1.3.1 Phospholipids form bilayers in water due to the amphipathic properties of the molecules

Phospholipids form the membrane of the cell. They are amphipathic meaning that they display both hydrophilic and hydrophobic properties (the molecule are both attracted to water and repel away from water). This is because phospholipid molecules have two fatty acid tails and a phosphorylated alcohol (which is attached to a glycerol) head. Water is polar and it has positive and negative ends, water attracts other things that are polar (positive and negative attracts). So fatty acids, which are non-polar, are repelled by water and hydrophobic. While the phosphorylated alcohol head is polar and, therefore, attracted to water and is hydrophilic

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1.3.2 Membrane Proteins do a lot of things and have unique structures and positions

If you look at the diagram of the membrane bilayer you will see many different proteins with varied structures. The two main types of proteins, integral and peripheral. Integral proteins are all inside the membrane bilayer while peripheral proteins stick to the membrane on the outside.

The structure of the proteins is different as well, such as the channel protein which has a space for large particles to pass through past the cell membrane.

The main functions of the membrane proteins are

1.3.3-1.3.4 Cholesterol is a component of animal cell membranes, affecting fluidity and permeability

Cholesterol molecules are in various locations in the hydrophobic region of the phospholipid bilayer. Cholesterol determines the fluidity of the membrane at a wide range of temperatures. Basically, the cell needs to be able to bend and be flexible, this ability changes at different temperatures so cholesterol makes sure that the cell membrane retains its fluidity/bendiness/flexibilities at a wider range of temperatures

Cholesterol also makes it more difficult for certain solutes to pass through the membrane such as hydrogen ions and sodium ions which make the membrane less permeable (fewer things can pass through the membrane)

1.3.5 Be able to draw the fluid mosaic model

It’s already shown at the top

1.3.6 Analysis of evidence from electron microscopy for the falsification of the Davson-Danielli model that led to the Singer-Nicolson model

1.3.7 Analysis of the Davson-Danielli model that led to the Singer Nicolson Model

1.3.8 Amphipathic phospholipids have hydrophilic (water-loving) and hydrophobic (water-fearing) properties

1.3.9 When drawing a model of the cell membrane it can be two-dimensional, phospholipids are drawn as circles with 2 parallel line attached (so kinda like this but vertical O= ) you should also draw a range of proteins and a glycoprotein

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