BIO111 Exam 1 Actual Exam V3 | BIO111 General Biology (BIO111
Exam 1) | University of California, Los Angeles
1. A scientist observes that a specific plant species grows taller in sunlight than in shade and
proposes that light intensity directly affects growth rate. This proposal is an example of which
step in the scientific method?
A. A hypothesis
B. A scientific theory
C. A controlled experiment
D. A statistical analysis
Answer: A
Rationale: A hypothesis is a tentative explanation for an observation that can be tested
through experimentation. It serves as a starting point for further investigation rather than
a proven fact. In this scenario, the scientist is making an educated guess about the
relationship between light and growth.
2. Which type of chemical bond involves the unequal sharing of electrons between two
atoms, resulting in partial charges?
A. Polar covalent bond
B. Ionic bond
C. Hydrogen bond
D. Nonpolar covalent bond
Answer: A
Rationale: Polar covalent bonds occur when atoms with different electronegativities share
electrons. This causes one atom to pull electrons closer, creating a dipole with partial
positive and negative regions. Water molecules are a classic example of this type of
bonding.
3. Water has a high specific heat, which means it can absorb a large amount of heat with only
a slight change in temperature. What is the primary reason for this property?
A. The density of ice compared to liquid water
B. The formation and breaking of hydrogen bonds
C. The presence of ionic bonds between oxygen and hydrogen
D. The low molecular weight of water
,Answer: B
Rationale: Hydrogen bonds require energy to break before water molecules can move
faster and increase in temperature. When the temperature drops, many hydrogen bonds
form, releasing energy. This buffering capacity is crucial for maintaining stable
temperatures in biological systems.
4. If the pH of a solution is decreased from 7 to 5, how has the concentration of hydrogen ions
(H+) changed?
A. It has decreased by 2 times
B. It has increased by 2 times
C. It has decreased by 100 times
D. It has increased by 100 times
Answer: D
Rationale: The pH scale is logarithmic, meaning each unit represents a tenfold change in
H+ concentration. Moving from pH 7 to pH 5 involves two units, which is 10 times 10, or
100. A lower pH indicates a higher concentration of hydrogen ions.
5. Which of the following functional groups is characteristic of alcohols and helps increase the
solubility of organic molecules in water?
A. Carboxyl group
B. Amino group
C. Hydroxyl group
D. Sulfhydryl group
Answer: C
Rationale: The hydroxyl group consists of a hydrogen atom bonded to an oxygen atom (-
OH). It is polar due to the electronegativity of oxygen, allowing it to form hydrogen bonds
with water. This polarity makes molecules like ethanol and glucose soluble in aqueous
environments.
6. What is the chemical reaction mechanism by which cells build polymers from monomers?
A. Dehydration synthesis
B. Hydrolysis
C. Ionic ionization
D. Hydrogenation
Answer: A
, Rationale: Dehydration synthesis involves the removal of a water molecule to create a
covalent bond between two monomers. One monomer provides a hydroxyl group while the
other provides a hydrogen atom. This process is essential for the formation of complex
macromolecules like proteins and DNA.
7. Starch and cellulose are both polymers of glucose, yet humans can digest starch but not
cellulose. Why is this the case?
A. Starch is made of glucose, while cellulose is made of fructose
B. Starch contains nitrogen while cellulose does not
C. Cellulose is too large to be absorbed by the human gut
D. The glycosidic linkages in starch and cellulose have different configurations
Answer: D
Rationale: Starch consists of alpha-glucose monomers, while cellulose consists of beta-
glucose monomers. Human enzymes are specific to the alpha-linkages and cannot break the
beta-linkages found in cellulose. This structural difference highlights the relationship
between molecular shape and biological function.
8. Which class of lipids is characterized by a skeleton consisting of four fused rings?
A. Phospholipids
B. Steroids
C. Triglycerides
D. Saturated fats
Answer: B
Rationale: Steroids like cholesterol and testosterone have a unique structure of four
interconnected carbon rings. Unlike other lipids, they do not contain fatty acid tails. They
function primarily as signaling molecules or structural components of cell membranes.
9. What type of bond maintains the secondary structure of a protein, such as an alpha-helix
or a beta-pleated sheet?
A. Peptide bonds between amino acids
B. Hydrogen bonds between the backbone atoms
C. Disulfide bridges between R-groups
D. Hydrophobic interactions
Answer: B
Rationale: Secondary structure is formed by hydrogen bonding between the oxygen of the
carboxyl group and the hydrogen of the amino group in the polypeptide backbone. These
Exam 1) | University of California, Los Angeles
1. A scientist observes that a specific plant species grows taller in sunlight than in shade and
proposes that light intensity directly affects growth rate. This proposal is an example of which
step in the scientific method?
