Biology Chapter 5

24 July 2022
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macromolecules
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large molecules that are complex
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carbohydrates
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Include sugars and the polymers of sugars. The simplest carbohydrates are monosaccharides, or simple sugars. Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks.
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lipids
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the one class of large biological molecules that does not include true polymers. The unifying feature of lipids is that they mix poorly, if at all, with water. Lipids are hydrophobic becausethey consist mostly of hydrocarbons, which form nonpolar covalent bonds. The most biologically important lipids are fats, phospholipids, and steroids.
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proteins
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Proteins account for more than 50% of the dry mass of most cells. Some proteins speed up chemical reactions. Other protein functions include defense, storage, transport, cellular communication, movement, or structural support.
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nucleic acids
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genes consist of DNA and RNA.
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polymer
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long molecule consisting of many similar building blocks. carbohydrates, lipids, proteins, nucleic acids
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monomer
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repeating units that serve as building blocks
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enzymes
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specialized macromolecules that speed up chemical reactions such as those that make or break down polymers
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dehydration reaction
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occurs when two monomers bond together through the loss of a water molecule
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hydrolysis
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reaction that is essentially the reverse of the dehydration reaction
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sugars
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Monosaccharides have molecular formulas that are usually multiples of CH2O. Glucose (C6H12O6) is the most common monosaccharide. Monosaccharides are classified by The location of the carbonyl group (as aldose or ketose). The number of carbons in the carbon skeleton.
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monosaccharide
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Though often drawn as linear skeletons, in aqueous solutions many sugars form rings. Monosaccharides serve as a major fuel for cells and as raw material for building molecules.
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disaccharide
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A disaccharide is formed when a dehydration reaction joins two monosaccharides. This covalent bond is called a glycosidic linkage.
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polysaccharides
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Polysaccharides, the polymers of sugars, have storage and structural roles. The architecture and function of a polysaccharide are determined by its sugar monomers and the positions of its glycosidic linkages.
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storage polysaccharides
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Starch, a storage polysaccharide of plants, consists entirely of glucose monomers Plants store surplus starch as granules within chloroplasts and other plastids The simplest form of starch is amylose
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structural polysaccharides
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The polysaccharide cellulose is a major component of the tough wall of plant cells Like starch, cellulose is a polymer of glucose, but the glycosidic linkages differ The difference is based on two ring forms for glucose: alpha and beta. Starch (a configuration) is largely helical Cellulose molecules (b configuration) are straight and unbranched. Some hydroxyl groups on the monomers of cellulose can hydrogen bond with hydroxyls of parallel cellulose molecules.
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chitin
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structural polysaccharide found in the exoskeleton of arthropods. provides structural support for the cell walls of fungi
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fats
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constructed from two types of smaller molecules: glycerol and fatty acids. Glycerol is a three-carbon alcohol with a hydroxyl group attached to each carbon. A fatty acid consists of a carboxyl group attached to a long carbon skeleton. Fats separate from water because water molecules hydrogen-bond to each other and exclude the fats. In a fat, three fatty acids are joined to glycerol by an ester linkage, creating a triacylglycerol, or triglyceride. The fatty acids in a fat can be all the same or of two or three different kinds.
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saturated fatty acid
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have the maximum number of hydrogen atoms possible and no double bonds. solid at room temp. most animal fats are this.
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unsaturated fatty acid
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have one or more double bonds. liquid at room temp. plants and fish fats are this.
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hydrogenation
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the process of converting unsaturated fats to saturated fats by adding hydrogen
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major function of fats
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energy storage Humans and other mammals store their long-term food reserves in adipose cells Adipose tissue also cushions vital organs and insulates the body
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phospholipid
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two fatty acids and a phosphate group are attached to glycerol The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head. When phospholipids are added to water, they self-assemble into double-layered structures called bilayers. At the surface of a cell, phospholipids are also arranged in a bilayer, with the hydrophobic tails pointing toward the interior. The structure of phospholipids results in a bilayer arrangement found in cell membranes. The existence of cells depends on phospholipids
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steroids
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lipids characterized by a carbon skeleton consisting of four fused rings Cholesterol, a type of steroid, is a component in animal cell membranes and a precursor from which other steroids are synthesized A high level of cholesterol in the blood may contribute to cardiovascular disease
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enzymatic proteins
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selective acceleration of chemical reactions. digestive enzymes catalyze the hydrolysis of bonds in food molecules.
