Ions, Molecules and Chemical Bonds

Test 1 - Chapter 2: The Chemistry of Life Ions ● Ions: charged particles with unequal numbers if protons and electrons ○ Can consist of a single atom with a positive or negative charge (such as Na+ or Cl-); a group of atoms such as phosphate (PO43-) and bicarbonate (HCO3 -) ions; or a molecule as large as a protein with many charges on it ○ Form because elements with one or three valence electrons tend to give them up, and those with four or seven electrons tend to gain more ● Ionization: the process by which an atom or molecule acquires a negative or positive charge by gaining or losing electrons to form ions ○ Anion: the particle that gains electrons (acquires a negative charge) ○ Cation: the particle that loses electrons (acquires a positive charge because it then has a surplus of protons) ● Some elements exist in two or more ionized forms. ○ E.g., Iron has ferrous (Fe2+) and ferric (Fe3+) ions. ● Valence: the charge on an ion Molecules and Chemical Bonds ● Molecules: chemical particles composed of two or more atoms ○ Atoms may be identical, as in nitrogen (N2), or different, as in glucose (C6H12O6). ● Compounds: molecules composed of two or more elements ○ E.g., CO2 ● Molecules are represented by molecular formulae that identify their elements and show how many atoms of each are present. ● Isomers: molecules with identical molecular formulae but different arrangements of their atoms ● Molecular Weight (MW): the sum of the weights of the atoms of a compound ● Chemical Bonds: hold molecules together and attract molecules to each other ● Bonds of greatest physiological interest: ○ Ionic Bonds ○ Covalent Bonds ○ Hydrogen Bonds ○ Van der Waals Forces ● Ionic Bond: Relatively weak attraction between an anion and a cation. Easily disrupted in water, as when salt dissolves. ● Covalent Bond: Sharing of one or more pairs of electrons between nuclei. ○ Single Covalent: Sharing of one electron pair. ○ Double Covalent: Sharing of two electron pairs. Often occurs between carbon atoms, between carbon and oxygen, and between carbon and nitrogen. ○ Nonpolar Covalent: Covalent bond in which electrons are equally attracted to both nuclei. May be single or double. Strongest type of chemical bond. ○ Polar Covalent: Covalent bond in which electrons are more attracted to one nucleus than to the other, resulting in slightly positive and negative regions in one molecule. May be single or double. ○ Hydrogen Bond: Weak attraction between polarized molecules or between Test 1 - Chapter 2: The Chemistry of Life polarized regions of the same molecule. Important in the three-dimensional folding and coiling of large molecules. Easily disrupted by temperature and pH changes. ○ Van der Waals Forces: Weak, brief attraction due to random disturbances in the electron clouds of adjacent atoms. Weakest of all bonds. ● Mixture: substances that are physically blended but not chemically combined ○ E.g., body fluids Buffers (Section 24.3) ● Buffer: any mechanism that resists pH changes by converting a strong acid or base to a weak one ● The body has both physiological and chemical buffers. ● Physiological Buffer: a system - namely, the respiratory or urinary system - that stabilizes pH by controlling the body’s output of acids, bases, or CO2. ● Chemical Buffer: a substance that binds H+ and removes it from solution as its concentration falls ● Buffer System = weak acid + weak base Classes of Chemical Reactions ● Chemical Reaction: a process in which a covalent or ionic bond is formed or broken ● Chemical Equation: symbolizes the course of a chemical reaction; typically shows the reactants on the left, the products on the right, and an arrow pointing from the reactants to the products ● Decomposition Reaction: a large molecule breaks down into two or more smaller ones AB → A + B ● Synthesis Reaction: two or more smaller molecules combine to form a larger one A + B → AB ● Exchange Reaction: two molecules exchange atoms or groups of atoms AB + CD → AC + BD ● Reversible Reaction: can go in either direction under different circumstances CO2 + H2O ⇋ H2CO3 ⇋ HCO3 - + H+ ● Reversible reactions follow the law of mass action: They proceed from the reactants in greater quantity to the substances with the lesser quantity. ● In the absence of upsetting influences, reversible reactions exist in a state of equilibrium, in which the ratio of products to reactants is stable. Reaction Rates ● Chemical reactions are based on molecular motion and collisions. ● All molecules are in constant motion, and reactions occur when mutually reactive molecules collide with sufficient force and the right orientation. ● The rate of a reaction depends on the nature of the reactants and on the frequency and force of these collisions. ● Some factors that affect reaction rates: ○ Concentration: Reaction