Essentials of Human Anatomy & Physiology, Chapter 2, Basic Chemistry, Thirteenth Edition PDF

Essentials of Human Anatomy & Physiology Thirteenth Edition Chapter 2 Basic Chemistry Lecture Presentation by Patty Bostwick...

Essentials of Human Anatomy & Physiology Thirteenth Edition Chapter 2 Basic Chemistry Lecture Presentation by Patty Bostwick-Taylor Florence-Darlington Technical College Copyright © 2021 Pearson Education, Inc. All Rights Reserved Matter and Energy (1 of 5) Matter—anything that occupies space and has mass Matter may exist as one of three states – Solid: definite shape and volume – Liquid: definite volume; shape of container – Gaseous: neither a definite shape nor volume Copyright © 2021 Pearson Education, Inc. All Rights Reserved Matter and Energy (2 of 5) Matter may be changed – Physically ▪ Changes do not alter the basic nature of a substance ▪ Examples include changes in the state of matter (solid, liquid, or gas) – Chemically ▪ Changes alter the chemical composition of a substance Copyright © 2021 Pearson Education, Inc. All Rights Reserved Matter and Energy (3 of 5) Energy—the ability to do work – Has no mass and does not take up space – Kinetic energy: energy is doing work – Potential energy: energy is inactive or stored Copyright © 2021 Pearson Education, Inc. All Rights Reserved Matter and Energy (4 of 5) Forms of energy – Chemical energy is stored in chemical bonds of substances – Electrical energy results from movement of charged particles – Mechanical energy is energy directly involved in moving matter – Radiant energy travels in waves; energy of the electromagnetic spectrum Copyright © 2021 Pearson Education, Inc. All Rights Reserved Matter and Energy (5 of 5) Energy form conversions – ATP (adenosine triphosphate) traps the chemical energy of food in its bonds Copyright © 2021 Pearson Education, Inc. All Rights Reserved Composition of Matter (1 of 2) Elements—fundamental units of matter – 96 percent of the body is made from four elements: 1. Oxygen (O)—most common; 65% of the body’s mass 2. Carbon (C) 3. Hydrogen (H) 4. Nitrogen (N) Periodic table contains a complete listing of elements Copyright © 2021 Pearson Education, Inc. All Rights Reserved Table 2.1 Common Elements Making Up the Human Body (1 of 3) Major (96.1%) Element Atomic Percentage of Role symbol body mass Oxygen O 65.0 A major component of both organic and inorganic molecules; as a gas, essential to the oxidation of glucose and other food fuels, during which cellular energy (A TP) is produced. Carbon C 18.5 The primary element in all organic molecules, including carbohydrates, lipids, proteins, and nucleic acids. Hydrogen H 9.5 A component of all organic molecules; as an ion (a charged atom), it influences the pH of body fluids. Nitrogen N 3.2 A component of proteins and nucleic acids (genetic material). Copyright © 2021 Pearson Education, Inc. All Rights Reserved Table 2.1 Common Elements Making Up the Human Body (2 of 3) Lesser (3.9%) Element Atomic Percentage of Role symbol body mass Calcium Ca 1.5 Found as a salt in bones and teeth; in ionic form, required for muscle contraction, neural transmission, and blood clotting. Phosphorus P 1.0 Present as a salt, in combination with calcium, in bones and teeth; also present in nucleic acids and many proteins; forms part of the high-energy compound ATP. Potassium K 0.4 In its ionic form, the major intracellular cation; necessary for the conduction of nerve impulses and for muscle contraction. Sulfur S 0.3 A component of proteins (particularly contractile proteins of muscle). Copyright © 2021 Pearson Education, Inc. All Rights Reserved Table 2.1 Common Elements Making Up the Human Body (3 of 3) Lesser (3.9%) Element Atomic Percentage Role symbol of body mass Sodium Na 0.2 As an ion, the major extracellular cation; important for water balance, conduction of nerve impulses, and muscle contraction. Chlorine Cl 0.2 In ionic (chloride) form, the most abundant extracellular anion. Magnesiu Mg 0.1 Present in bone; also an important cofactor for enzyme activity m in a number of metabolic reactions. Iodine I 0.1 Needed to make functional thyroid hormones. Iron Fe 0.1 A component of the functional hemoglobin molecule (which transports oxygen within red blood cells) and some enzymes. Trace (less than 0.01%)* Chromium (Cr), Cobalt (Co), Copper (Cu), Fluorine (F), Manganese (M n), Molybdenum (M o), Selenium (S e), Silicon (S i), Tin (Sn), Vanadium (V), Zinc (Z n) *Referred to as the trace elements because they are required in very small amounts; many are found as part of enzymes or are required for enzyme activation Copyright © 2021 