CHAPTER 2 Cellular Chemistry 2. 15 List some inorganic compounds important in living organisms Water, oxygen, carbon dioxide, salts, acids, bases, and electrolytes(e. g, Na, K, and Cl) Electrolytes have tremendous clinical significance. They function in every body sys- tem and are often an essential link in a body process. Electrolytes form when certain solutes held together by ionic bonds dissolve in water, yielding free ions in the water solution. The most important of these ions are potassium(K), sodium(Nat), chlo- ride(CI), and calcium(Caf). Electrolytes are important in the transmission of nerve impulses, maintenance of body fluids, and functioning of enzymes and hormones. Many disorders, such as kidney failure, muscle cramps, and some cardiovascular diseases, involve imbalances in electrolyte levels 2.16 List the four major families of organic compounds and give examples of each See table 2.5 TABLE 2.5 Organic Compounds and Examples Carbohydrates Glucose, cellulose, glycogen Phospholipids, steroids, prostaglandins Proteins Enzymes, insulin, albumin, hemoglobin, collagen Nucleic acids DNA RNA Abbreviations: DNA, deoxyribonucleic acid; RNA, ribonucleic acid. 2.17 Describe how biochemical compounds are formed and broken down All large biochemical molecules are formed by connecting small units together into large macromolecules in a process called dehydration synthesis. In this process, two units are joined, creating one large mole- cule and a single molecule of water. Hydrolysis is the reverse of this reaction. It is the use of water to break down macromolecules into their component building blocks. Dehydration synthesis and hydrolysis are the most important biological reactions In living organisms, these reactions are usually catalyzed by enzymes, which are proteins that enhance and speed up reactions Objective I To describe the three types of carbohydrates. All carbohydrates are composed of carbon, hydrogen, and oxygen. The ratio of hydrogen to oxy oTvey gen in carbohydrates is 2 to 1. Carbohydrates are classified as monosaccharides(simple sugars such as glucose), disaccharides(double sugars, such as sucrose), or polysaccharides(complex sugars, usually composed of thousands of glucose units, such as glycogen). 2.18 What role do carbohydrates play in the body? serve as the principal source of body energy contribute to cell structure and synthesis of cell products. 3. They form part of the structure of DNA and rna (deoxyribose and ribose are both sugars) 4. They are converted into proteins and fats 5. They function in food storage(glycogen storage in the liver and skeletal muscles 2. 19 Describe the various forms a monosaccharide may take Trioses are three-carbon sugars, tetroses are four-carbon sugars, pentoses are five-carbon sugars, hexoses are six-carbon sugars, and heptoses are seven-carbon sugars Structures for the hexose glucose are shown in fig. 2.5, and structures of two important pentoses are shown in fig. 2.6
2.15 List some inorganic compounds important in living organisms. Water, oxygen, carbon dioxide, salts, acids, bases, and electrolytes (e.g., Na, K, and Cl). Electrolytes have tremendous clinical significance. They function in every body system and are often an essential link in a body process. Electrolytes form when certain solutes held together by ionic bonds dissolve in water, yielding free ions in the water solution. The most important of these ions are potassium (K), sodium (Na), chloride (Cl), and calcium (Ca2). Electrolytes are important in the transmission of nerve impulses, maintenance of body fluids, and functioning of enzymes and hormones. Many disorders, such as kidney failure, muscle cramps, and some cardiovascular diseases, involve imbalances in electrolyte levels. 2.16 List the four major families of organic compounds and give examples of each. See table 2.5. CHAPTER 2 Cellular Chemistry 25 TABLE 2.5 Organic Compounds and Examples Carbohydrates Glucose, cellulose, glycogen, starch Lipids Phospholipids, steroids, prostaglandins Proteins Enzymes, insulin, albumin, hemoglobin, collagen Nucleic acids DNA, RNA Abbreviations: DNA, deoxyribonucleic acid; RNA, ribonucleic acid. 2.17 Describe how biochemical compounds are formed and broken down. All large biochemical molecules are formed by connecting small units together into large macromolecules in a process called dehydration synthesis. In this process, two units are joined, creating one large molecule and a single molecule of water. Hydrolysis is the reverse of this reaction. It is the use of water to break down macromolecules into their component building blocks. Dehydration synthesis and hydrolysis are the most important biological reactions. In living organisms, these reactions are usually catalyzed by enzymes, which are proteins that enhance and speed up reactions. Objective I To describe the three types of carbohydrates. All carbohydrates are composed of carbon, hydrogen, and oxygen. The ratio of hydrogen to oxygen in carbohydrates is 2 to 1. Carbohydrates are classified as monosaccharides (simple sugars, such as glucose), disaccharides (double sugars, such as sucrose), or polysaccharides (complex sugars, usually composed of thousands of glucose units, such as glycogen). 