Молекулярная гастрономия для креативных шеф-поваров (англ. язык) - страница 17

Молекулярная гастрономия для креативных шеф-поваров (англ. язык)

H2N C C OH

R O

H

Amino group Carboxyl group

C = carbon atom

H = hydrogen atom

O = oxygen atom

N = nitrogen atom

R = refers to the part of the amino acid that varies between the different amino acids.

There are twenty different amino acids that are commonly found in proteins. Proteins consist of long

chains of these amino acids, which are held together by strong bonds, called peptide bonds, like

beads on a necklace (in this analogy the beads represent the amino acids, and the string represents

the bonds). Because there are so many different amino acids, each of which may be joined to any of

the other amino acids, there is a very large amount of different proteins that can exist, and each one

has slightly different properties depending on its amino acid composition.

Depending on whether the “R” group of a protein is charged depends on whether the amino acid is

charged, or “hydrophilic”, or whether it is non-charged, or “hydrophobic”. An example of a hydrophobic

and a hydrophilic amino acid is shown below:

Arginine has a polar/charged head, so is hydrophilic

NH2

O

HO

leucine Leucine does not contain any charged groups, so is hydrophobic

Proteins are mainly found in the kitchen in meat and fish products, as well as eggs; and to a smaller

extent in various vegetable seeds.

IV/II - 2 (of 6)

Protein structure

In food sources, proteins are usually found in the presence of water. Their native form is ...

>

extent in various vegetable seeds.

IV/II - 2 (of 6)

Protein structure

In food sources, proteins are usually found in the presence of water. Their native form is not in the

form of these long straight chains, but rather in the form of highly folded chains (almost like balls of

string) that form a 3-dimensional structure that is unique to each protein, and depends on its amino

acid sequence. The chain is folded in such a way that all the amino acids that are “hydrophobic” are

protected inside the protein, while those that like to be in contact with water are kept on the surface,

where there are in contact with the water. The protein is held in this form by a number of forces

between their side chains – these include bonds formed between sulphur groups (these are called

sulphur bridges, and are among the strongest of all the forces), positive and negative parts of a protein

Страницы: Пред. | 1 | ... | 15 | 16 | 17 | 18 | 19 | ... | 253 | След.

Еще статьи