Pearson Education, Inc. All Rights Reserved Composition of Matter (2 of 2) Atoms – Building blocks of elements – Atoms of elements differ from one another – Atomic symbol is chemical shorthand for each element Copyright © 2021 Pearson Education, Inc. All Rights Reserved The Basic Atomic Subparticles (1 of 2) Protons (p ) are positively charged Neutrons (n0 ) are uncharged or neutral Electrons (e ) are negatively charged Copyright © 2021 Pearson Education, Inc. All Rights Reserved The Basic Atomic Subparticles (2 of 2) All atoms are electrically neutral – Number of protons equals numbers of electrons in an atom – Positive and negative charges cancel each other out Ions are atoms that have lost or gained electrons Copyright © 2021 Pearson Education, Inc. All Rights Reserved Planetary and Orbital Models of an Atom (1 of 3) Planetary model – Portrays the atom as a miniature solar system – Protons and neutrons are in the atomic nucleus – Electrons are in orbitals around the nucleus Copyright © 2021 Pearson Education, Inc. All Rights Reserved Planetary and Orbital Models of an Atom (2 of 3) Orbital model – Electrons are depicted by an electron cloud, a haze of negative charge, outside the nucleus Copyright © 2021 Pearson Education, Inc. All Rights Reserved Planetary and Orbital Models of an Atom (3 of 3) Electrons determine an atom’s chemical behavior and bonding properties Although outdated, the planetary model is simple and easy to understand and use Copyright © 2021 Pearson Education, Inc. All Rights Reserved Identifying Elements (1 of 2) To identify an element, we need to know the: – Atomic number – Atomic mass number – Atomic weight Copyright © 2021 Pearson Education, Inc. All Rights Reserved Identifying Elements (2 of 2) Atomic number—equal to the number of protons that the atom contains – Unique to atoms of a particular element – Indirectly tells the number of electrons in an atom Atomic mass number—sum of the protons and neutrons contained in an atom’s nucleus Atomic weight—approximately equal to the mass number of the element’s most abundant isotope (to be discussed in a moment) Copyright © 2021 Pearson Education, Inc. All Rights Reserved Atomic Weight and Isotopes Isotopes – Atoms that have the same number of protons and electrons but vary in the number of neutrons – Isotopes have the same atomic number but different atomic masses Copyright © 2021 Pearson Education, Inc. All Rights Reserved Atomic Weights and Isotopes Radioisotope – Heavy isotope of certain atoms – Tends to be unstable – Decomposes to more stable isotope Radioactivity—process of spontaneous atomic decay – Used to tag and trace biological molecules through the body Copyright © 2021 Pearson Education, Inc. All Rights Reserved Molecules and Compounds (1 of 2) Molecule—two or more atoms of the same elements combined chemically Example of a chemical reaction, shown as a chemical equation, resulting in a molecule: H (atom)  H (atom) H2 (molecule) – The reactants are the atoms on the left – The product is the molecule on the right, represented by a molecular formula Copyright © 2021 Pearson Education, Inc. All Rights Reserved Molecules and Compounds (2 of 2) Compound—two or more atoms of different elements combined chemically to form a molecule of a compound Example of a chemical reaction resulting in a compound: 4H  C CH4 (methane) Copyright © 2021 Pearson Education, Inc. All Rights Reserved Chemical Bonds and Chemical Reactions Chemical reactions occur when atoms combine with or dissociate from other atoms Chemical bonds are energy relationships involving interactions among the electrons of reacting atoms Copyright © 2021 Pearson Education, Inc. All Rights Reserved Role of Electrons (1 of 4) Electrons occupy energy levels called electron shells (or energy levels) Electrons closest to the nucleus are most strongly attracted to its positive charge Distant electrons further from the nucleus are likely to interact with other atoms Copyright © 2021 Pearson Education, Inc. All Rights Reserved Role of Electrons (2 of 4) Each electron shell has distinct properties How to fill the atom’s electrons shells – Shell 1 can hold a maximum of 2 electrons – Shell 2 can hold a maximum of 8 electrons – Shell 3 can hold a maximum of 18 electrons – Subsequent shells can hold more electrons Bonding involves interactions only between electrons in the outermost (valence) shell Atoms with full valence shells do not form bonds Copyright © 2021 Pearson Education, Inc. All Rights Reserved Role of Electrons (3 of 4) Rule of eights – The key to chemical reactivity – Atoms are considered stable when their outermost (valence) shell has 8 electrons – Atoms with 8 electrons in the valence shell are considered stable and chemically inactive (inert) – The exception to this rule of eights is shell 1, which can hold only 2 electrons Copyright © 2021 Pearson Education, Inc. All Rights Reserved Role of Electrons (4 of 4) Reactive elements – Atoms will gain, lose, or share electrons to complete their outermost orbitals when fewer than 8 electrons are in the valence shell – Chemical bonding helps atoms achieve a stable valence shell Copyright © 2021 Pearson Education, Inc. All Rights Reserved Types of Chemical Bonds (1 of 6) Ionic bonds – Form when electrons are completely transferred from one atom to another – Allow atoms to achieve stability through the transfer of electrons Copyright © 2021 Pearson Education, Inc. All Rights Reserved Types of Chemical Bonds (2 of 6) Ions – Result from the loss or gain of electrons ▪ Anions have negative charge due to gain of electron(s) ▪ Cations have positive charge due to loss of electron(s) – Tend to stay close together because opposite charges attract Copyright © 2021 Pearson Education, Inc. All Rights Reserved Figure 2.6 Formation of an Ionic Bond Copyright © 2021 Pearson Education, Inc. All Rights Reserved Types of Chemical Bonds (3 of 6) Covalent bonds – Atoms become stable through shared electrons – Electrons are shared in pairs – Single covalent bonds share one pair of electrons – Double covalent bonds share two pairs of electrons Copyright © 2021 Pearson Education, Inc. All Rights Reserved Types of Chemical Bonds (4 of 6) Covalent bonds can be described as either nonpolar or polar – Nonpolar covalent bonds ▪ Electrons are shared equally between the atoms of the molecule ▪ Electrically neutral as a molecule ▪ Example: carbon dioxide Copyright © 2021 Pearson Education, Inc. All Rights Reserved Types of Chemical Bonds (5 of 6) Covalent bonds can be described as either nonpolar or polar – Polar covalent bonds ▪ Electrons are not shared equally between the atoms of the molecule ▪ Molecule has a positive and negative side, or pole ▪ Example: water Copyright © 2021 Pearson Education, Inc. All Rights Reserved Types of Chemical Bonds (6 of 6) Hydrogen bonds – Extremely weak chemical bonds – Formed when a hydrogen atom is attracted to the negative portion, such as an oxygen or nitrogen atom, of a polar molecule – Responsible for the surface tension of water – Important for forming intramolecular bonds, as in protein structure Copyright © 2021 Pearson Education, Inc. All Rights Reserved Patterns of Chemical Reactions (1 of 3) Synthesis reaction (A  B AB) – Atoms or molecules combine to form a larger, more complex molecule – Energy is absorbed for bond formation – Underlies all anabolic (building) activities in the body Decomposition reaction (AB A  B) – Molecule is broken down into smaller molecules – Chemical energy is released – Underlies all catabolic (destructive) activities in the body Copyright © 2021 Pearson Education, Inc. All Rights Reserved Patterns of Chemical Reactions (2 of 3) Exchange reaction AB  C AC  B and AB  CD AD  CB – Involves simultaneous synthesis and decomposition reactions as bonds are both made and broken – Switch is made between molecule parts, and different molecules are made Copyright © 2021 Pearson Education, Inc. All Rights Reserved Patterns of Chemical Reactions (3 of 3) Most chemical reactions are reversible Reversibility is indicated by a double arrow – When arrows differ in length, the longer arrow indicates the more rapid reaction or major direction of progress Factors influencing the rate of chemical reactions are shown in Table 2.4 Copyright © 2021 Pearson Education, Inc. All Rights Reserved Table 2.4 Factors Increasing the Rate of Chemical Reactions Factor Mechanism to increase the number of collisions  temperature increasing  the kinetic energy of the molecules, which in turn move increasing more rapidly and collide more forcefully. concentration of reacting particles the number of collisions because of increased numbers of reacting particles. increasing increasing  decreasing particle size Smaller particles have more kinetic energy and move faster  than larger ones, hence they take part in more collisions. Presence of catalysts the amount of energy the molecules need to interact by decreasing holding the reactants in the proper positions to interact.  