Bio Chemistry

BIOCHEMISTRY 3(2+1)

Lesson 5 : Cell Structure and Functions

Surface

Cell Membrane

1. Structure - composed of protein and lipid (fat) molecules
2. Function
• acts as a boundary layer to contain the cytoplasm (fluid in cell)
• interlocking surfaces bind cells together
• selectively permeable to select chemicals that pass in and out of cells

Cell wall Structure a non-living secretion of the cell membrane, composed of cellulose cellulose fibrils deposited in alternating layers for strength contains pits (openings) that make it totally permeable Function provides protection from physical injury together with vacuole, provides skeletal support
Plasma membrane Outer membrane of cell that controls cellular traffic Contains proteins (left, gray) that span through the membrane and allow passage of materials Proteins are surrounded by a phospholipid bi-layer