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PRACTICE QUESTIONS: THE BIOCHEMISTRY OF LIFE
1. Water has a high capacity for heat (thermal capacity). This is an advantage in living cells
because …. (Select one of the following statements)
any rise in temperature is small in comparison with the amount of heat absorbed by
a cell
any rise in temperature is large in comparison with the amount of heat absorbed by
a cell
the 75% water in a cell does not retain a lot of heat
any change in temperature will cause a cell to heat up or cool down quickly.
2. (a) Give three examples of cell structures which contain structural proteins.
(b) What is the other type of protein in a cell?
3. Name the chemical elements present in a protein.
4. What name is given to the sub-units which make up all proteins?
5. A protein molecule which is denatured, has
split into smaller molecules
changed its shape
combined with another molecule
been diluted..
6. What kind of substance is a lipid?
7. In a cell, where are lipids found?
8. (a) What are the two types of chemical compound that combine to form a lipid?
(b) What elements are present in a lipid?
9. (a) Name four examples of compounds which are classed as carbohydrate.
(b) What elements are present in carbohydrates?
10. Write the formula for glucose.
11. If
molecule.
represents a glucose molecule draw (a) a maltose molecule, (b) part of a starch
12. Select the most appropriate words from the list below to complete the following
paragraph All cells contain ……. which are ……. and act as …..…. which ….…. chemical
reactions. The reactions do not ….….the ….…. which can take part in further reactions.
substances, proteins, enzymes, catalysts, speed up, use up, slow down
13. Enzymes will usually react with only one substance. This can be explained by the 'lock
and key' theory. If this theory is correct, which of the following substances, represented
by P, Q, R and S would be acted on by enzyme A?
A
P
Q
R
S
14. If an enzyme-controlled reaction normally takes place at 10ºC, in general terms how will
the reaction be affected by :
a fall in temperature to 2°C ,
a rise in temperature to 20°C.
a rise in temperature to 65°C?
15. If an enzyme is denatured, why does it no longer work?
17 The graph shows the rate of an enzyme
reaction at different levels of acidity or
alkalinity (pH). From the graph, what is the
optimum pH for this enzyme?
rate of
(a) pH 2 (c) pH 10
reaction
(b) pH 7 (d) none of these.
pH
2
4
18 A protein-digesting enzyme when mixed with starch solution would
(a) have no action
(c) produce glucose
(b) produce amino acids (d) digest the starch?
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8
10
Select the most appropriate words from the list below to complete the following
paragraph.
All enzymes are produced inside ……. Enzymes which do their work outside cells are
called ……. Enzymes which do their work inside cells are called …….. Most of our digestive
enzymes are examples of ……. enzymes.
animals, extra-cellular, intra-cellular, cells, digestive, nuclei, catalysts.
What does the enzyme catalase do?
Substance A is being investigated to see if it is an enzyme. When substance A is mixed with
substance B a reaction takes place. A control experiment is conducted using a sample of A
which has been boiled.
a. Why is boiling used as a control?
b. If the reaction still worked after A had been boiled, what might be your
interpretation?
Short Answer questions
1. Explain the relationship among atoms, elements and compounds (i.e. define each term and then explain
how the terms are related).
2. Explain the phenomena of cohesion and adhesion as they apply to water. Give an example of each property.
(4 points)
3. Explain the relationship between monomers and polymers, using polysaccharides as an example.
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question. WRITE YOUR ANSWERS IN
CAPITAL LETTERS: A, B, C, D, E.
Basic Chemistry
____
4. About 25 of the 92 natural elements are known to be essential to life. Which four of these 25
elements make up approximately 96% of living matter?
A. Carbon, sodium, chlorine, nitrogen
B. Carbon, sulfur, phosphorus, hydrogen
C. Oxygen, hydrogen, calcium, sodium
D. Carbon, hydrogen, nitrogen, oxygen
E. Carbon, oxygen, sulfur, calcium
____
5. Which of the following statements is false?
A. Atoms of the various elements differ in their number of subatomic particles.
B. All atoms of a particular element have the same number of protons in their nuclei.
C. The neutrons and protons present in the nucleus of an atom are almost identical in mass
D. An atom is the smallest unit of an element that still retains the properties of the
element.
E. Protons and electrons are electrically charged particles, in which protons have one unit
of negative charge, and electrons have one unit of positive charge.
____
6. How do isotopes of the same element differ from each other?
A. Number of protons
B. Number of electrons
C. Number of neutrons
D. Valence electron distribution
E. Amount of radioactivity
Use the information extracted from the periodic table in the figure below to answer the following
questions.
____
7. From its atomic number of 15, it is possible to predict that the phosphorus atom has
A. 15 neutrons and 15 electrons.
B. 15 protons and 15 electrons.
C. 16 protons and 15 neutrons.
D. 8 electrons in its outermost electron shell.
E. Both B and C are correct
____
8. How many neutrons are present in the nucleus of the phosphorus (P) atom above?
A. 8
B. 15
C. 16
D. 31
E. 46
____
9.
What results from an unequal sharing of electrons between atoms?
A. A nonpolar covalent bond
B. A polar covalent bond
C. An ionic bond
D. A hydrogen bond
____ 10. Which of the following is possible due to the high surface tension of water?
A. Lakes don't freeze solid in winter, despite low temperatures.
B. A water strider can walk across the surface of a small pond.
C. Organisms resist temperature changes, although they give off heat due to chemical
reactions.