rate increases when the reactants are more Test 1 - Chapter 2: The Chemistry of Life concentrated. This is because the molecules are more crowded and collide more frequently. ○ Temperature: Reaction rate increases as the temperature rises. This is because heat causes molecules to move more rapidly and collide with greater force and frequency. ○ Catalysts: These are substances that temporarily bind to reactants, hold them in a favorable position to react with each other, and may change the shapes of reactants in ways that make the more likely to react. By reducing the element of chance in molecular collisions, a catalyst speeds up a reaction. It then releases the products and is available to repeat the process with more reactants. The most important biological catalysts are enzymes. Metabolism, Oxidation and Reduction ● Metabolism: all the chemical reactions in the body ○ Catabolism: consists of energy-releasing decomposition reactions ○ Exergonic: energy-releasing reactions ○ Anabolism: consists of energy-storing synthesis reactions ○ Endergonic: reactions that require an energy input ● Oxidation: any chemical reaction in which a molecule gives up electrons and releases energy ○ A molecule is oxidized by this process, and whatever molecule takes the electrons from it is an oxidizing agent (electron acceptor). ○ The term oxidation stems from the fact that oxygen is often involved as the electron acceptor. ○ We can sometimes recognize an oxidation reaction from the fact that oxygen has been added to a molecule. ● Reduction: a chemical reaction in which a molecule gains electrons and energy ○ When a molecule accepts electrons, it is said to be reduced; a molecule that donates electrons to another is therefore called a reducing agent. ● The oxidation of one molecule is always accompanied by the reduction of another, so these electron transfers are known as oxidation-reduction (redox) reactions. Table 2.5: Energy-Transfer Reactions in the Human Body Exergonic Reactions Reactions in which there is a net release of energy. The products have less total free energy than the reactants did. Oxidation An exergonic reaction in which electrons are removed from a reactant. Electrons may be removed one or two at a time and may be Test 1 - Chapter 2: The Chemistry of Life removed in the form of hydrogen atoms (H or H2). The product is then said to be oxidized. Decomposition A reaction such as digestion and cell respiration, in which larger molecules are broken down into smaller ones. Catabolism The sum of all decomposition reactions in the body. Endergonic Reactions Reactions in which there is a net input of energy. The products have more total free energy than the reactants did. Reduction An endergonic reaction in which electrons are donated to a reactant. The product is then said to be reduced. Synthesis A reaction such as protein and glycogen synthesis, in which two or more smaller molecules are combined into a combined into a larger one. Anabolism The sum of all synthesis reactions in the body. Carbohydrates ● Carbohydrate: a hydrophilic organic molecule with the general formula (CH2O)n, where n represents the number of carbon atoms ● Have a 2:1 ratio of hydrogen to oxygen ● The names of individual carbohydrates are often built on the root word sacchar- or the suffix -ose, both of which mean “sugar” or “sweet.” ● The most familiar carbohydrates are sugars and starches. ● Monosaccharides: the simplest carbohydrates; monomers; simple sugars ○ Glucose, Fructose, Galactose → C6H12O6 → Isomers of each other ■ Obtained mainly by the digestion of more complex carbohydrates ○ Glucose is the “blood sugar” that provides energy to most of our cells. ○ Ribose and deoxyribose are important components of DNA and RNA. ● Disaccharides: sugars composed of two monosaccharides ○ Sucrose = Glucose + Fructose ■ Produced by sugarcane and sugar beets ■ Used as common table sugar ○ Lactose = Glucose + Galactose ■ Milk sugar ○ Maltose = Glucose + Glucose ■ A product of starch digestion ■ Present in a few foods such as malt beverages and germinating wheat ● Oligosaccharides: short chains of three or more monosaccharides ○ Generally a chain of 10 or 20 monosaccharides ● Polysaccharides: long chains (up to thousands) of monosaccharides Test 1 - Chapter 2: The Chemistry of Life ○ Generally a chain of 50 or more monosaccharides ○ Can be thousands of sugars long ○ May have molecular weights of 500,000 or more (compared with 180 for a single glucose) ○ Glycogen, Starch, and Cellulose - all composed solely of glucose ○ Animals, including ourselves, make glycogen, whereas starch and cellulose are plant products. ○ Glycogen: an energy-storage polysaccharide made by cells of the liver, muscles, brain, uterus, and vagina ■ A long, branched, glucose polymer ■ Produced by the liver after a meal, when the blood glucose