Lecture 6 Flashcards
Carbs, Lipids, and Cell Membranes
Starch Structure
Starch is a polymer of glucose found in plants. It has 1-4 linkages of alpha glucose monomers.The alpha linkages in starch are more reactive to enzymes meaning they easily break and alpha-glucose is less stable.
Cellulose Structure
Cellulose is a polymer of glucose found in plants. It has 1-4 linkages of beta glucose. There is H bonding within the beta glucose monomers making cellulose very strong.
What are the functions of starch and cellulose in plants?
Cellulose is used for structure and support. Starch is used for energy storage.
Why can most animals and humans digest starch and not cellulose.
Humans & animals cannot digest cellulose as most contain enzymes that can hydrolyse the weaker alpha glycosidic linkages of the starch but not the strong beta glycosidic linkages of cellulose.
Why are lipids not polymers?
A polymer is a linear linkage of covalently bonded monomers of the same component. Lipids are made up of different components, 1 glycerol and 3 fatty acids, which are not the same monomers thus they cannot be polymers.
What is the structure of phospholipids?
Phospholipids are amphipathic, they have a hydrophobic tail and hydrophilic head. They are self organising molecules, arranging themselves in aqueous solutions so their polar heads interact with the water and their non-polar tails do not. There are no covalent bonds between molecules, as the hydrophobic interactions keep the tails away from the water.
How does the structure of phospholipids relate to the function of membranes.
As the phospholipid is self organising it creates a lipid bilayer with the heads on the outer sides of the membrane protecting the tails. Membranes are flexible due to the lack of covalent bonds as a result of the hydrophobic interactions.
What is the function of membranes?
Phospholipids are the main component of cell membranes, they are arrange in a bilayer with the polar head on the outside and the non-polar tails within. There are hydrophilic interactions on the outsides of the membrane and hydrophobic interactions within the membrane. Membranes are not solid structures and have fluidity, the phospholipids move laterally in one layer of the bilayer. Cholesterol is used to control the fluidity of the membrane. Cell membranes maintain cell structure, regulate flow of materials, and contain important proteins.
What is the function of membrane proteins?
Different cells have different proteins with different functions. Membrane proteins are involved in a variety of dynamic cellular processes, such as ionic and molecular transport, electron transport, signal transduction, enzymatic reactions and intercellular communication.
