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 examines a normal somatic cell and finds that its DNA has
been packaged with histone proteins into repeating structural units.
Which structure is the fundamental unit of chromatin organization
described by this finding?
A. Ribosome
B. Nucleosome
C. Centrosome
D. Proteasome
,Correct Answer: B. Nucleosome
Rationale: A nucleosome consists of DNA wrapped around a core of
histone proteins and represents the basic structural unit of chromatin.
Ribosomes synthesize proteins, centrosomes organize microtubules,
and proteasomes degrade proteins. Chromatin organization allows the
genome to be compacted while permitting regulated access to DNA.
Question 2
A cell contains a newly synthesized protein that must remain within the
cytosol to perform its function. Which cellular structure is primarily
responsible for degrading misfolded cytosolic proteins?
A. Lysosome
B. Golgi apparatus
C. Proteasome
D. Peroxisome
Correct Answer: C. Proteasome
Rationale: The ubiquitin-proteasome system is a major pathway for
degradation of damaged, misfolded, or short-lived cytosolic and nuclear
proteins. Lysosomes primarily degrade materials delivered through
endocytic or autophagic pathways. The Golgi modifies and sorts
proteins, whereas peroxisomes participate in lipid metabolism and
detoxification reactions.
Question 3
A patient has a hereditary disorder caused by a mutation that changes a
single nucleotide in a gene and results in production of a structurally
, altered protein. Which level of biological information has been directly
altered?
A. Genome
B. Extracellular matrix
C. Plasma membrane lipid composition
D. Cytoskeletal organization
Correct Answer: A. Genome
Rationale: A nucleotide sequence is part of the genome, which contains
the genetic information directing cellular structure and function. A
mutation can alter a protein's amino acid sequence or its expression.
The extracellular matrix, membrane composition, and cytoskeleton may
be affected secondarily but are not the primary site of the described
change.
Question 4
Which organelle is most directly responsible for sorting newly
synthesized proteins and directing them to appropriate intracellular or
extracellular destinations?
A. Golgi apparatus
B. Mitochondrion
C. Nucleolus
D. Peroxisome
Correct Answer: A. Golgi apparatus
Rationale: The Golgi apparatus modifies, sorts, and packages proteins
received from the endoplasmic reticulum for delivery to lysosomes,
secretory vesicles, or other destinations. Mitochondria generate ATP,
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 examines a normal somatic cell and finds that its DNA has
been packaged with histone proteins into repeating structural units.
Which structure is the fundamental unit of chromatin organization
described by this finding?
A. Ribosome
B. Nucleosome
C. Centrosome
D. Proteasome
,Correct Answer: B. Nucleosome
Rationale: A nucleosome consists of DNA wrapped around a core of
histone proteins and represents the basic structural unit of chromatin.
Ribosomes synthesize proteins, centrosomes organize microtubules,
and proteasomes degrade proteins. Chromatin organization allows the
genome to be compacted while permitting regulated access to DNA.
Question 2
A cell contains a newly synthesized protein that must remain within the
cytosol to perform its function. Which cellular structure is primarily
responsible for degrading misfolded cytosolic proteins?
A. Lysosome
B. Golgi apparatus
C. Proteasome
D. Peroxisome
Correct Answer: C. Proteasome
Rationale: The ubiquitin-proteasome system is a major pathway for
degradation of damaged, misfolded, or short-lived cytosolic and nuclear
proteins. Lysosomes primarily degrade materials delivered through
endocytic or autophagic pathways. The Golgi modifies and sorts
proteins, whereas peroxisomes participate in lipid metabolism and
detoxification reactions.
Question 3
A patient has a hereditary disorder caused by a mutation that changes a
single nucleotide in a gene and results in production of a structurally
, altered protein. Which level of biological information has been directly
altered?
A. Genome
B. Extracellular matrix
C. Plasma membrane lipid composition
D. Cytoskeletal organization
Correct Answer: A. Genome
Rationale: A nucleotide sequence is part of the genome, which contains
the genetic information directing cellular structure and function. A
mutation can alter a protein's amino acid sequence or its expression.
The extracellular matrix, membrane composition, and cytoskeleton may
be affected secondarily but are not the primary site of the described
change.
Question 4
Which organelle is most directly responsible for sorting newly
synthesized proteins and directing them to appropriate intracellular or
extracellular destinations?
A. Golgi apparatus
B. Mitochondrion
C. Nucleolus
D. Peroxisome
Correct Answer: A. Golgi apparatus
Rationale: The Golgi apparatus modifies, sorts, and packages proteins
received from the endoplasmic reticulum for delivery to lysosomes,
secretory vesicles, or other destinations. Mitochondria generate ATP,
