1. Cellulose and starch are both polymers of glucose but fulfil very different functions in cells. Explain the roles and properties of the two polymers and speculate which of their properties may have aided the evolution of their current function. Use the following terms in your explanation: Glycosidic bonds; Starch; Cellulose; Cell wall; Energy storage.
Cellulose and starch are both important polysaccharides made from glucose, that perform different roles within plant cells. Even though starch is somewhat soluble and easier to digest in most animals in contrast to cellulose, the only difference between the two polymers are their structure. Starch is made from alpha glucose whereas cellulose is made from beta glucose, such that the alcohol group on the sugar faces downwards or upwards respectively. This means that alpha glucose is able to be easily linked side by side, compared to beta glucose molecules that must link in a flipped manner. Both types of glucose are linked by glycosidic bonds, where water is released in the attachment of the alcohol groups from either sugar. Starch is therefore bent and branched in shape compared to the linear structure of cellulose. The bent structure of starch aids in its function of storing energy, likewise to the linear structure of cellulose supporting its roles in building the strong cell wall.
In speculation, the property which may have had the biggest impact on the polymer’s functions today is the evolution of glucose itself. Originally glucose may have been the same looking molecule and split into its two defining groups of alpha and beta over time. This differentiation between the two sugar molecules led to the difference in structure of the polymers and hence the roles they now play.
· Cellulose and starch are both polysaccharides made from glucose
· Perform different roles (due to structure)
· Cellulose if insoluble not easily digested (vice versa for starch)
· Cellulose has beta glucose (alcohol group on sugar faces upwards), starch has alpha (alcohol faces downwards)
· Glysocidic bonds link glucoses together (water released through attachment of alcohol groups)
· Alpha can be linked side by side (bent structure) – storing energy
· Beta has flipped linkage (linear structure) – rigid cell wall
· Evolution of glucose impacts polymers function (beta vs glucose) therefore both glucoses evolved from one
2. Why do all cells need membranes, and why is it important that membranes are made out of phospholipids? Incorporate the following terms into your answer: hydrophobic; hydrophilic; semi-permeable.
All cells, whether, prokaryotic or eukaryotic need cell membranes, as cell membranes play a fundamental role in cells. Cell membranes protect and organise cells. They serve as barriers and/or gatekeepers of the cell. Cell membranes are responsible for regulating what comes in and what goes out of the cell. The cell membrane of a cell, is semi-permeable, meaning that whilst some molecules...