Biochemistry Short Answer Nelson
Short Answer
1. Why is it important to have an understanding of biochemistry when studying biology?
2. How are radioisotopes used in research and medical applications?
3. What are valence electrons and why are they important?
4. Use diagrams to explain why helium and neon are extremely stable.
5. Compare ionic bonds and covalent bonds.
6. Describe the contribution of Canadian scientist Ronald Gillespie to the field of chemistry. Use a diagram in
your explanation.
7. Why is water called the “universal solvent?” Is this an accurate label? Explain your answer.
8. Do you agree or disagree with the following statement: Water’s unique properties make it essential to life on
Earth. Explain your answer.
9. Why are buffers important in the human body?
10. A student states that although rainwater is acidic, it should have a pH close to 7 since this is the pH of pure
water. Is this statement correct? Provide support for your answer.
11. (a) What is a functional group?
(b) Draw three different functional groups and give an example of a substance that contains each group.
12. What is the charge of DNA? How do you know?
13. Draw the functional group(s) of an amino acid. Explain how the functional group(s) gives amino acids their
characteristics.
14. An alcohol has the formula C2H6O. Draw and name the molecule, and indicate the functional group.
15. Compare a monosaccharide with a disaccharide and a polysaccharide.
16. Would you prefer to have a monosaccharide sweetener or a disaccharide sweetener? Explain your choice.
17. Compare and contrast carbohydrates and lipids.
18. In this chapter, you learned about fats. Why do you think that a low-fat diet would not necessarily be healthy?
19. Relate the chemical structure of phospholipids to their physical properties and uses. Use a diagram in your
answer.
20. Select a lipid discussed in this chapter that you have encountered in your daily life. Describe the lipid and
explain how its function is related to its structure. How does this knowledge affect the way the lipid is used?
21. In this chapter, you learned about carbohydrates and lipids.
(a) Was this information easy or difficult for you to understand?
(b) If so, how did you overcome your difficulty?
(c) If not, what was it about the information that made it easy for you to understand?
22. Describe the role that polymerization plays in the formation of proteins and nucleic acids.
23. Discuss how the structure of a protein relates to its function. Give three examples in your answer.
24. Explain how a protein’s primary and secondary structures are responsible for different characteristics of the
protein.
25. Compare DNA with RNA in terms of function and structure.
26. How do amino acids bond together? Use a diagram to show how amino acids serine, tyrosine, and cysteine
(shown below) would bond together.
27. Extreme conditions of temperature and pH can cause proteins to denature. Give an example from daily life of
protein denaturation.
28. A fragment of a strand of DNA has the following base sequence: GTTACCTAG. What is the base sequence
of the complementary strand? How do you know?
29. In this chapter, you learned about carbohydrates, lipids, proteins, and nucleic acids. Will you make any
changes to your daily diet based on the information presented here?
30. How do you think that Linus Pauling’s position as a highly regarded scientist influenced his ability to speak
out about nuclear weapons testing?
31. What do you think about Linus Pauling’s position on consuming megadoses of vitamin C as an alternative to
chemotherapy?
32. In this chapter, you learned about enzymes.
(a) What did you know about enzymes before reading this chapter?
(b) How has your understanding of enzymes changed?
33. Why is the term “lock and key” used to describe the way an enzyme works? Do you feel that this is an
accurate analogy?
34. In this chapter, you learned that scientists had originally thought that enzymes and substrates worked liked a
lock and key. This theory was disproved and replaced with a new theory of induced fit. This is an example of
how scientific knowledge is constantly changing. Do you feel this weakens the validity of scientific
knowledge?
Give a reason for your answer.
35. How might a change in pH affect the function of an enzyme? Give an example in your answer.
36. Describe how changing the temperature affects the function of the enzyme. Use a diagram in your answer.
37. Design an experiment using catalase and hydrogen peroxide to investigate the influence of pH on the activity
of an enzyme. What information concerning the structure of an enzyme could you infer from your
experiment?
38. Discuss three industrial and commercial uses of enzymes.
39. Make a chart comparing the structures found in a eukaryotic cell with those found in a prokaryotic cell.
40. (a) Label the organelles shown in the diagram.
(b) Is the cell a plant cell or an animal cell? How do you know?
41. Both the terms eukaryote and prokaryote are based on the Greek word for kernel or nucleus, “karyon.” The
Greek word “eu” means true while the Greek word “pro” means before. Do you think that these terms are
accurate descriptions of the cells? Explain your answer.
42. Describe the organelles in the endomembrane system. How do they all function together as part of the
endomembrane system?
43. What are the similarities and differences between a plant cell and an animal cell? Use a Venn diagram in your
answer.
44. Explain the theory of endosymbiosis. Do you think this theory is plausible? Why?
45. You can think of a cell as a factory. For example, the ribosome is like a machine in a factory, producing
polypeptide chains in accordance to the instructions provided by the nucleus. What other organelles play a
role in the factory? Explain your answer.
46. Would you expect to find more mitochondria in a muscle cell or a skin cell? Explain your answer.
47. Compare the structure and function of a mitochondrion and a chloroplast.
48. Compare the structure and function of flagella and cilia.
49. How does the plasma membrane compare in structure and function with the nuclear envelope?
50. In this chapter, you learned about cell structures and organelles.
(a) Was this information easy or difficult for you to understand?
(b) If it was difficult, how did you overcome your difficulty?
(c) If it was easy, what was it about the information that made it easy for you to understand?
51. Explain how the cystic fibrosis transmembrane conductance regulator (CFTR) functions. Use a diagram in
your answer.
52. What is the fluid mosaic model? Do you think that this name is accurate?
53. What are the major components of a cell membrane and how does each component contribute to the
functioning of the membrane?
