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## [DOMAIN 1: CELL BIOLOGY, ADAPTATION & INJURY - 50 Questions]
### Cell Structure & Organelles
* *Question 1**
Which organelle serves as the "power plant" of the cell, transforming organic compounds into
ATP and regulating apoptosis?
) Lysosome
A
B) Golgi apparatus
C) Mitochondria **[CORRECT]**
D) Rough endoplasmic reticulum
* *Rationale:** Mitochondria are responsible for aerobic metabolism and ATP production through
oxidative phosphorylation. They contain their own DNA and are self-replicating. Additionally,
mitochondria play a crucial role in regulating apoptosis (programmed cell death) by releasing
cytochrome c and other pro-apoptotic factors. The other options are incorrect: lysosomes
contain digestive enzymes, the Golgi apparatus packages proteins, and the rough ER
synthesizes proteins.
---
* *Question 2**
A patient with chronic alcoholism presents with liver dysfunction. Which organelle is primarily
responsible for lipid synthesis and detoxification processes that would be affected?
) Rough endoplasmic reticulum
A
B) Smooth endoplasmic reticulum **[CORRECT]**
C) Ribosomes
,D) Nucleus
* *Rationale:** The smooth endoplasmic reticulum (SER) is the major site of lipid synthesis and
contains enzymes for detoxification of drugs and alcohol. Chronic alcohol exposure induces
proliferation of SER in hepatocytes. The rough ER contains ribosomes for protein synthesis,
ribosomes are protein synthesis sites, and the nucleus houses genetic material.
---
* *Question 3**
Which cellular component maintains cell shape using microtubules and microfilaments?
) Cytoplasm
A
B) Cytoskeleton **[CORRECT]**
C) Cell membrane
D) Proteasome
* *Rationale:** The cytoskeleton is a network of protein filaments including microtubules
(composed of tubulin) and microfilaments (composed of actin) that maintain cell shape, enable
cell movement, and facilitate intracellular transport. Cytoplasm is the fluid matrix, the cell
membrane provides barrier function, and proteasomes degrade proteins.
---
* *Question 4**
In a patient with myocardial infarction, which serum marker indicates injury to cardiac muscle
cells due to its role in muscle contraction regulation?
) Aspartate aminotransferase (AST)
A
B) Lactate dehydrogenase (LDH)
C) Troponin **[CORRECT]**
D) Alanine aminotransferase (ALT)
* *Rationale:** Troponin is a regulatory protein complex (troponin I, T, and C) essential for
cardiac muscle contraction. Cardiac-specific troponin I and T are released into circulation when
cardiomyocytes are damaged, making them highly specific markers for myocardial injury. AST
and LDH are less specific, and ALT is primarily a liver enzyme.
---
* *Question 5**
Which organelle functions as the cell's "quality control" system and is involved in programmed
cell death by degrading damaged proteins?
, ) Lysosome
A
B) Proteasome **[CORRECT]**
C) Peroxisome
D) Mitochondria
* *Rationale:** Proteasomes are protein complexes that degrade unneeded or damaged proteins
through proteolysis. They recognize ubiquitin-tagged proteins and are essential for quality
control, cell cycle regulation, and apoptosis. Lysosomes degrade extracellular material and worn
organelles, peroxisomes break down fatty acids and hydrogen peroxide, and mitochondria
produce ATP.
---
* *Question 6**
The cell membrane is described as a semipermeable lipid bilayer. Which function is NOT
typically associated with the cell membrane?
) Conducting electric currents
A
B) Providing receptors for hormones
C) Synthesizing ATP **[CORRECT]**
D) Enabling cell-to-cell recognition
* *Rationale:** ATP synthesis occurs in mitochondria, not the cell membrane. The cell membrane
(plasma membrane) functions include: acting as a semipermeable barrier, conducting electrical
signals via ion channels, housing receptors for hormones and neurotransmitters, and containing
glycoproteins/glycolipids for cell recognition and adhesion.
---
* *Question 7**
Which structure is responsible for packaging proteins, enzymes, and hormones after they are
synthesized?
) Rough endoplasmic reticulum
A
B) Golgi apparatus **[CORRECT]**
C) Mitochondria
D) Ribosomes
* *Rationale:** The Golgi apparatus works in conjunction with the endoplasmic reticulum to
modify, package, and sort proteins and lipids into vesicles for transport to their final destinations.
The rough ER synthesizes proteins, mitochondria produce energy, and ribosomes are the actual
protein synthesis sites.
---
, * *Question 8**
In a patient with Pompe disease (glycogen storage disease), which organelle is defective due to
lack of acid alpha-glucosidase enzyme?
) Mitochondria
A
B) Lysosomes **[CORRECT]**
C) Peroxisomes
D) Nucleus
* *Rationale:** Pompe disease results from deficiency of acid alpha-glucosidase (GAA), a
lysosomal enzyme that breaks down glycogen. Lysosomes contain hydrolytic enzymes that
degrade cellular waste, foreign substances, and macromolecules. When lysosomal enzymes
are deficient, substrate accumulation occurs, causing cellular dysfunction.
---
* *Question 9**
Which cellular structure contains the nucleolus and is surrounded by a nuclear envelope?
) Mitochondria
A
B) Nucleus **[CORRECT]**
C) Golgi apparatus
D) Centrioles
* *Rationale:** The nucleus is the control center of the cell containing DNA, chromatin, and the
nucleolus (site of ribosomal RNA synthesis). It is surrounded by a double-membrane nuclear
envelope with nuclear pores regulating transport. Mitochondria have their own DNA but no
nucleolus, the Golgi apparatus processes proteins, and centrioles organize microtubules.
---
* *Question 10**
Ribosomes are the site of protein synthesis. Where are ribosomes NOT typically found?
) Attached to rough endoplasmic reticulum
A
B) Free in the cytoplasm
C) Within the nucleus **[CORRECT]**
D) Inside mitochondria
* *Rationale:** Ribosomes are found attached to rough ER (for secretory/membrane proteins),
free in cytoplasm (for cytosolic proteins), and within mitochondria (for mitochondrial proteins
synthesized from mitochondrial DNA). However, ribosomes are not found within the nucleus