2.18 What role do carbohydrates play in the body? 1. They serve as the principal source of body energy. 2. They contribute to cell structure and synthesis of cell products. 3. They form part of the structure of DNA and RNA (deoxyribose and ribose are both sugars). 4. They are converted into proteins and fats. 5. They function in food storage (glycogen storage in the liver and skeletal muscles). 2.19 Describe the various forms a monosaccharide may take. Trioses are three-carbon sugars, tetroses are four-carbon sugars, pentoses are five-carbon sugars, hexoses are six-carbon sugars, and heptoses are seven-carbon sugars. Structures for the hexose glucose are shown in fig. 2.5, and structures of two important pentoses are shown in fig. 2.6. Survey
CHAPTER 2 Cellular Chemistry Ho→C-H H-C-OH CH OH H-C-OH HOCH HOC Straight ch igure25 Structures of glucose. Figure 2.6 Sugars of RNA and DNA. 2.20 How are disaccharides built up from monosaccharides? a disaccharide forms when two monosaccharides combine in a dehydration synthesis reaction, usually catalyzed by enzymes. The synthesis of maltose(a disaccharide composed of two bonded glucoses) chown in fig. 2.7. CH OH CH OH H OH H OH Glucose Glucose Maltose Figure 2. 7 The formation of maltose(a disaccharide) from two glucoses(monosaccharides) In a similar fashion: glucose t galactose lactose glucose fructose sucrose(table sugar) The reverse of these dehydration synthesis reactions, the hydrolysis of the disaccharides, is the first step in the digestive process for these carbohydrates in the gastrointestinal(GI) tract. Specific nzymes help to break down disaccharides into their component monosaccharides. Some common disorders of the body are due to the lack of these enzymes. The most notable is lactose intolerance, in which the enzyme lactase that breaks down lactose into glucose and galactose is lacking. Because lactose is the sugar in milk and other dairy products, a person unable to digest this sugar will experience gas pains and cramps, as well as diarrhea, after eating foods that contain milk. The lactose becomes food for bacteria in the Gi tract. The person may be administered doses of the needed enzyme in order to digest 2.21 Distinguish between saturated and unsaturated fats, and give examples of each In saturated fats, each carbon in the molecule is bonded to as many hydrogens as possible; there are no double bonds between carbons. Unsaturated fats have at least one pair of carbons joined by a double bond
2.20 How are disaccharides built up from monosaccharides? A disaccharide forms when two monosaccharides combine in a dehydration synthesis reaction, usually catalyzed by enzymes. The synthesis of maltose (a disaccharide composed of two bonded glucoses) is shown in fig. 2.7. 26 CHAPTER 2 Cellular Chemistry Straight chain H C OH OH OH OH H H H H H HO CH2 OH O H H C OH H C OH HO C H H C OH C H O Ring structure HH H H O OH H HH H HOH HOCH2 OH OH HOCH2 O OH Ribose Deoxyribose Figure 2.5 Structures of glucose. Figure 2.6 Sugars of RNA and DNA. CH2 OH CH2 OH CH2 OH CH2 OH H H H H H HH H H H H H H H HOH OH HO OH OH OH HOH OH OH H HO + H H H HO OH OH O H O O OO O –H2 O +H2 O Glucose + Glucose Maltose Figure 2.7 The formation of maltose (a disaccharide) from two glucoses (monosaccharides). In a similar fashion: glucose galactose lactose glucose fructose sucrose (table sugar) The reverse of these dehydration synthesis reactions, the hydrolysis of the disaccharides, is the first step in the digestive process for these carbohydrates in the gastrointestinal (GI) tract. Specific enzymes help to break down disaccharides into their component monosaccharides. Some common disorders of the body are due to the lack of these enzymes. The most notable is lactose intolerance, in which the enzyme lactase that breaks down lactose into glucose and galactose is lacking. Because lactose is the sugar in milk and other dairy products, a person unable to digest this sugar will experience gas pains and cramps, as well as diarrhea, after eating foods that contain milk. The lactose becomes food for bacteria in the GI tract. The person may be administered doses of the needed enzyme in order to digest the sugar. 2.21 Distinguish between saturated and unsaturated fats, and give examples of each. In saturated fats, each carbon in the molecule is bonded to as many hydrogens as possible; there are no double bonds between carbons. Unsaturated fats have at least one pair of carbons joined by a double bond.
