HOLE'S Essentials of Human Anatomy & Physiology: Chemical Basis of Life PDF

Because learning changes everything.® Chapter 02 Chemical Basis of Life HOLE’S ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY Fifteenth Edition Charles J. Welsh and Cynthia Prentice-Craver © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written co...

Because learning changes everything.® Chapter 02 Chemical Basis of Life HOLE’S ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY Fifteenth Edition Charles J. Welsh and Cynthia Prentice-Craver © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  2.1: Introduction Chemistry is the branch of science that deals with the composition and characteristics of chemicals A knowledge of chemistry is necessary for the understanding of physiology because chemicals participate in body processes Our foods, liquids and medications are composed of chemicals Cells and their organelles are assemblies of molecules, which are composed of chemicals © McGraw Hill, LLC 2  2.2: Fundamentals of Chemistry Matter is anything that has weight (mass) and takes up space (living and nonliving things). All matter is composed of elements. Elements are the smallest units of matter with specific chemical properties. Living organisms require about 20 elements, of which oxygen, carbon, hydrogen, and nitrogen are most abundant. Elements are composed of atoms; atoms of different elements vary in size, weight, and interaction with other atoms Atoms are the smallest unit of an element Attractions between two or more atoms are called chemical bonds © McGraw Hill, LLC 3  Major Elements of the Body 1 TABLE 2.1 Elements in the Body Approximate Percentage of the Human Major Elements Symbol Body (by weight) Oxygen O 65.0 Carbon C 18.5 Hydrogen H 9.5 Nitrogen N 3.2 Calcium Ca 1.5 Phosphorus P 1.0 Potassium K 0.4 Sulfur S 0.3 Chlorine Cl 0.2 Sodium Na 0.2 Magnesium Mg 0.1 Total 99.9% © McGraw Hill, LLC 4  Major Elements of the Body 2 TABLE 2.1 Elements in the Body Trace Elements Chromium Cr Cobalt Co Copper Cu Fluorine F Together less lodine I than 0.1% Iron Fe Manganese Mn Zinc Zn © McGraw Hill, LLC 5  Atomic Structure An atom consists of a central nucleus containing protons and neutrons, and electrons in orbit around the nucleus in shells. Protons have a positive charge and are about equal in size to neutrons. Neutrons are uncharged. Electrons are much smaller than protons and neutrons and have a negative charge. An electrically neutral atom has equal numbers of protons and electrons. Atoms that gain or lose one or more electrons become charged and are called ions. © McGraw Hill, LLC 6  Atomic Number and Mass Number The number of protons in the atoms of an element is the atomic number of that element. The number of protons plus the number of neutrons in the nucleus of an atom is its mass number. Electron mass is very small compared to the mass of a proton or neutron, so it is not included in the calculation of the atomic number and mass number. © McGraw Hill, LLC 7  Isotopes and Atomic Weight All atoms of an element have the same atomic number because they have the same number of protons. Atoms with the same atomic number, but different mass numbers, are isotopes of that element: Example: All carbon atoms have 6 protons, but may have 6, 7, or 8 neutrons. These atoms have atomic weights of 12, 13, or 14 respectively. Samples of elements often include more than one isotope. The atomic weight of each element is the average of the mass numbers present in the sample. Some isotopes are stable. Unstable isotopes are radioactive and give off radiation in the form of energy or atomic fragments. © McGraw Hill, LLC 8  Figure 2.1: The Subatomic Particles of an Atom Access the text alternative for these images © McGraw Hill, LLC 9  2.3: Bonding of Atoms Atoms form chemical bonds by attaching to each other by gaining, losing, or sharing electrons. Electrons are found in shells (areas of space) around the nucleus. In elements with atomic numbers up to 18: The first shell, closest to the nucleus, holds a maximum of two electrons. The second and third energy shells each hold a maximum of eight electrons. Atoms of elements that have their outermost shells filled are stable and chemically inert (inactive). © McGraw Hill, LLC 10  Figure 2.2: Electron Orbits in the Shells of Atoms Access the text alternative for these images © McGraw Hill, LLC 11  Ionic Bonding Atoms with incompletely filled outermost shells tend to be reactive, in order to form stable outer shells of 2 or 8 electrons. When atoms gain