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Answers to Text Questions
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Inquiry Questions
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Self Test

1). Proteins, nucleic acids, lipids and carbohydrates all have certain characteristics in common. Which of the following is not a common characteristic?
    a). They are organic, which means they are all living substances.
    b). They all contain the element carbon.
    c). They contain simpler units that are linked together making larger molecules.
    d). They all contain functional groups.
Answer: a

2). A peptide bond forms by:
    a). a condensation reaction.
    b). dehydration synthesis.
    c). the formation of a covalent bond.
    d). all of these.
Answer: d

3). Protein motifs are considered a type of
    a). primary structure.
    b). secondary structure.
    c). tertiary structure.
    d). quaternary structure.
Answer: b

4). The substitution of one amino acid for another
    a). will change the primary structure of the polypeptide.
    b). can change the secondary structure of the polypeptide.
    c). can change the tertiary structure of the polypeptide.
    d). All of these are correct.
Answer: d

5). Chaperone proteins function by
    a). providing a protective environment in which proteins can fold properly.
    b). degrading proteins that have folded improperly.
    c). rescuing proteins that folded incorrectly and allow them to refold into the proper configuration.
    d). providing a template for how the proteins should fold.
Answer: c

6). Which of the following lists the purine nucleotides?
    a). adenine and cytosine
    b). guanine and thymine
    c). cytosine and thymine
    d). adenine and guanine
Answer: d

7). The two strands of a DNA molecule are held together through base-pairing. Which of the following best describes the base-pairing in DNA?
    a). Adenine forms two hydrogen bonds with thymine.
    b). Adenine forms two hydrogen bonds with uracil.
    c). Cytosine forms two hydrogen bonds with guanine.
    d). Cytosine forms two hydrogen bonds with thymine.
Answer: a


8). A characteristic common to all lipids is
    a). that they contain long chains of C-H bonds.
    b). that they are insoluble in water.
    c). that they have a glycerol backbone.
    d). All of these are characteristics of all lipids.
Answer: b

9). Carbohydrates have many functions in the cell. Which of the following is an incorrect match of the carbohydrate with its function?
    a). sugar transport in plants--disaccharides
    b). energy storage in plants--starches
    c). energy storage in plants--lactose
    d). sugar transport in humans--glucose
Answer: c

10). Which of the following carbohydrates is associated with plants?
    a). glycogen
    b). amylopectin
    c). chitin
    d). levo-glucose
Answer: b

Test Your Visual Understanding

1). The amino acids of a polypeptide affect the shape of the protein. Assume this is a section of a longer polypeptide chain. Predict where each of the following amino acid pairs would be found in the protein–facing toward the outside or folded in toward the interior–and explain why:
a). Both amino acids are valine.
b). One amino acid is aspartic acid, and the other is serine.
c). Both amino acids are glycine.
d). One amino acid is alanine, and the other is isoleucine
Answer: a). Valine is a nonpolar amino acid and is repelled by water, therefore this section of the polypeptide chain would be folded in toward the interior away from the watery environment.
b). Aspartic acid is a charged amino acid and serine is a polar amino acid; both are attracted to water, therefore this section of the polypeptide chain would be facing toward the outside.
c). Glycine is a polar amino acid and is attracted to water, therefore this section of the polypeptide chain would be facing toward the outside.
d). Alanine and isoleucine are both nonpolar amino acids and are repelled by water, therefore this section of the polypeptide chain would be folded in toward the interior away from the watery environment.

2). Describe the DNA template that produced this molecule of RNA by indicating the DNA bases that are complementary to the RNA bases numbered.
Answer:
    #1--A
    #2--T
    #3--G
    #4--C
    #5--T
    #6--A
    #7--C


Apply Your Knowledge
1). How many molecules of water are used up in the breakdown of a polypeptide 15 amino acids in length?
Answer: A polypeptide that has fifteen amino acids is held together by fourteen peptide bonds. One molecule of water is consumed in the breaking of a peptide bond, therefore:
1 molecule of water x number of peptide bonds or:
1 x 14 = 14 water molecules

2).Why do you suppose the monosaccharide glucose is circulated in the blood of humans rather than a disaccharide, such as sucrose, which is the transport sugar found in plants?
Answer: Humans use glucose in metabolic pathways for the generation of cellular energy. Glucose flows into metabolic pathways directly. A disaccharide, such as sucrose, would require an additional step before entering into a metabolic pathway. Therefore, it is more efficient for humans to transport sugar in the blood as glucose. Plants, on the other hand, use the carbohydrates they produce as building blocks of cellular tissues, therefore, the transportation of carbohydrates as sucrose is more efficient in plants.







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