CHAPTER 2 Cellular Chemistry H HHHHHHH H HHHHHHHHH HH Palmitic acid (saturat HHHH HH -C--C-C-C--C-C-C-C-C C-C-C-C-C--C-H HHHHHH Linolenic acid (unsaturated) Figure 2.8 Lipid Structures Objective J To describe the chemical composition of proteins Proteins are large complex molecules formed by the dehydration synthesis of amino acids. The bonds between amino acids in a protein molecule are called peptide bonds and link the amino group(N, )of one amino acid to the acid carboxyl group(COoh) of another amino acid, which of the cha hay be the same as or different from that of the first amino acid (fig 2.8). If the molecular weight in exceeds 10,000, the molecule is called a protein; smaller chains are called polypeptides. The function of the protein is determined by the character of the amino acids it contains. Proteins are the most diverse class of molecules, and their functions vary widely C-CoOH+NH→C 20 Figure 2. 9 The formation of a peptide bond between amino acids 2.22 In what ways do polysaccharides differ from monosaccharides and disaccharides? Polysaccharides, or starches, are sometimes called complex carbohydrates because they contain many chemical bonds. The body is able to break them down in a more efficient and steady manner, supplying energy over a longer period of time, than is possible from the digestion of monosaccharides or disaccha- rides. Also, polysaccharides lack the characteristic sweet taste of monosaccharides and disaccharides Objective K To describe the chemical composition of lipids The building blocks of lipids(fats and oils) are fatty acids, which have long chains of carbon atoms bonded together and to hydrogen atoms. These fatty acids bond to a glycerol(a special three-carbon alcohol)to form the basic lipid molecule(fig. 2.10 apid(fat) + Ho o回+H-C-R OH +HO Figure 2.10 The formation of a basic lipid molecule (a triacylglycerol)
Objective J To describe the chemical composition of proteins. Proteins are large complex molecules formed by the dehydration synthesis of amino acids. The bonds between amino acids in a protein molecule are called peptide bonds and link the amino group (NH2 ) of one amino acid to the acid carboxyl group (COOH) of another amino acid, which may be the same as or different from that of the first amino acid (fig. 2.8). If the molecular weight of the chain exceeds 10,000, the molecule is called a protein; smaller chains are called polypeptides. The function of the protein is determined by the character of the amino acids it contains. Proteins are the most diverse class of molecules, and their functions vary widely. CHAPTER 2 Cellular Chemistry 27 2.22 In what ways do polysaccharides differ from monosaccharides and disaccharides? Polysaccharides, or starches, are sometimes called complex carbohydrates because they contain many chemical bonds. The body is able to break them down in a more efficient and steady manner, supplying energy over a longer period of time, than is possible from the digestion of monosaccharides or disaccharides. Also, polysaccharides lack the characteristic sweet taste of monosaccharides and disaccharides. Objective K To describe the chemical composition of lipids. The building blocks of lipids (fats and oils) are fatty acids, which have long chains of carbon atoms bonded together and to hydrogen atoms. These fatty acids bond to a glycerol (a special three-carbon alcohol) to form the basic lipid molecule (fig. 2.10). Survey H COOH + NH2 H HC NC C H H Glycine Glycine Peptide bond COOH H NH2 H O H COOH –H2 O C H C NH2 Figure 2.9 The formation of a peptide bond between amino acids. HO(a) Palmitic acid (saturated) C C HO H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H H HO(b) Linolenic acid (unsaturated) C C HO H C H H C H H C H H C H H C H H C H H C H C H C H H C H C H C H H C H C H C C HH HH H Figure 2.8 Lipid Structures H H O C H O C H O H + HO H + HO C H + HO R˝C R´C R O C O O H Glycerol + 3 fatty acids Lapid (fat) –3H2 O +3H2 O H H O C H O C H O C R˝C R´C R O C O O H Figure 2.10 The formation of a basic lipid molecule (a triacylglycerol)