54. What is membrane asymmetry and why is it an important characteristic of membranes?
55. What four functional roles do membrane proteins play? Use a diagram in your answer.
56. Why do phospholipids form a bilayer? Use a diagram in your answer.
57. How do sterols help maintain the fluidity of a membrane? Give an example.
58. How do the positions of the membrane proteins relate to their functions?
59. In this chapter, you learned about how the structure of a membrane relates to its function.
(a) What did you know about membranes before reading this chapter?
(b) How has your understanding of membranes changed?
60. How would you teach the structure and functions of a membrane to a student who was having difficulties
understanding the concepts?
61. Think of a career in which knowledge of the structure and function of membranes would be beneficial.
Explain how knowledge about membranes is applicable to the career you selected.
62. How do you think nano-sized robots could be used in medicine? Give an example.
63. Think of a career related to nanobots. Explain how a knowledge about membranes would help in this career.
64. Compare how a channel protein works with how a carrier protein works. Use diagrams in your answer.
65. A student thinks that he can show diffusion and osmosis using a tea bag, hot water, and a cup. Is he correct?
Explain.
66. What do you predict might happen to the cells of a fish that is accustomed to living in salt water if the fish
were placed in fresh water? Explain your answer.
67. Compare the different ways that substances move passively across membranes.
68. How could you design an experiment to look at the effects of isotonic, hypotonic, and hypertonic solutions on
animal and plant cells?
69. Describe what happens to cells in hypotonic, hypertonic, and isotonic solutions. Use diagrams for each
example.
70. Imagine that you have given blood, but a sample of your red blood cells is accidentally stored in distilled
water instead of saline solution. Predict what would happen to the cells. Explain your answer.
71. One method for preserving meat is to add salt to it. Why is this an effective technique for preserving meat?
Explain.
72. Why is the sodium–potassium transport mechanism called a “pump”? Do you think this is an accurate name
for it? Why or why not?
73. Compare exocytosis with endocytosis. Use diagrams in your answer.
74. In this chapter, you learned about the types of transport across membranes. What helped you differentiate
between all the methods of transport?
75. Which concept in this chapter did you find most difficult to comprehend? How did you overcome your
difficulty in understanding this concept?
76. In this chapter, you learned about osmosis. Why do you think that hypotonic and hypertonic solutions are so
important in the medical field?
Biochemistry Short Answer Nelson
Answer Section
SHORT ANSWER
1. ANS:
It is important to have an understanding of biochemistry because the properties of life begin with millions of
chemical reactions involving thousands of compounds. Understanding fundamental concepts of biochemistry
helps us understand how living systems function.
PTS: 1
OBJ: 1.1 The Fundamental Chemistry of Life
LOC: B2.1
MSC: Reflect on Your Learning
2. ANS:
Since radioisotopes decay at a predictable rate, they can be used to date rocks and fossils. Melvin Calvin used
14
C, a radioactive isotope of carbon, to study the sequences of the reactions involved in photosynthesis.
Radioisotopes are also used in the diagnosis and treatment of diseases such as cancer.
PTS: 1
REF: A
OBJ: 1.1 The Fundamental Chemistry of Life
LOC: B2.1
MSC: Analysis and Application
3. ANS:
Valence electrons are electrons in the outermost energy shell of an atom. The valence electrons determine the
chemical reactivity of an atom. Atoms with a filled valence shell are more stable than atoms with an unfilled
valence shell.
PTS: 1
REF: T/I
OBJ: 1.1 The Fundamental Chemistry of Life
LOC: B2.1
MSC: Analysis and Application
4. ANS:
Helium and neon have full valence shells. Helium has only one energy level, which can hold up to two
electrons. Neon’s outermost shell contains eight electrons, which is the maximum number. Atoms with full
valence shells do not easily form compounds because their electron arrangement is very stable.
PTS: 1
REF: C
OBJ: 1.1 The Fundamental Chemistry of Life
LOC: B2.1
MSC: Analysis and Application
5. ANS:
Both ionic bonds and covalent bonds are types of chemical bonds. An ionic bond forms between a positive
ion and a negative ion, while a covalent bond forms when atoms share one or more pairs of electrons. In an
ionic bond, one atom loses one or more electrons to become a cation and one atom gains one or more
electrons to become an anion. The forces of attraction between the oppositely charged ions leads to an ionic
bond. In a covalent bond, two atoms share their electrons to fill the valence shell of each atom.
PTS: 1
LOC: B2.1
REF: T/I
MSC: Evaluation
OBJ: 1.1 The Fundamental Chemistry of Life
6. ANS:
Gillespie studied the shape of molecules and helped develop the Valence Shell Electron Pair Repulsion
(VSEPR) theory. The theory is used to predict the shapes of molecules. According to the theory, valence pairs
of electrons will move as far as possible from each other. For example, in a water molecule, oxygen has four
non-bonding electrons that force the electron pairs in the O–H bonds into a 104 angle (see diagram).
PTS: 1
REF: C
OBJ: 1.1 The Fundamental Chemistry of Life
LOC: A2.2
MSC: Analysis and Application
7. ANS:
Water is called the universal solvent because of its ability to dissolve polar substances and charged molecules
and ions. It can do this because water molecules are small and very polar. Water molecules surround ions and
reduce the attraction between charged ions. Water does not dissolve non-polar molecules such as oils and fats,
so it cannot be considered to be a universal solvent that dissolves everything.
PTS: 1
REF: C
OBJ: 1.2 Water: Life's Solvent
LOC: B2.1
MSC: Evaluation
8. ANS:
Answers may vary. Possible answer: I agree with the statement. Water has unique properties, which allows it
to perform essential functions. For example, water molecules are able to stick to each other and to other polar
molecules because of the ability to form hydrogen bonds. The properties of cohesion and adhesion allows for
capillary action in which water moves up the xylem tubes in plants. The water molecules stick together
because of cohesion as they travel up the tubes. The water molecules also stick to the cell walls because of
adhesion. Water has a high specific heat capacity because of hydrogen bonding, which causes water to absorb
large amounts of thermal energy as the temperature increases or to lose large amounts of thermal energy as
the temperature decreases. This property means that the body is able to maintain a constant body temperature.
