Q.40 A T-flask is seeded with 105 anchorage-dependent cells. The available area of the T-flask is
25 cm2 and the volume of the medium is 25 ml. Assume that the cells are rectangles of size
5 µm × 2 µm. If the cells grow to monolayer confluence after 50 h, the growth rate in number of
cells/(cm2·h) is ______ × 105.
Growth Rate of Anchorage-Dependent Cells at Monolayer Confluence
Anchorage-dependent cells proliferate by attaching to a solid surface.
When such cells reach monolayer confluence, their growth is
limited by the available surface area rather than the volume of the medium.
This problem calculates the growth rate of anchorage-dependent cells
in a T-flask.
Given Data
- Initial number of cells = 105
- Surface area of T-flask = 25 cm2
- Volume of medium = 25 mL
- Cell size = 5 µm × 2 µm
- Time to reach confluence = 50 h
Step-by-Step Solution
Step 1: Area Occupied by One Cell
Cell area = 5 µm × 2 µm = 10 µm2
Since 1 µm = 10-4 cm,
1 µm2 = 10-8 cm2
Therefore, cell area = 10 × 10-8 = 10-7 cm2
Step 2: Maximum Number of Cells at Confluence
Maximum number of cells = 25 cm2 ÷ 10-7 cm2 = 2.5 × 108 cells
Step 3: Net Increase in Cell Number
Increase in cells = (2.5 × 108) − (105)
≈ 2.5 × 108 cells
Step 4: Growth Rate Calculation
Growth rate = (2.5 × 108) ÷ (25 × 50)
= (2.5 × 108) ÷ 1250
= 2 × 105 cells/cm2·h
Final Answer
Growth rate = 2 × 105 cells/cm2·h
Important Note
The volume of the medium does not influence the final cell number because
anchorage-dependent cells are limited by surface area, not volume, at
monolayer confluence.
