OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What is lysis in the context of cellular biology?

1. The process of cell division

2. A method of cell death

3. The bursting of a cell due to excess water

4. The shrinking of a cell due to dehydration

The correct answer is: The bursting of a cell due to excess water

Lysis refers specifically to the bursting of a cell as a result of an accumulation of excess water within it. This phenomenon typically occurs in hypotonic environments, where the concentration of solutes outside the cell is lower than inside. Water moves into the cell by osmosis, causing it to swell. When the internal pressure becomes too great, the cell membrane can no longer contain the contents of the cell, leading to its rupture. This process can affect various types of cells, including animal cells, which do not have a rigid cell wall to prevent bursting. Understanding this concept highlights the importance of osmotic balance in maintaining cell integrity. It contrasts sharply with the other processes listed, such as cell division, where cells replicate and produce new cells; methods of cell death, which may involve programmed pathways like apoptosis; and the shrinking of a cell due to dehydration, a process known as crenation. Each of these other processes involves different mechanisms and outcomes for cell function and survival.