Chapter Questions
Describe three proteins and identify their functions.Describe three proteins and identify their functions.
Compare the structures of amino acids, dipeptides, polypeptides, and proteins.Which has the largest molecular mass? The smallest?
Draw the structure of the dipeptide Gly-Ser, circling the peptide bond.
Evaluate How do the properties of proteins make them such useful catalysts?How do they differ from other catalysts you have studied?
Explain three roles of proteins in cells, and give an example of each role.
Categorize Identify an amino acid from Table 23.1 that can be classifiedinto each of the categories in the following pairs.a. nonpolar v. polarb. aromatic v. aliphaticc. acidic v. basic
Explain the functions of carbohydrates in living things.
Describe the structures of monosaccharides, disaccharides, and polysaccharides.Which has the largest molecular mass? The smallest?
Compare and contrast the structures of starch and cellulose. How do thestructural differences affect our ability to digest these two polysaccharides?
Cholesterol Use the library or the Internet to researchcholesterol. Write a newspaper article about cholesterolthat is written for a teenage audience. Make sure the fol-lowing questions are answered in the article. Where isthis molecule used in your body? What is its function?Why is too much dietary cholesterol considered to bebad for you? Is genetics a factor in high cholesterol?
Interpret Scientific Illustrations Copy the illustration of sucrose on aseparate sheet of paper, and circle the ether functional group that bonds themonomer sugars together.
Describe the function of lipids.
Describe the structures of fatty acids, triglycerides, phospholipids, and steroids.
List an important function of each of these types of lipids.a. triglyceridesc. waxesb. phospholipidsd. steroids
Identify two reactions that fatty acids undergo.
Describe the structure and function of cell membranes.
Write the equation for the complete hydrogenation of the polyunsaturated fattyacid linoleic acid, $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{4} \mathrm{CH}=\mathrm{CHCH}_{2} \mathrm{CH}=\mathrm{CH}\left(\mathrm{CH}_{2}\right)_{7} \mathrm{COOH} .$
Interpret Scientific Illustrations Draw the general structure of a phospho-lipid. Label the polar and nonpolar portions of the structure.
Explain the primary function of RNA and DNA.
Identify the specific structural components of both RNA and DNA.
Relate the function of DNA to its structure.
Relate the function of RNA to its structure.
Analyze the structure of nucleic acids to determine what structural featuremakes them acidic.
Predict what might happen if the DNA that coded for a protein contained thewrong base sequence.
Compare and contrast the processes of anabolism and catabolism.
Explain the role of ATP in the metabolism of living organisms.
Compare and contrast the processes of photosynthesis, cellular respiration,and fermentation.
Determine whether each process is anabolic or catabolic.a. photosynthesisb. cellular respirationc. fermentation
Evaluate Why is it necessary to use sealed casks when making wine?
Calculate How many moles of ATP would a yeast cell produce if 6 mol ofglucose were oxidized completely in the presence of oxygen? How many molesof ATP would the yeast cell produce from 6 mol of glucose if the cell weredeprived of oxygen?
What should you call a chain of eight amino acids? Achain of 200 amino acids?
Name the two types of functional groups that reacttogether to form a peptide bond, and name thefunctional group in the peptide bond itself.
Using the four symbols shown to represent four differ-ent amino acids, draw structures four possible peptidesfor a four-member chain that can be made by linkingthem together in different orders.$$\begin{array}{l}{\text { Amino acid } 1 : 1} \\ {\text { Amino acid } 2 :}\end{array}$$$$\begin{array}{l}{\text { Amino acid } 3 :} \\ {\text { Amino acid } 4 :}\end{array}$$
Human Anatomy Name five parts of the body that contain structural proteins.
List four major functions of proteins, and give oneexample of a protein that carries out each function.
Describe two common shapes found in the three dimensional folding of proteins.
Name the organic functional groups in the side chains ofthe following amino acids.$$\begin{array}{ll}{\text { a. glutamine }} & {\text { c. glutamic acid }} \\ {\text { b. serine }} & {\text { d. lysine }}\end{array}$$
Explain how the active site of an enzyme functions.
Name an example of an amino acid that has an aromatic ring in its side chain.
Name two nonpolar and two polar amino acids.
The structure shown in Figure 23.31 is tryptophan.Describe some of the properties you would expect tryptophan to have, based on its structure. In what class oflarge molecules is tryptophan a member? Explain.
Is the dipeptide lysine-valine the same compound as thedipeptide valine-lysine? Explain.
