Protiens Flashcards
What are amino acids
Monomer units of a proteins, 20 different r groups make up the 20 amino acids
Diepeptide
2 amino acids joined by a peptide bond
OH from carboxyl group combine with H from amine group to make a h20 molecule
Condensation reaction
primary structure
Polypeptide chains
Chains of 3 or more amino acids
Secondary structure
A- helix : polypeptide chain coiled into cylindrical shape , h bonds
B- pleated sheet, different polypeptide chains become linked in Parallel flat sheets
Tertiary structure
Further folding of the secondary structure of proteins involving interactions between r groups
Each protein has a unique tertiary structure, which is responsible for properties and functions
Held together by bonds between r groups
Types of interactions of r groups in tertiary structure
Hydrophobic interaction Polypeptide backbone H bonds Disulphides bridge Ionic bonds
Quaternary structure
The association of 2 or more protein subunits
Same interaction as in the tertiary but between different proteins
structure of haemoglobin
red oxygen carrying pigment
polypeptide chain of amino acids linked by peptide bonds
secondary structure - alpha helix and beta pleated sheets linked by h bonds
tertiary - folding on secondary structure leading to more interactions hydrophobic/hydrophilic/ionic, r groups move depending on whether they are hydrophobic/phillic
quaternary - 4 polypeptide chains 2 alpha 2 beta become linked, each contain a haem group which has fe2+ present
What chemical elements can make up a protein
Carbon , hydrogen, oxygen, nitrogen , sulphur
General structure of an amino acid
Amine group (h-n-h) R group-c-h Carboxyl group (o=c-o-h)
Importance of hydrophobic/hydrophilic interactions
Depending on wether the r group is hydrophilic or hydrophobic , dictates the way the protein will fold
Breakdown of peptides
Protease enzymes catalyse the reaction
Turning peptides back into amino acids
Water molecule is needed to break peptide bond in hydrolysis reaction
Amine and carboxylic acid groups are reformed
Example of prosthetic group
Haem groups contains fe2+
Conjugated proteins
gobular proteins that contain a non-protein component called a prosthetic group
Insulin
Globular protein
Hormone that Regulates blood glucose concentration
Hormones are transported in the bloodstream need to be soluble
Must have precise shapes to fit into specific receptors on cell surface membranes
Catalase
In an enzyme
Catalyse is a quaternary protein contains 4 haem prosthetic groups
Catalyses the breakdown of hydrogen peroxide due to fe2+ presence
Hydrogen peroxide -> oxygen and water
3 fibrous proteins
Keratin- group of fibrous proteins present in hair, skin, nails, creates disulphide bonds ( determining flexibility
elastin- found in elastic fibres, present in walls of blood vessels and in the lungs- they give these structures flexibility
collagen - connective tissue found in : skin, tendons, ligaments, and nervous system
Cations
Calcium ca2+ Sodium Na+ Potassium k+ Hydrogen h+ ammonium NH4*+
Anions
Nitrate NO3*- Hydrogencarbonate HCO3*- Chloride Cl- Phosphate PO4*3- Hydroxide OH-
Differences between globular and fibrous proteins
Fibrous proteins are long and insoluble, have structural roles
Globular proteins are compact and soluble and have metabolic roles
Structure and properties of collagen
Peptide bonds between amino acids
Left handed helix
twisting of 3 polypeptide chain allowing molecule to be tight
Many H bonds between
Every third amino acids is glycine which is very small allowing a closely packed triple helix
Insoluble
Fibril molecule
Flexible, not elastic, strong
In some tissues multiple fibers of clooagen combine into large bundle forming tendons - ligemnts which are resistant to tearing
Bonds between amino acids
Peptide
property of collagen that makes it useful as a component of blood vessels
Strength
Insoluble
Fiberous protiens properties
Formed from long insouble molecules
High proportion of amino acids with hydrophobic r groups in their primary structres
Very organised and repetitive amino acid sequnce and therefore organised structure
Not folded into 3 dimesional shapes like gobular protiens
Structure and properties of elastin
Linking many tropoelastin protien molecules to make a very large, insousble, stable cross linked structre
Linked by hydrophobic interactions and covelant bonds
Tropelastin moleces are able to strech and recoil without breaking
Role of polypeptides
Enzymes that catalyse reactions
Hormones
Receptor protiens
Strucutral proteins - collagen, keratin, actin
How do R group interaction detriment tertiary structure
H bonds Ionic bonds between opposing charges Some R groups atract/repel If R group is hydrophobic/hydrophilic it will face inwards/outwards from the cell Disulphide bridges
Meaning of primary structure
Sequence of amino acids