A. A hypothesis
B. A scientific theory
C. A controlled experiment
D. A statistical analysis
Answer: A
Rationale: A hypothesis is a tentative explanation for an observation that can be tested
through experimentation. It serves as a starting point for further investigation rather than
a proven fact. In this scenario, the scientist is making an educated guess about the
relationship between light and growth.
2. Which type of chemical bond involves the unequal sharing of electrons between two
atoms, resulting in partial charges?
A. Polar covalent bond
B. Ionic bond
C. Hydrogen bond
D. Nonpolar covalent bond
Answer: A
Rationale: Polar covalent bonds occur when atoms with different electronegativities share
electrons. This causes one atom to pull electrons closer, creating a dipole with partial
positive and negative regions. Water molecules are a classic example of this type of
bonding.
3. Water has a high specific heat, which means it can absorb a large amount of heat with only
a slight change in temperature. What is the primary reason for this property?
A. The density of ice compared to liquid water
B. The formation and breaking of hydrogen bonds
C. The presence of ionic bonds between oxygen and hydrogen
D. The low molecular weight of water
,Answer: B
Rationale: Hydrogen bonds require energy to break before water molecules can move
faster and increase in temperature. When the temperature drops, many hydrogen bonds
form, releasing energy. This buffering capacity is crucial for maintaining stable
temperatures in biological systems.
4. If the pH of a solution is decreased from 7 to 5, how has the concentration of hydrogen ions
(H+) changed?
A. It has decreased by 2 times
B. It has increased by 2 times
C. It has decreased by 100 times
D. It has increased by 100 times
Answer: D
Rationale: The pH scale is logarithmic, meaning each unit represents a tenfold change in
H+ concentration. Moving from pH 7 to pH 5 involves two units, which is 10 times 10, or
100. A lower pH indicates a higher concentration of hydrogen ions.
5. Which of the following functional groups is characteristic of alcohols and helps increase the
solubility of organic molecules in water?
A. Carboxyl group
B. Amino group
C. Hydroxyl group
D. Sulfhydryl group
Answer: C
Rationale: The hydroxyl group consists of a hydrogen atom bonded to an oxygen atom (-
OH). It is polar due to the electronegativity of oxygen, allowing it to form hydrogen bonds
with water. This polarity makes molecules like ethanol and glucose soluble in aqueous
environments.
6. What is the chemical reaction mechanism by which cells build polymers from monomers?
A. Dehydration synthesis
B. Hydrolysis
C. Ionic ionization
D. Hydrogenation
Answer: A
, Rationale: Dehydration synthesis involves the removal of a water molecule to create a
covalent bond between two monomers. One monomer provides a hydroxyl group while the
other provides a hydrogen atom. This process is essential for the formation of complex
macromolecules like proteins and DNA.
7. Starch and cellulose are both polymers of glucose, yet humans can digest starch but not
cellulose. Why is this the case?
A. Starch is made of glucose, while cellulose is made of fructose
B. Starch contains nitrogen while cellulose does not
C. Cellulose is too large to be absorbed by the human gut
D. The glycosidic linkages in starch and cellulose have different configurations
Answer: D
Rationale: Starch consists of alpha-glucose monomers, while cellulose consists of beta-
glucose monomers. Human enzymes are specific to the alpha-linkages and cannot break the
beta-linkages found in cellulose. This structural difference highlights the relationship
between molecular shape and biological function.
8. Which class of lipids is characterized by a skeleton consisting of four fused rings?
A. Phospholipids
B. Steroids
C. Triglycerides
D. Saturated fats
Answer: B
Rationale: Steroids like cholesterol and testosterone have a unique structure of four
interconnected carbon rings. Unlike other lipids, they do not contain fatty acid tails. They
function primarily as signaling molecules or structural components of cell membranes.
9. What type of bond maintains the secondary structure of a protein, such as an alpha-helix
or a beta-pleated sheet?
A. Peptide bonds between amino acids
B. Hydrogen bonds between the backbone atoms
C. Disulfide bridges between R-groups
D. Hydrophobic interactions
Answer: B
Rationale: Secondary structure is formed by hydrogen bonding between the oxygen of the
carboxyl group and the hydrogen of the amino group in the polypeptide backbone. These
