Section 2.6: Natural Polymers
Section 2.6 Questions, page 105
1. Both starch and cellulose are polymers of glucose. Cellulose is a linear polymer,
whereas starch is linear and branched.
2.
Glucose has 5 OH groups, which allow it to form up to 5 bonds with other glucose
molecules. For this reason, glucose can form different types of polymers that have
straight and/or branched chains.
3. (a)
(b) Cellulose is the product of a condensation reaction. The oxygen atom that links two
glucose molecules is what remains when a hydroxyl group on one glucose molecule
reacts with a hydrogen atom from a hydroxyl group from the other glucose molecule to
form a water molecule.
4. A carbohydrate-rich food like crackers contains starch, which is a polymer of glucose.
When your saliva begins to break down the starch polymer, you start to taste the glucose
molecules that are released. These glucose molecules taste sweet.
5. (a) There are 6 possible combinations of these 3 amino acids (if directionality is
important):
gly ser phe; ser phe gly; phe gly ser; phe ser gly; gly phe ser; ser gly phe
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Chapter 2: Polymers
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(b) Answers may vary. Sample answer:
+
–
(c) The 20 amino acids can be assembled in any order; so there are a huge number of
possible protein structures.
6. (a) Phenylalanine is hydrophobic because it has a non-polar R group (a benzene ring).
(b) Serine is hydrophilic because it has polar R group.
(c) Leucine is hydrophobic because it has a non-polar R group.
(d) Arginine hydrophilic because it has polar R group that is also positively charged.
7. (a)
(b) Ribose has an additional hydroxyl group bonded to the ring.
8. Answers may vary. Sample answer:
Cotton
Polyester
Advantages
–porous material, allows
–less porous than cotton,
moisture to escape from
does not allow moisture to
skin
escape as easily away
–biodegradable
from skin
–wears out very slowly
Disadvantages
–wears out fairly quickly
–non-biodegradable
9. Answers may vary. Sample answer should include the following information:
When getting a perm, the hair is first treated with sodium thioglycolate, a reduction lotion
that breaks disulfide bonds in the keratin of hair strands. The hair is then wrapped around
rods, and hydrogen peroxide, an oxidation lotion, is applied to form new disulfide bonds
to reform the hair to the shape of the rods. The chemicals are harsh, so they need to be
applied in a way that minimizes skin contact. If a perm is poorly done, it does not fix the
new disulfide bonds, which causes hair to break and fall out.
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Chapter 2: Polymers
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10. Answers may vary. Sample answer:
Recombinant insulin is one application of recombinant DNA technology that has largely
replaced insulin acquired from previous sources, such as insulin from pigs. Recombinant
insulin is very similar to human insulin. It has been modified slightly so that it is a
monomer, a smaller molecule that can be absorbed and take effect more quickly than
regular human insulin. Another version is a long-lasting version that only needs to be
taken once per day. Both versions of recombinant insulin have improved the lives of
people with insulin-dependent diabetes.
Another application is herbicide-resistant crops. These crops have been genetically
engineered to be resistant to glyphosate, a herbicide used for weed control, thereby
allowing farmers to control weeds more easily. Use of these crops has increased the use
of the herbicide. However, some weeds are now resistant to glyphosate. Also, the longterm effects on people who consume herbicide-resistant crops are unknown.
11. Answers may vary. Sample answer:
Protein
Function
Number of Amino Acids
insulin
controls blood sugar levels alpha chain: 21
in animals and humans
beta chain: 30
hemoglobin
transports oxygen from
alpha chain: 141
lungs to tissues and carbon beta chain: 146
dioxide from tissues to
lungs in blood
keratin
structural protein in skin,
18
hair, and nails
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Chapter 2: Polymers
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