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| Pregunta | Respuesta |
| 1.3 U Phosolipids form bilayers in water due to the ampithatic properties of phospholipid molecules. | Some substances are attracted to water-hydrophilic (phosphate head). Substances that are not attracted to water- hydrophobic (hydrocarbon tail). In phospholipids, they have both, which is- amphipathic. Cholesterol is a lipid steroid in the membrane that helps give strength. |
| 1.3 U Membrane proteins are diverse in terms of structure, position in the membrane and function. | The primary function is to form a barrier where ions and hydrophilic molecules cannot easily pass. This is carried out by the phospholipid bilayer. All other functions are carried out by protein membranes; Pumps, channels, cell to cell, cell adhesion, immobilize, and hormone binding sites. |
| 1.3 U Cholesterol is a component of animal cell membranes. | The two main components of cell membranes are phospholipids and proteins, all containing cholesterol. Cholesterol that belongs to a group of steroids. Cholesterol molecules are positioned between phospholipids in the membrane. |
| 1.3 A Cholesterol in mammalian membranes reduces membrane fluidity and permeability to some solutes. | Cholesterol is a type of lipid that is mostly hydrophobic. However, one end of it is hydrophobic so it is therefore positioned between phospholipids in the membrane. |
| 1.3 Skills .Drawing of fluid mosaic model | Fluid Mosaic Model- Model of the cell membrane, it moves and is made up of many parts. |
| 1.3 Skills .Analysis of evidence from electron microscopy that led to the proposal of the Davson- Danielli model. | Davson- Danielli Model- A 30 year old theory of membrane structure. A free- etched electron micrograph technique, involves rapid freezing of cells and then fracturing them. Proposed layers of protein adjacent to phospholipid bilayer on both sides of membrane "Sandwich Model". Thought it would explain how membranes despite thinness, are a very effective barrier to movement of some substances, "railroad track"- 2 dark lines, with lighter band between- proteins dark, phospholipids light. |
| 1.3 Skills .Analysis of the falsification of the Davson-Danielli model that lead to the Singer-Nicolson model. | It was wrong because the fracture is on weakness lines, including center of membranes. Globular structures are scattered through freeze-etched images of the center of membranes being interpreted as transmembrane proteins. Membranes found to be varied in size, and globular in shape, forming continuous layers on peripherary of the membrane. Proteins were hydrophobic on part of the surface, being attracted to the hydro-carbon tails. |
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