PTS: 1
REF: C
OBJ: 1.2 Water: Life's Solvent
LOC: B2.1
MSC: Evaluation
9. ANS:
The maintenance of the pH within cells is important for the optimal functioning of life. Any change in a cell’s
pH level can drastically affect biological reactions. Correct blood pH levels are essential for maintaining good
health. The pH levels in the stomach are also critical for proper digestion and for defence against microorganisms.
PTS: 1
REF: A
OBJ: 1.2 Water: Life's Solvent
LOC: B2.1
MSC: Analysis and Application
10. ANS:
The statement that all rainwater is acidic is correct because the pH of rainwater is around 5.5. Carbonic acid
makes rainwater naturally acidic. However, only pure water has a pH of 7 in which the concentration of H+
equals the concentration of OH–. Rainwater is not pure water.
PTS: 1
LOC: B2.1
REF: T/I
MSC: Evaluation
OBJ: 1.2 Water: Life's Solvent
11. ANS:
(a) A functional group is a group of atoms that participate in chemical reactions.
(b) Answers may vary. Sample answer: The carboxyl group is found in organic acids. An example is acetic
acid. The amino group is found in amino acids. An example is alanine. The phosphate group is found in
nucleic acids and nucleotide. An example is ribonucleic acid.
PTS: 1
REF: C
OBJ: 1.3 The Carbon Chemistry of Life
LOC: B3.3
MSC: Analysis and Application
12. ANS:
The charge of DNA is negative. DNA is an acid that contains many phosphate groups. The phosphate groups
release H+ ions to become negatively charged.
PTS: 1
REF: T/I
OBJ: 1.3 The Carbon Chemistry of Life
LOC: B3.3
MSC: Understanding
13. ANS:
Amino acids contain both a carboxyl group and an amino group. The carboxyl group makes the amino acid an
acid because it can release H+ in water. The amino group makes the amino acid a weak base because it can
bond to an H+ to become NH3+.
PTS: 1
REF: C
OBJ: 1.3 The Carbon Chemistry of Life
LOC: B3.3
MSC: Analysis and Application
14. ANS:
The alcohol is ethyl alcohol and it has a hydroxyl group (–OH).
PTS: 1
REF: C
OBJ: 1.3 The Carbon Chemistry of Life
LOC: B3.3
MSC: Analysis and Application
15. ANS:
Monosaccharides, disaccharides, and polysaccharides are all types of carbohydrates. They are also all used for
an energy source or storage. Monosaccharides contain one sugar. Monosaccharides occur in linear form, but
fold back to form a ring when formed in water. Glucose is an example of a monosaccharide. There are two
possible arrangements of the –OH group in glucose: -glucose and -glucose. Monosaccharides are very
hydrophilic and are the sweetest sugars.
Disaccharides consist of two monosaccharides linked together with glycosidic bonds. As in
monosaccharides, linkages can be - or - depending on the arrangements of the –OH group on carbon 1.
Disaccharides are also very hydrophilic because they contain the same functional group as monosaccharides.
However, disaccharides are less sweet than monosaccharides. Examples of disaccharides include sucrose and
lactose.
Polysaccharides are polymers of monosaccharides. As with monosaccharides and disaccharides,
polysaccharides contain - or -linkages. Although polysaccharides are polar and, thus, are hydrophilic,
because they are such huge molecules, they attract water, but cannot dissolve. Polysaccharides are used for
structural support in cells, for cell-to-cell communication, and for energy storage. Examples of
polysaccharides are starch and cellulose.
PTS: 1
REF: C
OBJ: 1.4 Carbohydrates and Lipids
LOC: B3.2
MSC: Evaluation
16. ANS:
Answers may vary. Sample answer: I would prefer to have a monosaccharide sweetener because
monosaccharides are sweeter than disaccharides.
PTS: 1
OBJ: 1.4 Carbohydrates and Lipids
LOC: B3.2
MSC: Reflect on Your Learning
17. ANS:
Both carbohydrates and lipids are made of carbon, hydrogen, and oxygen, although lipids contain less oxygen
than carbohydrates. Both carbohydrates and lipids function as energy sources. Carbohydrates are hydrophilic
molecules that dissolve in water, while lipids are non-polar and do not dissolve in water. Carbohydrates are
the most common biological molecules. Polymers are formed from linking subunits (monosaccharides).
Carbohydrates play a role in structural support and cell-to-cell communication. Carbohydrates also form the
building blocks of amino acids, lipids, and nucleic acids.
There are five types of lipids: fatty acids, fats, phospholipids, steroids, and waxes. Phospholipids are
ideal for forming cell membranes. Steroids regulate cellular activities, and waxes provide water resistance and
protection. Lipids do not form polymers.
PTS: 1
REF: T/I
OBJ: 1.4 Carbohydrates and Lipids
LOC: B3.2
MSC: Evaluation
18. ANS:
Fats, especially triglycerides, function efficiently as stored energy. Fats yield more than twice as much energy
as carbohydrates. Therefore, fats are an excellent source of energy in a diet. Storing fat is a very efficient way
of storing energy. Storing fatty tissue under the skin also provides insulation.
PTS: 1
OBJ: 1.4 Carbohydrates and Lipids
LOC: B3.2
MSC: Reflect on Your Learning
19. ANS:
A phospholipid consists of glycerol bound to two hydrophobic fatty acids and one charged phosphate group,
which binds to another hydrophilic group. This means that a phospholipid has a polar end (hydrophilic) and a
non-polar (hydrophobic) end. Phospholipids make up the lipid bilayer of cell membranes by facing the
hydrophilic end toward water and the hydrophobic end toward each other. The lipid bilayer allows some
molecules to diffuse into or out of the cell.
