LIMIT TO CELL GROWTH NOTES

WHICH TURTLE HAS BIGGER CELLS?

Neither!!!

Their cells are the same size… this one just has MORE!

WHY DON’T CELLS CONTINUE TO GROW?There are two main reason why cells

divide instead of continue to grow:1. The larger the cell becomes, the more

demands the cell places on its DNA2. The cell has more trouble moving

enough nutrients and wastes across the cell membrane.

DNA “OVERLOAD” Information that controls a cell’s

function is stored in a molecule knows as DNA

In eukaryotic cells, DNA is found in the nucleus

DNA “OVERLOAD” When a cell is small, the information

stored in the DNA is able to meet all of the cell’s needs

If a cell was too large an “information crisis” would occur and the cell would not function properly

EXAMPLE: SMALL LIBRARY IN A LARGE CITY

EXCHANGING MATERIALS Food, water and nutrients enter the cell

through its cell membrane Waste products leave in the same way

EXCHANGING MATERIALSExample: Small streets in a big town

EXCHANGING MATERIALS The relationship between a cell’s

volume and its surface area is the key to understanding why cells must divide as they grow!

RATIO OF SURFACE AREA TO VOLUME

RATIO OF SURFACE AREA TO VOLUME The volume increases much faster than the

surface area, causing the ratio of surface area to volume to decrease.

This decrease creates serious problems for the cell.

Formula for calculating ratio:

Ratio = Surface Area/Volume

LAB SURFACE/VOLUME RATIOCAN WE FIND THIS EXPERIMENTALLY???

Problem: What happens to the surface/volume ratio when a cube gets really big?

Background:

1. How do you find surface area? Volume? Ratio?

Hypothesis:

Materials: pg 275 in book

Methods:

Result table in excel:

Conclusion: