TEST BANK FOR PRINCIPLES OF
BIOCHEMISTRY 4TH EDITION BY
ROBERT A. HORTON
Test Bank for Principles of Biochemistry 4th Edition by Robert A. Horton
Chapter 1: Introduction to Biochemistry
1) Wohler showed that a chemical found only in living organisms can be made from inorganic
substances when he synthesized
A) Ammonium cyanate
B) Amino acids
C) Urea
D) Uric acid
Answer: C
Rationale: Friedrich Wöhler synthesized urea in 1828 from ammonium cyanate, demonstrating that
organic compounds could be produced from inorganic substances. This was a landmark experiment that
helped disprove vitalism, the belief that organic compounds could only be produced by living organisms.
2) The lock-and-key theory described the action of
A) enzymes as keys that fit different chemicals.
B) substrates as keys that fit different enzymes.
C) enzymes as locks that fit other enzymes.
D) substrates as locks that fit different enzymes.
Answer: B
Rationale: Emil Fischer's lock-and-key model proposed that the enzyme acts as the "lock" with a specific
shape, and the substrate acts as the "key" that fits into that specific lock. Only substrates with the
correct complementary shape can bind to the enzyme's active site.
3) According to Crick's Central Dogma of molecular Biology, there can be NO transfer of information
from
,A) DNA to RNA.
B) RNA to RNA.
C) RNA to protein.
D) protein to RNA.
Answer: D
Rationale: The Central Dogma states that genetic information flows from DNA to RNA to protein. It
specifically excludes the transfer of information from protein to RNA or DNA. While some exceptions
exist (like reverse transcription from RNA to DNA in retroviruses), information never flows from protein
back to nucleic acids.
4) What is the correct order in which these key breakthroughs in biochemistry occurred?
I. Watson and Crick DNA structure
II. Crick Central dogma
III. Avery, MacLeod and McCarty DNA work on Streptococcus
IV. Widespread use of computers
A) I, II, III, IV
B) III, I, II, IV
C) II, I, III, IV
D) IV, III, I, II
Answer: B
Rationale: The correct chronological order is: III (Avery, MacLeod and McCarty's work showing DNA is
the genetic material, 1944), I (Watson and Crick's DNA structure, 1953), II (Crick's Central Dogma, 1958),
IV (widespread use of computers in biochemistry, 1970s onward).
5) Which elements account for more than 97% of the weight of most organisms?
A) C, H, N, Mg, O, S
B) C, H, N, O, P, S
C) C, H, N
D) Fe, C, H, O, P
E) Ca<⁺, K⁺, Na⁺, Mg<⁺, Cl⁻
Answer: B
,Rationale: Carbon (C), hydrogen (H), nitrogen (N), oxygen (O), phosphorus (P), and sulfur (S) together
account for more than 97% of the weight of most organisms. These six elements are the essential
building blocks of biological molecules including carbohydrates, lipids, proteins, and nucleic acids.
6) Which linkage(s) occur extensively in nucleotides?
A) Amide.
B) Phosphoanhydride.
C) Phosphate ester.
D) Ether.
E) Both B and C above.
Answer: E
Rationale: Nucleotides contain both phosphoanhydride bonds (between phosphate groups, as in ATP)
and phosphate ester bonds (connecting the phosphate group to the sugar). Amide bonds are found in
proteins, and ether linkages are not characteristic of nucleotides.
7) Which functional group is shown?
[image]
A) Primary amine.
B) Acyl.
C) Amide.
D) Anhydride.
E) Nitrile.
Answer: C
Rationale: The functional group shown is an amide bond, which consists of a carbonyl group (C=O)
directly bonded to a nitrogen atom (N-H). This is the characteristic linkage found in peptide bonds
between amino acids in proteins.
8) Proteins in biological membranes may be
A) porous.
B) attached to the membrane surface.
C) span the membrane.
D) all of the above.
E) B and C only.
, Answer: D
Rationale: Membrane proteins can exist in various forms: they can span the entire membrane
(transmembrane proteins), be attached to the membrane surface (peripheral proteins), or form
pores/channels. Some membrane proteins combine these features in complex arrangements.
9) A dipeptide forms when a ______ functional group of one amino acid reacts with the ______
functional group of another amino acid to form a ______ bond.
A) carboxylate, amino, double
B) carboxylate, amino, enzyme
C) amino, carboxylate, phosphate
D) amino, carboxylate, peptide
Answer: D
Rationale: A dipeptide forms through a dehydration synthesis reaction where the amino group (-NH₂) of
one amino acid reacts with the carboxylate group (-COOH) of another amino acid, forming a peptide
bond (C-N bond) with the release of water.
10) Sugars such as glucose are monomers of polysaccharides that are linked together when covalent
bonds form between one ______ group of one sugar to the same group on another sugar.
A) ester
B) carboxyl
C) amino
D) hydroxyl
Answer: D
Rationale: Polysaccharides are formed when glycosidic bonds connect sugar monomers. These bonds
form between the hydroxyl (-OH) groups of adjacent sugar molecules through dehydration synthesis
reactions, releasing water.
11) Which statement about cellulose is false?
A) It is the most abundant polysaccharide in nature.
B) Its monomers are joined by glycosidic bonds.
C) It is present in the stems of flowering plants.
D) The hydroxyl groups of neighboring cellulose molecules interact to form strong, insoluble fibers.
