# Are there limits to cell size?

## Presentation on theme: "Are there limits to cell size?"— Presentation transcript:

Are there limits to cell size?

Demonstration Recap: Using 3 different sized agar blocks to represent cells (3 cm, 2 cm, and 1 cm), we observed the “nutrient uptake” of each when placed in solution. Although the nutrients traveled into the “cells” at the same speed, the “cell” that appeared to receive the most nourishment was the smallest one. This can be explained by the distance a particle from outside the cell would need to travel inwards to reach the center. In the small cell, this distance is the smallest.

Data: Surface Areas & Volumes
(6 x w x l) Volume = (w x l x h) Surface Area Volume 1 cm Cube 6 x 1 x 1 = 6 1 x 1 x 1 = 1 6/1 = 6 2 cm 6 x 2 x 2 = 24 2 x 2 x 2 = 8 24/8 = 3/1 = 3 3 cm 6 x 3 x 3 = 54 3 x 3 x 3 = 27 54/27 = 2/1 = 2

Data: Observations 1 cm Cube: (SA/V = 6) 2 cm Cube: (SA/V = 3)

Which “cell” was most efficient?
This is the cell in which the nutrients (pink) got closest to reaching the core of the “cell”. Answer: the smallest cell Based on this answer, can you tell me…

What is the relationship between cell size and the rate at which nutrients reach the core of the cell? The “cell” that received the most nutrition for all of its organelles was the smallest cell. It has a surface area to volume ratio of 6 to 1, which is the highest of all three “cells”. This means more of the cell was able to receive nutrients because it was directly exposed to the nutrient solution. The part of the cell that was not exposed did not receive nutrients until they traveled into the area. However, since the cell took up very little space (has a very small volume), the nutrients did not have far to travel once they got inside the cell.

Does a cell have to be round?
No, any shape is possible- however, the ratio of Surface Area to Volume may vary.

What is the best shape and size for a cell?
The best shape and size for a cell is one where the ratio of surface area to volume is high enough that the cell gets complete nourishment with minimal harm inflicted on itself in the process. HUH?! What?

For instance… IF you had a cell with a very small SA/V ratio (volume is very large), your cell might be so big that nutrients cannot reach their destination in time, and the cell will die.

But on the other hand… IF you have a cell with a very large SA/V ratio (surface area is very large), your cell will become very fragile and thin. It could die easily from heat exposure or snags.

The best cell shape… Would probably be a cell that is long and thin, tube-like. Good examples: nerve cells, muscle cells, xylem and phloem cells in plants.

Biggest & Smallest Cells
How big is the biggest cell? The biggest cell is an ostrich egg (about the size of a football). What are the smallest cells? Bacteria- Ever wonder why bacteria can produce a new generation in 20 – 30 minutes? And over ten million cells in less than a day?
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