Proteins

Proteins

1. Amino acids and polypeptides

   • amino acids condensed into polypeptides
   • on ribosomes by translation
   • main or only component of proteins
   • condensation reaction: anime group (NH2) of one aa and carboxyl group (COOH) of one aa
   • water eliminated; peptide bond formed
   • dipeptide = 2 aa bonded by a peptide bond
   • polypetide = chain of many aa
   • oligopeptides = less than 20 aa

2. The diversity of amino acids

   • 20 diff aa
   • carbon atom in centre linked to amine group, carboxyl group, hydrogen atom
   • C bonded to diff R group in every aa
   • aa chemically diverse due to wide range of R groups
   • polypeptides may contain modified aa

3. Polypeptide diversity

   • aa can link in any sequence so polypeptides diverse
   • ribosome can make peptide bond between any aa
   • number of aa = n possible sequences = 20^n

4. Genes and polypeptides

   • aa sequence coded by genes
   • polypeptide structure stored in gene's base sequence
   • most gene cells store aa sequences
   • three bases needed to code for every aa
   • open reading frame = base sequence coding for polypeptides
   • open reading frames only occupy small proportion of total DNA

5. Proteins and polypeptides

   • proteins = single or many linked polypeptides
   • Integrin can fold any way
   • Collagen is twisted like a rope for structure
   • 4 parts of haemoglobin interact

6. Protein conformations

   • 3D conformation determined by aa sequence
   • 3D structure
   • fibrous proteins elongated with repeating structure
     • folding prevented
   • globular proteins are intricate with helical or sheet-like parts
     • stabilized by R groups of aa
     • fold as created
     • if water soluble - hydrophobic R inside; hydrophilic R outside
     • regions with hydrophobic R outside attracted to hydrophobic membrane centre

7. Protein functions

   • catalysis
   • muscle contraction
   • cytoskeletons
   • tensile strengthening
   • blood clotting
   • Transport of nutrients and gases
   • Cell adhesion
   • Membrane transport
   • Hormones
   • Receptors
   • Packing of DNA
   • Immunity
   • other uses in book (non-biological)

8. Proteomes

   • unique in every individual
   • all proteins produced
   • separated by gel electrophresis
   • variable and different even though strong similarities in species

Imagens e arquivos do mapa