or lose electrons, they become ions with a charge. Whether they gain or lose electrons depends on how many electrons they have in their outermost shell. Oppositely-charged ions attract each other and form an ionic (electrovalent) bond: Form crystal arrays, not molecules Formula gives the ratio of ions, not the actual numbers Sodium atoms, for example, contain 1 electron in their outermost shells; they tend to lose 1 electron to form ionic bonds. © McGraw Hill, LLC 12  Figure 2.3: The Structure of a Sodium Atom Access the text alternative for these images © McGraw Hill, LLC 13  Figure 2.4: An Ionic Bond Between Sodium and Chlorine Atoms to form Sodium Chloride (Salt) Access the text alternative for these images © McGraw Hill, LLC 14  Covalent Bonding Covalent bonds are formed when atoms share electrons, in order to fill their outermost shells and become stable: One pair of electrons shared between two atoms forms a single covalent bond Example: A hydrogen molecule is formed when 2 hydrogen atoms form a covalent bond by sharing a pair of electrons Two pairs of electrons shared between atoms form a double covalent bond Three pairs of electrons shared between atoms forms a triple covalent bond © McGraw Hill, LLC 15  Figure 2.5: Covalent Bonding of Two Hydrogen Atoms Access the text alternative for these images © McGraw Hill, LLC 16  Polar Covalent and Hydrogen Bonds Carbon and hydrogen atoms form covalent bonds, in which the electrons are shared equally. Some molecules contain polar covalent bonds, in which the electrons are not shared equally, but reside closer to one of the atoms in the bond. These molecules with unequal charge distribution are called polar molecules. Polar molecules contain equal numbers of protons and electrons, so they are electrically neutral. A hydrogen bond forms from the relatively weak attraction between the slightly positive “H” end of a polar molecule and the slightly negative “N” or “O” end of a nearby polar molecule. © McGraw Hill, LLC 17  Figure 2.6: Hydrogen Bonds between Water Molecules Access the text alternative for these images © McGraw Hill, LLC 18  2.4: Molecules, Compounds, and Chemical Reactions A molecule is formed when two or more atoms form a chemical bond If atoms of the same element bond, a molecule of that element is formed (O2 is an oxygen molecule) If atoms of different elements combine, the molecule is called a compound: Compounds always have definite types and numbers of atoms For example, 2 atoms of H and 1 atom of O can bind to form a molecule of water, H2O; since it contains different types of atoms, it is classified as a compound © McGraw Hill, LLC 19  Figure 2.7: Molecules and Compounds Access the text alternative for these images © McGraw Hill, LLC 20  Formulas 1 A molecular formula represents the numbers and types of atoms in a molecule: A formula uses symbols for each element Example: Glucose = C6H12O6, water = H2O Glucose contains 6 C atoms, 12 H atoms, and 6 O atoms Water, H2O, contains 2 H atoms and 1 O atom Various representations, called structural formulas, can be used to illustrate how atoms are joined and arranged in molecules © McGraw Hill, LLC 21  Formulas 2 Each atom forms a specific number of covalent bonds, based on the number of electrons it contains in its outermost shell: H atoms form single bonds, since they each have 1 electron to share O atoms form double bonds, since they can share the 2 electrons in their outermost shell Structural formulas use single lines to illustrate single bonds, double lines represent double bonds, etc. Three-dimensional molecular models show spatial relationships between atoms © McGraw Hill, LLC 22  Figure 2.8: Structural and Molecular Formulas Access the text alternative for these images © McGraw Hill, LLC 23  Figure 2.9: Three-dimensional Molecular Models (a, b): John W. Hole Access the text alternative for these images © McGraw Hill, LLC 24  Chemical Reactions 1 A chemical reaction occurs as bonds are formed or broken between atoms, ions, or molecules Substances that are changed by the reaction are called the reactants; those formed are the products During synthesis reactions (such as those used in growth and repair), two or more atoms or molecules bond together, forming a more complex product: A + B → AB During decomposition reactions, larger molecules (such as food molecules) are broken into smaller ones, by breaking chemical bonds: AB + A → B © McGraw Hill, LLC 25  Chemical Reactions 2 Exchange reactions (such as acid-base reactions) occur as parts of molecules switch places, by breaking chemical bonds and forming new ones: AB + CD → AD + CB Reversible reactions are ones in which the products can change back into the reactants; they are symbolized by using double arrows: AB + CD  AD + CB Catalysts influence the speed of chemical reactions without being used up in the process; catalysts in the body are called enzymes. © McGraw Hill, LLC 26  2.5: Acids and Bases Substances that release ions in water are called electrolytes; these can carry electric charge in the body When ionically bound substances are put into water, they dissociate, as the slightly positive ends of water molecules attract the negative ions, and the slightly negative ends of water molecules attract the positive ions; the ions then interact with the water molecules instead Electrolytes that release hydrogen ions in water are called acids Electrolytes that release ions that combine with hydrogen ions in water are called bases The concentrations of H + and OH + in the body are very important to physiology, since they affect chemical reactions that control many physiological functions + pH represents the concentration of hydrogen ions [H ] in solution © McGraw Hill, LLC 27  Figure 2.10: The Dissociation of NaCl in H2O Access the text alternative for these images © McGraw Hill, LLC 28  The pH Scale The pH scale runs from 0 to 14, and measures H + ion concentration A pH of 7 indicates a neutral solution with equal numbers of hydrogen ions and hydroxide (OH - ) ions. A pH in the range of 0 to 7 to 14 indicates the presence of more hydroxide ions than hydrogen ions and is considered basic or alkaline. The higher the pH, the more basic the solution is. Between each whole number on the pH scale there is a tenfold difference in hydrogen ion concentration. A solution with a pH of 3 contains ten times more H + ions than a solution with a pH of 4. Buffers are chemicals that combine with excess acids or bases to help minimize pH changes in body fluids. © McGraw Hill, LLC 29  Figure 2.11: The pH Scale Access the text alternative for these images © McGraw Hill, LLC 30  2.6: Chemical Constituents of Cells Chemicals in nature can be divided into 2 categories: organic and inorganic Organic molecules or compounds contain both hydrogen and carbon; many dissolve in water, but do not release ions; these are called nonelectrolytes Examples of organic substances in the body are carbohydrates, lipids, proteins and nucleic acids. All other compounds are considered inorganic; they usually dissolve in water and release ions, making them electrolytes Examples of common inorganic substances are water, oxygen, carbon dioxide, and salts © McGraw Hill, LLC 31  Inorganic Substances: Water Water is the most abundant compound in living things, and makes up two-thirds of the weight of a human adult Water is an important solvent, and most metabolic reactions occur in water; a solvent is a substance in which other substances dissolve Water is important in transporting solutes (dissolved substances) in the body, since it is the major component of blood and other body fluids Water absorbs and transports heat through the body © McGraw Hill, LLC 32  Other Inorganic Compounds Oxygen: needed to release energy from nutrients; this energy is used to drive the cell's metabolism; inspired into the lungs Carbon Dioxide: released as a waste product during energy- releasing metabolic reactions; expired from the lungs Salts: Compounds consisting of oppositely charged ions Salts provide necessary ions, such as sodium, chloride, potassium, calcium, magnesium, phosphate, carbonate, bicarbonate, and sulfate These electrolytes play important roles in many of the body's metabolic processes, such as nerve impulse conduction, muscle contraction, and transport of substances across cell membranes © McGraw Hill, LLC 33  Common Inorganic Substances 1 TABLE 2.2 Inorganic Substances Common in the Body Substance Symbol or Formula Functions 1. Inorganic molecules Water H2O Medium in which most biochemical reactions occur (section 1.5, Maintenance of Life); major component of body fluids (section 2.6, Chemical Constituents of Cells); helps regulate body temperature (section 6.4, Skin Functions); transports chemicals (section 12.1, Introduction) Oxygen O2 Used in energy release from glucose molecules (section 4.4, Energy for Metabolic Reactions) Carbon dioxide CO2 Waste product that results from metabolism (section 4.4, Energy for Metabolic Reactions); reacts with water to form carbonic acid (section 16.6, Gas Transport) 2. Inorganic ions Bicarbonate