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defensive proteins
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protection against disease. antibodies inactivate and help destroy viruses and bacteria
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storage proteins
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storage of amino acid. Casein, the protein of milk, is the major source of amino acids for baby mammals. Plants have storage proteins in their seeds. Ovalbumin is the protein of egg white, used as an amino acid source for the developing embryo.
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transport proteins
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transport of substances. Hemoglobin, the iron-containing protein of vertebrate blood, transports oxygen from the lungs to other parts of the body. Other proteins transport molecules across membranes, as shown here.
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hormonal proteins
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coordination of an organisms activities. Insulin, a hormone secreted by the pancreas, causes other tissues to take up glucose, thus regulating blood sugar, concentration.
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receptor proteins
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response of cell to chemical stimuli. Receptors built into the membrane of a nerve cell detect signaling molecules released by other nerve cells.
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contractile and motor proteins
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movement. Motor proteins are responsible for the undulations of cilia and flagella. Actin and myosin proteins are responsible for the contraction of muscles.
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structural proteins
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support. Keratin is the protein of hair, horns, feathers, and other skin appendages. Insects and spiders use silk fibers to make their cocoons and webs, respectively. Collagen and elastin proteins provide a fibrous framework in animal connective tissues.
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catalysts
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enzymes are proteins that speed up chemical reactions
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polypeptide
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Amino acids are linked by covalent bonds called peptide bonds A polypeptide is a polymer of amino acids Polypeptides range in length from a few to more than a thousand monomers Each polypeptide has a unique linear sequence of amino acids, with a carboxyl end (C-terminus) and an amino end (N-terminus)
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four levels of protein structure
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The primary structure of a protein is its unique sequence of amino acids Secondary structure, found in most proteins, consists of coils and folds in the polypeptide chain Tertiary structure is determined by interactions among various side chains (R groups) Quaternary structure results when a protein consists of multiple polypeptide chains
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secondary structure
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The coils and folds of secondary structure result from hydrogen bonds between repeating constituents of the polypeptide backbone Typical secondary structures are a coil called an helix and a folded structure called a pleated sheet
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tertiary structure
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the overall shape of a polypeptide, results from interactions between R groups, rather than interactions between backbone constituents These interactions include hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals interactions Strong covalent bonds called disulfide bridges may reinforce the protein's structure
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quaternary structure
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results when two or more polypeptide chains form one macromolecule Collagen is a fibrous protein consisting of three polypeptides coiled like a rope Hemoglobin is a globular protein consisting of four polypeptides: two alpha and two beta chains
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sickle cell disease
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an inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin
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denaturation
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loss of proteins native structure
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protein folding
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It is hard to predict a protein's structure from its primary structure Most proteins probably go through several stages on their way to a stable structure Chaperonins are protein molecules that assist the proper folding of other proteins Diseases such as Alzheimer's, Parkinson's, and mad cow disease are associated with misfolded proteins
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gene
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consist of DNA, a nucleic acid made of monomers called nucleotides
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DNA
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provides direction for its own replication. controls protein synthesis
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RNA
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protein synthesis
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flow of genetic information
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DNA to RNA to protein
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nucleotide
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Each polynucleotide is made of monomers called nucleotides Each nucleotide consists of a nitrogenous base, a pentose sugar, and one or more phosphate groups The portion of a nucleotide without the phosphate group is called a nucleoside
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nucleotide/ side
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Nucleoside = nitrogenous base + sugar There are two families of nitrogenous bases Pyrimidines (cytosine, thymine, and uracil) have a single six-membered ring Purines (adenine and guanine) have a six-membered ring fused to a five-membered ring In DNA, the sugar is deoxyribose; in RNA, the sugar is ribose Nucleotide = nucleoside + phosphate group
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nucleotide polymers
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Nucleotides are linked together to build a polynucleotide Adjacent nucleotides are joined by a phosphodiester linkage, which consists of a phosphate group that links the sugars of two nucleotides These links create a backbone of sugar-phosphate units with nitrogenous bases as appendages The sequence of bases along a DNA or mRNA polymer is unique for each gene
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DNA structure
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DNA molecules have two polynucleotides spiraling around an imaginary axis, forming a double helix The backbones run in opposite 5 → 3 directions from each other, an arrangement referred to as antiparallel One DNA molecule includes many genes
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1) Which of these classes of biological molecules does NOT include polymers?
