Robbins Basic Pathology
10th Edition
Author(s)Vinay Kumar; MBBS; MD;
FRCPath; Abul K. Abbas; MBBS and
Jon C. Aster; MD; PhD
Print ISBN: 9780323353175
,Question 1
A cell is exposed to a brief reduction in ATP availability that does not
immediately cause membrane rupture or nuclear dissolution. Which
cellular function is most likely to become impaired first because of
reduced ATP?
A. DNA replication
B. Maintenance of the Na⁺/K⁺ ATPase gradient
C. Formation of peptide bonds in ribosomes
D. Transcription of messenger RNA
,Correct Answer: B. Maintenance of the Na⁺/K⁺ ATPase gradient
Rationale: The plasma membrane Na⁺/K⁺ ATPase requires ATP to
maintain normal intracellular ion concentrations. Early ATP depletion
reduces pump activity, causing sodium and water to accumulate inside
the cell and producing cellular swelling. DNA replication and
transcription are not the earliest consequences of mild ATP depletion,
and peptide-bond formation is not the primary ATP-dependent process
affected in this setting.
Question 2
A mutation prevents a newly synthesized protein from being properly
folded in the rough endoplasmic reticulum. Which cellular organelle is
primarily responsible for recognizing and processing this protein as part
of the cell's quality-control system?
A. Golgi apparatus
B. Lysosome
C. Endoplasmic reticulum
D. Peroxisome
Correct Answer: C. Endoplasmic reticulum
Rationale: The endoplasmic reticulum contains molecular chaperones
and quality-control mechanisms that monitor newly synthesized
proteins and promote proper folding. Misfolded proteins may be
retained and targeted for degradation rather than transported through
the Golgi apparatus. Lysosomes and peroxisomes perform other
specialized degradative and metabolic functions.
Question 3
, A patient has a hereditary disorder caused by a mutation in a structural
gene that produces an abnormal protein despite otherwise normal
transcriptional machinery. Which level of cellular organization is most
directly affected?
A. Genome
B. Protein structure
C. Extracellular fluid volume
D. Plasma membrane lipid composition
Correct Answer: B. Protein structure
Rationale: A mutation in a structural gene can alter the amino acid
sequence and therefore the structure and function of the encoded
protein. The genome contains the altered information, but the
immediate functional consequence described is an abnormal protein
product. Extracellular fluid and membrane lipid composition are not the
primary molecular abnormalities in this situation.
Question 4
A cardiac myocyte experiences prolonged impairment of mitochondrial
oxidative phosphorylation. Which consequence is most directly
expected?
A. Increased ATP generation
B. Reduced oxidative metabolism and ATP production
C. Increased protein synthesis from ribosomes
D. Enhanced DNA repair
Correct Answer: B. Reduced oxidative metabolism and ATP production
10th Edition
Author(s)Vinay Kumar; MBBS; MD;
FRCPath; Abul K. Abbas; MBBS and
Jon C. Aster; MD; PhD
Print ISBN: 9780323353175
,Question 1
A cell is exposed to a brief reduction in ATP availability that does not
immediately cause membrane rupture or nuclear dissolution. Which
cellular function is most likely to become impaired first because of
reduced ATP?
A. DNA replication
B. Maintenance of the Na⁺/K⁺ ATPase gradient
C. Formation of peptide bonds in ribosomes
D. Transcription of messenger RNA
,Correct Answer: B. Maintenance of the Na⁺/K⁺ ATPase gradient
Rationale: The plasma membrane Na⁺/K⁺ ATPase requires ATP to
maintain normal intracellular ion concentrations. Early ATP depletion
reduces pump activity, causing sodium and water to accumulate inside
the cell and producing cellular swelling. DNA replication and
transcription are not the earliest consequences of mild ATP depletion,
and peptide-bond formation is not the primary ATP-dependent process
affected in this setting.
Question 2
A mutation prevents a newly synthesized protein from being properly
folded in the rough endoplasmic reticulum. Which cellular organelle is
primarily responsible for recognizing and processing this protein as part
of the cell's quality-control system?
A. Golgi apparatus
B. Lysosome
C. Endoplasmic reticulum
D. Peroxisome
Correct Answer: C. Endoplasmic reticulum
Rationale: The endoplasmic reticulum contains molecular chaperones
and quality-control mechanisms that monitor newly synthesized
proteins and promote proper folding. Misfolded proteins may be
retained and targeted for degradation rather than transported through
the Golgi apparatus. Lysosomes and peroxisomes perform other
specialized degradative and metabolic functions.
Question 3
, A patient has a hereditary disorder caused by a mutation in a structural
gene that produces an abnormal protein despite otherwise normal
transcriptional machinery. Which level of cellular organization is most
directly affected?
A. Genome
B. Protein structure
C. Extracellular fluid volume
D. Plasma membrane lipid composition
Correct Answer: B. Protein structure
Rationale: A mutation in a structural gene can alter the amino acid
sequence and therefore the structure and function of the encoded
protein. The genome contains the altered information, but the
immediate functional consequence described is an abnormal protein
product. Extracellular fluid and membrane lipid composition are not the
primary molecular abnormalities in this situation.
Question 4
A cardiac myocyte experiences prolonged impairment of mitochondrial
oxidative phosphorylation. Which consequence is most directly
expected?
A. Increased ATP generation
B. Reduced oxidative metabolism and ATP production
C. Increased protein synthesis from ribosomes
D. Enhanced DNA repair
Correct Answer: B. Reduced oxidative metabolism and ATP production
