Bellwork: 11/19 Put phone up  Week 11/19-11/21 Find the surface area to volume ratio of a cell that is 5cm L x 2cm W x 1cm H Why is it important that cells maintain a large SA:V ratio?

Objective Students will begin to learn about the importance of cell size to maintain proper function

Today: Bellwork Finish Part 3 Notes Cell Size POGIL

This Week: Mon/Tues: Cell Size POGIL Wednesday: Plasma Membrane Notes & Diffusion Demo Thurs/Fri: THANKSGIVING

Materials Unit book Cell Size POGIL

Homework Cell Size POGIL Quiz Thursday – Organelles & Cell Size Due Thursday Quiz Thursday – Organelles & Cell Size

Unit III: Cells

Part III: Cell Size

Intro ? Could you come across a 2 ton single-celled organism? Why or why not?

Cell Size Most cells are quite small in size Need to maximize surface area to volume ratio

Surface Area to Volume Ratio For a perfect cube: A cube that is 2cm L x 2cm W x 2cm H. What is its surface area/volume ratio? Surface area = L x W x # sides __cm x __cm x __ sides = ___cm2 Volume = L x W x H __cm x __cm x __cm = ___cm3 Surface Area/Volume Ratio = SA/V ___cm2/___cm3 = ___cm-1

With a Partner What is the surface area to volume ratio of a cube that is 4mm x 4mm x 4mm?

Are all cells perfect cubes?

Answer! For a perfect cube: A cube that is 4mm L x 4mm W x 4mm H. What is its surface area/volume ratio? Surface area = L x W x # sides 4mm x 4mm x 6 sides = 96mm2 Volume = L x W x H 4cm x 4cm x 4cm = 64mm3 Surface Area/Volume Ratio = SA/V 96mm2/64mm3 = 1.5mm-1

Surface Area to Volume Ratio For an imperfect cube: A cube that is 3mm L x 2mm W x 1mm H. What is its surface area/volume ratio? Surface area = __ mm2 3mm x 1mm x 2 sides = ___mm2 3mm x 2mm x 2 sides = ___mm2 2mm x 1mm x 2 sides = ___mm2 Volume = L x W x H ___mm x ___mm x ___mm = ___mm3 Surface Area/Volume Ratio = SA/V ___mm2/___mm3 = ____mm-1

With a Partner Calculate the surface/volume ratio of a cell that is 4mm L x 3mm W x 2mm H.

Answer For an imperfect cube: A cube that is 4mm L x 3mm W x 2mm H. What is its surface area/volume ratio? Surface area = 52mm2 4mm x 2mm x 2 sides = 16mm2 4mm x 3mm x 2 sides = 24mm2 3mm x 2mm x 2 sides = 12mm2 Volume = L x W x H 4mm x 3mm x 2mm = 24mm3 Surface Area/Volume Ratio = SA/V 52mm2/24mm3 = 2.2mm-1

Why are Cells Small? Maintain a large surface area to volume ratio Uptake of oxygen, nutrients, and removal of waste is more efficient Better for the cell If the volume becomes too large, surface area to volume ratio becomes small Therefore, the uptake of nutrients & removal of waste becomes less efficient Detrimental for the cell

Why are Cells Small? In larger cells Transport of materials from one region of the cytoplasm to another takes longer Nucleus controls cellular activity The nucleus communicates with the outer parts of the cell If the cell becomes too large, it takes longer for chemical signals to reach the outer parts of the cell

With a Partner If the cubes to the right represented a cell, which cube got food, water, or something needed by the cell distributed to all its parts. Why?

Answer ?s in Note Guide

Cell Size POGIL