Proteins 1&2 Flashcards
Aliphatic amino acids
Alkane/organic
Basic amino acid
Alkaline
Aromatic amino acids
Benzene
Other amino acid
Proline
Peptide bond
Formation of covalent bond with loss of water
Primary structure
Sequence of amino acids in polypeptide
Versatility in protein structure and function
Secondary structure
Spatial arrangement of amino acid residues near each other in linear sequence
Alpha helix
Held in place by hydrogen bonds
Beta pleated sheets
Hydrogen bonds between amide groups of linear polypeptide chain - porin
Tertiary structure
Spatial arrangement of amino acid residues that are far apart in a linear sequence
Examples of tertiary structure
hydrophobic interactions
Disulphide bridges
Van der waals
Hydrogen bonds
Ionic interactions
2 close oppositely charged R groups strong but rare
Van der waals
Non specific weak
Stabilise structure as strong together
Hydrogen bonds
Strong and permanent
1/20 strength of hydrogen bonds
Hydrophobic interactions
Intra polypeptide
Disulphide bridges
2 cysteine residues
Quaternary structure
Spatial arrangement of individual polypeptide chains in a multi sub-unit protein
CRP - high when infected and haemoglobin
Denaturation - causes
Acids, heats, solvents, cross link reagents, chaotropic agents - molecule in water which disrupts bonds, disulphide bond reducers
What structures are effected by denaturation?
Secondary and tertiary
What are the effects of denaturation
- decreased solubility
- loss of water binding capacity
- Loss of biological activity
- Improved digestibility
Peptidases
Cleave peptide bonds
Endopeptidase
Cleave internal bonds
Exopeptidase
Cleave one amino acid at a time
Carboxypeptidase
Cleave at COOH
Aminopeptidase
Cleave at NH2
What is protein structure dependent on?
DNA sequence
Name 3 other types of proteins
- glycoprotein
- Lipoproteins
- metalloprotein
Glycoprotein
Protein and carbohydrate
post translational modification
Sugar binds to amino acid
Example of glycoprotein
Antibody
Roles of glycoproteins
cell recognition and signalling
Protein stabilisation
solubility
Lipoprotein example
LDL, HDL
Roles of lipoprotein
Transport water insoluble fats around the body
Metalloprotein
1/3 of proteins - metal ion needed for activity
Functions of metalloprotein
Transport
Enzyme
Storage
Signalling
Globular proteins
Varied function including enzymes, hormones
Fibrous proteins
Structural function eg tendon, connective tissue
Membrane proteins
Cell/organelle proteins
Transporters and cell adhesion
Co-operative binding
Binding at one subunit causes a change in shape of other subunits altering affinity for substrate
Scurvy
Amino acid==>hydroxyamino acids
Weaker collagen
Acquired condition
Osteogenesis imperfecta
Small glycine substituted for larger amino acid
Not as tight coil, reduced fibril interaction
Loss of secondary and tertiary structure
Weak and brittle collagen
What is the main part of LDL
ApoB
What internalises LDL?
Glycoprotein
Where is LDL broken down?
Lysosomes
Classes of effects and mutations in receptor
- No receptor produced
- Receptors never reach cell surface
- Receptors cant bind LDL
- Receptors don’t internalise on binding LDL
- Receptors do not release LDL
FH
Autosomal dominant
Mutation in LDL receptor
Cryoglobulin
Proteins that precipitate in blood and solidify below 37 degrees which is a problem in extremities on a cold day