level is high, and then is broken down between meals to maintain blood glucose levels when there is no food intake ■ Stored by muscles for their own energy needs ■ Used by the uterus in early pregnancy to nourish the embryo. ○ Starch: the corresponding energy-storage polysaccharide in plants ■ Stored by plants when sunlight and nutrients are available and draw from it when photosynthesis is not possible (for example, at night and in winter, when a plant has shed its leaves) ■ The only significant digestible polysaccharide in the human diet ○ Cellulose: a structural polysaccharide that gives strength to the cell walls of plants ■ The principal component of wood, cotton, and paper ■ Consists of a few thousand glucose monomers joined together, with every other monomer “upside down” relative to the next ■ The most abundant organic compound on Earth ■ A common component of the diets of humans and other animals - yet we have no enzymes to digest it and thus derive no energy or nutrition from it ■ Swells with water in the digestive tract ■ Helps remove other materials through the intestine Carbohydrates (Cont’d) ● A source of energy that can be quickly mobilized ● All digested carbohydrate is ultimately converted to glucose, and glucose is oxidized to make ATP, a high-energy compound. ● Often conjugated with (covalently bound to) proteins and lipids ● Many of the lipid and protein molecules at the external surface of the cell membrane have chains of up to 12 sugars attached to them, thus forming glycolipids and glycoproteins. ● Glycoproteins ○ A major component of mucus, which traps particles in the respiratory system, resists infection, and protects the digestive tract from its own acid and enzymes ● Proteoglycans: macromolecules in which the carbohydrate component is dominant and a peptide or protein forms a smaller component Test 1 - Chapter 2: The Chemistry of Life ○ Form gels that help hold cells and tissues together ○ Form a gelatinous filler in the umbilical cord and eye ○ Lubricate the joints of the skeletal system ○ Account for the tough rubbery texture of cartilage ○ Have a protein moiety and a carbohydrate moiety ● Moiety: each chemically different component of a conjugated macromolecule Lipids ● Lipid: a hydrophobic organic molecule, usually composed only of carbon, hydrogen, and oxygen, with a high ratio of hydrogen to oxygen ● Less oxidized than carbohydrates, and thus have more calories per gram ● Much more variable in structure than other macromolecules ● Five Primary Types of Lipids ○ Fatty Acids ○ Triglycerides ○ Phospholipids ○ Eicosanoids ○ Steroids Table 2.7: Lipid Functions Type Function Bile Acids Steroids that aid in fat digestion and nutrient absorption Cholesterol Component of cell membranes; precursor of other steroids Eicosanoids Chemical messengers between cells Fat Soluble Vitamins (A, D, E, and K) Involved in a variety of functions including blood clotting, wound healing, vision, and calcium absorption Fatty Acids Precursor of triglycerides; source of energy Phospholipids Major component of cell membranes; aid in fat digestion Steroid Hormones Chemical messengers between cells Triglycerides Energy storage, thermal insulation; filling space; binding organs together; cushioning organs ● Fatty Acid: a chain of usually 4 to 24 carbon atoms with a carboxyl group at one end and a methyl group at the other ○ Saturated ○ Unsaturated ● Saturated Fatty Acid: has as much hydrogen as it can carry. No more could be added without exceeding four covalent bonds per carbon atom; thus, it is “saturated” with Test 1 - Chapter 2: The Chemistry of Life hydrogen. ● Unsaturated Fatty Acid: some carbon atoms are joined by double covalent bonds. Each of these could potentially share one pair of electrons with another hydrogen atom instead of the adjacent carbon, so hydrogen could be added to this molecule. ● Polyunsaturated Fatty Acid: multiple C=C bonds ● Most fatty acids can be synthesized by the human body, but a few, called essential fatty acids, must be obtained from the diet because we cannot synthesize them. ● Triglyceride: a molecule consisting of a three-carbon alcohol called glycerol linked to three fatty acids; triglycerides are more correctly, although less widely, also known as triacylglycerols ○ Each bond between a fatty acid and glycerol is formed by dehydration synthesis. ○ Once joined to a glycerol, a fatty acid can no longer donate a proton to solution and is therefore no longer an acid. ■ For this reason, triglycerides are also called neutral fats. ○ Broken down by hydrolysis reactions, which split each of these bonds apart by the addition of water ○ Oils: triglycerides that are liquid at room temperature ○ Animal fats are usually made of saturated fatty acids, so they are called saturated fats. ■ Solid at room or body temperature ○ Most plant triglycerides are polyunsaturated fats. ■ Generally remain liquid at room temperature ● Saturated fats contribute more to cardiovascular disease than unsaturated fats, and this reason it is healthier to cook with vegetable oils than with lard, bacon fat, or butter. ● The primary function of fat is energy storage, but when concentrated in adipose tissue, it also provides thermal insulation and acts as a shock-absorbing cushion for vital organs. Triglyceride (Fat) Synthesis: ● Phospholipids: an amphipathic molecule composed of two fatty acids and a phosphatecontaining group bonded to the three carbons of a glycerol molecule; composes most of the molecules of the plasma membrane and other cellular membranes ○ A phosphate is bonded a nitrogenous group called choline. ○ Have a dual nature ○ Two fatty acid “tails” are hydrophobic and phosphate “head” is hydrophilic ■ Amphipathic ○ Most important function: the structural foundation of cell membranes ● Eicosanoids: 20-carbon compounds derived from a fatty acid called arachidonic acid ○ Function primarily as hormonelike chemical signals between cells ○ Prostaglandins: five of the carbon atoms are arranged in a ring ■ The most functionally diverse eicosanoids ■ Originally found in the secretions of bovine prostate glands, but are now produced in almost all tissues ■ Play a variety of signaling roles in inflammation, blood clotting, hormone action, labor contractions, control of blood vessel diameter, and other Test 1 - Chapter 2: The Chemistry of Life processes ● Steroid: a lipid with 17 of its carbon atoms arranged in four rings ○ Cholesterol: the “parent” steroid from which the other steroids are synthesized ○ Others include cortisol, progesterone, estrogens, testosterone, and bile acids ■ Differ from each other in the location of C=C bonds within the rings and in the functional groups attached to the rings ■ We obtain dietary cholesterol only from foods of animal origin; plants make only trace amounts of no dietary importance. ■ The average adult contains over 200 g (half a pound) of cholesterol. ■ Has a bad reputation as a factor in cardiovascular disease ■ Hereditary and dietary factors can elevate blood cholesterol to dangerously high levels. ■ A natural product of the body that is necessary for human health ■ An important component of cell membranes ■ Required for proper nervous system function ■ Only about 15% of our cholesterol comes from the diet; the other 85% is internally synthesized, primarily by the liver. Proteins ● Protein: a polymer of amino acids; a large polypeptide; polypeptides over 50 amino acids long are generally classified as proteins ● Amino Acid: a small organic molecule with an amino group and a carboxyl group; the monomer of which proteins are composed, and also function as neurotransmitters and in other roles ● The 20 amino acids used to make proteins are identical except for a third functional group called the radical (R group) attached to the central carbon. ● In the simplest amino acid, glycine, R is merely a hydrogen atom, whereas in the largest amino acids it includes rings of carbon. ● Some radicals are hydrophilic and some are hydrophobic. ● Being composed of many amino acids, proteins as a whole are therefore often amphiphatic. ● Peptide: any molecule composed of two or more amino acids joined by peptide bonds ● Peptide Bond: formed by dehydration synthesis; joins the amino group of one amino acid to the carboxyl group of the next ● Peptides are named for the number of amino acids they have - for example, dipeptides have two and tripeptides have three. ● Oligopeptides: chains of fewer than 10 or 15 amino acids ● Polypeptides: chains of more than 10 or 15 amino acids Protein Structure: ● Proteins have complex coiled and folded structures that are critically important to the roles they play. ● Even slight changes in their conformation (three-dimensional shape) can destroy protein function. ● Primary Structure: the protein’s sequence of amino acids, which is encoded in the genes Test 1 - Chapter 2: The Chemistry of Life ● Secondary Structure: a coiled or folded shaped held together by hydrogen bonds between the slightly negative -C=O group of one peptide bond and the slightly positive -NH group of another one some distance away. ○ Alpha (�) Helix: springlike shape ○ Beta (�) Sheet (�-Pleated Sheet): pleated, ribbonlike shape ○ Many proteins have multiple -helical and β-pleated regions joined by short segments with less orderly geometry. ○ A single protein molecule may fold back on itself and have two or more β-pleated regions linked to one another by hydrogen bonds. ○ Separate, parallel protein chains also may be hydrogen-bonded to each other through their β-pleated regions. ● Tertiary Structure: formed by the the further bending and folding of proteins into various globular and fibrous shapes ○ Results from hydrophobic radicals associating with each other and avoiding water while hydrophilic radicals are attracted to the surrounding water ○ Van der Waals forces play a significant role in stabilizing tertiary structure. ○ Globular proteins have a compact tertiary structure wells suited for proteins embedded in cell membranes and proteins that must move around freely in the body fluids, such as enzymes and antibodies. ○ Fibrous proteins are slender filaments better suited for such roles as muscle contraction and providing strength to skin, hair, and tendons. ○ Disulfide Bridges: hold separate polypeptide chains together in such molecules as antibodies and insulin ○ Denaturation: a more drastic conformational change in response to conditions such as extreme heat or pH ■ Makes a protein unable to perform its normal function ■ Sometimes reversible, but usually it permanently destroys protein function ○ Conjugated proteins have a non-amino acid moiety called a prosthetic group covalently bound to them. Protein Function: ● Structure: Keratin, a tough structural protein, gives strength to the nails, hair, and skin surface. Deeper layers of the skin, as well as bones, cartilage, and teeth, contain an abundance of the durable protein collagen. ● Communication: Some hormones and other cell-to-cell signals are proteins, as are the receptors to which the signal molecules bind in the receiving cell. Any hormone or other molecule that reversibly binds to a protein is called ligand. ● Membrane Transport: Some proteins form channels in cell membranes that govern what passes through the membranes and when. Others act as carriers that briefly bind to solute particles and transport them to the other side of the membrane. Among their other roles, such proteins turn nerve muscle activity on and off. ● Recognition and Protection: Antibodies and other proteins attack and neutralize organisms that invade the body. Clotting proteins protect the body against blood loss. ● Movement: Movement is fundamental to all life, from the intracellular transport of Test 1 - Chapter 2: The Chemistry of Life molecules to the galloping of a racehorse. Proteins, with their special ability to change shape repeatedly, are the basis of for all such movement. Some proteins are called molecular motors (motor proteins) for this reason. ● Cell Adhesion: Proteins bind cells to each other, which enable sperm to fertilize eggs, enables immune cells to bind to enemy cancer cells, and keeps tissues from falling apart. Enzymes and Metabolism ● Enzymes: proteins that function as biological catalysts ● Enable biochemical reactions to occur rapidly at normal body temperatures ● Substrate: the substance the enzyme acts upon ○ Sometimes refers to the enzyme’s action ○ Adds the suffix -ase ● Activation Energy: the energy needed to get the reaction started Enzyme Structure and Action 1. A substrate molecule approaches a pocket on the enzyme surface called the active site. Amino acid side groups in this region of the enzyme are arranged so as to bind functional groups on the substrate molecule. Many enzymes have two active sites, enabling them to bind two different substrates and bring them together in a way that makes them react more readily with each other. 2. The substrate binds to the enzyme, forming an enzyme-substrate complex. The fit between a particular enzyme and its substrate is often compared to a lock and key. Just as only one key fits a particular lock, sucrose is the only substrate that fits the active site of sucrase. Sucrase cannot digest other disaccharides such as maltose or lactose. This selectivity is called enzyme-substrate specificity. Unlike a simple lock and key, however, the substrate slightly changes the shape of the enzyme to create a better fit between the two, as shown by the arrows in the figure. 3. Sucrase breaks the bond between the two sugars of sucrose, adding -H+ and -OH- groups from water. This hydrolyzes sucrose to two monosaccharides, glucose and fructose, which are then released by the enzyme as its reaction products. The enzyme remains unchanged and is ready to repeat the process if another sucrose is available. ● Since an enzyme is not consumed by the reaction it catalyzes, one enzyme molecule can consume millions of substrate molecules, and at astonishing speed. ● Factors that change the shape of an enzyme - notably temperature and pH - tend to alter or destroy the ability of the enzyme to bind its substrate. ○ Disrupt the hydrogen bonds and other weak forces that hold the enzyme in its proper conformation, essentially changing the shape of the “lock” so that the “key” no longer fits ● Enzymes vary in optimum pH according to where in the body they normally function. ● All human enzymes have a temperature optimum near 37°C at which they produce their fastest reaction rates. Cofactors: ● About two-thirds of human enzymes require a nonprotein partner called a cofactor. ○ Examples of inorganic cofactors: iron, copper, zinc, magnesium, and calcium ions ■ Some work by binding to the enzyme and inducing it to fold into a shape Test 1 - Chapter 2: The Chemistry of Life that activates its active site ● Coenzymes: organic cofactors usually derived from niacin, riboflavin, and other watersoluble vitamins ○ Accept electrons from an enzyme in one metabolic pathway and transfer them to an enzyme in another Metabolic Pathways: ● Metabolic Pathway: a chain of reactions with each step usually catalyzed by a different enzyme ATP, Other Nucleotides, and Nucleic Acids ● Nucleotides: organic compounds with three principal compounds: a single or double carbon-nitrogen ring called a nitrogenous base, a monosaccharide, and one or more phosphate groups ● Adenosine Triphosphate (ATP): the body’s most important energy-transfer molecule ○ Nitrogenous Base → Double Ring → Adenine ○ Sugar: Ribose ○ Three phosphate groups ○ Briefly gains energy from exergonic reactions such as glucose oxidation and releases it within seconds for physiological work such as polymerization reactions, muscle contraction, and pumping ions through cell membranes ○ Second and third phosphate groups of ATP are attached to the rest of the molecule by high-energy covalent bonds traditionally indicated by a wavy line (~) in the structural formula ○ Since phosphate groups are negatively charged, they repel each other. ■ Requires a high-energy bond to overcome that repellent force and hold them together - especially to add the third phosphate group to a chain that already has two negatively charged phosphates ■ Most energy transfers to and from ATP involve adding or removing that third phosphate. ● Enzymes called adenosine triphosphatases (ATPases) are specialized to hydrolyze the third phosphate bond, producing adenosine diphosphate (ADP) and an inorganic phosphate group (Pi). ○ Releases 7.3 kilocalories (kcal) of energy for every mole (505g) of ATP ■ Most of this energy escapes as heat, but we live on the portion of it that does useful work ● The free phosphate groups released by ATP hydrolysis are often added to enzymes or other molecules to activate them. ○ This addition of Pi, called phosphorylation, is carried out by enzymes called kinases. ■ The phosphorylation of an enzyme is sometimes the “switch” that turns the metabolic pathway on or off. ● Glycolysis: the first stage in glucose oxidation; “sugar splitting”; its major effect is to split the six-carbon glucose molecule into two three-carbon molecules of pyruvate ○ A little ATP is produced in this stage (a net of 2 ATP per glucose), but most of the Test 1 - Chapter 2: The Chemistry of Life chemical energy of the glucose is still in the pyruvate. The Source and Uses of ATP: ● When the demand for ATP outpaces the oxygen supply, excess pyruvate is converted to lactate by a pathway called anaerobic fermentation. ○ Disadvantages: ■ Does not extract any energy from pyruvate ■ The lactate it produces is toxic, so most cells can use anaerobic fermentation only as a temporary measure. ○ Advantage: ■ Enable glycolysis to continue and thus enables a cell to continue producing a small amount of ATP ● If enough oxygen is available, a more efficient pathway called aerobic respiration occurs. ○ Breaks pyruvate down to carbon dioxide and water and generates up to 36 more molecules of ATP for each of the original glucose molecules. ○ The reactions of aerobic respiration are carried out in the cell’s mitochondria, so mitochondria are regarded as a cell’s principal “ATP factories.” Other Nucleotides: ● Guanosine Triphosphate (GTP): involved in energy transfers ○ Donates phosphate groups to other molecules in some reactions ■ E.g., it can donate its third phosphate group to ADP to regenerate ATP ● Cyclic Adenosine Monophosphate (cAMP): formed by the removal of both the second and third phosphate groups from ATP ○ In many cases, when a hormone or other chemical signal (“first messenger”) binds to a cell surface, it triggers an internal reaction that converts ATP to cAMP. ○ The cAMP then acts as a “second messenger” to activate metabolic effects within the cell. Nucleic Acids: ● Nucleic Acids: polymers of nucleotides ● Deoxyribonucleic Acid: the largest nucleic acid; typically 100 million to 1 billion nucleotides long ○ Constitutes our genes ○ Gives instructions for synthesizing all of the body’s proteins ○ Transfers hereditary information from cell to cell when cells divide and from generation to generation when organisms reproduce ■ Three forms of ribonucleic acid (RNA), which range from 70 to 10,000 nucleotides long, carry out those instructions and synthesize the proteins, assembling amino acids in the right order to produce each protein “described” by the DNA.