Proteins Flashcards
(13 cards)
What is the general structure of an amino acid?
-carboxylic acid group (COOH)
-amine/ amino group (NH2)
-R variable
How do polypeptides form?
Condensation reactions between amino acids form peptide bonds
Define primary structure of a protein?
Primary: sequence, number and type of amino acids in the polypeptide, determined by sequence of codons of mRNA
Secondary:
Describe the secondary structure of a protein?
Hydrogen bonds determine type of folding
-alpha-helix: all N-H bonds on same side of protein chain, spiral shape, H-bonds parallel to helical axis
-beta-pleated sheet: N-H & C=O groups alternate from one side to the other
Describe the secondary structure of a protein?
Hydrogen bonds determine type of folding
-alpha-helix: all N-H bonds on same side of protein chain, spiral shape, H-bonds parallel to helical axis
-beta-pleated sheet: N-H & C=O groups alternate from one side to the other
Describe the tertiary structure of a protein?
3D structure formed by further folding
-Disulfide bridges: strong covalent S-S bonds between molecules of the amino acid cysteine
-ionic bonds: relatively strong bonds between charged R group (pH bond cause these bonds to break)
-Hydrogen bonds: numerous & easily broken
Define quaternary structure of a protein?
-proteins consisting of more than one polypeptide
- precise 3D structures held together by the same types of bond as tertiary structure
-may involve addition of prosthetic groups e.g metal ions or phosphate groups
Define quaternary structure of a protein?
-proteins consisting of more than one polypeptide
- precise 3D structures held together by the same types of bond as tertiary structure
-may involve addition of prosthetic groups e.g metal ions or phosphate groups
Describe the structure and function of globular proteins-
-spherical & compact
-hydrophilic R group face outwards & hydrophobic R groups face inwards= usually water soluble
-involved in metabolic processes e.g enzymes, insulin, haemoglobin
Describe the structure of haemoglobin?
-globular conjugated protein with prosthetic group
-2 a-chains, 2 b-chains, 4 prosthetic haem groups
-water-soluble dissolves in plasma
-tertiary structure changes so it is easier for subsequent O2 molecules to bind
Describe structure and function of fibrous proteins
-can form long chains or fibres
-insoluble in water
-useful for structure and support e.g collagen in skin
List the function of collagen, elastin and keratin
Collagen: components of bones, cartilage, connective tissue, tendons
Elastin: provides elasticity to connective tissues, arteries, skin, lung, cartilage, ligaments
Keratin: structural components of hair, nails hooves/claws, horns epithelial cells of outer layer of skin
How do you test for proteins in a sample?
1) add equal volume of sodium hydroxide to sample at room temperature
2) add drops of dilute copper (II) Sulfate solution. Swirl to mix
3)positive result: colour change from blue to purple
Negative result: remains blue
