Are there limits to cell size?Are there limits to cell size?

Demonstration Recap:Demonstration Recap: Using 3 different sized agar Using 3 different sized agar

blocks to represent cells (3 cm, blocks to represent cells (3 cm, 2 cm, and 1 cm), we observed 2 cm, and 1 cm), we observed the “nutrient uptake” of each the “nutrient uptake” of each when placed in solution.when placed in solution.

Although the nutrients traveled Although the nutrients traveled into the “cells” at the same into the “cells” at the same speed, the “cell” that appeared speed, the “cell” that appeared to receive the most to receive the most nourishment was the smallest nourishment was the smallest one. This can be explained by one. This can be explained by the distance a particle from the distance a particle from outside the cell would need to outside the cell would need to travel inwards to reach the travel inwards to reach the center. In the small cell, this center. In the small cell, this distance is the smallest.distance is the smallest.

Data: Surface Areas & VolumesData: Surface Areas & Volumes

Surface Area =Surface Area =

(6 x w x l)(6 x w x l)

Volume =Volume =

(w x l x h)(w x l x h)

Surface AreaSurface Area

VolumeVolume

1 cm 1 cm

CubeCube

6 x 1 x 1 = 66 x 1 x 1 = 6 1 x 1 x 1 = 11 x 1 x 1 = 1 6/1 = 66/1 = 6

2 cm 2 cm

CubeCube

6 x 2 x 2 = 246 x 2 x 2 = 24 2 x 2 x 2 = 82 x 2 x 2 = 8 24/8 = 3/1 = 324/8 = 3/1 = 3

3 cm 3 cm

CubeCube

6 x 3 x 3 = 546 x 3 x 3 = 54 3 x 3 x 3 = 273 x 3 x 3 = 27 54/27 = 2/1 = 254/27 = 2/1 = 2

Data: ObservationsData: Observations

1 cm Cube:1 cm Cube: (SA/V = 6)(SA/V = 6)

2 cm Cube: 2 cm Cube: (SA/V = 3)(SA/V = 3)

3 cm Cube:3 cm Cube: (SA/V = 2)(SA/V = 2)

Which “cell” was most efficient?Which “cell” was most efficient?

This is the cell in which the nutrients (pink) This is the cell in which the nutrients (pink) got closest to reaching the core of the got closest to reaching the core of the “cell”.“cell”.

Answer: the smallest cellAnswer: the smallest cell

Based on this answer, can you tell me…Based on this answer, can you tell me…

What is the relationship between What is the relationship between cell cell sizesize and the and the rate at which nutrients rate at which nutrients

reach the core of the cellreach the core of the cell??

The “cell” that received the most nutrition for all of its The “cell” that received the most nutrition for all of its organelles was the smallest cell.organelles was the smallest cell.

It has a surface area to volume ratio of 6 to 1, which is 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 the highest of all three “cells”. This means more of the cell was able to receive nutrients because it was directly cell was able to receive nutrients because it was directly exposed to the nutrient solution. The part of the cell that exposed to the nutrient solution. The part of the cell that was not exposed did not receive nutrients until they was not exposed did not receive nutrients until they traveled into the area. However, since the cell took up traveled into the area. However, since the cell took up very little space (has a very small volume), the nutrients very little space (has a very small volume), the nutrients did not have far to travel once they got inside the cell. did not have far to travel once they got inside the cell.

Does a cell have to be round?Does a cell have to be round?

No, any No, any shape is shape is possible- possible- however, the however, the ratio of ratio of Surface Area Surface Area to Volume to Volume may vary.may vary.

What is the best shape and size for What is the best shape and size for a cell?a cell?

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

HUH?! What?HUH?! What?

For instance…For instance…

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

But on the other hand…But on the other hand…

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

The best cell shape…The best cell shape…

Would probably be a Would probably be a cell that is long and cell that is long and thin, tube-like.thin, tube-like.

Good examples: Good examples: nerve cells, muscle nerve cells, muscle cells, xylem and cells, xylem and phloem cells in plants.phloem cells in plants.

Biggest & Smallest CellsBiggest & Smallest Cells

How big is the biggest How big is the biggest cell?cell?

The biggest cell is an The biggest cell is an ostrich egg (about the size ostrich egg (about the size of a football).of a football).

What are the smallest What are the smallest cells?cells?

Bacteria- Ever wonder why Bacteria- Ever wonder why bacteria can produce a bacteria can produce a new generation in 20 – 30 new generation in 20 – 30 minutes? And over ten minutes? And over ten million cells in less than a million cells in less than a day? day?