CHAPTER 2 Cellular Chemistry 2.23 List the 20 amino acids and give their abbreviations See table 2.6 2. 24 What is the meaning of the term essential amino acid"? The body is able to convert certain amino acids to others; 12 of the 20 amino acids can be synthesized in this way. The remaining eight are known as the essential amino acids because they must be supplied in the diet Table 2.6 The 20 Amino acids NONPOLAR POLAR, UNCHARGED POLAI ARGED Glycine(Gly) Serine(ser) ysine (Lys) Alanine(Ala) Threonine(thr) arginine(Arg) Valine (val) Asparagine(Asn) Histidine(his) Leucine ( leu) Glutamine(Gln) Aspartic acid(Asp) Isoleucine ( lle) Tyrosine (Tyr) Glutamic acid (Glu) Methionine(Met) Cysteine(Cys) Tryptophan(Trp) 2.25 List some major functions of proteins and give some common examples See table 2.7 TABLE 2.7 Functions of Proteins and Examples FUNCTION OF PROTEINS EXAMPLES Trypsin, chymotrypsin, Transport and storage of molecules Hemoglobin, myoglobin Actin, myosin, tubulin(ciliary motion Structural support Collagen, elastin Antibodies(immunoglobulins) Neural communication Endorphins, rhodopsin(pigment for light reception in the eye) Intercellular messenger Insulin, glucagon, growth hormones Objective L To describe the chemical composition of nucleotides, the components of nucleic acids. fvey tose sugar, and a nitrogenous base (oval). The pentose is always ribose in rna and deoxyri- bose in DNA. The phosphate remains constant from one nucleotide to the next, but the base (in DNA)may be one of the following four: adenine(A), thymine(T), guanine(G), or cytosine C). RNA substitutes uracil (U) for thymine. The nucleotides are joined together by dehydration syn- hesis into macromolecules. The structure and function of the dna and rna molecules are discussed in chapter 3 2.26 Explain the difference between purines and pyrimidines. Of the four nitrogenous bases of DNA, two are called purine bases, and two are called pyrimidine bases. g. 2.11 shows two ring structures that contain nitrogen as well as carbon atoms. A comparison with fig. 2.12 shows that adenine and guanine are built on the purine ring, whereas cytosine and thymine are built on the pyrimidine ring
2.23 List the 20 amino acids and give their abbreviations. See table 2.6. 2.24 What is the meaning of the term essential amino acid? The body is able to convert certain amino acids to others; 12 of the 20 amino acids can be synthesized in this way. The remaining eight are known as the essential amino acids because they must be supplied in the diet. 28 CHAPTER 2 Cellular Chemistry TABLE 2.6 The 20 Amino Acids NONPOLAR POLAR, UNCHARGED POLAR, CHARGED Glycine (Gly) Serine (Ser) Lysine (Lys) Alanine (Ala) Threonine (Thr) Arginine (Arg) Valine (Val) Asparagine (Asn) Histidine (His) Leucine (Leu) Glutamine (Gln) Aspartic acid (Asp) Isoleucine (Ile) Tyrosine (Tyr) Glutamic acid (Glu) Methionine (Met) Cysteine (Cys) Proline (Pro) Phenylalanine (Phe) Tryptophan (Trp) Objective L To describe the chemical composition of nucleotides, the components of nucleic acids. As indicated in fig. 2.10, nucleotides have three parts: a phosphate group (solid circle), a pentose sugar, and a nitrogenous base (oval). The pentose is always ribose in RNA and deoxyribose in DNA. The phosphate remains constant from one nucleotide to the next, but the base (in DNA) may be one of the following four: adenine (A), thymine (T), guanine (G), or cytosine (C). RNA substitutes uracil (U) for thymine. The nucleotides are joined together by dehydration synthesis into macromolecules. The structure and function of the DNA and RNA molecules are discussed in chapter 3. 2.26 Explain the difference between purines and pyrimidines. Of the four nitrogenous bases of DNA, two are called purine bases, and two are called pyrimidine bases. Fig. 2.11 shows two ring structures that contain nitrogen as well as carbon atoms. A comparison with fig. 2.12 shows that adenine and guanine are built on the purine ring, whereas cytosine and thymine are built on the pyrimidine ring. TABLE 2.7 Functions of Proteins and Examples FUNCTION OF PROTEINS EXAMPLES Enzyme Trypsin, chymotrypsin, sucrase, amylase Transport and storage of molecules Hemoglobin, myoglobin Motion Actin, myosin, tubulin (ciliary motion) Structural support Collagen, elastin Immunity Antibodies (immunoglobulins) Neural communication Endorphins, rhodopsin (pigment for light reception in the eye) Intercellular messenger Insulin, glucagon, growth hormones Survey 2.25 List some major functions of proteins and give some common examples. See table 2.7
CHAPTER 2 Cellular Chemistry Pyrimidine ring Puring ring Guanine Figure 2.11 Basic ring structures Figure 2.12 Nitrogenous bases of dNA Adenosine triphosphate(ATP) may be termed a nucleic acid because it is a dinu- cleotide(a molecule consisting of two nucleotides). ATP, the final product from the breakdown of glucose and all other foods, is the universal energy ("currency")mol- ecule of the body. Any time a cell or tissue needs energy, it breaks an ATP mole cule apart to get that energy. The amount of ATP the body uses daily is staggering If the molecules were not recycled, each day we would need a store of ATP that weighed approximately Review Exercises Multiple Choice 1. A neutral atom contains(a) the same number of electrons as it does protons, (b)more protons than electrons, (c)the same number of electrons as it does neutrons, (d)more electrons than protons 2. The number of protons in an atom is given by the(a)mass number, (b)atomic number, (c)difference between the atomic number and the mass number (d) atomic weight 3. A compound is a molecule(a) composed of two or more atoms, (b)composed of only one type of atom, (c)linked only by covalent bonds, (d) containing carbon 4. Bonds that result from shared electrons are called (a)ionic bonds, (b)covalent bonds, (c) peptide bonds, (d) covalent or peptide bonds, (e)ionic or covalent bonds 5. Bonds that result from shared electrons are called(a)ionic bonds, (b) covalent bonds, (c) peptide bonds, (d) polar bonds, (e)all of the preceding 6. Molecules composed only of hydrogen and carbon are called (a)carbohydrates, (b) inorganic molecules, (c) lipids, (d) hydrocarbons (a)Carbohydrates are linked through dehydration reactions (b) Carbohydrates are composed of carbon, hydrogen, and oxygen (c) Carbohydrates consist of a carbon chain with an acid carboxyl group at one end. (d) Carbohydrates are classed as monosaccharides, disaccharides, and polysaccharides 8. Fats are reaction products of fatty acids and(a)amino acids, (b) glycerol, (c)monosaccharides, (d) nucleic acids 9. Proteins differ from carbohydrates in that proteins(a) are not organic compounds, (b)are united by covalent bonds, (c)contain nitrogen, (d) provide most of the bodys energy 10. Which is not a component of a nucleic acid? (a)a purine base, (b)a five-carbon sugar, (c)a pyrimidine base, (d) glycerol,(e) a phosphate grot
CHAPTER 2 Cellular Chemistry 29 N N N N N H N Pyrimidine ring Puring ring HN O O CH3 H2 N N O H H H N N HN N N Adenine Cytosine Guanine Thymine NH2 N N N H N NH2 N H O Figure 2.11 Basic ring structures Figure 2.12 Nitrogenous bases of DNA. Adenosine triphosphate (ATP) may be termed a nucleic acid because it is a dinucleotide (a molecule consisting of two nucleotides). ATP, the final product from the breakdown of glucose and all other foods, is the universal energy (“currency”) molecule of the body. Any time a cell or tissue needs energy, it breaks an ATP molecule apart to get that energy. The amount of ATP the body uses daily is staggering. If the molecules were not recycled, each day we would need a store of ATP that weighed approximately 50 pounds. Review Exercises Multiple Choice 1. A neutral atom contains (a) the same number of electrons as it does protons, (b) more protons than electrons, (c) the same number of electrons as it does neutrons, (d) more electrons than protons. 2. The number of protons in an atom is given by the (a) mass number, (b) atomic number, (c) difference between the atomic number and the mass number, (d) atomic weight. 3. A compound is a molecule (a) composed of two or more atoms, (b) composed of only one type of atom, (c) linked only by covalent bonds, (d) containing carbon. 4. Bonds that result from shared electrons are called (a) ionic bonds, (b) covalent bonds, (c) peptide bonds, (d) covalent or peptide bonds, (e) ionic or covalent bonds. 5. Bonds that result from shared electrons are called (a) ionic bonds, (b) covalent bonds, (c) peptide bonds, (d) polar bonds, (e) all of the preceding. 6. Molecules composed only of hydrogen and carbon are called (a) carbohydrates, (b) inorganic molecules, (c) lipids, (d) hydrocarbons. 7. Which of the following is a false statement? (a) Carbohydrates are linked through dehydration reactions. (b) Carbohydrates are composed of carbon, hydrogen, and oxygen. (c) Carbohydrates consist of a carbon chain with an acid carboxyl group at one end. (d) Carbohydrates are classed as monosaccharides, disaccharides, and polysaccharides. 8. Fats are reaction products of fatty acids and (a) amino acids, (b) glycerol, (c) monosaccharides, (d) nucleic acids. 9. Proteins differ from carbohydrates in that proteins (a) are not organic compounds, (b) are united by covalent bonds, (c) contain nitrogen, (d) provide most of the body’s energy. 10. Which is not a component of a nucleic acid? (a) a purine base, (b) a five-carbon sugar, (c) a pyrimidine base, (d) glycerol, (e) a phosphate group