Protiens Flashcards
What is a protein?
One or more polypeptide chain arranged in a complex macromolecule
State the 4 protein structures?
- primary
- secondary
- tertiary
- quaternary
What is a Primary structure?
- A sequence of amino acids held together by covalent peptide bonds via condensation reaction (removal of water)
- Directed by the DNA
- amino acids determine how the polypeptide folds into its structure and its function
What is a Secondary structure
- The simple fold of polypeptide into either 2 structure/shapes.
- hydrogen bonds between an amine group of a amino acid and carboxyl group of another amino acid.
- Alpha helix shape: Hydrogen bonds within the amino acid chain pulls into a helix shape
- beta pleated sheet: polypeptide chain is parallel to each other and joined by hydrogen bonds forming a sheet like structure. Appear Pleated due to the patterns formed by individual amino acids
What is a Tertiary structure?
- The complex folding of a single polypeptide chain into its final structure and function
- R groups of a amino acid joins with a R group of another amino acid forming additional bonding.
- Additional bonding: Disulphide, hydrogen, ionic bonding and hydrophobic and hydrophilic interactions.
State and describe the additional bonding’s you can find in both tertiary and quaternary structure.
- Disulphide bonds = between cysteine (amino acids containing sulphur atoms) = strongest but not common (used to stabilise) = Broken down by oxidation
- Ionic bonds = between non polar R groups = stronger than hydrogen bonding but not common = Broken down by pH changes
- Hydrogen bonds = between polar R groups = weakest but most common.
- Hydrophilic interactions
- Hydrophobic interactions
What is Quaternary structure?
- The final/compete fold of more than one polypeptide chain into is structure and function
- Contains the additional bonding’s found in Tertiary structure
Globular proteins shape/structure & Amino acid sequence.
Shape: compact, spherical shape that folds into a tertiary structure because of..
- The polar hydrophobic R groups orientate towards the centre of the protein away from the aqueous environment and the non polar R groups orientate themselves to the surface of the protein.
possesses a specific shape due to the interactions between R groups.
Amino acid sequence: Irregular
Globular proteins Function & Examples
Function: Physiological/Functional.
- Roles used for catalysing enzymes metabolic reactions and antibodies to respond to antigens.
Examples:
Insulin
- A hormone that is involved in regulating the concentration of glucose in the blood. Needs to fit into specific receptors to function so a specific shape is needed
Globular proteins Solubility
Soluble in water
Conjugated protein: Haemoglobin
A pigment that can combine and carry oxygen, is found in red blood cells.
- Quaternary protein made up of 4 subunits( 2 alpha and 2 beta subunits)
- Each subunit contains a prosthetic haem group
- The Fe2+ ions in the haem group are each able to combine reversibly with an oxygen molecule in the lung + transport the 02 to the tissue to be used for aerobic metabolic pathways.
Fibrous protein: Keratin
- strong, insoluble and inflexible.
- Structure contains a lot of cysteine(Amino acids containing sulphur atoms) which has many disulphide bonds (strong bonds)
Fibrous protein: Collagen
- connective tissue found in the tendons, ligaments, and nervous system.
- made up of 3 polypeptides wound together in a long, thin, strong rope-like structure.
Fibrous protein: Keratin
- Strong, inflexible and insoluble due to may cysteine(amino acids contain sulphur atoms) which haave alot of disulphide bonds(strong bonds)
- Found in hair, nails and skin
Fibrous proteins structure/shape & Amino acid sequence
Shape/Structure:
- thin and structural/organized proteins
- Don’t fold into 3D shapes like globular proteins
Amino acid sequence: Repetitive = organized structure