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A) lipids B) carbohydrates C) proteins D) nucleic acids Answer: A
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2) Which of the following is NOT a polymer?
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A) glucose B) starch C) cellulose D) DNA Answer: A
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3) How many molecules of water are used to completely hydrolyze a polymer that is 11 monomers long?
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A) 12 B) 11 C) 10 D) 9 Answer: C
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4) Which of the following best summarizes the relationship between dehydration reactions and hydrolysis?
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A) Dehydration reactions assemble polymers; hydrolysis reactions break polymers apart. B) Dehydration reactions eliminate water from membranes; hydrolysis reactions add water to membranes. C) Dehydration reactions and hydrolysis reactions assemble polymers from monomers. D) Hydrolysis reactions create polymers and dehydration reactions create monomers. Answer: A
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5) The molecular formula for glucose is C6H12O6. What would be the molecular formula for a molecule made by linking three glucose molecules together by dehydration reactions?
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A) C18H36O18 B) C18H32O16 C) C6H10O5 D) C18H30O15 Answer: B
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6) What is the difference between an aldose sugar and a ketose sugar?
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A) the number of carbons B) the position of the hydroxyl groups C) the position of the carbonyl group D) One is a ring form, the other is a linear chain/ Answer: C
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7) What is the major structural difference between starch and glycogen?
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A) the types of monosaccharide subunits in the molecules B) the type of glycosidic linkages in the molecule C) whether glucose is in the α or β form D) the amount of branching that occurs in the molecule Answer: D
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8) Which polysaccharide is an important component in the structure of many animals and fungi?
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A) chitin B) cellulose C) amylopectin D) amylose Answer: A
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9) What does the term insoluble fiber refer to on food packages?
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A) cellulose B) polypeptides C) starch D) amylopectin Answer: A
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10) A molecule with the chemical formula C6H12O6 is probably a _____.
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A) fatty acid B) polysaccharide C) nucleic acid D) monosaccharide Answer: D
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11) Lactose, a sugar in milk, is composed of one glucose molecule joined by a glycosidic linkage to one galactose molecule. How is lactose classified?
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A) as a hexose B) as a monosaccharide C) as a disaccharide D) as a polysaccharide Answer: C
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12) Starch and cellulose _____.
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A) are polymers of glucose B) are cis-trans isomers of each other C) are used for energy storage in plants D) are structural components of the plant cell wall Answer: A
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13) Humans can digest starch but not cellulose because _____.
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A) humans have enzymes that can hydrolyze the α-glycosidic linkages of starch but not the β- glycosidic linkages of cellulose B) starch monomers are joined by covalent bonds and cellulose monomers are joined by ionic bonds C) the monomer of starch is glucose, while the monomer of cellulose is galactose D) the monomer of starch is fructose, while the monomer of cellulose is glucose Answer: A
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15) A glycosidic linkage is analogous to which of the following in proteins?
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A) an amino group B) a peptide bond C) a disulfide bond D) a β-pleated sheet Answer: B
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16) Cooking oil and gasoline (a hydrocarbon) are not amphipathic molecules because they _____.
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A) do not have a polar or charged region B) do not have a nonpolar region C) have hydrophobic and hydrophilic regions D) are highly reduced molecules Answer: A
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17) How do phospholipids interact with water molecules?
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A) The polar heads avoid water; the nonpolar tails attract water (because water is polar and opposites attract). B) Phospholipids do not interact with water because water is polar and lipids are nonpolar. C) The polar heads interact with water; the nonpolar tails do not. D) Phospholipids dissolve in water. Answer: C
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18) Phospholipids and triglycerides both _____.
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A) contain serine or some other organic compound B) have three fatty acids C) have a glycerol backbone D) have a phosphate Answer: C
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19) Which of the following is the best explanation for why vegetable oil is a liquid at room temperature while animal fats are solid?
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A) Vegetable oil has more double bonds than animal fats. B) Vegetable oil has fewer double bonds than animal fats. C) Animal fats have no amphipathic character. D) Vegetable oil has longer fatty-acid tails than animal fats have. Answer: A
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20) Which of the following statements is FALSE? Saturated fats _____.
