because the positive and negative regions of water molecules are attracted to oppositely charged ions or partially charged regions of polar molecules -for example: NaCl dissolves in water. -Water molecules surround the NaCl molecules the slightly negative oxygen atoms are attracted to the positive Na atoms, while the slightly positive hydrogen atoms are attracted to the negative Cl atoms this pulls the NaCl molecules apart “Like dissolves like” -Polar solvents dissolve polar solutes and ionic solutes -Nonpolar solvents dissolve nonpolar solutes -This is why oil (nonpolar) and water (polar) don’t mix Hydrophilic = has an affinity for water due to electrical attractions and hydrogen bonding -Polar and ionic substances are hydrophilic -Large hydrophilic substances may not dissolve, but become suspended in an aqueous solution forming a mixture called a colloid Hydrophobic = does not easily mix with or dissolve in water Importance in Biology Nonpolar and polar interactions help transport nutrients -Nutrients diffuse across cell membranes Neutral pH A water molecule can dissociate into a hydrogen ion, H+, and a hydroxide ion, OH–. -In water, the concentrations of [H+] to [OH–] are the same = 1 x 10–7 When acids or bases dissolve in water, the H+ and OH– balance shifts. -Acids donate H+ ions -Bases accept H+ ions add OH– ions An increase in [H+] results in a decrease in [OH–] (and vice versa) ©SarahStudyGuides 5 Water has a neutral pH and a pOH of 7 -Because cells are mostly water, most cells have an internal pH close to 7. -The difference between each pH is a tenfold difference (For example: the difference between 2 and 3 is 10 while the difference between 2 and 4 is 100) Importance in Biology Keeps cells functioning at a neutral pH -This is one of the reasons why most body fluids are around 7 Buffers are chemicals that prevent pH from changing too much -Buffers may be acid-base pairs which accept excess H+ ions or donate H+ ions when H+ concentration decreases -enzymes are very pH sensitive, so the pH must be constant ©SarahStudyGuides 6 Chapter 4 Organic chemistry is the study of carbon compounds. Compounds on can either be inorganic or organic. If it’s organic, it contains carbon and involves living things and often H and O as well. Before, chemists couldn’t synthesize the complex molecules found in living organisms, so they believed that life did not involve physical and chemical laws, a belief called vitalism. Mechanism, which organic chemistry is based on, holds that physical and chemical explanations account for all natural life. The Miller Urey Experiment -It was designed to test the Halding hypothesis (Halding’s hypothesis: the atmosphere contains hydrogen, not oxygen) -They found that you can take inorganic molecules and get organic molecules (contain H, C, O, and N) -This is an example of molecular evolution, science as a process, and science, technology, and science Chemistry of Carbon Has 4 valence electrons (=outermost energy level) . .C. . Its electron configuration: 1s22s22p2 This electron configuration allows LIKE: carbon to form 4 bonds with other atoms. This is called carbon’s tetravelence. H H C H H Methane: 4 single nonpolar covalent bonds, symmetrical, tetrahedral shape It exists as a gas because it’s not attracted to itself. Carbon atoms can form diverse molecules by bonding to four other atoms. Carbon has 4 valence electrons, so it can form at most 4 covalent bonds. This tetravalence allows the formation of large, complex, diverse molecules. Carbon can form single, double, or triple covalent bonds. -4 single bonds around carbon creates a tetrahedral shape. -A double bond between carbons leads to a flat molecule. Carbon can bond with other elements and other carbons forms short or long chains, branches, and rings Carbon skeletons can vary in: 1) Length 2) Branching 3) Placement of double bonds 4) Location of atoms of other elements Molecular Diversity Arising from Carbon Skeleton Variation Hydrocarbons ©SarahStudyGuides 7 Hydrocarbons consist of only carbon and hydrogen The nonpolar C – H bonds in hydrocarbon chains result in their hydrophobic properties -Many cells have hydrocarbon regions, like the hydrophobic fatty acid tails Hydrocarbons can undergo reactions that release a large amount of energy. -In fats, hydrocarbons help cells store fat molecules as a reserve. The fat tails can be broken down to provide energy. Isomers Isomers are compounds with the same molecular formula but different structures and properties Structural isomers have different covalent arrangements of their atoms -For example: C6H12O6 is the molecular formula for glucose, fructose, and galactose. Glucose and galactose are hexagons, but fructose is a pentagon and is sweeter than the others. Geometric isomers have the same covalent arrangements but differ in spacial arrangements around a Carbon-Carbon double bond -Always around a C = C bond -A cis isomer has the same atoms attached to double-bonded carbons on the same side of the double bond (see figure 4.7 in the book) -A trans isomer has these atoms on opposite sides of the double bond. Enantiomers are isomers that are mirror images of each other around an asymmetrical carbon -An asymmetrical carbon is a carbon that is covalently bonded to four kinds of atoms or groups of atoms, whose arrangement can result in mirror images -They’re left and right handed versions of each other and can differ greatly in their biological activity -For example: Our hands are mirror images of each other.2 isomers are designated the L and D isomers L for the left hand, D for the right hand. Enantiomers can’t be superimposed on each other. Characteristic chemical groups help control how biological molecules function In an organic molecule, the chemical groups that attach to the carbon skeleton are essential to the distinctive properties of the molecule The Chemical Groups Most Important in the Process of Life Different chemical groups affect the molecules shape This affects function!! *So these important chemical groups are called functional groups For example: sex hormones are similar in shape, but different in function. -Both are steroids, organic molecules in the form of 4 fused rings. -They only differ in the chemical groups attached to the rings. -The body takes in cholesterol, which binds to the hormones. Other examples = enzymes and antibodies. Their shape is essential because they have to fit into special binding spots. ©SarahStudyGuides 8 The 7 most important chemical groups are listed below. The 1st 6 act as functional groups and are hydrophilic, increasing solubility of compounds in water. But methyl is unreactive. Structure Name of Compound Hydroxyl Oxygen and hydrogen (–OH ) Alcohols (names usually end in –ol) Carbonyl Carbon double bonded to an oxygen Aldehyde if carbonyl group is at the end of the skeleton CO Ketone if it’s in the middle Carboxyl Carbon double bonded to an oxygen and bonded to an –OH group –COOH Amino Sulfhydrl A nitrogen atom bonded to 2 hydrogens Carboxylic acids or organic acids They tend to release H+, becoming a carboxylate ion (–COO- ) Amines –NH2 Can act as bases, picking up a hydrogen ion becoming –NH3 + A sulfur atom bonded to a hydrogen Thiols –SH Phosphate A phosphorus atom is bonded to 4 oxygen atoms: on oxygen is bonded to the carbon skeleton, 2 oxygens carry negative charges Organic phosphates –OPO3 2-Methyl A carbon bonded to three hydrogens –CH3 Methylated compounds may have their function modified due to the addition of the methyl group ©SarahStudyGuides 9 Chapter 5 Organic compounds: 1) 2) 3) 4) Carbohydrates Lipids Proteins Nucleic acids Macromolecules Carbohydrates, proteins, and nucleic acids are all macromolecules Polymers are chain-like molecules formed from the linking together of many similar or identical small molecules called monomers. Monomers are the repeating units that serve as the building blocks of a polymer. The Synthesis and Breakdown of Polymers Condensation/dehydration reaction: the reaction in which 2 molecules are covalently bonded to each other through loss of a water molecule -monomers are connected through dehydration reactions -One monomer contributes a hydroxyl group (—OH) and the other provides a hydrogen (—H) -Enzymes are specialized macromolecules that catalyze both dehydration reactions and hydrolysis. Hydrolysis: a process that breaks bond between monomers by adding a water molecule -it’s the reverse of dehydration reactions -A hydrogen from the water molecule attaches to one monomer, and the hydroxyl group attaches to the other monomer -For example: digestion -organic material in our food is broken down, with the help of enzymes, through hydrolysis Carbohydrates Functions of carbohydrates: 1) Quick energy (4-5 calories per gram) 2) Structure and support (cellulose and chitin) Empirical formula for all carbohydrates= CH2O -literally a carbon + a water molecule a hydrated carbon molecule a carbohydrate -All carbohydrates contain C, H, and O Sugars may be aldoses or ketoses, depending on the location of the carbonyl group. -Aldoses = aldehyde sugars = carbonyl group on the end of the molecule -example: glucose and galactose -Ketoses = ketone sugars = carbonyl group in the middle of the molecule -example: fructose ©SarahStudyGuides 10 Sugars many also be classified according to the length of their carbon skeletons. -The size of the carbon skeleton ranges from 3 to 7 sugars, with hexoses (C6H12O6 = glucose, fructose, galactose), trioses, and pentoses found most commonly. -Even though a fructose molecule has 5 sides, it is still a hexose because it has 6 carbons Sugar molecules may be enantiomers due to the spatial arrangements of parts around asymmetrical carbons (like glucose and galactose- see figure 5.3) Most carbons form rings because it’s the