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Protein structure

Proteins are macromolecular compounds constructed from amino acid residues. The variety of proteins is huge, although protein amino acids only number around twenty. It is important which amino acids are included in the protein and how they are combined with each other.

Amino acids can be joined by a peptide bondpeptide bondpeptide bond. Remind yourself of how to combine two molecules of the amino acid into the simplest construction – glycine.

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Grafika slajdu, na niebieskim tle tekst: tworzenie dipeptydu w reakcji glicyny z alaniną, the formation of a dipeptide in the reaction of glycine with alanine

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Rysunek przedstawia glicynę, glicyne i alaninę, alanine które są niezbędnymi aminokwasami. Jakie związki mogą powstać w wyniku ich reakcji?

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Glicyna, glicyne plus alanina, alanine strzałka w prawo dipeptide (glycyl-alanine), dipeptyd (glicyloalanina) plus woda

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Rysunek przedstawiający wiązanie peptydowe, peptide bond. Wiązanie peptydowe łączy grupę α-aminową jednego aminokwasu z grupą α-karboksylową drugiego aminokwasu.

Proteins are conventionally called compounds whose chain contains more than 100 amino acid residues, and shorter chain compounds are included in the polypeptides.

The protein chain can be described by the general formula:

Protein chains may have a different spatial structure, e.g. they twist in spirals or ribbons.

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Grafika przedstawia łańcuchy białkowe, które mogą mieć różną strukturę przestrzenną, m.in. skręcają się w spirale lub wstęgi.

Biochemists often refer to distinct aspects of a protein's structure:

Primary structure: the amino acid sequence. A protein is a polyamide.

Secondary structure: regularly repeating local structures stabilized by hydrogen bonds. The most common examples are the α‑helix, β‑sheet and turns. Because secondary structures are local, many regions of different secondary structure can be present in the same protein molecule.

Tertiary structure: the overall shape of a single protein molecule; the spatial relationship of the secondary structures to one another. Tertiary structure is generally stabilized by nonlocal interactions, most commonly the formation of a hydrophobic core, but also through salt bridges, hydrogen bonds, disulfide bonds, and even posttranslational modifications. The tertiary structure is what controls the basic function of the protein.

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Schemat przedstawia regularnie powtarzające się struktury lokalne stabilizowane wiązaniami wodorowymi. Najczęstsze przykłady struktury drugorzędowej to α-helisa, β-arkusz i skręty. Ponieważ struktury wtórne są lokalne, wiele regionów o różnej strukturze drugorzędowej może być obecnych w tej samej cząsteczce białka.

Proteinogenic amino acids are amino acids that are incorporated biosynthetically into proteins during translation. The word „proteinogenic” means „protein creating”. Throughout known life, there are 22 genetically encoded (proteinogenic) amino acids, 20 in the standard genetic code and an additional 2 that can be incorporated by special translation mechanisms.

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Grafika przedstawia proteinogenne aminokwasy, proteinogenic amino aid, które są włączane biosyntetycznie do białek podczas translacji. Słowo „proteinogeniczny” oznacza „tworzenie białka”.

Summary

• The molecules of all proteins are mainly composed of atoms of four elements: carbon, hydrogen, oxygen and nitrogen. Some of the proteins may include sulfur atoms, phosphorus and other elements.

• The basic elements building proteins are amino acids.

• Proteins are macromolecular chemical compounds, made up of amino acid residues joined by peptide bonds.

• Proteins are the main building blocks of organisms. They perform functions: building, transport, regulating and others.

• The source of animal protein include eggs, dairy, meat, fish, and vegetable – cereals and legumes, such as beans, soy and lentils.

Keywords

protein, protein structure, elemental composition of proteins

Glossary