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A) are more common in animals than in plants B) have many double bonds in the carbon chains of their fatty acids C) usually solidify at room temperature D) contain more hydrogen than unsaturated fats that consist of the same number of carbon atoms Answer: B
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21) Lipids _____.
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A) are insoluble in water B) are made from glycerol, fatty acids, and nitrogen C) contain less energy than proteins and carbohydrates D) are made by dehydration reactions Answer: A
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22) The label on a container of margarine lists "hydrogenated vegetable oil" as the major ingredient. Hydrogenated vegetable oil _____.
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A) is solid at room temperature B) has more "kinks" in the fatty acid chains C) has fewer trans fatty acids D) is less likely to clog arteries Answer: A
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23) Saturated fatty acids _____.
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A) have double bonds between carbon atoms of the fatty acids B) are the principal molecules in lard and butter C) are usually liquid at room temperature D) are usually produced by plants Answer: B
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24) Steroids are considered to be lipids because they _____.
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A) are essential components of cell membranes B) are not soluble in water C) are made of fatty acids D) contribute to atherosclerosis Answer: B
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27) Which one of the following is NOT a component of each monomer used to make proteins?
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A) a phosphorus atom, P B) an amino functional group, NH2 C) a side chain, R D) a carboxyl group, COOH Answer: A
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28) What component of amino acid structure varies among different amino acids?
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A) the long carbon-hydrogen tails of the molecule B) the presence of a central C atom C) the components of the R-group D) the glycerol molecule that forms the backbone of the amino acid Answer: C
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29) You disrupt all hydrogen bonds in a protein. What level of structure will be preserved?
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A) primary structure B) secondary structure C) tertiary structure D) quaternary structure Answer: A
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30) Which of the following is the strongest evidence that protein structure and function are correlated?
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A) Proteins function best at certain temperatures. B) Proteins have four distinct levels of structure and many functions. C) Enzymes tend to be globular in shape. D) Denatured (unfolded) proteins do not function normally. Answer: D
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31) You have just sequenced a new protein found in mice and observe that sulfur-containing cysteine residues occur at regular intervals. What is the significance of this finding?
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A) Cysteine residues are required for the formation of α-helices and β-pleated sheets. B) It will be important to include cysteine in the diet of the mice. C) Cysteine residues are involved in disulfide bridges that help form tertiary structure. D) Cysteine causes bends, or angles, to occur in the tertiary structure of proteins. Answer: C
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32) Proteorhodopsin consists of a single polypeptide chain. What is the highest level of structure found in this protein?
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A) primary B) secondary C) tertiary D) quaternary Answer: C
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33) All of the following contain amino acids EXCEPT _____.
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A) hemoglobin B) cholesterol C) enzymes D) insulin Answer: B
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34) Which level of protein structure do the α-helix and the β-pleated sheet represent?
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A) primary B) secondary C) tertiary D) quaternary Answer: B
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35) The tertiary structure of a protein is the _____.
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A) order in which amino acids are joined in a polypeptide chain B) unique three-dimensional shape of the fully folded polypeptide C) organization of a polypeptide chain into an α-helix or β-pleated sheet D) overall protein structure resulting from the aggregation of two or more polypeptide subunits Answer: B
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36) The R-group, or side chain, of the amino acid serine is -CH2-OH. The R-group, or side chain, of the amino acid leucine is -CH2-CH-(CH3)2. Where would you expect to find these amino acids in a globular protein in aqueous solution?
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A) Serine would be in the interior, and leucine would be on the exterior of the globular protein. B) Leucine would be in the interior, and serine would be on the exterior of the globular protein. C) Serine and leucine would both be in the interior of the globular protein. D) Serine and leucine would both be on the exterior of the globular protein. Answer: B
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37) Misfolding of polypeptides is a serious problem in cells. Which of the following diseases are associated with an accumulation of misfolded polypeptides?
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A) Alzheimer's only B) Parkinson's only C) diabetes mellitus only D) Alzheimer's and Parkinson's only Answer: D
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38) Changing a single amino acid in a protein consisting of 325 amino acids would _____.