most stable configuration -Carbons are numbered 1 through 6: these numbers refer to their location 1) Monosaccharides C6H12O6 o Glucose o Fructose o Galactose *galactose is never found by itself -Same molecular formula, but different structural formulas they’re structural isomers -Glucose= major source of nutrition for cells -It is broken down to yield energy in cellular respiration 2) Disaccharides C12H22O11 o Maltose = glucose + glucose o Sucrose = glucose + fructose o Lactose = glucose + galactose *Condensation/ Dehydration reactions: -A glycoside linkage is a covalent bond between any 2 monosaccharides. -Glycoside linkages form through dehydration reactions, when a water molecule is removed (hydroxyl group is removed from one monosaccharide and a hydrogen is removed from the other) -Glycoside linkages form between different carbons depending on the monosaccharide: -Glucose + glucose forms 1-4 glycoside linkages. (This means that Carbon 1 from the 1st glucose is bonded to Carbon 4 from the other) -Fructose + glucose forms 1-2 glycoside linkages 3) Polysaccharides Polysaccharides are storage or structural macromolecules made from a few hundred to a few thousand monosaccharides. They’re polymers of glucose. a. Starch = amylose -unbranched *found in plants -1-4 alpha linkages: bonds are below the plane of the molecule -We have enzymes that can digest alpha linkages -These linkages give starch a helical shape ©SarahStudyGuides 11 -Starch doesn’t dissolve in water. When you cook potatoes or pasta, they get soft because you’re breaking glycoside bonds and getting the molecules to uncoil. b. Cellulose -1-4 beta linkages: bonds are alternative above the plane of the molecule -So 1-4 linkages in amylose and cellulose have the same composition, but the configuration of the ring form of glucose and the resulting geometry of the glycosidic bonds are different *We cannot digest cellulose because we do not have the enzymes needed to break down cellulose -Enzymes must fit their substrate, so different enzymes break down starch and cellulose. We don’t have enzymes that can break down beta linkages. -Only a few organisms (some microbes and fungi) have enzymes that can digest cellulose. -Cows have enzymes from prokaryotes and bacteria that help them digest cellulose. Bacteria make vitamin K that helps break it down. -Foods with cellulose include fruits and vegetables – have natural sugars, provide fiber in our diet, and fill you up more with fewer calories. *Cellulose is the major component plant cell walls. -Hydrogen bonds between hydroxyl groups hold parallel cellulose molecules together to form strong microfibrils. -It’s the most abundant organic compound on Earth c. Glycogen -highly branched and complex -Found in animals (often called animal starch) -it’s stored in liver and muscle tissue as quick energy that’s readily available *Short term energy storage d. Amylopectin -branched form of starch -found in plants -it has alpha linkages – we can digest it e. Chitin -structural polysaccharide formed from glucose monomers with a nitrogencontaining group -provides structure and support -forms the exoskeleton of arthropods and the cell walls of many fungi -We can’t break it down or get nutrients from it because it also has beta linkages Lipids -All lipids are hydrophobic -long term storage of energy ©SarahStudyGuides 12 -Lipids are a more condensed and packed way to store energy, and they have more categories important to animals who are always on the move -provides 9-10 cal per gram -has the elements C, H, and O -mostly consist of hydrocarbons 1) Triglycerides Glycerol + 3 Fatty acids Triglyceride + 3H2O -3 ester linkages = bond between glycerol and fatty acid -This is a dehydration reaction: loss of a water molecule -The carbonoxyl end of the fatty acid loses an – OH. The glycerol loses an – H. -Fatty acids- consists of a long hydrocarbon chain with a carboxyl group at one end Fats are hydrophobic because the fatty acid chains are nonpolar -The nonpolar hydrocarbons make it nonpolar Unsaturated fats: -has double bonds -fewer hydrogens per carbon -healthy -liquids at room temperature -the cis double bonds create a kink in the hydrocarbon chain and prevents fat molecules that contain unsaturated fatty acids from packing closely together and becoming solidified and fixed -The fats of fish and plants are generally unsaturated and are called oils -examples: vegetable, olive, peanut, sunflower, and corn oils Saturated fats: -only have single bonds -unhealthy -increases blood pressure and leads to heart disease -solids at room temperature -from animals o Trans fats are made in the process of hydrogenation: converting from unsaturated to saturated fats to make the molecules solid -extremely unhealthy and leads to heart disease -example: oreos Functions of fats: 1) Excellent energy storage molecules -Contains 2x the energy reserves of carbohydrates 