Cell Biology — Common Exam Question Types

1.Question 1. Which of the following structures is shared by both prokaryotic and eukaryotic cells? Options: A, nuclear membrane; B, mitochondria; C, ribosomes; D, endoplasmic reticulum.

2.Answer: C, ribosomes. Prokaryotic cells have seventy S ribosomes and eukaryotic cells have eighty S ribosomes — both possess ribosomes. Options A, B, and D are all membrane-bound organelles found only in eukaryotic cells.

3.Question 2. A red blood cell is placed in a zero point three percent sodium chloride solution — normal saline is zero point nine percent. What happens? Options: A, no change; B, swelling or hemolysis; C, crenation; D, swelling then crenation.

4.Answer: B. Since zero point three percent is less than zero point nine percent, the solution is hypotonic. Water enters the red blood cell by osmosis, causing swelling or even hemolysis.

5.Question 3. What is the correct pathway for a protein from synthesis to secretion? Options: A, ribosome to smooth ER to Golgi to cell membrane; B, ribosome to rough ER to Golgi to cell membrane; C, ribosome to Golgi to rough ER to cell membrane; D, smooth ER to ribosome to Golgi to cell membrane.

6.Answer: B. The secretory protein pathway: ribosomes on the rough ER synthesize the protein; it enters the rough ER lumen for folding and modification; transport vesicles carry it to the Golgi for further modification and sorting; finally, secretory vesicles fuse with the cell membrane via exocytosis.

7.Question 4. Which of the following statements about meiosis is incorrect? Options: A, homologous chromosomes undergo synapsis during meiosis one; B, crossing over occurs in prophase one; C, sister chromatids separate during meiosis two; D, meiosis produces two haploid cells.

8.Answer: D. Meiosis produces four haploid cells, not two. Options A, B, and C are all correct statements about meiosis.

9.Question 5. Which of the following is a tumor suppressor gene? Options: A, ras; B, myc; C, p53; D, src.

10.Answer: C. p53 is a tumor suppressor gene; loss of its function leads to uncontrolled cell division. Options A, B, and D are all proto-oncogenes which, when mutated, become oncogenes that over-promote cell division.

11.Question 6. After a GPCR is activated, the first molecule activated downstream is usually which of the following? Options: A, cyclic AMP; B, G protein; C, protein kinase A; D, adenylyl cyclase.

12.Answer: B. The cascade is GPCR, then G protein, then adenylyl cyclase, then cyclic AMP, then protein kinase A. The G protein is the first molecule downstream of the GPCR.