Copyright © 2021 Pearson Education, Inc. All Rights Reserved Biochemistry: The Chemical Composition of Living Matter Inorganic compounds – Lack carbon – Tend to be small, simple molecules – Include water, salts, and many (not all) acids and bases Organic compounds – Contain carbon – All are large, covalent molecules – Include carbohydrates, lipids, proteins, and nucleic acids Copyright © 2021 Pearson Education, Inc. All Rights Reserved Inorganic Compounds (1 of 12) Water – Most abundant inorganic compound in the body – Accounts for two-thirds of the body’s weight – Vital properties include: ▪ High heat capacity ▪ Polarity/solvent properties ▪ Chemical reactivity ▪ Cushioning Copyright © 2021 Pearson Education, Inc. All Rights Reserved Inorganic Compounds (2 of 12) High heat capacity – Water absorbs and releases a large amount of heat before it changes temperature – Prevents sudden changes in body temperature Copyright © 2021 Pearson Education, Inc. All Rights Reserved Inorganic Compounds (3 of 12) Polarity/solvent properties – Water is often called the “universal solvent” – Solvents are liquids or gases that dissolve smaller amounts of solutes – Solutes are solids, liquids, or gases that are dissolved or suspended by solvents – Solution forms when solutes are very tiny – Colloid forms when solutes of intermediate size form a translucent mixture Copyright © 2021 Pearson Education, Inc. All Rights Reserved Inorganic Compounds (4 of 12) Chemical reactivity – Water is an important reactant in some chemical reactions – Reactions that require water are known as hydrolysis reactions – Example: water helps digest food or break down biological molecules Copyright © 2021 Pearson Education, Inc. All Rights Reserved Inorganic Compounds (5 of 12) Cushioning – Water serves a protective function – Examples: cerebrospinal fluid protects the brain from physical trauma, and amniotic fluid protects a developing fetus Copyright © 2021 Pearson Education, Inc. All Rights Reserved Inorganic Compounds (6 of 12) Salts – Ionic compound – Contain cations other than H and anions other than OH – Easily dissociate (break apart) into ions in the presence of water – Vital to many body functions ▪ Example: sodium and potassium ions are essential for nerve impulses Copyright © 2021 Pearson Education, Inc. All Rights Reserved Inorganic Compounds (7 of 12) Salts – All salts are electrolytes – Electrolytes are ions that conduct electrical currents Copyright © 2021 Pearson Education, Inc. All Rights Reserved Inorganic Compounds (8 of 12) Acids – Electrolytes that dissociate (ionize) in water and release hydrogen ions (H ) – Proton (H ) donors – Example: HCl H  Cl– – Strong acids ionize completely and liberate all their protons – Weak acids ionize incompletely Copyright © 2021 Pearson Education, Inc. All Rights Reserved Inorganic Compounds (9 of 12) Bases – Electrolytes that dissociate (ionize) in water and release hydroxyl ions (OH ) – Proton (H ) acceptors – Example: NaOH Na   OH– Copyright © 2021 Pearson Education, Inc. All Rights Reserved Inorganic Compounds (10 of 12) Neutralization reaction – Type of exchange reaction in which acids and bases react to form water and a salt – Example: NaOH  HCl H2O  NaCl Copyright © 2021 Pearson Education, Inc. All Rights Reserved Inorganic Compounds (11 of 12) pH – pH measures relative concentration of hydrogen (and hydroxide) ions in body fluids – pH scale is based on the number of protons in a solution – pH scale runs from 0 to 14 – Each successive change of 1 pH unit represents a tenfold change in H concentration Copyright © 2021 Pearson Education, Inc. All Rights Reserved Inorganic Compounds (12 of 12) pH – Neutral ▪ 7 is neutral ▪ Neutral means that the number of hydrogen ions exactly equals the number of hydroxyl ions – Acidic solutions have a pH below 7 ▪ More H than OH – Basic solutions have a pH above 7 ▪ Fewer H than OH – Buffers—chemicals that can regulate pH change Copyright © 2021 Pearson Education, Inc. All Rights Reserved Figure 2.12 The pH Scale and pH Values of Representative Substances Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (4 of 26) Carbohydrates – Contain carbon, hydrogen, and oxygen – Include sugars and starches – Classified according to size and solubility in water ▪ Monosaccharides—simple sugars and the structural units of the carbohydrate group ▪ Disaccharides—two simple sugars joined by dehydration synthesis ▪ Polysaccharides—long-branching chains of linked simple sugars Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (5 of 26) Monosaccharides—simple sugars – Single-chain or single-ring structures – Contain three to seven carbon atoms – Examples: glucose (blood sugar), fructose, galactose, ribose, deoxyribose Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (6 of 26) Disaccharides—two simple sugars joined by dehydration synthesis – Examples include sucrose, lactose, and maltose – Too large to pass through cell membranes Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (7 of 26) Polysaccharides: long, branching chains of linked simple sugars – Large, insoluble molecules – Function as storage products – Examples include starch and glycogen Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (8 of 26) Lipids – Most abundant are the triglycerides, phospholipids, and steroids – Contain carbon, hydrogen, and oxygen ▪ Carbon and hydrogen outnumber oxygen – Insoluble in water, but soluble in other lipids Copyright © 2021 Pearson Education, Inc. All Rights Reserved Table 2.5 Representative Lipids Found in the Body (1 of 2) Lipid type Location/function Triglycerides (neutral fats) Found in fat deposits (subcutaneous tissue and around organs); protect and insulate the body organs; the major source of stored energy in the body. Phospholipids Found in cell membranes; participate in the transport of lipids in plasma; abundant in the brain and the nervous tissue in general, where they help to form insulating white matter Steroids Cholesterol The basis of all body steroids. Bile salts A breakdown product of cholesterol; released by the liver into the digestive tract, where they aid in fat digestion and absorption. Vitamin D A fat-soluble vitamin produced in the skin on exposure to U V (ultraviolet) radiation (sunshine); necessary for normal bone growth and function. Sex hormones Estrogen and progesterone (female hormones) and testosterone (a male hormone) produced from cholesterol; necessary for normal reproductive function; deficits result in sterility. Corticosteroids (adrenal cortical Cortisol, a glucocorticoid, is a long-term antistress hormone that is necessary hormones) for life; aldosterone helps regulate salt and water balance in body fluids by targeting the kidneys. Copyright © 2021 Pearson Education, Inc. All Rights Reserved Table 2.5 Representative Lipids Found in the Body (2 of 2) Lipid type Location/function Other lipid-based substances Fat-soluble vitamins Found in orange-pigmented vegetables (carrots) and fruits (tomatoes); part of A the photoreceptor pigment involved in vision. E Taken in via plant products such as wheat germ and green leafy vegetables; may promote wound healing and contribute to fertility, but not proven in humans; an antioxidant; may help to neutralize free radicals (highly reactive particles believed to be involved in triggering some types of cancers). K Made available largely by the action of intestinal bacteria; also prevalent in a wide variety of foods; necessary for proper clotting of blood. Prostaglandins Derivatives of fatty acids found in cell membranes; various functions depending on the specific class, including stimulation of uterine contractions (thus inducing labor and miscarriages), regulation of blood pressure, and control of motility of the gastrointestinal tract; involved in inflammation. Lipoproteins Lipoid and protein-based substances that transport fatty acids and cholesterol in the bloodstream; major varieties are high-density lipoproteins (H DLs) and low-density lipoproteins (L DLs). Glycolipids Component of cell membranes. Lipids associated with carbohydrate molecules that determine blood type, play a role in cell recognition or in recognition of foreign substances by immune cells. Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (9 of 26) Triglycerides, or neutral fats – Found in fat deposits – Source of stored energy – Composed of two types of building blocks—fatty acids and one glycerol molecule ▪ Saturated fatty acids ▪ Unsaturated fatty acids Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (10 of 26) Fatty acid chains of triglycerides – Saturated fats ▪ Contain only single covalent bonds ▪ Chains are straight ▪ Exist as solids at room temperature since molecules pack closely together – Unsaturated fats ▪ Contain one or more double covalent bonds, causing chains to kink ▪ Exist as liquid oils at room temperature ▪ “Heart healthy” Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (11 of 26) Trans fats – Oils that have been solidified by the addition of hydrogen atoms at double bond sites – Increase risk of heart disease Omega-3 fatty acids – Found in cold-water fish and plant sources, including flax, pumpkin, and chia seeds; walnuts and soy foods – Appear to decrease risk of heart disease Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (12 of 26) Phospholipids – Contain two fatty acids chains rather than three; they are hydrophobic (“water fearing”) – Phosphorus-containing polar “head” carries an electrical charge and is hydrophilic (“water loving”) – Charged “head” region interacts with water and ions while the fatty acid chains (“tails”) do not – Form cell membranes Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (13 of 26) Steroids – Formed of four interlocking rings – Include cholesterol, bile salts, vitamin D, and some hormones – Some cholesterol is ingested from animal products; the liver also makes cholesterol – Cholesterol is the basis for all steroids made in the body Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (14 of 26) Proteins – Account for over half of the body’s organic matter ▪ Provide for construction materials for body tissues ▪ Play a vital role in cell function ▪ Act as enzymes, hormones, and antibodies – Contain carbon, oxygen, hydrogen, nitrogen, and sometimes sulfur – Built from building blocks called amino acids Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (18 of 26) Fibrous (structural) proteins – Appear in body structures – Exhibit secondary, tertiary, or even quaternary structure – Bind structures together and exist in body tissues – Stable proteins – Examples include collagen and keratin Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (19 of 26) Globular (functional) proteins – Function as antibodies, hormones, or enzymes – Exhibit at least tertiary structure – Hydrogen bonds are critical to the maintenance of structure – Can be denatured and no longer perform physiological roles – Active sites “fit” and interact chemically with other molecules Copyright © 2021 Pearson Education, Inc. All Rights Reserved Table 2.6 Representative Classes of Functional Proteins Functional class Role(s) in the body Antibodies (immunoglobulins) Highly specialized proteins that recognize, bind with, and inactivate bacteria, toxins, and some viruses; function in the immune response, which helps protect the body from “invading” foreign substances. Hormones Help to regulate growth and development. Examples include Growth hormone—an anabolic hormone necessary for optimal growth. Insulin—helps regulate blood sugar levels. Thyroid hormone—regulates the rate at which glucose used by body cells. Transport proteins Hemoglobin transports oxygen in the blood; other transport proteins in the blood carry iron, cholesterol, or other substances. Enzymes (catalysts) Essential to virtually every biochemical reaction in the body; increase the rates of chemical reactions by at least a millionfold; in their absence (or destruction), biochemical reactions cease. Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (20 of 26) Enzymes – Act as biological catalysts – Increase the rate of chemical reactions – Bind to substrates at an active site to catalyze reactions – Can be recognized by their –ase suffix ▪ Hydrolase ▪ Oxidase Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (21 of 26) Nucleic acids – Form genes – Composed of carbon, oxygen, hydrogen, nitrogen, and phosphorus atoms – Largest biological molecules in the body – Two major kinds: ▪ DNA ▪ RNA Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (22 of 26) Nucleic acids are built from building blocks called nucleotides Nucleotides contain three parts 1. A nitrogenous base ▪ A = Adenine ▪ G = Guanine ▪ C = Cytosine ▪ T = Thymine ▪ U = Uracil 2. Pentose (five-carbon) sugar 3. A phosphate group Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (23 of 26) Deoxyribonucleic acid (DNA) – The genetic material found within the cell’s nucleus – Provides instructions for every protein in the body – Organized by complementary bases to form a double- stranded helix – Contains the sugar deoxyribose and the bases adenine, thymine, cytosine, and guanine – Replicates before cell division Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (24 of 26) Ribonucleic acid (RNA) – Carries out DNA’s instructions for protein synthesis – Created from a template of DNA – Organized by complementary bases to form a single- stranded helix – Contains the sugar ribose and the bases adenine, uracil, cytosine, and guanine – Three varieties are messenger, transfer, and ribosomal RNA Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (25 of 26) Adenosine triphosphate (ATP) – Composed of a nucleotide built from ribose sugar, adenine base, and three phosphate groups – Chemical energy used by all cells – Energy is released by breaking high-energy phosphate bond Copyright © 2021 Pearson Education, Inc. All Rights Reserved Organic Compounds (26 of 26) ADP (adenosine diphosphate) accumulates as ATP is used for energy ATP is replenished by oxidation of food fuels Three examples of how ATP drives cellular work are shown next Copyright © 2021 Pearson Education, Inc. All Rights Reserved