2) Cushions organs and insulates the body -example: adipose tissue, which is made of fat storage cells 2) Phospholipids Phospholipids consist of a glycerol linked to 2 fatty acids and a negatively charged phosphate group, to which other small molecules are attached. ©SarahStudyGuides 13 Insoluble in water: -phosphate head = polar -phosphate group -carries a large negative charge -hydrophilic -fatty acid tails tails = nonpolar -fatty acids -hydrophobic Function: STRUCTURE- they are the primary component in cell membranes: -form the phospholipid bilayer -regulates the types of material that move in and out of cells -keeps animal cells flexible Extacellular fluid =H20 outside of cell nucleus cell membrane Phospholipid Bilayer cytoplasm Hydrophilic head Hydrophobic tails Cell cytoplasm = H20 inside of cell The hydrophilic head turns outward towards water. The hydrophobic tails turn inward away from water. 3) Steroids 4 fused carbon rings with attached groups -Have a totally different structure – they’re only classified as lipids because of their insolubility -Typically come from animals Function: Many are hormones or pre-cursors to hormones Examples: cholesterol is an important steroid that is a common component of animal cell membranes. -It is a pre-cursor for other steroids, including estrogen and testosterone. Cholesterol molecules are modified to form sex hormones and can act as signaling molecules. -Heart disease: too much cholesterol can lead to narrowed arteries and blocked blood vessels, increasing blood pressure This causes heart disease and atherosclerosis -Structure: cholesterol increases the fluidity of cell membranes Are found in: -Cholesterol - cell membranes -Hormones – reproductive organs Proteins -Contain carbon, hydrogen, oxygen, and nitrogen (*carbs and lipids don’t have nitrogen) ©SarahStudyGuides 14 Variety of Functions 1) Structural – provides structure and support. -Keratin is the protein of hair, fur, claws, beak, nails. -Actin and myosin are the proteins of muscle tissue, and are responsible for muscle movement. 2) Enzymes – catalyze reactions -Digestive enzymes like amylase catalyze the hydrolysis of polymers in food. -break down (catabolism) or build up molecules (anabolism) 3) Transport – across cell membranes -In red blood cells, hemoglobin transports oxygen from the lungs to other parts of the body 4) Defense – protection against disease -antibodies – combat bacteria and viruses 5) Storage – store energy -Proteins in meat, egg white (protein = albumin), legumes, milk (protein =casein) -provide 4-5 cal per gram of energy 6) Information receptors – response of cell to chemical stimuli -Receptors on the cell surface of a nerve cell detect chemical signals released by other nerve cells. 7) Hormones – signaling molecules that help with the coordination of an organism’s activities -Insulin regulates concentration of sugar. Somatotropin is the protein in HGH (human growth hormones). Polypeptides A polypeptide is a polymer of amino acids. A peptide bond is a bond between amino acids. -links the carboxyl group of one amino acid with the amino group of another A protein consists of one or more polypeptide chains folded into a specific 3-D shape Amino Acid Structure: amino group H H variable group R O N–C–C OH H carboxylic acid group **Composed of an asymmetric carbon (called the alpha carbon) bonded to a hydrogen, a carboxyl group, an amino group, and a variable side chain called the R group** At the pH in a cell, the amino and carboxyl groups are usually ionized. The R group is the variable group and it differs in different kinds of amino acids. -It confers the unique physical and chemical properties of each amino acid. -There are 20 different R groups. -Side chains may be either nonpolar and hydrophobic, or polar and charged (acidic or basic) and hydrophilic. ©SarahStudyGuides 15 Amino acids usually end in –ine 20 different amino acids Polypeptide chains are several amino acids linked by peptide bonds. Polypeptide chains have an amino end (N-terminus) with a free amino group, and a carboxyl end (C-terminus) with a free carboxyl group. Protein Structure and function A protein has a unique 3-dimensional shape, or structure, created by the twisting or folding of one or more polypeptide chains Protein structure depends on the interactions between the amino acids that make up the polypeptide chain and usually arises spontaneously as the protein is synthesized in the cell The unique structure of a protein enables it to recognize and bind to other molecules 4 Levels of Protein Structure 1) Primary Structure -The unique, genetically coded sequence of amino acids within a protein -DNA encodes the sequence and determines how amino acids are put together 2) Secondary Structure -Involves the coiling and folding of the polypeptide backbone -An alpha helix = coils -produced by hydrogen bonding between every 4th amino acids -A beta pleated sheet = folds -is also held by repeated hydrogen bonds along regions of polypeptide backbone lying parallel to each other -pleated sheets make up the core of many globular proteins -This is stabilized by hydrogen bonds between the repeating constituent amino acids of the polypeptide backbone -Hydrogen bonds form between the electronegative oxygen of one peptide bond and the weakly positive hydrogen attached to the nitrogen of another peptide bond -The cell cytoplasm is made of water, so: -The hydrophilic parts of the polypeptide chain turn outward -The hydrophobic parts turn inward 3) Tertiary Structure -Tertiary structure result from interactions between the various side chains (R groups) of the constituent amino acids -These interactions include: -Hydrophobic interactions between nonpolar side groups clumped in the center of the molecule due to their repulsion by water -Van der Waals interactions among those nonpolar side chains (very weak) -Hydrogen bonds between polar side chains -Ionic bonds between negatively and positively charged side chains ©SarahStudyGuides 16 *These interactions produce the stable and unique shape of the protein -Strong covalent bonds, called disulfide bridges, may reinforce the protein’s structure -may occur between the sulfhydryl side groups of cysteine monomers that have been brought closer together by the folding of the polypeptide 4) Quaternary structure -2 or more polypeptide subunits combine and interact with each other -occurs in proteins that are composed of more than one polypeptide chain -the individual polypeptide subunits are held together in a precise structural arrangement -For example: In hemoglobin proteins, each subunit has a nonpolypetpide component called a heme, with an iron atom that binds oxygen Proteins can change shape Folding of polypeptides normally occurs as the protein is being synthesized within the cell. However, protein conformation also depends on the physical and chemical conditions of the protein’s environment. Denaturation is a change in original protein shape, usually resulting from a change in the pH, temperature, salt concentration, or exposure to chemicals -Because it is misshapen, the denatured protein is biologically inactive -Most proteins become denatured if they’re transferred form an aqueous environment to an organic solvent. If a denatured protein remains dissolved, it can often renature when the chemical and physical aspects of its environment are restored to normal Defective Proteins -a problem with encoding DNA can have serious effects on protein shape and function Sickle cell anemia -Results from a simple change in the primary level in 1 amino acid -called a point mutation, resulting from substitution -This changes the shape of the secondary and tertiary levels too the hemoglobin protein is misshapen Muscular dystrophy -defective protein within muscle (actin/myosin) Tay-Sachs -enzymes are defective Hemophilia -clotting protein is defective Cystic fibrosis -transmembrane protein is defective (Cl—ions) ©SarahStudyGuides 17 Nucleic Acids -information molecules that carry genetic code DNA -is inherited from one generation to the next and is copied whenever a cell divides so that all cells of an organism contain its DNA -polymer of nucleotides -nucleotide: 1. 5-carbon sugar (deoxyribose) 2. Phosphate group 3. Nitrogenous base -Adenine -Thymine (*Only in DNA) -Guanine -Cytosine -found in the nucleus in chromosomes RNA -directs protein synthesis -polymer of nucleotides -nucleotide: 1. 5-carbon sugar (ribose) 2. Phosphate group 3. Nitrogenous base -Adenine -Uracil (*Only in RNA) -Guanine -Cytosine -found throughout the cell -in the nucleus (mRNA), in ribosomes (rRNA), and as transport (tRNA) Structure of Nucleic Acids Polynucleotides are polymers of nucleotides—monomers that consist of a pentose (5-carbon sugar), a phosphate group, and a nitrogenous base A monomer without the phosphate group is called a nucleoside There are 2 types of nitrogenous bases: 1. Pyrimidines= 6-membered rings of carbon and nitrogen -cytosine (C), thymine (T), and uracil (U) 2. Purines = add a 5-membered ring of carbon and nitrogen to the pyrimidines ring -adenine (A) and guanine (G) Covalent bonds between sugar, phosphate and the base ©SarahStudyGuides 18 Hydrogen bonds between nitrogenous bases -Easily broken Phosphodiester linkages = covalent bonds between nucleotides -Between the sugar of one nucleotide and the phosphate of the next -This bonding results in a sugar-phosphate backbone with repeating sugar and phosphate units The polymer has 2 distinct ends: a 5’ end with a phosphate attached to a 5’carbon of a sugar and a 3’ end with a hydroxyl group on a 3’ sugar -The nitrogenous bases extend from this backbone of repeating sugar-phosphate units -The unique sequence of bases in a gene codes for the specific amino acid sequence of a protein ©SarahStudyGuides