In this IBDP Biology topic, you will learn more details about cell wall.

• Cellulose is an unbranched chain of glucose units.
• Made of a different form of glucose than that of starch; it comprises of beta glucose units (starch is made of alpha glucose units).

• The glucose units in cellulose join by losing a water molecule in a condensation reaction, and comprise of 1,4 glycosidic bonds between beta-glucose molecules.
• This is only possible if every other molecule is rotated 180 degrees.
• This allows it to be a straight unbranched chain.

• Long straight chains then naturally pack together in bundles and held together by hydrogen bonds. These are microfibrils.
• The hydrogen bonds form between the OH groups in neighboring cellulose chains.
• The layers of microfibrils then layer over each other at angles to one another, forming a complete structure.
• The substance that holds these microfibrils together is a short, branched polysaccharide called hemicelluloses and pectins.

• Using pages 174-175 in orange books, write down some uses for pectins in plants and in the industry.

• Narrow fluid-filled channels crossing the cells walls.
• These allow substances to move freely between cells and make cell walls fully permeable.

This is the end of the topic

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Photo references:

1. https://amapex.net/enzymatic-hydrolysis-cellulosic-biomass/?lang=en
2. https://www.cell.com/trends/plant-science/fulltext/S1360-1385(99)01507-1
3. https://healthjade.net/pectin/
4. https://zh.wikipedia.org/wiki/%E5%8E%9F%E7%94%9F%E8%B3%AA%E7%B5%B2