PTS: 1
REF: C
OBJ: 1.4 Carbohydrates and Lipids
LOC: B3.2
MSC: Analysis and Application
20. ANS:
Answer may vary. Sample answer: I use butter on my toast every morning. Butter is a fat that is derived from
animals. It is a saturated fat because it contains only saturated fatty acids with single bonds in the
hydrocarbon chain. Since the fatty acid chains are long and straight, they can be packed closely together to
form a solid. This tells me that butter is solid at room temperature, which is why I can spread it on my toast.
PTS: 1
OBJ: 1.4 Carbohydrates and Lipids
LOC: B3.2
MSC: Reflect on Your Learning
21. ANS:
Answers may vary. Sample answer:
(a) I found the information about carbohydrates and lipids easy to understand.
(c) I liked that the information about carbohydrates and lipids were summarized in a table. The tables made it
easy to remember the different types of carbohydrates and lipids.
PTS: 1
OBJ: 1.4 Carbohydrates and Lipids
LOC: B3.2
MSC: Reflect on Your Learning
22. ANS:
Polymerization is the linking together of monomers to form polymers through dehydration synthesis. Peptide
bonds form between the –NH2 group of one amino acid and the –COOH group of another amino acid.
Proteins are one or more polypeptide chains of more than 50 amino acids. Nucleic acids are formed from the
polymerization of nucleotides. One nucleotide is linked to another nucleotide by a phosphodiester bond,
which is a link formed between the nucleotides by a phosphate bridge.
PTS: 1
LOC: B3.2
REF: T/I
OBJ: 1.5 Proteins and Nucleic Acids
MSC: Analysis and Application
23. ANS:
The structure of a protein is related to the protein’s function. For example, long linear proteins, such as the
fibres of collagen and keratin, are structural proteins that provide framework support. Carrier proteins tend to
be compact globular proteins so that they can be easily transported around the body. Hemoglobin protein is an
example of a carrier protein. Enzymes that are involved in cellular respiration have prosthetic groups that
contain metal ions to help them function. Amylase is an example of an enzyme.
PTS: 1
REF: T/I
OBJ: 1.5 Proteins and Nucleic Acids
LOC: B3.2
MSC: Analysis and Application
24. ANS:
The primary structure of a protein refers to the sequence of amino acids in a polypeptide chain. If the
sequence is changed, the protein is changed. The secondary structure of a protein refers to its shape. Portions
of the polypeptide coil or fold into patterns because of hydrogen bonding. Two common secondary structures
are an -helix and a -pleated sheet. An -helix is a coil held together by hydrogen bonds. In a -pleated
sheet, the polypeptide chains are arranged side-by-side.
PTS: 1
REF: C
OBJ: 1.5 Proteins and Nucleic Acids
LOC: B3.2
MSC: Evaluation
25. ANS:
DNA and RNA are both nucleic acids that have different functions. DNA stores the hereditary information.
RNA is involved in protein synthesis. Both contain a 5-carbon ring-shaped sugar. DNA contains deoxyribose
while RNA contains ribose. DNA is a long polymer that contains four different nitrogenous bases: adenine,
guanine, cytosine, and thymine. In RNA, the bases are adenine, guanine, cytosine, and uracil. DNA is a
double-stranded molecule that has the shape of a double helix. RNA is a single stranded molecule.
PTS: 1
REF: C
OBJ: 1.5 Proteins and Nucleic Acids
LOC: B3.2
MSC: Evaluation
26. ANS:
Peptide bonds form between the amino acids to link them together. For example, the peptide bond forms
between the carboxyl group of serine and the amino group of tyrosine, and between the carboxyl group of
tyrosine and the amino group of cysteine.
PTS: 1
REF: C
OBJ: 1.5 Proteins and Nucleic Acids
LOC: B3.2
MSC: Analysis and Application
27. ANS:
Answers may vary. Sample answer: The boiling of an egg causes the egg white to denature.
PTS: 1
LOC: B3.2
28. ANS:
REF: A
OBJ: 1.5 Proteins and Nucleic Acids
MSC: Analysis and Application
The base sequence of the complementary strand is CAATGGATC. In DNA, G only bonds with C and T only
bonds with A.
PTS: 1
REF: T/I
OBJ: 1.5 Proteins and Nucleic Acids
LOC: B3.2
MSC: Analysis and Application
29. ANS:
Answers may vary. Sample answer: After reading about saturated fats, I will try and use less animal fats such
as butter. Before I read this chapter, I knew that there were concerns about fats and cholesterol, but I did not
really know what they were. I will also try and make sure that I get the eight essential amino acids in my diet.
PTS: 1
OBJ: 1.5 Proteins and Nucleic Acids
LOC: B3.2
MSC: Reflect on Your Learning
30. ANS:
Answers may vary. Sample answer: Linus Pauling was a respected scientist. This position helped him speak
out about nuclear weapons testing. He would have attracted audiences to hear him speak because of his
position. As a scientist, he was able to present scientific data and statistics to show that radioactive fallout
causes an increase in incidences of cancer, genetic disorders, and birth defects.
PTS: 1
REF: A
OBJ: 1.6 Biology Journal: Linus Pauling: Creativity and Controversy in Science and Society
LOC: B3.2
MSC: Evaluation
31. ANS:
Answers may vary. Sample answer: Linus Pauling claimed that consuming high doses of vitamins,
particularly vitamin C, could be used to treat cancer instead of chemotherapy. Although other studies did not
verify his work, Pauling refused to change his theory or to consider the evidence. Since Pauling was a
respected scientist, he should have been able to examine the evidence presented in the studies and made
conclusions based on the evidence rather than adamantly maintaining his position.
PTS: 1
OBJ: 1.6 Biology Journal: Linus Pauling: Creativity and Controversy in Science and Society
LOC: B3.2
MSC: Reflect on Your Learning
32. ANS:
Answers may vary. Sample answer:
(a) Before I read this chapter, I knew that each enzyme had a specific shape and catalyzed specific reactions.
But I did not know how enzymes worked exactly.
