CLEP Biology Cell Organelle Structure/Function 5 — Questions and Answers
Question 1: Tay-Sachs disease results from a deficiency of a lysosomal enzyme that normally breaks down gangliosides. In which organelle do the undegraded gangliosides accumulate?
- Mitochondria
- Lysosomes (Correct answer)
- Smooth ER
- Golgi apparatus
Correct answer: Lysosomes
Without the functional hydrolase (hexosaminidase A), gangliosides cannot be broken down and accumulate within lysosomes, causing neuronal dysfunction.
Question 2: Which property of the plasma membrane allows it to function as a selective barrier?
- Its attachment to the cell wall
- The amphipathic nature of phospholipids forming a bilayer (Correct answer)
- The presence of glycogen on its outer surface
- Its single-layered structure
Correct answer: The amphipathic nature of phospholipids forming a bilayer
Phospholipids are amphipathic (with hydrophilic heads and hydrophobic tails) and spontaneously form a bilayer that restricts the passage of most polar and charged molecules.
Question 3: Which organelle would you expect to be most prominent in a liver cell due to its role in detoxifying drugs and alcohol?
- Rough endoplasmic reticulum
- Smooth endoplasmic reticulum (Correct answer)
- Golgi apparatus
- Nucleus
Correct answer: Smooth endoplasmic reticulum
Smooth ER contains enzymes (especially cytochrome P450s) that detoxify drugs, alcohol, and other lipid-soluble compounds, and it proliferates in liver cells exposed to these substances.
Question 4: The signal recognition particle (SRP) directs ribosomes to which cellular location during translation of secretory proteins?
- The mitochondrial outer membrane
- The rough endoplasmic reticulum membrane (Correct answer)
- The nuclear pore complex
- The Golgi cis cisterna
Correct answer: The rough endoplasmic reticulum membrane
SRP recognizes the signal sequence on a nascent polypeptide and directs the ribosome-mRNA complex to the rough ER membrane, where translation continues into the ER lumen.
Question 5: Which of the following pairs correctly matches an organelle with its membrane characteristic?
- Mitochondria — single membrane enclosing the matrix
- Chloroplast — double outer membrane plus internal thylakoid membranes (Correct answer)
- Lysosome — double membrane with a low internal pH
- Nucleus — single membrane with no transport channels
Correct answer: Chloroplast — double outer membrane plus internal thylakoid membranes
Chloroplasts have an outer double membrane (envelope) surrounding the stroma and an internal network of thylakoid membranes where light reactions occur.
Question 6: Colchicine inhibits tubulin polymerization. A cell treated with colchicine would be unable to properly perform which of the following?
- Transcription and RNA processing
- Organelle movement along microtubule tracks and chromosome separation (Correct answer)
- Protein synthesis on ribosomes
- Phospholipid biosynthesis in the ER
Correct answer: Organelle movement along microtubule tracks and chromosome separation
Microtubules serve as tracks for motor proteins (kinesins, dyneins) that move organelles, and they form the mitotic spindle needed for chromosome separation.
Question 7: A cell with many mitochondria that have extremely dense cristae would most likely be which cell type?
- A fat storage cell (adipocyte) in an inactive state
- A highly active cardiac muscle cell requiring constant ATP (Correct answer)
- A red blood cell transporting oxygen
- A skin epithelial cell with minimal energy demands
Correct answer: A highly active cardiac muscle cell requiring constant ATP
Cardiac muscle cells contract continuously and require enormous amounts of ATP; their mitochondria have densely packed cristae to maximize oxidative phosphorylation capacity.
CLEP Biology Cell Organelle Structure/Function 5
Tay-Sachs disease results from a deficiency of a lysosomal enzyme that normally breaks down gangliosides.
In which organelle do the undegraded gangliosides accumulate?