Histology Certification Cellular Structures 3 — Questions and Answers
Question 1: In electron microscopy, the smooth endoplasmic reticulum (SER) is distinguished from the rough endoplasmic reticulum (RER) by the absence of:
- A lipid bilayer membrane
- Ribosomes on its cytoplasmic surface (Correct answer)
- Continuity with the nuclear envelope
- Calcium-sequestering function
Correct answer: Ribosomes on its cytoplasmic surface
The RER bears ribosomes on its cytoplasmic face giving it a 'rough' appearance in EM, whereas the SER lacks ribosomes and appears smooth.
Question 2: Peroxisomes detoxify harmful substances and are particularly abundant in hepatocytes. Their key enzyme for hydrogen peroxide decomposition is:
- Superoxide dismutase
- Catalase (Correct answer)
- Glutathione peroxidase
- Cytochrome P450
Correct answer: Catalase
Catalase converts the H₂O₂ generated by peroxisomal oxidases into water and oxygen, preventing oxidative cellular damage.
Question 3: The centrosome, which serves as the main microtubule-organizing center in animal cells, consists of:
- Two centrioles surrounded by pericentriolar material (Correct answer)
- A pair of basal bodies embedded in the plasma membrane
- A ring of actin filaments and γ-tubulin
- Dense fibrillar component and granular component
Correct answer: Two centrioles surrounded by pericentriolar material
The centrosome contains two centrioles (a mother and daughter) embedded within pericentriolar material (PCM) that nucleates microtubule polymerization.
Question 4: Which microscopic finding best indicates active apoptosis in a histological section?
- Nuclear swelling with pale chromatin
- Cellular and nuclear fragmentation into membrane-bound apoptotic bodies (Correct answer)
- Loss of plasma membrane integrity with cytoplasmic spilling
- Marked inflammatory infiltrate surrounding individual cells
Correct answer: Cellular and nuclear fragmentation into membrane-bound apoptotic bodies
Apoptosis produces condensed chromatin, nuclear fragmentation (karyorrhexis), and blebbing of the membrane to form apoptotic bodies, without eliciting inflammation.
Question 5: The glycocalyx coating the luminal surface of endothelial cells is composed primarily of:
- Collagen fibrils
- Proteoglycans and glycoproteins (Correct answer)
- Phospholipids and cholesterol
- Fibronectin and laminin only
Correct answer: Proteoglycans and glycoproteins
The glycocalyx is a carbohydrate-rich layer formed by proteoglycans, glycoproteins, and glycolipids anchored to the plasma membrane, mediating cell–cell and cell–matrix interactions.
Question 6: Annulate lamellae are cytoplasmic organelles that structurally resemble:
- Smooth endoplasmic reticulum
- Stacked Golgi cisternae
- Portions of the nuclear envelope with nuclear pore complexes (Correct answer)
- Outer mitochondrial membrane
Correct answer: Portions of the nuclear envelope with nuclear pore complexes
Annulate lamellae are stacks of membrane cisternae studded with pore complexes morphologically identical to nuclear pore complexes, likely derived from excess nuclear envelope material.
Question 7: Which cytoskeletal element provides the mechanical basis for cilia and flagella movement?
- Actin microfilaments
- Intermediate filaments
- Microtubules arranged in a 9+2 axoneme pattern (Correct answer)
- Septin filaments
Correct answer: Microtubules arranged in a 9+2 axoneme pattern
Cilia and flagella contain an axoneme of nine outer doublet microtubules surrounding a central pair, with dynein motor proteins generating the sliding force for movement.
Histology Certification Cellular Structures 3
In electron microscopy, the smooth endoplasmic reticulum (SER) is distinguished from the rough endoplasmic reticulum (RER) by the absence of: