Essential of biochemistry

1. How does the structure of proteins determine their function?

Protein function is dependent on its stable native conformation which is, in turn, determined by its primary structure or sequence.

2. What is the secondary structure of proteins?

It is the arrangement in space of the atoms in the backbone of the polypeptide chain.

The α-helix and β-pleated sheet hydrogen-bonded arrangements are two different types of secondary structure

In very large proteins, the folding of parts of the chain can occur independently of the folding of other parts. Such independently folded portions of proteins are referred to as domains or super- secondary structure.

3. How do we extract pure proteins from cells?

The first step is called homogenization and involves the breaking open of the cells.

After the cells are homogenized, they are subjected to differential centrifugation.

After the proteins are solubilized, they are often subjected to a crude purification based on solubility. Ammonium sulfate is the most common reagent to use at this step, and this procedure is referred to as salting out.

The separation and isolation, or purification, of proteins constitute an essential first step for experimentation.

In general separation techniques focus on three properties that can be the sources of differences among molecules: size, charge, and polarity.

Chromatography, one of two common general methods, makes use of differences in all three properties.

Electrophoresis, the other general method, depends on charge and size.

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