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

Surface Area =

(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

Cube

6 x 2 x 2 = 24 2 x 2 x 2 = 8 24/8 = 3/1 = 3

3 cm

Cube

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)

3 cm Cube:

(SA/V = 2)

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?