BIOS 255 Exam 2 Exam Questions and
Correct Answers (Verified Answers) Plus
Rationale 2027 Q&A| Instant Download
Pdf
1. Which organelle is primarily responsible for producing ATP
through aerobic cellular respiration?
A. Golgi apparatus
B. Lysosome
C. Mitochondrion
D. Ribosome
Rationale: Mitochondria are the primary sites of aerobic cellular
respiration in eukaryotic cells. The citric acid cycle occurs in the
mitochondrial matrix, while the electron transport chain and oxidative
phosphorylation occur along the inner mitochondrial membrane,
producing most of the cell's ATP.
2. Which phase of the cell cycle is characterized by DNA replication?
,A. G₁ phase
B. S phase
C. G₂ phase
D. M phase
Rationale: DNA replication occurs during the S (synthesis) phase of
interphase. The G₁ phase involves cell growth and normal cellular
activity, while G₂ prepares the cell for mitosis and the M phase
includes mitosis and cytokinesis.
3. What is the primary function of ribosomes?
A. Lipid storage
B. DNA replication
C. ATP production
D. Protein synthesis
Rationale: Ribosomes translate messenger RNA (mRNA) into
polypeptide chains during translation. Ribosomes may be free in the
cytoplasm or attached to the rough endoplasmic reticulum.
4. Which type of transport requires cellular energy in the form of
ATP?
A. Simple diffusion
B. Osmosis
,C. Facilitated diffusion
D. Active transport
Rationale: Active transport moves substances across a membrane
against their concentration or electrochemical gradient and therefore
requires energy. Simple diffusion, osmosis, and facilitated diffusion
are forms of passive transport.
5. A cell is placed in a solution that has a higher solute concentration
than the cell. What will most likely happen?
A. The cell will gain water
B. The cell will remain unchanged
C. The cell will lose water
D. Solutes will automatically leave the cell
Rationale: A hypertonic solution has a higher effective solute
concentration than the cell. Water moves out of the cell by osmosis
toward the region with greater solute concentration, causing the cell
to lose water.
6. Which molecule carries genetic information from DNA to
ribosomes?
A. tRNA
B. rRNA
, C. ATP
D. mRNA
Rationale: Messenger RNA carries genetic instructions copied from
DNA to the ribosome. The ribosome reads the mRNA sequence during
translation to determine the amino acid sequence of a protein.
7. Which enzyme unwinds the DNA double helix during DNA
replication?
A. DNA polymerase
B. Ligase
C. Helicase
D. Primase
Rationale: Helicase breaks the hydrogen bonds between
complementary DNA bases and separates the two strands. This
creates the replication fork where the DNA strands can serve as
templates.
8. What is the complementary DNA sequence for 5'-ATGC-3'?
A. 5'-ATGC-3'
B. 5'-TACG-3'
C. 3'-TACG-5'
D. 3'-UACG-5'
Correct Answers (Verified Answers) Plus
Rationale 2027 Q&A| Instant Download
1. Which organelle is primarily responsible for producing ATP
through aerobic cellular respiration?
A. Golgi apparatus
B. Lysosome
C. Mitochondrion
D. Ribosome
Rationale: Mitochondria are the primary sites of aerobic cellular
respiration in eukaryotic cells. The citric acid cycle occurs in the
mitochondrial matrix, while the electron transport chain and oxidative
phosphorylation occur along the inner mitochondrial membrane,
producing most of the cell's ATP.
2. Which phase of the cell cycle is characterized by DNA replication?
,A. G₁ phase
B. S phase
C. G₂ phase
D. M phase
Rationale: DNA replication occurs during the S (synthesis) phase of
interphase. The G₁ phase involves cell growth and normal cellular
activity, while G₂ prepares the cell for mitosis and the M phase
includes mitosis and cytokinesis.
3. What is the primary function of ribosomes?
A. Lipid storage
B. DNA replication
C. ATP production
D. Protein synthesis
Rationale: Ribosomes translate messenger RNA (mRNA) into
polypeptide chains during translation. Ribosomes may be free in the
cytoplasm or attached to the rough endoplasmic reticulum.
4. Which type of transport requires cellular energy in the form of
ATP?
A. Simple diffusion
B. Osmosis
,C. Facilitated diffusion
D. Active transport
Rationale: Active transport moves substances across a membrane
against their concentration or electrochemical gradient and therefore
requires energy. Simple diffusion, osmosis, and facilitated diffusion
are forms of passive transport.
5. A cell is placed in a solution that has a higher solute concentration
than the cell. What will most likely happen?
A. The cell will gain water
B. The cell will remain unchanged
C. The cell will lose water
D. Solutes will automatically leave the cell
Rationale: A hypertonic solution has a higher effective solute
concentration than the cell. Water moves out of the cell by osmosis
toward the region with greater solute concentration, causing the cell
to lose water.
6. Which molecule carries genetic information from DNA to
ribosomes?
A. tRNA
B. rRNA
, C. ATP
D. mRNA
Rationale: Messenger RNA carries genetic instructions copied from
DNA to the ribosome. The ribosome reads the mRNA sequence during
translation to determine the amino acid sequence of a protein.
7. Which enzyme unwinds the DNA double helix during DNA
replication?
A. DNA polymerase
B. Ligase
C. Helicase
D. Primase
Rationale: Helicase breaks the hydrogen bonds between
complementary DNA bases and separates the two strands. This
creates the replication fork where the DNA strands can serve as
templates.
8. What is the complementary DNA sequence for 5'-ATGC-3'?
A. 5'-ATGC-3'
B. 5'-TACG-3'
C. 3'-TACG-5'
D. 3'-UACG-5'
