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 researcher studies a eukaryotic cell and finds that a newly synthesized
protein remains within the cytosol rather than entering the secretory
pathway. Which cellular feature most directly explains why this protein
is translated on free cytosolic ribosomes?
A. Presence of an N-terminal mitochondrial targeting sequence
B. Absence of a signal sequence directing the ribosome to the rough
endoplasmic reticulum
,C. Presence of a lysosomal targeting signal
D. Binding of the protein to extracellular matrix receptors
Correct Answer: B. Absence of a signal sequence directing the ribosome
to the rough endoplasmic reticulum
Rationale: Proteins destined for secretion, insertion into cellular
membranes, or many organelles of the endomembrane system
generally enter the rough endoplasmic reticulum through targeting
signals. In the absence of such a signal, translation occurs on free
ribosomes and the protein generally remains in the cytosol.
Mitochondrial targeting sequences direct proteins toward
mitochondria, lysosomal targeting occurs through the secretory
pathway and subsequent sorting, and extracellular matrix receptors do
not determine where translation occurs.
Question 2
A patient has a germline mutation that inactivates both copies of a gene
encoding an important DNA repair protein. Which consequence is most
directly expected from failure of this cellular function?
A. Increased fidelity of DNA replication
B. Increased accumulation of genomic mutations
C. Complete inhibition of mitochondrial ATP production
D. Increased synthesis of extracellular collagen
Correct Answer: B. Increased accumulation of genomic mutations
Rationale: DNA repair mechanisms preserve genomic integrity by
correcting replication errors and DNA damage. Loss of effective repair
increases the persistence and accumulation of mutations, which can
contribute to genomic instability and disease, including cancer. DNA
, repair does not normally increase replication fidelity beyond baseline,
and the mutation does not directly abolish mitochondrial ATP synthesis
or specifically increase collagen production.
Question 3
Which process is most important for maintaining the integrity of a
differentiated cell by selectively removing damaged or unnecessary
intracellular components?
A. Autophagy
B. Glycolysis
C. Exocytosis
D. DNA recombination
Correct Answer: A. Autophagy
Rationale: Autophagy is a lysosome-dependent process that allows cells
to degrade and recycle damaged organelles, proteins, and other
cytoplasmic components. It contributes to cellular housekeeping and
adaptation, especially during nutrient deprivation and cellular stress.
Glycolysis generates ATP from glucose, exocytosis exports cellular
products, and DNA recombination concerns genetic material rather
than direct removal of damaged cytoplasmic components.
Question 4
A hepatocyte exposed to prolonged fasting maintains ATP production
despite limited extracellular glucose. Which metabolic adaptation most
directly helps preserve cellular energy under these conditions?
A. Increased dependence on oxidative phosphorylation from available
metabolic substrates
B. Complete cessation of mitochondrial activity
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 researcher studies a eukaryotic cell and finds that a newly synthesized
protein remains within the cytosol rather than entering the secretory
pathway. Which cellular feature most directly explains why this protein
is translated on free cytosolic ribosomes?
A. Presence of an N-terminal mitochondrial targeting sequence
B. Absence of a signal sequence directing the ribosome to the rough
endoplasmic reticulum
,C. Presence of a lysosomal targeting signal
D. Binding of the protein to extracellular matrix receptors
Correct Answer: B. Absence of a signal sequence directing the ribosome
to the rough endoplasmic reticulum
Rationale: Proteins destined for secretion, insertion into cellular
membranes, or many organelles of the endomembrane system
generally enter the rough endoplasmic reticulum through targeting
signals. In the absence of such a signal, translation occurs on free
ribosomes and the protein generally remains in the cytosol.
Mitochondrial targeting sequences direct proteins toward
mitochondria, lysosomal targeting occurs through the secretory
pathway and subsequent sorting, and extracellular matrix receptors do
not determine where translation occurs.
Question 2
A patient has a germline mutation that inactivates both copies of a gene
encoding an important DNA repair protein. Which consequence is most
directly expected from failure of this cellular function?
A. Increased fidelity of DNA replication
B. Increased accumulation of genomic mutations
C. Complete inhibition of mitochondrial ATP production
D. Increased synthesis of extracellular collagen
Correct Answer: B. Increased accumulation of genomic mutations
Rationale: DNA repair mechanisms preserve genomic integrity by
correcting replication errors and DNA damage. Loss of effective repair
increases the persistence and accumulation of mutations, which can
contribute to genomic instability and disease, including cancer. DNA
, repair does not normally increase replication fidelity beyond baseline,
and the mutation does not directly abolish mitochondrial ATP synthesis
or specifically increase collagen production.
Question 3
Which process is most important for maintaining the integrity of a
differentiated cell by selectively removing damaged or unnecessary
intracellular components?
A. Autophagy
B. Glycolysis
C. Exocytosis
D. DNA recombination
Correct Answer: A. Autophagy
Rationale: Autophagy is a lysosome-dependent process that allows cells
to degrade and recycle damaged organelles, proteins, and other
cytoplasmic components. It contributes to cellular housekeeping and
adaptation, especially during nutrient deprivation and cellular stress.
Glycolysis generates ATP from glucose, exocytosis exports cellular
products, and DNA recombination concerns genetic material rather
than direct removal of damaged cytoplasmic components.
Question 4
A hepatocyte exposed to prolonged fasting maintains ATP production
despite limited extracellular glucose. Which metabolic adaptation most
directly helps preserve cellular energy under these conditions?
A. Increased dependence on oxidative phosphorylation from available
metabolic substrates
B. Complete cessation of mitochondrial activity