D. Water can act as a solvent.
E. The pH of water remains exactly neutral.
____ 11. Water's high specific heat is mainly a consequence of the
A. Small size of the water molecules.
B. High specific heat of oxygen and hydrogen atoms.
C. Absorption and release of heat when hydrogen bonds break and form.
D. Fact that water is a poor heat conductor.
E. Inability of water to dissipate heat into dry air.
____ 12. At what temperature is water most dense?
A. 0°C
B. 4°C
C. 32°C
D. 100°C
E. 273°C
____ 13. Hydrophobic substances such as vegetable oil are
A. Nonpolar substances that repel water molecules.
B. Nonpolar substances that have an attraction for water molecules.
C. Polar substances that repel water molecules.
D. Polar substances that have an affinity for water.
E. Charged molecules that hydrogen-bond with water molecules.
____ 14. What would be the pH of a solution with a hydrogen ion [H+] concentration of 10-8 M?
A. pH 2
B. pH 4
C. pH 6
D. pH 8
E. pH 10
____ 15. Which of the following solutions has the greatest concentration of hydroxide ions [OH-]?
A. Lemon juice at pH 2
B. Vinegar at pH 3
C. Tomato juice at pH 4
D. Urine at pH 6
E. Seawater at pH 8
____ 16. Which of the following statements is true about buffer solutions?
A. They maintain a constant pH when bases are added to them but not when acids are
added to them.
B. They maintain a constant pH when acids are added to them but not when bases are
added to them.
C. They maintain a constant pH of exactly 7 in all living cells and biological fluids.
D. They maintain a relatively constant pH.
E. They are found only in living systems and biological fluids.
Use the molecules shown in the figure below to answer the following questions.
____ 17. Which molecule would be a component of an amino acid?
A. Molecule A
B. Molecule B
C. Molecule C
D. Molecule D
E. Molecule E
____ 18. Polymers of polysaccharides, fats, and proteins are all synthesized from monomers by which
process?
A. Connecting monosaccharides together (condensation reactions)
B. The addition of water to each monomer (hydrolysis)
C. The removal of water (dehydration reactions)
D. Ionic bonding of the monomers
E. The formation of disulfide bridges between monomers
____
19.
Lactose, a sugar in milk, is composed of one glucose molecule joined by a glycosidic
linkage to one galactose molecule. How is lactose classified?
A. As a pentose
B. As a hexose
C. As a monosaccharide
D. As a disaccharide
E. As a polysaccharide
____ 20. Which of the following is true of cellulose?
A. It is a polymer composed of sucrose monomers.
B. It is a storage polysaccharide for energy in plant cells.
C. It is a storage polysaccharide for energy in animal cells.
D. It is a major structural component of plant cell walls.
E. It is a major structural component of animal cell plasma membranes.
____ 21. Which of the following is (are) true for the class of large biological molecules known as lipids?
A. They are insoluble in water.
B. They are an important constituent of cell membranes.
C. They contain twice as much energy (kilocalories) as an equivalent weight of
polysaccharide.
D. Only A and B are correct.
E. A, B, and C are correct.
____ 22. The molecule shown in the figure below is a
A. Polysaccharide.
B. Polypeptide.
C. Saturated fatty acid.
D. Triacylglycerol.
E. Unsaturated fatty acid.
____ 23. The 20 different amino acids found in polypeptides exhibit different chemical and physical
properties because of different
A. Carboxyl groups attached to an alpha
B. Amino groups attached to an alpha
C. Side chains (R groups).
D. Alpha
carbons.
E. Asymmetric carbons.
carbon
carbon
____ 24. The chemical reaction illustrated in the figure below results in the formation of a (an)
A. Ionic bond.
B. Peptide bond.
C. Glycosidic linkage.
D. Ester linkage.
E. Phosphodiester linkage
____25. Why can water have no net charge but have slight charges in different parts of the molecule?
A. The oxygen end is slightly negative and the hydrogen end is slightly positive
B. The hydrogen end is slightly negative and the oxygen end is slightly positive
C. The hydrogen and oxygen ends change in polarity
D. Because it is hydrophobic
____ 26. What are the three components of ribonucleic acid?
A. Ribose, phosphate and a nitrogen-containing base
B. Deoxyribose, phosphate and a nitrogen-containing base
C. Two ribose sugars and a nitrogen containing base
D. Ribose, phosphate and two nitrogen-containing bases
E. Ribose, phosphate and a sulphur-containing base
____ 27. Which two functional groups are found in all amino acids?
A. Amino and carboxyl
B. Amino and ketone
C. Alcohol and carboxyl
D. Alcohol and hydroxyl
E. Hydroxyl and carbonyl
____ 28. The
helix and the
pleated sheet are both common polypeptide forms found in which level of
protein structure?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
E. All of the above
____ 29. Double helix describes the structure of:
A. Quaternary structure of a protein
B. Cholesterol
C. Phospholipid
D. Deoxyribonucleic acid
E. Starch
____ 30. Which of the following descriptions best fits the class of molecules known as nucleotides?
A. A nitrogenous base and a phosphate group
B. A nitrogenous base and a pentose sugar
C. A nitrogenous base, a phosphate group, and a pentose sugar
D. A phosphate group and an adenine or uracil
E. A pentose sugar and a purine or pyrimidine
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