Proteins Flashcards
Proteins
- MONOMER= Amino acid
- POLYMER= Polypetide
- Polypeptides combine to form proteins
- 100 amino acids identified, but 20 amino acids occur naturally in proteins
- Made up of hydrogen, nitrogen, carbon & oxygen
- Have a specific shape to its function - change of shape leads to less function/protein to work differently
Peptide bonds
- Formed during the combining of amino acids through a condensation reaction (rejects water)
- Bond forms between carboxyl group (COOH) and H
- When 2 amino acids join together they form a dipeptide
- Covalent
Function of proteins
- Forms hair, nails and skin
- Hormones
- Enzymes
- Structural role in bones, tendons + muscles
- Antibodies
Structure of proteins
- Amino group (-NH2)- basic group from which the ‘amino’ from amino acid is derived
- Carboxyl group (-COOH)- acidic group from which ‘acid’ is derived from amino acid
- Hydrogen atom (-H)
-
R-group (variable)- a variety of different chemical group that varies in each amino acid
* Split into primary, secondary, tertiary and quaternary structure to fold polypeptide into a specific shape for a specific function
Primary structure
the order/sequence of amino acids
* change in the primary structure leads to a change in shape of a protein
Secondary structure
the curling/folding of a polypeptide into a-helices + b-pleated sheets due to formation of H bonds
* there
Tertiary structure
the overall 3-D shape of a protein, determined by interactions between R-group properties
* a-helices and b-pleated sheets twist and turn to give protein a complex, unique structure
* 3-D structure is determined by hydrophillic and hydrophobic R-groups also
* Compact ball shape for transport
* Complex structure is maintained by a number of different bonds:
1. Hydrogen bonds- formed between polar R-groups
2. Ionic bonds- formed between carboxyl (negative) and amino (positive) groups, aren’t involved in forming peptide bonds, 2nd weakest bond, easily broken down by changes in pH
3. Disulfide bonds- forms between sulfide atoms in R-groups, creates more folds to stabilise molecule, not easily broken down, fairly strong
Quaternary structure
specific 3-D shape of a protein that is determined by multiple polypeptide/prosthetic groups bonded together
* Proteins are formed when multiple polypeptide chains link in various ways
* Non-protein (prosthetic) groups may associate with the polypeptide chains forming conjugated molecules e.g iron containing ‘haem’ group in haemoglobin
Collogen
- FIBROUS PROTEIN
- Long polypeptide chain with repeating sequences of amino acids
- Insoluble- due to non-polar R-groups
- Form fibres that make them stronger due to cross-bridges
- Provides stength e.g. artery walls to prevent vessels from bursting from high pressure
- Found in tendons- connects muscles to bone to allow skeleton to move
- Found in skin-
Haemoglobin
- GLOBULAR PROTEIN
- roughly spherical in shape + has specific shapes and function
- Used as transport, hormones + enzymes
- Protein found in red blood cells- transports oxygen from lungs to body tissue
- Quaternary structure- made up of 4 polypeptide chains
- Conjugated protein- has a prosthetic group attached to each polypeptide chain (haem- iron containing ions)
- Soluble
