Membrane Structure and Function_Chapter 7

1. What is the structure of cell membrane and how are the materials arranged?

2. Why is the cell membrane fluid?

3. What are the differences between passive and active transport?

The structure of cell membrane :

Phospholipids and proteins. There are hydrophilic head and hydrophobic tails. Proteins are outside and inside and phospholipid bilayer is in these protein surface. Proteins are hydrophilic and phosphate bilayer is hydrophobic. There are two protein structure. One is integral, bigger, and the other is peripheral, still connected to the membrane. It also has some cholesterol inside the membrane.

The fluidity of cell membrane.

Phospholipids and proteins move in the membrane freely. The unsaturated hydrocarbon tails of some phospholipids kept the membrane fluid at lower temperature. The cholesterol acts as a temperature buffer. Molecules are not bonded together. It needs to be fluid to function correctly.

Active transport vs Passive Transport.

Active transport, energy used. 3 types; carrier mediated, endocytosis, exocytosis. Passive transport, energy is not used. High concentration to low concentration.. 3 types; diffusion, osmosis, facilitated diffusion.

Videos on active and passive transports :

http://www.youtube.com/watch?v=VUnvwrx8Wq4&feature=related

http://www.youtube.com/watch?v=K7yku3sa4Y8&feature=related

5 main facts about this chapter :

. Carrier mediated transport is against the concentration gradients. (low to high)

. Davson-Danielli model (1935) is also called the sandwich model since it looks like that.

. According to the evidence obtained by use of TEM Microscopes, we know the structure of cell membrane.

. Proteins in cell membrane function differently. Transportation, enzymatic activity, receptor sited for signals, cell adhesion, cell-cell recognition, attachment to the cytoskeleton.

. Integral proteins stick to the membrane by the solubility of their amino acids.

In this chapter, we learnt about the function and structure of cell membrane. Cell membrane is found both in animal and plant cells. It has several functions. It transport materials from outside and inside of the cell. According to the use of energy, the function, structure of the transport change. Cell membrane is fluid because of the unsaturated lipids in the cell membrane. We now know the hydrophilic and hydrophobic parts of the cells and what they contain such as proteins and phospholipids.