Surface Area to Volume Ratio Concept Glucose Nutrients Amino acids Carbon dioxide Metabolic waste eg. urea Volume determines the amount metabolism in the cytoplasm Metabolism will require inputs that will need to enter the cell Metabolism will result in production of Waste products which will need to be removed from the cell and excreted. Secretions that will need to be exported from the cell Oxygen

Surface Area to Volume Ratio Concept Metabolism occurs here Uptake and removal occur via the membrane Volume determines the amount metabolism in the cytoplasm Metabolism will require inputs that will need to enter the cell Metabolism will result in production of Waste products which will need to be removed from the cell and excreted. Secretions that will need to be exported from the cell

Surface area Exchange of materials with the environment occurs across the cell surface Surface area will effect the rate of the exchange Bigger cells would generally have more metabolically active site But they will would have a relatively small surface area across which to supply the metabolic needs And the sites of metabolism in bigger cells will be further from the surface of the cell

Investigating effect of size on rate of diffusion into a cell Let practise working this out Investigating effect of size on rate of diffusion into a cell     Let practise working this out Size of cube Side length (mm) Surface Area Volume Surface area: volume 1mm SA=lxlx6   = 1X1x6 =6 mm2 V= l x l x l =1x1x1 = 1mm3 SA:V 6: 1 Or 6 units of SA per unit of Volume 2mm     SA=2x2x6   =24 mm2  V= 2x2x2 = 8mm3  24: 8 Or 3 units of SA per unit of Volume 3 mm   SA=3x3x6   =54 mm2  V= 3x3x3 = 27mm3  54: 27 Or 2 units of SA per unit of Volume Time taken to turn yellow  

Comparing Surface Area and Volume changes   Side length of cubic cell(µm) 1 2 3 4 5 6 Surface Area (µm2) 24 54 96 150 216 Volume (µm3) 8 27 64 125 SA:VOL 6:1 3:1 2:1 3:2 1.5:1 150:125 6:5 1.2:1 1:1

Comparing Surface Area and Volume changes Length of cube side (um) Surface area( um2) Or Volume (um3) © 2007 Paul Billiet ODWS

Surface Area:Volume Ratio © 2007 Paul Billiet ODWS

Surface Area to Volume Ratio Concept Why are cells so small?

Increasing surface area when a faster rate of uptake is needed

Throw out extensions Microvilli of small intestine epithelium © copyright 2001 Gwen V. Childs, Ph.D., University of Arkansas for Medical Sciences Microvilli of small intestine epithelium

Flatten into a thin film © Developmental Biology Online © Developmental Biology Online Chick blastodisc

Divide the cytoplasm into smaller volumes 8-cell Embryo Early human embryos Zygote © Reproductive Medicine and Fertility Center

Multicellular organisms show the same adaptations Flowering plants have an extensive, branched rooting system to absorb water and minerals © Illinois Enviromental Protection Agency © Text 2007 Paul Billiet ODWS

Multicellular organisms show the same adaptations Mammals have a long small intestine with internal folding to absorb digested food lithograph plate 20th U.S. edition of Gray's Anatomy of the Human Body, originally published in 1918. This image is in the public domain because its copyright has expired © Text 2007 Paul Billiet ODWS

Breaking up big things to speed rates of movement up