ions HCO−3 Helps maintain acid-base balance (section 18.5, Acid-Base Balance) Calcium ions Ca +2 Necessary for bone tissue (section 7.2, Bone Structure), muscle contraction (section 8.3, Skeletal Muscle Contraction), and blood clotting (blood coagulation) (section 12.4, Hemostasis) Carbonate ions Ca −32 Component of bone tissue (section 7.3, Bone Function) © McGraw Hill, LLC 34  Common Inorganic Substances 2 TABLE 2.2 Inorganic Substances Common in the Body Substance Symbol or Formula Functions Chloride ions C l raised to the minus Major extracellular negatively charged ion (section 18.2, Distribution of Body Fluids) power Hydrogen ions H raised to the plus pH of the internal environment (section 18.5, Acid-Base Balance) power Magnesium ions M g raised to the plus 2 Component of bone tissue (section 7.3, Bone Function); required for certain metabolic power processes (section 15.11, Nutrition and Nutrients) Phosphate ions P O sub 4 raised to the Required for synthesis of ATP, nucleic acids, and other vital substances (section 4.4, Energy minus 3 power for Metabolic Reactions; section 4.5, DNA (Deoxyribonucleic Acid)); component of bone tissue (section 7.3, Bone Function); helps maintain polarization of cell membranes (section 9.5, Charges Inside a Cell) Potassium ions K raised to the plus Required for polarization of cell membranes (section 9.5, Charges Inside a Cell) power Sodium ions N a raised to the plus Required for polarization of cell membranes (section 9.5, Charges Inside a Cell); helps power maintain water balance (section 11.7, Adrenal Glands) Sulfate ions S O sub 4 raised to the Helps maintain polarization of cell membranes (section 9.5, Charges Inside a Cell) minus 2 power © McGraw Hill, LLC 35  Organic Substances: Carbohydrates Carbohydrates: Provide energy for cellular activities and materials for synthesizing various cell structures; stored as energy reserves Composed of carbon, hydrogen, and oxygen, typically with twice as many H atoms as O atoms Monosaccharides (simple sugars): the smallest carbohydrates; contain 5 to 6 C atoms; examples: glucose, fructose, galactose, ribose, deoxyribose Disaccharides (double sugars): consist of 2 simple sugars; examples: lactose, sucrose, maltose Polysaccharides (many simple sugars): consist of many glucose molecules joined together; examples: glycogen, starch © McGraw Hill, LLC 36  Figure 2.12: Structural Formulas for Glucose Access the text alternative for these images © McGraw Hill, LLC 37  Figure 2.13: Mono-, Di-, and Polysaccharides Access the text alternative for these images © McGraw Hill, LLC 38  Organic Substances: Lipids Lipids are organic substances that are insoluble in water Lipids include fats (triglycerides), phospholipids, and steroids Triglycerides (fats) are the most abundant type of lipids Triglycerides store and supply energy for cellular function Triglycerides, like carbohydrates, consist of carbon, hydrogen, and oxygen, but have a smaller proportion of oxygen atoms than carbohydrates Triglycerides consist of glycerol and three fatty acids: Fatty acids with all single carbon-carbon bonds are called saturated fatty acids Those with one or more double bonds between carbon atoms are called unsaturated fatty acids © McGraw Hill, LLC 39  Figure 2.14: Structure of Triglycerides Access the text alternative for these images © McGraw Hill, LLC 40  Other Types of Lipids Phospholipids: Consist of glycerol, two fatty acids, and a phosphate group The phosphate “head” is hydrophilic and the fatty acid “tail” is hydrophobic Important in cellular structures, such as plasma membranes Steroids: Complex structures containing four carbon rings A very important steroid is cholesterol, which is used to synthesize the sex hormones and several hormones from the adrenal glands © McGraw Hill, LLC 41  Figure 2.15: Structure of Triglycerides and Phospholipids Access the text alternative for these images © McGraw Hill, LLC 42  Figure 2.16: Structure of Steroids Access the text alternative for these images © McGraw Hill, LLC 43  Groups of Lipids TABLE 2.3 Important Groups of Lipids Group Basic Molecular Structure Characteristics Triglycerides Three fatty acid molecules The most common lipids in the body; bound to a glycerol molecule stored in fat tissue as an energy supply; fat tissue also provides thermal insulation beneath the skin Phospholipids Two fatty acid molecules and Used as structural components in cell a phosphate group bound to membranes; abundant in liver and parts a glycerol molecule of the nervous system Steroids Four connected rings of Widely distributed in the body and have carbon atoms a variety of functions; include cholesterol, hormones of adrenal cortex and hormones from the ovaries and testes © McGraw Hill, LLC 44  Organic Substances: Proteins Proteins are organic compounds containing C, O, H, and N (nitrogen) atoms; some also contain S (sulfur) Proteins have a great variety of functions in the body: as structural materials, energy sources, certain hormones, receptors on cell membranes, antibodies, and enzymes to catalyze metabolic reactions Proteins consist of building blocks called amino acids, each of which contains a carboxyl group, an amino group and a side chain called the R group Most living organisms have 20 different amino acids that make up their proteins Amino acids bind together in polypeptide chains of 5000 amino acids © McGraw Hill, LLC 45  Figure 2.17: Structure of Amino Acids Access the text alternative for these images © McGraw Hill, LLC 46  Levels of Structure in Proteins Proteins have complex shapes held together by various types of chemical bonds: Primary structure: the sequence of amino acids Secondary structure: pleated or twisted coil structure, resulting from hydrogen bonds between some of the amino acids Tertiary structure: unique folded structure of a protein, due to attractions between amino acids in different parts of the protein molecule Quaternary structure: Another level of structure, found only in proteins that consist of more than one polypeptide chain; example: hemoglobin consists of 4 polypeptide chains © McGraw Hill, LLC 47  Figure 2.18: Levels of Structure in Proteins Access the text alternative for these images © McGraw Hill, LLC 48  Protein Conformation and Denaturation Conformation: Unique 3-dimensional shape of a protein, due to hydrogen and covalent bonding in different parts of the polypeptide chain Determines the function of a protein Can be long and fibrous or globular A slight, reversible change in conformation can be part of a protein’s normal functioning Denaturation: Irreversible disruption of a protein’s shape, and loss of function, due to breaking of hydrogen bonds Caused by pH changes, excessive temperature changes, radiation, or chemicals Example: Hard-boiling of an egg denatures the albumin © McGraw Hill, LLC 49  Organic Substances: Nucleic Acids Nucleic acids: Form genes and participate in protein synthesis Large organic molecules Contain carbon, hydrogen, oxygen, nitrogen, and phosphorus, which form building blocks called nucleotides Each nucleotide consists of a 5-carbon sugar, a phosphate group, and one of five nitrogenous bases Nucleic acid molecules are chains of nucleotides © McGraw Hill, LLC 50  Figure 2.20: Structure of a Nucleotide Access the text alternative for these images © McGraw Hill, LLC 51  Types of Nucleic Acids 1 Nucleic acids are of two major types (RNA and DNA): RNA (ribonucleic acid): Single-stranded Functions in protein synthesis Nucleotides contain the sugar, ribose Adenosine triphosphate (ATP): A modification of RNA that contains three phosphate groups Stores and provides energy for chemical reactions in the body © McGraw Hill, LLC 52  Types of Nucleic Acids 2 DNA (deoxyribonucleic acid): Double-stranded, twisted into a spiral, held together with hydrogen bonds Stores the molecular (genetic) code in genes, which is used by cells to synthesize proteins Nucleotides contain the sugar, deoxyribose © McGraw Hill, LLC 53  Figure 2.21: Nucleic Acid Structure: RNA and DNA Access the text alternative for these images © McGraw Hill, LLC 54  Figure 2.22: Structure of Adenosine Triphosphate (ATP) Access the text alternative for these images © McGraw Hill, LLC 55  Organic Compounds in Cells TABLE 2.4 Organic Compounds in Cells Compound Elements Present General Form Functions Examples Carbohydrates C,H,O Monosaccharide Provide energy, Glucose Disaccharide cell structure Sucrose Polysaccharide Glycogen In Table column 3 row 2 and 3, cells are Lipids C,H,O (often P) Triglyceride Provide energy, Fats containing three values. Phospholipid In Table column cell structure 5 Cholesterol row 2, cell isSteroid containing three values; and Proteins in row C,H,O,N (often3S)cellPolypeptide is containing two values. Chain Provide cell Albumins, structure, hemoglobin enzymes, energy Nucleic acids C,H,O,N,P Polynucleotide Store information RNA, DNA chain for protein synthesis; control cell activities © McGraw Hill, LLC 56  Because learning changes everything. ® www.mheducation.com © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.