Enzymes How do enzymes lower the activation energyfor a reaction?
Cellular Chemistry Most proteins with a globular shapeare oriented so that they have mostly nonpolar aminoacids on the inside and polar amino acids located on theouter surface. Does this make sense in terms of thenature of the cellular environment? Explain.
How many different ways can you arrange three different amino acids in a peptide? Four amino acids? Five amino acids?
How many peptide bonds are present in a peptide thathas five amino acids?
Proteins The average molecular weight of an aminoacid residue in a polypeptide is $110 .$ What is the approximate molecular weight of the following proteins?a. Insulin $(51$ amino acids $)$b. Myosin $(1750$ amino acids $)$
Determine how many amino acids and peptide bondsare in the peptide shown in Figure $23.32 .$
The average molecular mass of an amino acid is 110 $\mathrm{g} / \mathrm{mol}$ .Calculate the approximate number of amino acids in aprotein that has a molecular mass of $36,500 \mathrm{g} / \mathrm{mol}$ .
Carbohydrates Classify the following carbohydrates asmonosaccharides, disaccharides, or polysaccharides.$$\begin{array}{llll}{\text { a. starch }} & {\text { d. ribose }} & {\text { g. fructose }} \\ {\text { b. gucose }} & {\text { e. clululose }} & {\text { h. lactose }} \\ {\text { c. sucrose }} & {\text { f. glycosen }}\end{array}$$
Name two isomers of glucose.
What kind of bond is formed when two monosaccha rides combine to form a disaccharide?
Sugars Give a scientific term for each of the following.a. blood sugarb. fruit sugarc. table sugard. milk sugar
Cellulose and Starch The molecular structures ofcellulose and starch are shown in Figure 23.33 .Compare and contrast their molecular structures.
Infer how the different bonding arrangements in cellulose and starch give them such different properties.
The disaccharide maltose is formed from two glucosemonomers. Draw its structure.
The hydrolysis of cellulose, glycogen, and starch produces only one monosaccharide. Why is this so? Whatmonosaccharide is produced?
Digestion Disaccharides and polysacharides cannotbe broken down in the absence of water. Why do youthink this is so? Include an equation in vour answer.
Draw the structure of the open-chain form of fructose.Circle all chiral carbons, and then calculate the numberof stereoisomers with the same formula as fructose.
Historical Perspective Carbohydrates are not hydratesof carbon as the name suggests. Explain how this mis-conception occurred.
Complex Carbohydrates Stachyose is a tetrasaccharidethat contains two D-galactose units, one D-glucose unit,and one D-fructose unit. Each sugar unit has a molecularweight of 180 $\mathrm{g} / \mathrm{mol}$ before it is linked together in thisComplex Carbohydrates Stachyose is a tetrasaccharidethat contains two D-galactose units, one D-glucose unit,and one D-fructose unit. Each sugar unit has a molecularweight of 180 $\mathrm{g} / \mathrm{mol}$ before it is linked together in this
Compare and contrast the structures of a triglycerideand a phospholipid.
Predict whether a triglyceride from beef fat or a triglyc-eride from olive oil will have a higher melting point.Explain your reasoning.
Soaps and Detergents Explain how the structure ofsoaps makes them effective cleaning agents.
Draw a portion of a lipid bilayer membrane, labeling thepolar and nonpolar parts of the membrane.
What type oflipid does not contain fatty acid chains?Why are these molecules classified as lipids?
Soap Draw the structure of the soap sodium palmitate(palmitate is the conjugate base of the 16-carbon saturated fatty acid, palmitic acid). Label its polar and non polar ends.
Determine whether each structure is a fatty acid,triglyceride, phospholipid, steroid, or wax. Explainyour reasoning.
The fatty acid palmitic acid has a density of 0.853 $\mathrm{g} / \mathrm{mL}$at $62^{\circ} \mathrm{C}$ . What will be the mass of a 0.886 -L sample ofpalmitic acid at that temperature?
Polyunsaturated Fats How many moles of hydrogengas are required for complete hydrogenation of 1 mol oflinolenic acid, whose structure is shown below? Write abalanced equation for the hydrogenation reaction.$\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}=\mathrm{CHCH}_{2} \mathrm{CH}=\mathrm{CHCH}_{2} \mathrm{CH}=\mathrm{CH}$$\left(\mathrm{CH}_{2}\right)_{7} \mathrm{COOH}$
What three structures make up a nucleotide?
Name two nucleic acids found in organisms.
Explain the roles of DNA and RNA in the production ofproteins.