(b) I did not know that substrates only interact with specific active sites on an enzyme’s surface. I also better
understand how inhibitors prevent the action of enzymes and how enzymes are regulated by feedback
inhibition.
PTS: 1
OBJ: 1.7 Enzymes LOC: B3.4
MSC: Reflect on Your Learning
33. ANS:
Enzymes only react with specific substrates. Substrates with a particular shape (the key) can only bind to an
enzyme that has a complementary shape (the lock) in the same way as only a key with a particular shape will
open a specific lock. However the lock-and-key analogy is not completely accurate because an enzyme is not
a rigid object like a lock, but rather is able to change its shape to better accommodate the substrate. Since the
enzyme is able to change its shape, the active site is able to precisely bind with its substrate.
PTS: 1
34. ANS:
OBJ: 1.7 Enzymes LOC: B3.4
MSC: Reflect on Your Learning
Answers may vary. Sample answer: Scientific knowledge is constantly changing. I do not feel that this
weakens the validity of scientific knowledge. I believe it actually validates the knowledge because scientists
are constantly checking and revising scientific work. As well, theories are revised or updated as technology
makes it possible to discover new evidence.
PTS: 1
OBJ: 1.7 Enzymes LOC: B3.4
MSC: Reflect on Your Learning
35. ANS:
Enzymes have optimal pH values at which they work efficiently. A change in pH will affect the activity of
most enzymes. For example, pepsin, which is an enzyme in the stomach, has an optimal pH value of 1.5, the
pH of the stomach. If the pH of the stomach increases or decreases, the rate of the catalyzed reaction of pepsin
decreases.
PTS: 1
REF: A
OBJ: 1.7 Enzymes LOC: B3.4
MSC: Analysis and Application
36. ANS:
Changing the temperature affects an enzyme in two ways. Temperature can affect the rate of a chemical
reaction. As the temperature increases, the rate of a chemical reaction increases because the molecules start to
move around faster and there are more frequent collisions between reactants and enzymes. Temperature can
also affect the structure of an enzyme. Since most enzymes are proteins, high temperatures can cause enzymes
to denature as the hydrogen bonds involved in the protein’s tertiary structure break. When this happens, the
enzyme can no longer function. The two effects of temperature on an enzyme mean that as the temperature
increases, the reaction rate increases up to a point. At the point when the enzyme starts to denature, the
reaction rate decreases rapidly to zero.
PTS: 1
REF: C
OBJ: 1.7 Enzymes LOC: B3.4
MSC: Analysis and Application
37. ANS:
Answers may vary. Sample answer: We can use catalase and hydrogen peroxide to investigate how pH affects
the activity of the enzyme. Catalase breaks down hydrogen peroxide into water and oxygen gas. The
independent variable is pH, which can be altered by adding drops of acid, such as HCl, or base, NaOH, to a
particular volume of enzyme and substrate. The control variables are the temperature, and the volume and
concentration of catalase and hydrogen peroxide. The activity of the catalase is measured by how much
product (bubbles) is produced. We can infer that the pH is at the optimal value when the rate of the reaction is
at its maximum (there are plenty of bubbles produced). We can infer that the pH has denatured the enzyme
when the rate of reaction stops.
PTS: 1
REF: T/I
MSC: Analysis and Application
38. ANS:
OBJ: 1.7 Enzymes LOC: B3.4
Answers may vary. Sample answer: Enzymes are used in the production of various foods. For example,
cheese is produced using the enzyme chymosin. Bacteria are added to the milk and produce lactic acid as a
waste product. The lactic acid causes the pH of the milk to decrease, which causes the milk proteins to
denature. Chymosin is added to hydrolyze the milk protein casein, which causes the milk to coagulate into
cheese curds. Different fat-hydrolyzing enzymes are used to produce cheeses with different flavours.
Enzymes are also used to break down starch into glucose syrup that is used to sweeten different foods.
Enzymes are also used as cleaners. Laundry detergents contain enzymes that remove blood, grass, and
perspiration stains.
PTS: 1
REF: A
OBJ: 1.7 Enzymes LOC: B3.4
MSC: Analysis and Application
39. ANS:
Answers may vary. Sample answer: Chart comparing the structures in prokaryotic and eukaryotic cells is
shown below.
Structures
plasma membrane
nucleus
endomembrane system
ribosomes
Golgi bodies
mitochondria
cell wall
Prokaryotic cells
yes
no
no
yes
no
no
yes
flagellum or cilia
yes
PTS: 1
LOC: B3.1
40. ANS:
(a)
REF: C
MSC: Evaluation
Eukaryotic cells
yes
yes
yes
yes
yes
yes
no: animal cells
yes: plant cells, some protists, and fungal
cells
yes
OBJ: 2.1 Cell Structures
(b) The cell is a plant cell because it contains a cell wall, a central vacuole, and chloroplasts. Animal cells do
not have these organelles.
PTS: 1
REF: C
OBJ: 2.1 Cell Structures
LOC: B3.1
MSC: Evaluation
41. ANS:
These terms reflect the idea that prokaryotic cells evolved before the nucleus developed. I think that the terms
are accurate because prokaryotic cells do not have a nucleus and are more primitive than eukaryotic cells,
which have membrane-bound organelles that perform specific functions.
PTS: 1
OBJ: 2.1 Cell Structures
LOC: B3.1
MSC: Reflect on Your Learning
42. ANS:
The cell’s endomembrane system consists of the nucleus, rough and smooth ER, Golgi bodies, vesicles, and
plasma membrane all working together to allow the cell to function properly. The system’s major function is
to make and process the proteins and lipids that the cell uses or exports. In the nucleus, the DNA holds the
instructions for making the proteins. This information is transcribed into RNA, which exits the nucleus
through the nuclear membrane. The nucleolus produces ribosomes, which take positions on the rough
endoplasmic reticulum. Ribosomes synthesize polypeptide chains, which enter the rough ER, where they are
modified. Some polypeptides enter the smooth ER and become enzymes. Vesicles that bud from the ER
transport the proteins to the Golgi bodies. At the Golgi bodies, the proteins are sorted and packed into new
vesicles that carry them to the plasma membrane.
PTS: 1
LOC: B3.1
43. ANS:
REF: A
OBJ: 2.1 Cell Structures
MSC: Analysis and Application
PTS: 1
REF: C
OBJ: 2.1 Cell Structures
LOC: B3.1
MSC: Evaluation
44. ANS:
The theory of endosymbiosis is that bacteria became part of a host cell and evolved into mitochondria. I think
this is a plausible theory because mitochondria resemble bacteria in size, form, and biochemistry.
Mitochondria also contain their own DNA, which is similar to bacterial DNA. Mitochondria function
independently from the cell in that they divide and have their own ribosomes. Plastids may have also evolved
from endosymbiosis.
PTS: 1
REF: T/I
OBJ: 2.1 Cell Structures
LOC: B3.1
MSC: Evaluation
45. ANS:
The ribosomes produce the polypeptide chains, which are then sent to the endoplasmic reticulum to be
modified. This is like a production line where the product continues to another machine for fine-tuning. The
proteins are then sent to the Golgi bodies where they are sorted and packaged. This is like the packaging part
of a factory. The vacuoles act as a warehouse in the factory storing materials. The mitochondria provides the
energy for the factory. The lysosomes are the cleaning crew of the factory, breaking down waste materials.
PTS: 1
REF: C
OBJ: 2.1 Cell Structures
LOC: B3.1
MSC: Analysis and Application
46. ANS:
You would expect to find more mitochondria in a muscle cell. Since ATP is synthesized in the mitochondria,
cells with high demands for energy tend to have more mitochondria than cells that do not have high demand
for energy. Muscle cells have a high demand for energy and, thus, would have more mitochondria.
PTS: 1
REF: T/I
OBJ: 2.1 Cell Structures
LOC: B3.1
MSC: Analysis and Application
47. ANS:
Mitochondria and chloroplasts have related structures and functions. Both mitochondria and chloroplasts have
two membranes. Both organelles contain their own DNA. It is thought that mitochondria and chloroplasts
evolved from bacteria that were taken inside a host cell according to the theory of endosymbiosis. Both
organelles function to provide cells with energy (ATP). However, mitochondria make ATP in a series of
reactions known as cellular respiration while chloroplasts produce ATP through photosynthesis.
PTS: 1
REF: T/I
OBJ: 2.1 Cell Structures
LOC: B3.1
MSC: Evaluation
48. ANS:
Some eukaryotic and prokaryotic cells have one or more hairlike structures projecting from the cell’s surface.
Flagella tend to be long whiplike structures, while cilia tend to be tiny and numerous. The structure of flagella
and cilia are similar. Both are made of organized arrays of microtubules, which are long, hollow cylinders that
consist of subunits of the protein tubulin. Both flagella and cilia function to move the cell or to move water
and mucus around the cell.
PTS: 1
REF: T/I
OBJ: 2.1 Cell Structures
LOC: B3.1
MSC: Evaluation
49. ANS:
The plasma membrane forms a protective barrier around the cell, while the nuclear envelope surrounds the
nucleus. Both membranes regulate what enters and leaves the cell or nucleus. Both the plasma membrane and
the nuclear envelope consist of a phospholipid bilayer with different kinds of membrane proteins embedded in
the two lipid bilayers. The nuclear envelope contains nuclear pores. The nuclear membrane is a doubled
membrane.
PTS: 1
REF: T/I
OBJ: 2.1 Cell Structures
LOC: B3.1
MSC: Evaluation
50. ANS:
Answers may vary. Sample answer:
(a) I was already familiar with the structures of cells from previous grades so I found the information easy to
understand.
(c) I liked that the information about cell organelles was summarized in a table and a diagram. I could refer to
the table and diagram for a quick reminder of the function and location of the different organelles.
PTS: 1
OBJ: 2.1 Cell Structures
LOC: B3.1
MSC: Reflect on Your Learning
51. ANS:
CFTR is a membrane transport protein that moves negatively charged chloride ions out of lung and intestinal
tract cells to the surrounding mucus lining. This produces an electrical gradient across the membrane that
leads to positively charge sodium ions moving in the same direction. The high Na+ and Cl– concentrations on
the mucus side of the lining cause water to move by osmosis into the mucus lining.
PTS: 1
REF: C
OBJ: 2.2 Membrane Structure and Functions
LOC: B3.6
MSC: Analysis and Application
52. ANS:
The fluid mosaic model encompasses our current understanding of membrane structure. According to the
model, the membrane is a fluid lipid bilayer in which some proteins float freely. The term “mosaic” is used to
describe the wide assortment of proteins in the membrane. I think that “fluid mosaic model” is an accurate
name because it gives us a description of the membrane: a fluid layer with a mosaic of proteins.
PTS: 1
REF: T/I
OBJ: 2.2 Membrane Structure and Functions
LOC: B3.6
MSC: Evaluation
53. ANS:
The cell membrane is formed of lipids and proteins. Lipid molecules form the backbone of the membrane.
Phospholipids form a bilayer as the hydrophilic heads face outward and the hydrophobic tails face inward.
Membrane proteins are embedded in the lipid bilayer or positioned on the surface of the membrane. The
proteins transport substances through the membranes, provide enzymatic activity, trigger signals, and act as
attachment points and components in cell–cell recognition.
PTS: 1
LOC: B3.6
54. ANS:
REF: A
OBJ: 2.2 Membrane Structure and Functions
MSC: Analysis and Application
Membrane asymmetry refers to the fact that composition of proteins and other components of the internal
layer of the membrane bilayer differ from the external layer. Membrane asymmetry is an important
characteristic because each layer of the membrane performs different functions. For example, glycolipids and
carbohydrate groups attach to proteins on the external side of the membrane while the cytoskeleton binds to
proteins on the internal side of the membrane.