E) It is a branched polymer of glucose.
BIOCHEMISTRY 4TH EDITION BY
ROBERT A. HORTON
Test Bank for Principles of Biochemistry 4th Edition by Robert A. Horton
Chapter 1: Introduction to Biochemistry
1) Wohler showed that a chemical found only in living organisms can be made from inorganic
substances when he synthesized
A) Ammonium cyanate
B) Amino acids
C) Urea
D) Uric acid
Answer: C
Rationale: Friedrich Wöhler synthesized urea in 1828 from ammonium cyanate, demonstrating that
organic compounds could be produced from inorganic substances. This was a landmark experiment that
helped disprove vitalism, the belief that organic compounds could only be produced by living organisms.
2) The lock-and-key theory described the action of
A) enzymes as keys that fit different chemicals.
B) substrates as keys that fit different enzymes.
C) enzymes as locks that fit other enzymes.
D) substrates as locks that fit different enzymes.
Answer: B
Rationale: Emil Fischer's lock-and-key model proposed that the enzyme acts as the "lock" with a specific
shape, and the substrate acts as the "key" that fits into that specific lock. Only substrates with the
correct complementary shape can bind to the enzyme's active site.
3) According to Crick's Central Dogma of molecular Biology, there can be NO transfer of information
from
,A) DNA to RNA.
B) RNA to RNA.
C) RNA to protein.
D) protein to RNA.
Answer: D
Rationale: The Central Dogma states that genetic information flows from DNA to RNA to protein. It
specifically excludes the transfer of information from protein to RNA or DNA. While some exceptions
exist (like reverse transcription from RNA to DNA in retroviruses), information never flows from protein
back to nucleic acids.
4) What is the correct order in which these key breakthroughs in biochemistry occurred?
I. Watson and Crick DNA structure
II. Crick Central dogma
III. Avery, MacLeod and McCarty DNA work on Streptococcus
IV. Widespread use of computers
A) I, II, III, IV
B) III, I, II, IV
C) II, I, III, IV
D) IV, III, I, II
Answer: B
Rationale: The correct chronological order is: III (Avery, MacLeod and McCarty's work showing DNA is
the genetic material, 1944), I (Watson and Crick's DNA structure, 1953), II (Crick's Central Dogma, 1958),
IV (widespread use of computers in biochemistry, 1970s onward).
5) Which elements account for more than 97% of the weight of most organisms?
A) C, H, N, Mg, O, S
B) C, H, N, O, P, S
C) C, H, N
D) Fe, C, H, O, P
E) Ca<⁺, K⁺, Na⁺, Mg<⁺, Cl⁻
Answer: B
,Rationale: Carbon (C), hydrogen (H), nitrogen (N), oxygen (O), phosphorus (P), and sulfur (S) together
account for more than 97% of the weight of most organisms. These six elements are the essential
building blocks of biological molecules including carbohydrates, lipids, proteins, and nucleic acids.
6) Which linkage(s) occur extensively in nucleotides?
A) Amide.
B) Phosphoanhydride.
C) Phosphate ester.
D) Ether.
E) Both B and C above.
Answer: E
Rationale: Nucleotides contain both phosphoanhydride bonds (between phosphate groups, as in ATP)
and phosphate ester bonds (connecting the phosphate group to the sugar). Amide bonds are found in
proteins, and ether linkages are not characteristic of nucleotides.
7) Which functional group is shown?
[image]
A) Primary amine.
B) Acyl.
C) Amide.
D) Anhydride.
E) Nitrile.
Answer: C
Rationale: The functional group shown is an amide bond, which consists of a carbonyl group (C=O)
directly bonded to a nitrogen atom (N-H). This is the characteristic linkage found in peptide bonds
between amino acids in proteins.
8) Proteins in biological membranes may be
A) porous.
B) attached to the membrane surface.
C) span the membrane.
D) all of the above.
E) B and C only.
, Answer: D
Rationale: Membrane proteins can exist in various forms: they can span the entire membrane
(transmembrane proteins), be attached to the membrane surface (peripheral proteins), or form
pores/channels. Some membrane proteins combine these features in complex arrangements.
9) A dipeptide forms when a ______ functional group of one amino acid reacts with the ______
functional group of another amino acid to form a ______ bond.
A) carboxylate, amino, double
B) carboxylate, amino, enzyme
C) amino, carboxylate, phosphate
D) amino, carboxylate, peptide
Answer: D
Rationale: A dipeptide forms through a dehydration synthesis reaction where the amino group (-NH₂) of
one amino acid reacts with the carboxylate group (-COOH) of another amino acid, forming a peptide
bond (C-N bond) with the release of water.
10) Sugars such as glucose are monomers of polysaccharides that are linked together when covalent
bonds form between one ______ group of one sugar to the same group on another sugar.
A) ester
B) carboxyl
C) amino
D) hydroxyl
Answer: D
Rationale: Polysaccharides are formed when glycosidic bonds connect sugar monomers. These bonds
form between the hydroxyl (-OH) groups of adjacent sugar molecules through dehydration synthesis
reactions, releasing water.
11) Which statement about cellulose is false?
A) It is the most abundant polysaccharide in nature.
B) Its monomers are joined by glycosidic bonds.
C) It is present in the stems of flowering plants.
D) The hydroxyl groups of neighboring cellulose molecules interact to form strong, insoluble fibers.
E) It is a branched polymer of glucose.
