Histology Certification Cellular Structures 2 — Questions and Answers
Question 1: Which organelle is responsible for post-translational modification and sorting of proteins destined for secretion?
- Rough endoplasmic reticulum
- Golgi apparatus (Correct answer)
- Lysosome
- Peroxisome
Correct answer: Golgi apparatus
The Golgi apparatus processes, modifies (e.g., glycosylation), and sorts proteins received from the RER for secretion, lysosomal targeting, or membrane insertion.
Question 2: In histological sections stained with H&E, mitochondria are best described as:
- Basophilic granules visible at high magnification
- Eosinophilic structures that are generally below the resolution of light microscopy as individual organelles (Correct answer)
- Deeply basophilic rods due to their DNA content
- Clearly distinct membrane-bound vesicles staining purple
Correct answer: Eosinophilic structures that are generally below the resolution of light microscopy as individual organelles
Mitochondria are too small (~0.5–1 µm) to be individually resolved by light microscopy; their collective contribution gives cytoplasm a diffuse eosinophilic hue.
Question 3: The inner mitochondrial membrane is characterized by extensive folding into structures called:
- Cisternae
- Cristae (Correct answer)
- Lamellae
- Trabeculae
Correct answer: Cristae
Cristae are infoldings of the inner mitochondrial membrane that dramatically increase surface area for oxidative phosphorylation.
Question 4: Which cellular structure forms the primary diffusion barrier between the cytoplasm and the extracellular environment?
- Glycocalyx
- Plasma membrane (Correct answer)
- Cytoskeleton
- Nuclear envelope
Correct answer: Plasma membrane
The plasma membrane's phospholipid bilayer is the principal selective permeability barrier regulating molecular exchange between the cell and its environment.
Question 5: Free ribosomes in the cytoplasm predominantly synthesize proteins destined for:
- Secretion via exocytosis
- Lysosomal hydrolysis
- Cytosolic use or import into mitochondria and nucleus (Correct answer)
- Insertion into the plasma membrane
Correct answer: Cytosolic use or import into mitochondria and nucleus
Free ribosomes synthesize proteins used within the cytosol or targeted post-translationally to organelles like mitochondria, peroxisomes, and the nucleus.
Question 6: The nuclear lamina, located on the inner surface of the nuclear envelope, is composed primarily of:
- Actin filaments
- Intermediate filaments called lamins (Correct answer)
- Microtubules
- Spectrin molecules
Correct answer: Intermediate filaments called lamins
Lamins are type V intermediate filaments that polymerize to form the nuclear lamina, providing mechanical support to the nuclear envelope and anchoring chromatin.
Question 7: Which cellular compartment maintains an acidic pH (~4.5–5.0) essential for the activation of hydrolytic enzymes?
- Peroxisome
- Lysosome (Correct answer)
- Endosome
- Golgi lumen
Correct answer: Lysosome
Lysosomes maintain a luminal pH of ~4.5–5.0 via V-type H⁺-ATPase pumps, which is required to activate acid hydrolases for intracellular digestion.
Histology Certification Cellular Structures 2
Which organelle is responsible for post-translational modification and sorting of proteins destined for secretion?