Cell Size Introduction

Which is bigger? Which has larger cells, an ELEPHANT or an ANT? Why?

As you grow…. Do your cells keep getting bigger? Do you have the same number of cells now as you did when you were born? NO, they stay about the same size, but divide NO, you have trillions of cells as an adult, and you started out as just 1

The cells of Small and Large organisms are about the same size

The cells in both Adults and Newborns are the same size Why are cells so small?

How does cell size impact DNA? 1. DNA Overload Information that controls a cell’s functions is stored in the DNA. In a large cell, DNA is not able to keep up with all of the cell’s functions Information Crisis – too many requests from the DNA Classroom Analogy: Math classroom with 20 students = small cell Math teacher = DNA English classroom with 80 students = large cell English teacher = DNA A cell cannot get more DNA(another teacher) to run smoothly. DNA can only support the demands of a small cell.

2. Exchange of Materials Coming IN: water, oxygen, food Going OUT: waste and CO 2 plus proteins to other cells All this exchange occurs across the cell membrane. In a large cell: not enough places to enter & exit Movie Theater Analogy: Theater A: 3,000 People & 20 Exits Theater B: 200 People & 10 Exits

Hypothesis: Inside a large cell, it would take a _________(longer/shorter) amount of time to import or export important molecules, compared to a small cell. Jello Investigation: In this lab, we will be investigating how size of a cell affects the rate of diffusion of materials (how fast they spread). We are going to place BTB jello cubes of various sizes into a weak basic solution (baking soda dissolved in water). As the baking soda solution enters the cube, the cube will turn from yellow (gelatin is slightly acidic) to blue (basic). Then we will determine the time until the solution has diffused all the way to the center of the cube. Jello is a model for: ______________ Baking soda solution is a model for: ____________

Procedure 1. Take a small ‘block’ of jello to your table and place on paper towel or petri dish. Carefully cut three cubes from the block. DO NOT STAB OR PUNCTURE THE CUBE IN ANY WAY. Use caution while using the scalpels! You can use grid paper or a ruler to help measure. The cubes should approximately be the following sizes: 1 cm 0.5 cm 0.25 cm 2. Obtain a small beaker and fill halfway with baking soda solution. Gently place the blocks into the baking soda solution ALL AT THE SAME TIME and start the timer (you can use a timer on your phone). 3. For each block, record the time (in minutes) that it takes the cube to completely change from yellow to blue. Record times in data table. 4. Clean up! Put the ‘cells’ in the wastebasket (not the sink please!). Return all other materials (clean, of course ) to the spot you picked them up from.