PTS: 1
REF: T/I
OBJ: 2.2 Membrane Structure and Functions
LOC: B3.6
MSC: Analysis and Application
55. ANS:
Membrane proteins provide transport, enzymatic activity, triggering signals, and attachment and recognition
points. Membrane proteins form channels or shift shape to make it possible for substances to shuttle from one
side of the membrane to the other. Some membrane proteins function as enzymes. Other membrane proteins
bind to hormones to trigger changes on the inner surface of the membrane, which leads to a chain of events
within the cell. Some membrane proteins act as attachment points for various cytoskeleton substances and
substances involved in cell-to-cell recognition. Other membrane proteins can recognize disease-causing
microbes and trigger an immune response.
PTS: 1
REF: C
OBJ: 2.2 Membrane Structure and Functions
LOC: B3.6
MSC: Evaluation
56. ANS:
Phospholipids have a polar head group and two non-polar tails. In an aqueous solution, phospholipids will
form a bilayer. This shape allows the hydrophobic tails to be buried in the interior and the hydrophilic heads
to be exposed to water. Phospholipids can do this in one of two ways: they can form bilayer vesicles with the
tails inward or they can form fluid bilayers (shown below) with the hydrophobic tails sandwiched between the
hydrophilic head groups. Phospholipids form a bilayer because this arrangement requires the lowest energy.
PTS: 1
REF: C
OBJ: 2.2 Membrane Structure and Functions
LOC: B3.6
MSC: Evaluation
57. ANS:
Sterols influence membrane fluidity. At low temperatures, sterols occupy the spaces between the lipid
molecules, putting the hydrophilic end at the polar end of the bilayer and the hydrophobic end into the nonpolar interior. This prevents the fatty acid tails from sticking together and forming a non-fluid gel. At high
temperatures, sterols restrain the movement of the lipid molecules and reduce the fluidity of the membrane.
Cholesterol is a sterol found in the lipid bilayer of animal cells.
PTS: 1
REF: T/I
OBJ: 2.2 Membrane Structure and Functions
LOC: B3.6
MSC: Analysis and Application
58. ANS:
Membrane proteins are divided into two types depending on their location in the membrane: integral
membrane proteins and peripheral membrane proteins. Integral membrane proteins are found within the lipid
bilayer. Membrane proteins have roles in transport of substances through the membrane, enzymatic activity,
triggering signals by binding to specific chemicals, and providing attachment points for cytoskeleton
components and recognition for cell–cell communication. The peripheral membrane proteins are positioned
on the surface of a membrane and do not interact with the hydrophobic core of the membrane. They are held
to membrane surfaces by noncovalent bonds (hydrogen bonds and ionic bonds), usually by interacting with
the exposed portions of integral proteins as well as directly with membrane lipid molecules.
PTS: 1
REF: T/I
OBJ: 2.2 Membrane Structure and Functions
LOC: B3.6
MSC: Analysis and Application
59. ANS:
Answers may vary. Sample answer:
(a) I have learned about the function of membranes in previous biology courses. I had a basic understanding
of how membranes worked as a barrier.
(b) I now understand the different components that make up a membrane, such as phospholipids and proteins,
and how they work together to allow the membrane to function properly.
PTS: 1
OBJ: 2.2 Membrane Structure and Functions
LOC: B3.6
MSC: Reflect on Your Learning
60. ANS:
Answers may vary. Sample answer: Since there are many components playing different roles in the cell
membrane, it may help the student to draw and label, or construct a model of a membrane. The student would
be able to see how the different components interact. Using a computer simulation that shows the relationship
between the different components may also help the student understand the interactions.
PTS: 1
OBJ: 2.2 Membrane Structure and Functions
LOC: B3.6
MSC: Reflect on Your Learning
61. ANS:
Answers may vary. Possible answer: I am interested in a career as a medial researcher. Understanding how
membranes work and how they are affected by genetic disorders or different substances may lead to the
understanding and eradication of various diseases, such as cystic fibrosis and depression.
PTS: 1
LOC: B3.6
62. ANS:
OBJ: 2.2 Membrane Structure and Functions
MSC: Reflect on Your Learning
Answers may vary. Sample answer: I think that nano-sized robots could be used to diagnose cancer. The
nanobots would be injected into people to see what kind of cancer they have and where the primary tumour is
located. Nanobots could then be used to deliver chemotherapy drugs specifically to the cancer cells or they
could be used to deliver radioactive isotopes to the cancer cells to destroy them.
PTS: 1
REF: A
OBJ: 2.3 Explore Applications of Cell Biology: Nanotechnology in Medicine
LOC: B1.2
MSC: Analysis and Application
63. ANS:
Answers may vary. Sample answer: One career that would involve working with nanobots would be in
pharmaceutical research. Understanding how various drugs pass through membranes and how a nanobot
would be able to deliver the drug, but not pass across the membrane itself, would be useful to this career.
PTS: 1
OBJ: 2.3 Explore Applications of Cell Biology: Nanotechnology in Medicine
LOC: A2.1
MSC: Reflect on Your Learning
64. ANS:
Both channel proteins and carrier proteins are integral membrane proteins that function in the facilitated
diffusion of ions and polar molecules. The difference between them is how they transport molecules. Channel
proteins form hydrophilic (water loving) pathways through which water and some ions can pass. Some
channels are voltage-gated, which means that they switch between open and closed states depending on the
changes in voltage across the membrane. Carrier proteins also provide passageways through the membrane by
binding to a specific molecule and carrying it across the membrane. During the transportation process, the
carrier protein changes shape, which effectively moves the transported molecule from one side of the
membrane to the other.
PTS: 1
REF: C
OBJ: 2.4 Transport across Membranes
LOC: B3.6
MSC: Evaluation
65. ANS:
The student is partly correct, in that water does flow through the tea bag. However, the tea bag is porous, like
a screen, whereas with osmosis, the liquid passes through a semi-permeable membrane. The tea leaves in the
tea bag diffuse throughout the water turning the water brown. The water flows into the tea bag because it is a
hypotonic condition.
