Report

Cells are limited in size – you can’t see them without a microscope for good reason! As a cell gets larger and larger (as it eats more and more), it takes longer and longer to get food/waste in and out Cell becomes “bloated”, can’t compete as well with smaller, quicker cells Needs to divide to become competitive again Mitosis! Surface area – the total area on the outside of an object Volume – the amount of space taken up by an object The ratio between the two limits the sizes of cells! Surface Area (S.A.) = Area of all sides, added together 3cm cube 3 x 3 = 9cm2 6 sides to a cube Total surface area = 54cm2 Length x height x width Same cube 3x3x3 Total volume = 27cm3 Volume Ratio S.A.:Volume: Surface Area / volume 54:27 or 2:1 2cm cube Surface area: Volume: 2x2x6 24cm2 2x2x2 8cm3 Ratio S.A.:Volume: 24:8 3:1 Do calculations on your own Surface Area: Volume: 1x1x6 6cm2 1x1x1 1cm3 Ratio S.A.:Volume: 6:1 0.1cm cube Surface area = 0.06cm2 Volume = 0.001cm3 SA/V = 60:1 0.01cm cube Surface area = 0.0006cm2 Volume = 0.000001cm3 SA/V = 600:1 The smaller the cell, the higher the ratio is! This is why cells divide to stay small! Cutting cubes of agar into 1cm, 2cm, and 3cm cubes Phenolphthalein in the agar cubes is an indicator Turns pink in base Turns clear in acid We will be soaking the cubes in vinegar (acetic acid) Look to see how far it penetrates into larger vs. smaller cubes Which do you think will diffuse faster? Why? This is similar to how long it takes food/waste to diffuse in/out of larger vs. smaller cells Wear goggles AND aprons today Cut your agar block down the middle, and split between two groups Carefully cut out your 1cm, 2cm, and 3cm cubes from your agar Remember – cubes have the same height, length, and width! Be sure to accurately measure the length of the sides, so you can do proper calculations Place the three cubes in the 250ml beakers Cover with vinegar and wait until After 10 minutes has expired, pull cubes out of vinegar and gently rinse off Measure the remaining Nuclear Pink Agar Calculate the rate of diffusion Final Volume of Nuclear Pink Agar – Then Trash Clean up & answer analysis questions Return the following to Prep Table: Vinegar Ruler Plastic Knife, Milk Carton (Clean, Dry)