Protein Structures Part 3 Flashcards
Describe the structure of Globular Proteins ?(Functional )
Functions :
Enzyme:they catalyse chemical reactions and modify chemically their substrates.
Protective proteins against pathogens or animals
Lectins (aggregation)
Protective proteins function as protection against disease
Antibodies combat bacteria and viruses in animals
Signalling: Intracellular proteins function as cellular messenger molecules
that participate in intracellular signalling cascades
- Hormones:
Insulin: sends message for glucose storage in cells (when blood glucose levels are high, cells will transport glucose into the cells for use or storage)
Glucagon: sends message “we need more sugar in the blood” (when blood glucose is too low, cells will release glucose).
Cytokines/chemokines
Transport proteins function in the movement of other substances. Haemoglobin
Storage proteins function in the storage of amino acids
Ovalbumin is the protein in egg whites
Casein is the protein in milk, source of amino acids for baby mammals
Easily water soluble
Functional: Proteins perform specific catalytic or signalling activities.
enzymes, hormones, antibodies, haemoglobin (blood) and growth and maintenance proteins.
Ball, Spiral Shape
Serine
How do globular proteins help fin tertiary structure ?
The tertiary structure of globular proteins reflects their interaction with their aqueous solvent. At a simple level, a globular protein may be considered to consist of a hydrophobic core surrounded by a hydrophilic external surface which interacts with water
Hydrophobic interactions hold them together when they interact inside not outside.
Hydrophobic residues inside of proteins
This hydrophobic effect is held together by van der walls /London dispersion forces.
Hydrophobic will interact with hydrophobic portions
Hydrophilic will interact with hydrophilic portions which helps maintain a protein structure
Factors determining tertiary /quaternary structure (5)?
Hydrogen bonding :
Between R groups side chains
Polar
Serine, tyrosine, theorine, they have OH which can in their side chains be involved in hydrogen bonding.
Factors in determine tertiary /quaternary structure (4)?
Electrostatic interactions
Charged polar groups repel each other
Opposite amino acid- 5th amino /aspartate
acid/basic charged effect on each other.
Have an effect on overall 3D structure of protein causing it to bend.
Can be effected by pH changes
Factors in determine tertiary /quaternary structure (3) ?
Disulphide Bridges
Cysteine can form disulphide bridges
The side chains
S-H of you have two cysteine’s they can form a bond
S-S
Occur in oxidizing environment , get ride of hydrogen
Getting ride of hydrogen /create covalent
Breaking up -caused by reductive environment.
In non -covalent interact-Disulphide bond are covalent were creating or breaking covalent bonds
They can be messed up with reducing agent can destroy them reduction/oxidizing
Hydrophobic effect can be destroyed by detergents .
Hydrogen bonds can be disrupted by heat.
Mild Oxidation, maintain the structure of covalent bond stronger than dipole dipole.
Factors in deterning teartiray /quaternary structures ?
Hydrophobic interactions describe the relations between water and hydrophobes (low water-soluble molecules). Hydrophobes are nonpolar molecules and usually have a long chain of carbons that do not interact with water molecules.
The mixing of fat and water is a good example of this particular interaction. The common misconception is that water and fat doesn’t mix because the Van der Waals forces that are acting upon both water and fat molecules are too weak.
However, this is not the case. The behavior of a fat droplet in water has more to do with the enthalpy and entropy of the reaction than its intermolecular forces.
Hydrophobic Interactions are important for the folding of proteins
Besides from proteins, there are many other biological substances that rely on hydrophobic interactions for its survival and functions, like the phospholipid bilayer membranes in every cell of your body!
Strength of Hydrogen interatcion
Temperature: As temperature increases, the strength of hydrophobic interactions increases also. However, at an extreme temperature, hydrophobic interactions will denature.
Number of carbons on the hydrophobes: Molecules with the greatest number of carbons will have the strongest hydrophobic interactions.
The shape of the hydrophobes: Aliphatic organic molecules have stronger interactions than aromatic compounds. Branches on a carbon chain will reduce the hydrophobic effect of that molecule and linear carbon chain can produce the largest hydrophobic interaction.
This is so because carbon branches produce steric hindrance, so it is harder for two hydrophobes to have very close interactions with each other to minimize their contact to water.
What about Fibrous Proteins ?Structural
Polypeptide Backbone Doesn't fold on it own Long string of amino acids Collagen,keratin]Hair, nails Not water soluble
What about Fibrous Proteins ?Name some examples
Structural proteins: Shape and support function
Insects and spiders use silk fibers to make cocoons and webs
Collagen and elastin used in animal tendons & ligaments
Keratin: protein in feathers, horns and hairs
generated by bundling of 3D rod-shaped polypeptides
Fibrous Protein
Structural proteins: Shape and support function
Components of the cell cytoskeleton - Keratin - Vimentin - Desmin - Neurofilaments - Lamin
List some more examples of Fibrous Protein ?
Structural proteins: Shape and support function
Components of the extracellular matrix: - Fibronectin - Collagen - Fibrilin
Fibrous proteins:generated by polymerisation of globular proteins.
Structural proteins: Shape and support function
Components of the cell cytoskeleton
- F-actin (Filamentous actin): G-actin (Globular actin)
- Microbutules: Monomeric tubulin
Fibrous proteins:generated by polymerisation of globular proteins Examples ?
Actin interacts with myosin allowing for cell contraction
Contractile proteins allow for cell motility
How are fibrous Proteins formed ?
Formation by:
Oligomerisation of long polypeptides that bundle forming rods
Polymerisation of globular proteins
What is the function of Fibrous Proteins ?
Functions:
Structural
Cell contraction and movement
(motor proteins
