February 24, 2015 Journal: What is the sex of the individual who’s karyotype is above? Is the karyotype normal or does the individual have a chromosomal abnormality?

Diffusion and Cell Size

Discussion Questions: What types of things need to get into cells? What types of things need to be taken out of cells? How do you think these things get into and out of cells?

Diffusion One of the ways that substances get into cells Small, uncharged substances move from an area of higher concentration to an area of lower concentration

Diffusion Demonstration

Discussion Question: You have to draw a line from the outside of each circle to the middle of the circle. In which circle below, would it take less time to draw the line?

Discussion Question: So if an oxygen atom was diffusing into each of the cells below, in which cell would the oxygen atom get to the middle faster?

So why are cells so small? It takes too long for nutrients and other molecules to diffuse throughout the entire cell in large cells, so cells remain small so the entire cell can get enough nutrients, oxygen, water, etc.

Surface Area to Volume Ratio Surface Area: outside area of an object Volume: the amount of space inside an object Surface Area to Volume ratio: compares how much outside area and object has compared to how much space is inside an object

Surface Area to Volume Ratio As a cell grows, the surface area to volume ratio decreases This means that there is more area inside the cell that requires nutrients and less area on the outside for the nutrients to get into the cell It is harder for larger cells to get nutrients into their cells through diffusion because their volume is so large

How do cells stay small? Cells divide when they get too large.

Why do cells divide? Growth Reproduction Replace damaged cells When cells get too big nutrients cannot reach the middle of them