Where in living cells is DNA found?
Describe the types of bonds and attractions that link themonomers together in a DNA molecule.
Classify the nucleic acid structure shown in Figure 23.34as DNA or RNA and explain your reasoning.
In the double-helical structure of DNA, the base guanine is always bonded to cytosine, and adenine is alwaysbonded to thymine. What do you expect to be the relative proportional amounts of $A, T, C,$ and $G$ in a given length of DNA?
DNA Replication One strand in a DNA molecule hasthe following base sequence. What is the base sequenceof the other strand in the DNA molecule?$$\mathrm{C}-\mathrm{C}-\mathrm{G}-\mathrm{T}-\mathrm{G}-\mathrm{G}-\mathrm{A}-\mathrm{C}-\mathrm{A}-\mathrm{T}-\mathrm{T}-\mathrm{A}$$
Life Processes Compare the net reactions for photo-synthesis and cellular respiration with respect to reactants, products, and energy.
The genetic code is a triplet code, that is, a sequence ofthree bases in RNA codes for each amino acid in a pep-tide chain or protein. How many RNA bases arerequired to code for a protein that contains577 amino acids?
DNA Comparisons A cell of the bacterium Escherichiacoli has about $4.2 \times 10^{6}$ base pairs of DNA, whereas eachhuman cell has about $3 \times 10^{9}$ base pairs of DNA. Whatpercentage of the size of the human genome does theE. coli DNA represent?
How many grams of glucose can be oxidized completelyby 2.0 L of $\mathrm{O}_{2}$ gas at STP during cellular respiration?
Energy Calculate and compare the total energy in kJthat is converted to ATP during the processes of cellularrespiration and fermentation.
Draw the carbonyl functional groups present in glucoseand fructose. How are the groups similar? How are thegroups different?
List the names of the monomers that make up proteins,complex carbohydrates, and nucleic acids.
Write balanced equations for photosynthesis, cellularrespiration, and the hydrolysis of lactose.
Write a balanced equation for the synthesis of sucrosefrom glucose and fructose.
Make and Use Graphs A number of saturated fattyacids and values for some of their physical propertiesare listed in Table $23.2 .$a. Make a graph plotting number of carbon atomsversus melting point.a. Make a graph plotting number of carbon atomsversus melting point.
Calculate Approximately 38 mol of ATP are formedwhen glucose is completely oxidized during cellular res-piration. If the heat of combustion for 1 mol of glucoseis $2.82 \times 10^{3} \mathrm{kJ} / \mathrm{mol}$ and each mole of ATP stores 30.5 $\mathrm{kJ}$of energy, what is the efficiency of cellular respiration interms of the percentage of available energy that is storedin the chemical bonds of ATP?
Some diets suggest severely restricting the intake of lipids. Why is it not a good idea to eliminate all lipids from the diet?
Analyze Insulin is a protein that functions as an impor-tant hormone in the human body. People who are dia-betic often do not produce enough insulin, and mustinject themselves with an insulin solution to maintaintheir health. Use Figure 23.35 to infer how a personshould care for a bottle of insulin.
Calculate If a double-strand section of DNA has adenine as 20$\%$ of its bases, what percent of the other three bases are present in the DNA strand?
Calculate how many moles of ATP a human body can produce from the sugar in a bushel of medium-sized Red Delicious apples. Use the Internet to find the information you need to solve this problem.
a. Write the balanced equation for the synthesis ofethanol from ethene and water.b. If 448 L of ethene gas reacts with excess water at STP,how many grams of ethanol will be produced?(Chapter 13$)$
Identify whether each of the reactants in these reactionsis acting as an acid or a base. (Chapter 18$)$a. $\mathrm{HBr}+\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{H}_{3} \mathrm{O}^{+}+\mathrm{Br}^{-}$b. $\mathrm{NH}_{3}+\mathrm{HCOOH} \rightarrow \mathrm{NH}_{4}^{+}+\mathrm{HCOO}^{-}$c. $\mathrm{HCO}_{3}^{-}+\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{CO}_{3}^{-}+\mathrm{H}_{3} \mathrm{O}^{+}$
What is a voltaic cell? (Chapter 20)
Which type of fish had the most omega fatty acids?
Based on this study, which type of salmon wouldyou recommend to someone who wants to maximizethe amount of omega-3 and omega- 6 fatty acids intheir diet?
Infer from the graph why the farm-raised and super-market salmon contains more omega-3 and omega-6fatty acids than wild salmon.