Proteins Flashcards
Draw the basic structure of an amino acid
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How are polypeptides formed?
Amino acids joined together in condensation reactions, forming a peptide bone and eliminating a water molecule.
Primary structure of a protein
The basic amino acid sequence
Secondary structure of a protein
Whether the polypeptide chain is arranged in an alpha helix or beta pleated sheet.
Tertiary structure of a protein
Folding of the polypeptide chain due to interactions between side chains of amino acids. (Folding of the secondary structure into a complex shape). The shape is determined by the type of bonding present and the R group interactions.
Quaternary structure of a protein
the 3D arrangement of more than one polypeptide (not all proteins have this structure level)
What bonds can be found in proteins?
Hydrogen, ionic, disulphide bridges, peptide
How does the primary structure affect tertiary structure?
R group variations produce different bonds. Sulphur atoms form disulphide bridges, oppositely charged groups form ionic bonds, hydrogen bonds are always present as they occur between hydrogen and nitrogen/oxygen.
General functions of proteins
Antibodies, hormones, enzymes, ligaments, fundamentals in cell membrane, hair, muscles etc
What is the monomer of a protein
Amino acid
What is the polymer of proteins
Polypeptides
Fibrous protein examples
Collagen, keratin
Fibrous protein shape/structure level
Shape: long chain of several polypeptides coiled around each other and cross linked together with R group bonds.
Levels of structure: can be quaternary but each strand is secondary.
- hydrophobic amino acids on outside (why they cross link), soluble in water.
Globular protein examples
Enzymes, haemoglobin
Globular protein shape/structure level
Shape: compact, spherical
Levels of structure: tertiary or quaternary
- hydrophobic amino acids on inside and hydrophilic on outside so soluble in water. Water for a hydrogen bonds with other water.
Collagen
Collagen is an example of a fibrous protein. It has high tensile strength due to presence of both hydrogen and covalent bonds in the structure. Collagen molecules are made up of three polypep des which form an alpha triple helix which forms fibrils and strong collagen fibres. Collagen forms the structure of bones, car lage and connec ve ssue and is a main component of tendons which connect muscles to bones.
Haemoglobin
Haemoglobin is a water soluble globular protein which consists of four beta polypep de chains and a haem group. It carries oxygen in the blood as oxygen can bind to the haem (Fe2+) group and oxygen is then released when required.