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A) alter the primary structure of the protein but not its tertiary structure or function B) cause the tertiary structure of the protein to unfold C) always alter the biological activity or function of the protein D) always alter the primary structure of the protein, sometimes alter the tertiary structure of the protein, and sometimes affect its biological activity Answer: D
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39) Normal hemoglobin is a tetramer, consisting of two molecules of β hemoglobin and two molecules of α hemoglobin. In sickle-cell disease, as a result of a single amino acid change, the mutant hemoglobin tetramers associate with each other and assemble into large fibers. Based on this information alone, we can conclude that sickle-cell hemoglobin exhibits _____.
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A) only altered primary structure B) only altered tertiary structure C) only altered quaternary structure D) altered primary structure and altered quaternary structure; the secondary and tertiary structures may or may not be altered Answer: D
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40) What is the term used for a protein molecule that assists in the proper folding of other proteins?
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A) tertiary protein B) chaperonin C) renaturing protein D) denaturing protein Answer: B
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42) Nucleic acids are polymers made up of which of the following monomers?
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A) nucleotides B) sugars C) amino acids D) nitrogenous bases Answer: A
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43) Which of the following includes all of the pyrimidines found in RNA and DNA?
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A) cytosine and uracil B) cytosine and thymine C) cytosine, uracil, and thymine D) cytosine, uracil, and guanine Answer: C
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44) When nucleotides polymerize to form a nucleic acid _____.
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A) a covalent bond forms between the sugar of one nucleotide and the phosphate of a second B) a hydrogen bond forms between the sugar of one nucleotide and the phosphate of a second C) covalent bonds form between the bases of two nucleotides D) hydrogen bonds form between the bases of two nucleotides Answer: A
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45) Which of the following statements about the 5' end of a polynucleotide strand of RNA is correct?
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A) The end has a hydroxyl group attached to the number 5 carbon of ribose. B) The end has a phosphate group attached to the number 5 carbon of ribose. C) The end has phosphate attached to the number 5 carbon of the nitrogenous base. D) The end has a carboxyl group attached to the number 5 carbon of ribose. Answer: B
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46) One of the primary functions of RNA molecules is to _____.
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A) transmit genetic information to offspring B) function in the synthesis of proteins C) make a copy of itself, thus ensuring genetic continuity D) act as a pattern or blueprint to form DNA Answer: B
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47) If 14C-labeled uracil is added to the growth medium of cells, what macromolecules will be labeled?
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A) DNA B) RNA C) both DNA and RNA D) proteins Answer: B
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48) Which of the following descriptions best fits the class of molecules known as nucleotides?
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A) a nitrogenous base and a phosphate group B) a nitrogenous base and a sugar C) a nitrogenous base, a phosphate group, and a sugar D) a sugar and a purine or pyrimidine Answer: C
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49) If a DNA sample were composed of 10% thymine, what would be the percentage of guanine?
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A) 10 B) 40 C) 80 D) It is impossible to tell from the information given. Answer: B
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50) Which of the following statements best summarizes the differences between DNA and RNA?
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A) DNA encodes hereditary information, whereas RNA does not. B) The bases in DNA contain sugars, whereas the bases in RNA do not contain sugar. C) DNA nucleotides contain a different sugar than RNA nucleotides. D) DNA contains the base uracil, whereas RNA contains the base thymine. Answer: C
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51) If one strand of a DNA molecule has the sequence of bases 5'ATTGCA3', the other complementary strand would have the sequence _____.
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A) 5'TAACGT3' B) 5'TGCAAT3' C) 3'UAACGU5' D) 5'UGCAAU3' Answer: B
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Which statement correctly identifies the result that the optimum pH for amylase function is 7?
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A) The pH with the lowest absorbance values would indicate the optimum pH for amylase since this pH does not affect the structure or function of the protein. B) The pH with the highest absorbance values would indicate the optimum pH for amylase since this pH does not affect the structure or function of the protein. C) At pH 9, the enzyme is denatured and will lose its function, but not its structure. D) At pH 4, the structure of the enzyme will be altered, and the enzyme would not be able to catalyze the reaction. Answer: B
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23) Saturated fatty acids _____.
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A) have double bonds between carbon atoms of the fatty acids B) are the principal molecules in lard and butter C) are usually liquid at room temperature D) are usually produced by plants Answer: B