Introduction & Overview (L1 & L2) Flashcards
Name five biological functions of metals.
1) Structural
2) Communicative (Na, Ca, K)
3) Electron Reservior (Fe2 S2 clusters)
4) Oxygen Transport (Fe, Cu)
5) Catalysis with high selectivity
Name some examples of metal-catalysed reactions with high selectivity
- non-redox reactions: e.g. hydrolysis of CO2, amides, phosphates
- isomerases: sugars biochemistry
- reductases (ROH to RH) and dehydrogenases (RCH2OH to RCHO)
- protection from peroxides or super-oxides, e.g. catalases
- oxidases (RH to ROH)
- nitrogen fixation
- photosynthesis
- alkylation
Name 6 of the major organelles of a eukaryotic cell and their purposes
1) Nucleus - contains chromosomes, gene replication, mRNA synthesis, Ribosome production.
2) Mitochondria - Production of ATP.
3) Endoplasmic Reticulum - Rough (protein synthesis), Smooth (steroid hormone biosynthesis, Ca2+ storage).
4) Lysosomes - contain hydrolytic enzymes.
5) Peroxisomes - contain oxidative enzymes.
6) Golgi Complexes - process newly biosynthesised proteins.
What is the concept of Hard-Soft Acid-Base theory?
Soft donor atoms (large, polarisable, little electronegative)
bind preferentially to soft metal ions (large, polarisable, low charge)
Hard donor atoms bind preferentially to hard metal ions.
Name some Soft acids/bases.
Soft Acids: Cu(I), Au(I), Tl(I), Cd(II), Pt(II), Pb(II), Hg(II)
Bind to
Soft Bases: R2S, RS- (in AAs cysteine, methionine)
Name some Border-line acids/bases.
Border line Acids: Fe(II), Co(II), Ni(II), Cu(II), Zn(II)
bind to
Border-line Bases: NO2-, SO32-, aryl-NH2, imidazole (in AA histidine)
Name some Hard acids/bases.
Hard Acids: H+, Na+, K+, Mg2+,Ca2+, Mn2+, Al3+, Cr3+,Co3+, Fe3+
bind to
Hard Bases: H2O, RCOO-, ROPO32-, CO32-, NO3-, ROH, R2O, alkyl-NH2
Describe the Chelate effect.
Multidentate ligands have unusual complex stability over monodentate ligands (partly due to entropy)
Large macrocyclic ligands can bind metals very well:
porphyrin, corrin, but also proteins
Describe what is meant by an entatic state.
In 1968, Vallee and Williams postulated that active sites in enzymes are held by the protein in a geometry that approaches the structure of the transition state for the reaction catalysed by the enzyme.
This structure is referred to as the entatic state.
Ligands that have the donor atoms pre-organised in the same position as in the final metal complex will bind the metal much stronger.
What is the Irving-Williams Series
Ligand binding preference for first row metals (oxidation state II) in water;
Log Kf for complexes of the Oh M2+ ions of 3d series in water varies as (low to high):
Ca < Mg < Mn < Fe < Co < Ni < Cu >Zn
What is the template effect?
The template effect emphasizes the pre-organization provided by the coordination sphere, although the coordination modifies the electronic properties (acidity, electrophilicity, etc.) of ligands.
What are the amino acids we are expected to know the structures for?
Hystidine His (H) Cycteine Cys (C) Tyrosine Tyr (Y) Glutamate Glu (E) Aspartate Asp (D)
What is mean by Primary, Secondary, Tertiary and Quaternary structures of polypeptides?
Proteins are made up of polypeptide chains, and polypeptides are made up of amino acids linked by peptide bonds.
The primary structure of a protein is simply the order of amino acids in the polypeptide.
Hydrogen bonds are one type of interaction between amino acids, causing polypeptides to adopt a certain form of secondary structure, either alpha-helixes (where bonds are formed between neighbouring amino acids) or beta pleated sheets (where bonds are formed between amino acids in different areas of the polypeptide).
Tertiary structure describes the 3D shape of the protein in space. It is determined by interactions between the residual groups on each amino acid, such as Van der Waals forces, disulphide bridges and ionic bonds.
Often, proteins are made up of more than one polypeptide chain - either multiple copies of the same chain, or different polypeptides coming together. The number and arrangement of these subunits are described by the quaternary structure.
What are the forces responsible for protein folding?
1) Reduction of hydrophobic surface.
2) Hydrogen bridges
3) Covalent bonds between amino acids S-S (Cys-Cys)
4) Coordination of metals
4a) Preorganised coordination sphere
4b) well defined structural change upon metal coordination.
4c) unordered proteins get defined tertiary structure by metal coordination.
What are the Watson-Crick base pairs in DNA?
Cytosine (C) and Guanine (G)
Thymine (T) and Adenine (A)
