Proteins:

  • large molecules/macro-molecules
  • consist of one or more long chains of amino acids

Protein functions:

  1. catalysing metabolic reactions (enzymes in the TCA cycle/glycolysis etc.)
  2. transport molecules (carrying lipids, carbohydrates, hormones)
  3. structural motifs (part of the cytoskeleton, giving shape to cells)
  4. regulatory elements (p53, transcription factors, coactivator, corepressor)
  5. enzymes involved in the cell cycle (DNA replication, repair)

Levels of the protein organization
Figure 1. Levels of the protein organization
  1. Primary (AMINO ACID SEQUENCE)
  2. Secondary (ALPHA HELIX / BETA- SHEETS / TURNS AND LOOPS)
  3. Tertiary (THE 3D SHAPE OF THE FULLY FOLDED POLYPEPTIDE CHAIN (due to the side chain interaction))
  4. Quaternary (ARRANGEMENT OF SEVERAL POLYPEPTIDE CHAINS (full conformation with the subunits)) (Figure 1.)

Primary structure - amino acid sequence

STARTS every time with:

  • MET (Methionine - Sulphur containing essential amino acid)

The sequence is arranged together in the process called "translation" (cytosol) after the "transcription" has been done (nucleus).

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