PTS: 1
REF: T/I
OBJ: 2.4 Transport across Membranes
LOC: B3.6
MSC: Evaluation
66. ANS:
I predict that, if you put a saltwater fish into fresh water, it will die. This is because the freshwater solution
surrounding the cells of the fish contains a lower concentration of salt than the cells. Thus, the solution is
hypotonic to the cells. When a cell is in a hypotonic solution, water enters by osmosis and the cell tends to
swell to the point of bursting.
PTS: 1
REF: A
OBJ: 2.4 Transport across Membranes
LOC: B3.6
MSC: Evaluation
67. ANS:
Passive transport is the movement of a substance without using energy. There are three methods of passive
transport: simple diffusion, facilitated diffusion, and osmosis. Simple diffusion is the ability of small nonpolar molecules, such as oxygen and carbon dioxide, to cross a membrane easily from an area of high
concentration to an area of low concentration. Facilitated diffusion is the ability of ions and polar molecules
to cross the membrane with the help of transport proteins. Channel proteins form channels in the membrane
through which ions and water can pass. Carrier proteins bind to a solute, such as glucose, and transport it
across the membrane. The carrier protein does this by changing shape. Osmosis is the diffusion of water
through a membrane from an area of low solute concentration (high water concentration) to an area of high
solute concentration (low water concentration).
PTS: 1
REF: A
OBJ: 2.4 Transport across Membranes
LOC: B3.6
MSC: Evaluation
68. ANS:
Answers will vary. Sample answer: You will need some animal (sheep or pig) blood cells and some Elodea
leaves. Make three wet mount slides of the red blood cells. Dilute one slide with saline solution (isotonic).
Dilute the second slide with distilled water (hypotonic) and the third slide with concentrated saline solution (5
%, hypertonic). Look at the shapes of the red blood cells under a microscope. To test the plant cells, use pond
water (isotonic), distilled water, and concentrated saline solution. Look at the shapes of the plant cells under a
microscope.
PTS: 1
REF: A
OBJ: 2.4 Transport across Membranes
LOC: B3.6
MSC: Evaluation
69. ANS:
In a hypotonic condition, the solution surrounding a cell contains a lower concentration of dissolved
substances than the concentration in the cell. Water enters the cell and the cell expands. In a hypertonic
condition, the solution surrounding the cell contains a higher concentration of dissolved substances than the
concentration in the cell. Water leaves the cell and the cell shrinks. In an isotonic condition, the solution
surrounding the cell contains the same concentration of dissolved substances as the cell. There is no
movement of water and the cell stays the same.
PTS: 1
REF: C
OBJ: 2.4 Transport across Membranes
LOC: B3.6
MSC: Evaluation
70. ANS:
When the red blood cells are placed in distilled water, it is a hypotonic condition. In this case, the
concentration of water inside the red blood cell is lower than the concentration of water outside the cell. I
predict that water would enter the red blood cells and cause them to expand and perhaps burst.
PTS: 1
REF: A
OBJ: 2.4 Transport across Membranes
LOC: B3.6
MSC: Evaluation
71. ANS:
Adding salt to meat creates a hypertonic condition. The concentration of the salt outside the cells is higher
than it is inside the cells. This causes water to leave the cells and the meat becomes dehydrated. Bacteria
cannot grow easily in these conditions so the meat is preserved.
PTS: 1
LOC: B3.6
72. ANS:
REF: A
OBJ: 2.4 Transport across Membranes
MSC: Analysis and Application
The sodium–potassium pump uses energy in the form of ATP to pump molecules across a membrane. The
mechanism simultaneously pumps three Na+ ions out of the cell and two K+ ions into the cell. I believe that
the name is accurate because the mechanism pumps charged ions against the concentration gradient much like
you have to push air into an almost full tire using an air pump.
PTS: 1
REF: T/I
OBJ: 2.4 Transport across Membranes
LOC: B3.6
MSC: Evaluation
73. ANS:
Both endocytosis and exocytosis are methods used to transport large particles in and out of cells. Both
methods require energy. However, the methods are opposite of one another. In exocytosis, waste products are
placed in a secretory vesicle that moves through the cytosol to fuse with the plasma membrane. The contents
of the vesicle are released to the environment surrounding the cell. In endocytosis, proteins and other
substances are trapped in a pit in the plasma membrane. The pit pinches off into a vesicle that is inside the
cell. There are three types of endocytosis: bulk-phase endocytosis, where molecules are taken into the cell
along with the surrounding solution, receptor-mediated endocytosis, where molecules are taken in by receptor
proteins, and phagocytosis where the cell engulfs the material.
PTS: 1
REF: C
OBJ: 2.4 Transport across Membranes
LOC: B3.6
MSC: Evaluation
74. ANS:
Answers may vary. Sample answer: I found the diagrams showing the different transportation methods to be
helpful. However, the table that listed the characteristics of the transport mechanisms was the most helpful
because it provided a summary of the text.
PTS: 1
OBJ: 2.4 Transport across Membranes
LOC: B3.6
MSC: Reflect on Your Learning
75. ANS:
Answers may vary. Sample answer: I found the differences between hypotonic and hypertonic the most
difficult to comprehend. I found it helpful to draw each condition and indicate on the diagram the direction
that water moves (into or out of the cell).
PTS: 1
OBJ: 2.4 Transport across Membranes
MSC: Reflect on Your Learning
76. ANS:
LOC: B3.6
Answers may vary. Sample answer: I think that hypotonic and hypertonic solutions are important to the
ability of cells, such as red blood cells, to maintain their concentration of solutes. When you give blood, red
blood cells are kept in an isotonic plasma solution. If red blood cells were stored in water, water would enter
the cells and cause them to swell.
PTS: 1
OBJ: 2.4 Transport across Membranes
MSC: Reflect on Your Learning
LOC: B3.6