metals. metals essential for life: the role for most is uncertain na, k, mg, ca v, cr, mn, fe co,...
TRANSCRIPT
MetalsMetals
Metals essential for life:
The role for most is uncertain
Na, K, Mg, Ca
V, Cr, Mn, Fe Co, Ni, Cu, Zn
Mo, W
General roles of metal ions in biologyNa, K:Na, K: Charge carriers
Osmotic and electrochemical gradients
Nerve function
Mg, Ca:Mg, Ca: Enzyme activators
Structure promoters
Lewis acids
Mg2+: chlorophyll, photosynthesis
Ca2+: insoluble phosphates
Other metal ions: less well defined and Other metal ions: less well defined and more more
obscure rolesobscure roles
Zn:Zn: Metalloenzymes
Structure promoters
Lewis acid
Not a redox catalyst!
Fe, Cu, Mo:Fe, Cu, Mo: Electron-transfer
Redox proteins and enzymes
Oxygen carrying proteins
Nitrogen fixation
Biochemical Reactivity
Promotion of Appropriate Geometry Change acid/base character Change Redox potentials Change ionic concentration Formation of Unique species Formation of structural materials Activation of small molecules (NO)
Zinc and Copper
Zinc is found in more than 80 different enzymes. Carboxypeptidase
Catalyzes hydrolysis of peptide bonds Carbonic anhydrase
CO2 HCO3-
Copper Ceruloplasmin – blue-glycoprotein
Iron storage and oxidation/reduction Superoxide dismutase
Conversion of superoxide to peroxide to water. Also Lactase, ascorbate oxidase and plastocyanin
Alkali metals
Terrestrial distribution:Terrestrial distribution:
LiLi NaNa KK RbRb CsCs FrFr
0.060 nm 0.133 nm ionic radii
0.095 nm
Distribution in vivo:Distribution in vivo:
(Li)(Li) NaNa KK (Rb)(Rb)
Element % of total number of atoms in human body
Number of grams in a 70-kg Man
H 63 6580
O 25.5 48550
C 9.5 12590
N 1.4 1815
Ca 0.31 1700
P 0.22 680
K 0.06 250
S 0.05 100
Cl 0.03 115
Na 0.03 70
Mg 0.01 42
Fe < 0.01 7
Mn, Co, Cu,
Zn, Mo, V,
Cr, Ni, F, < 0.01 1
Si, Se, As
Role:
NaNa++
Extracellular fluid Osmotic balance „sodium pump” Acid-base balance Conformation of proteins
nucleic acids Electrical impulse of nerve system
Mg2+
3Na+ic + 2K+
ec + ATP4- + H2O
3Na+ec + 2K+
ic + ADP3- + HPO42- + H+
K+
Enzyme activator Conformation of proteins
RNA (replication)
Secretion of gastric acid Transmembrane potentials!
Complexes of alkali metals (Na+, K+)
Cyclic antibioticsValinomycinMonactinNonactin
polyethers syntheticcryptands
18-Crown-618-Crown-618-Crown-618-Crown-6
negative charge concentrated in cavity negative charge concentrated in cavity inside the moleculeinside the molecule
OO
OO OO
OO
OO
OO
18-Crown-618-Crown-618-Crown-618-Crown-6
negative charge concentrated in cavity negative charge concentrated in cavity inside the moleculeinside the molecule
OO
OO OO
OO
OO
OO
18-Crown-618-Crown-618-Crown-618-Crown-6
forms stable Lewis acid/Lewis base forms stable Lewis acid/Lewis base complex with Kcomplex with K++
OO
OO OO
OO
OO
OO
K+
18-Crown-618-Crown-618-Crown-618-Crown-6
forms stable Lewis acid/Lewis base forms stable Lewis acid/Lewis base complex with Kcomplex with K++
OO
OO OO
OO
OO
OO
K+
Alkaline Earth Metals
Terrestrial distribution:
Be Mg Ca Sr Ba Ra
Distribution in vivo:
Mg Ca
Be, Ba TOXIC!
Sr (not particularly toxic)90Sr accumulates in bones
Element % of total number of atoms in human body
Number of grams in a 70-kg Man
H 63 6580
O 25.5 48550
C 9.5 12590
N 1.4 1815
Ca 0.31 1700
P 0.22 680
K 0.06 250
S 0.05 100
Cl 0.03 115
Na 0.03 70
Mg 0.01 42
Fe < 0.01 7
Mn, Co, Cu,
Zn, Mo, V,
Cr, Ni, F, < 0.01 1
Si, Se, As
Mg2+
Plants chlorosis CHLOROPHYLL
nervous system (tetany) active transport (intracellular) enzyme activator (e.g. ATP-ase) Ca2+ antagonist
Ca2+
Inhibits Mg2+-activated enzymes Extracellular: clotting (10-3M)
Ca2+
prothrombin thrombin-fibrinogen-fibrin
Alkaline Earth Metals
ChlorophyllChlorophyll
The interactions between ATP, Mg2+, and arginine and lysine residues at the active site of an enzyme
Since all the negative charges in ATP are neutralized, ATP is readily approached by nucleophiles
- plasma proteins bones (hydroxyapatite)Ca5 (PO4)3 (OH)
- intracellular: enzymes10-8mol/dm3
- muscle contraction: troponin
- Calcium triggering: calmodulins (Ca-binding proteins)
largely helical and undergo helix/helix motion
Ca-binding hands: a short two-strand unit -sheet
CaCa2+2+ signal signal
metabolic controls
N T P
Protein phosphatase c-NMP
protein
DNADNA
New signals