Proteins of the Cell

1. Membrane Proteins.

2. Enzymatic Proteins.

3. DNA Binding/regulatory Proteins.

4. Non-membrane transport Proteins.

5. Structural Proteins.

6. Peptides and peptide hormones.

Membrane proteins:

One role of proteins in cells is for transport of molecules/ions into or out of cells. Three methods of doing this are through active, facilitated or passive transport. Other roles of membrane proteins are in cell recognition, receptors, cell to cell communication.

Types of Proteins:

Transmembrane Protein:

Globular Protein:

Glyco-protein: - Glyco-proteins are processed in the Endoplasmic reticulum, and a carbohydrate chain is added on.

A Functional look at Membrane Proteins:

Transport Proteins:

There are two ways that molecules pass through transmembrane proteins: uniport - which is where one molecule is transported, and cotransport - where 2 molecules are transferred. Also there are two basic types of cotransport: symport, which is where two molecules are transported in the same direction and antiport, where the molecules are transported opposite directions through the membrane (which will be shown by the Na - K ATPase pump coming up). Here are the types of transport.

2.1.4.1. Active Transport (these can be either uniport or cotransport):

This transport, which will require energy, is going against the electro-chemical gradient. An example of this can be found in the Na - K ATPase (The Sodium-Potassium ATPase pump), this is important especially in the nerves of all animals. This is commonly used to generate a membrane potential.

2.1.4.2. Facilitated Transport (these can be either uniport or cotransport):

Facilitated transport is as it sounds, facilitates transport. This occurs because it moves with the electro-chemical gradient.

2.1.4.3. Passive Transport:

Small molecules that are uncharged can move directly through the membrane in the direction of high concentration to low concentration. Molecules that have a charge (positive or negative) it will tend to move to the side of the membrane that have the opposite electrical potential.

Proteins role in this is through forming channels through the membrane that facilitate transfer of the molecules in accordance to the electrical and chemical gradients.

Putting these all together in a membrane is done in the following example of the Sodium-Potassium ATPase pump in conjunction with the Potassium leak, and the glucose symport with Sodium.

Cell Recognition: Cell recognition occurs through

Cell-Cell Communication:

Receptors:

Go back to Chapter 2.1: 'Cell/plasma Membrane'

Go back to Chapter 2.2.9: 'Cytoskeleton & Microtubules'

Please send questions/comments/suggestions to: Mark Dalton at markwdalton@gmail.com.