AERO 2200 Study Guide - Midterm Guide: Primary Cell, Plant Cell, Microscope
23 Nov 2016
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Unit 3: the microscope and cell biology: the cells of plants, fungi, bacteria and some protists have cell walls. Why, in your educated opinion, do animal cells lack a cell wall: plant cell walls are composed of both a primary and secondary layer. The primary layer is present as the cell grows, while the secondary develops after a cell has finished growing. Primary cell walls are composed of polysaccharides, the most common being cellulose. These protect the cell, provide support, and prevent the cell from bursting under osmotic pressure. The lack of cell walls in animals allows greater flexibility of the cells, as is necessary for locomotion. The tissues, organs and organ systems present in animals require more physical connection than plant cells to allow the passage of macromolecules between cells. Animals have skin, which acts as a barrier to the outside world and offers protection.
