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What is the primary function of calcium in bone and teeth?
What is the primary function of calcium in bone and teeth?
Buffering body Ca2+ and phosphate ions, as controlled by hormonal action
How does magnesium participate in the regulation of nucleotides and polynucleotides?
How does magnesium participate in the regulation of nucleotides and polynucleotides?
As a counterion to the negatively charged ROPO3H- groups
What is the coordination sphere of magnesium in its complex with phosphate anions?
What is the coordination sphere of magnesium in its complex with phosphate anions?
[Mg(H2O)6]2+, [Mg(H2O)5]2+, or [Mg(H2O)4]2+ with one or two phosphate oxygen atoms, respectively
What is the role of magnesium in the structure of RNA and DNA?
What is the role of magnesium in the structure of RNA and DNA?
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What is the primary form of adenosine diphosphate (ADP) and adenosine triphosphate (ATP) in the cell?
What is the primary form of adenosine diphosphate (ADP) and adenosine triphosphate (ATP) in the cell?
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What is the unique role of magnesium in the plant kingdom?
What is the unique role of magnesium in the plant kingdom?
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What is the composition of the mineral apatite found in bone and teeth?
What is the composition of the mineral apatite found in bone and teeth?
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How does calcium participate in regulatory processes in the cell?
How does calcium participate in regulatory processes in the cell?
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What is the difference in the biological roles of calcium and magnesium?
What is the difference in the biological roles of calcium and magnesium?
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What is the role of calcium in the action of extracellular enzymes?
What is the role of calcium in the action of extracellular enzymes?
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Study Notes
Methylcobalamin
- Involved in the metabolism of methane-producing bacteria
- Transfers CH3 groups to Hg II, TlM, Pel, and Au I
- Converts elemental mercury into the highly toxic methylmercury ion CH3Hg+
Vitamin B12
- Has a planar tetradentate ligand with amido-type nitrogen atoms
- Models have been synthesized and studied, such as bis(dimethylglyoximato) complexes
- Successfully models the reducibility to the cobalt(I) state and the formation and reactions of cobalt-carbon bonds
Carboxypeptidase
- Zinc ion is bound in a distorted tetrahedral environment with two histidine nitrogen atoms, one glutamate carboxyl oxygen atom, and a water molecule as ligands
- Substrate binding occurs with the carbonyl oxygen atom of the peptide linkage replacing the water molecule in the coordination sphere of the zinc ion
- Key step in the mechanism involves the peptide bond breaking with formation of an acid anhydride, followed by rapid hydrolysis of the anhydride
Copper Metalloenzymes
- More than 20 have been isolated, but structure and function are not well understood
- Examples include ascorbic acid oxidase, cytochrome oxidase, and tyrosinases
- Catalyze oxidations, such as the oxidation of ascorbic acid to dehydroascorbic acid
Calcium
- Essential for the action of extracellular enzymes and participates in many regulatory processes
- Complexed by the side-chain carboxyl groups of proteins, with additional bonding to peptide carbonyl groups and hydroxyl groups
- Found in bone and teeth, with a composition similar to the mineral apatite
Magnesium
- Plays biological roles that are very different from those of calcium
- Acts as a counterion to negatively charged ROPO3H- groups in nucleotides and polynucleotides
- Helps to stabilize the three-dimensional structure of RNA and DNA and is crucial to the proper functioning of the genetic machinery of the cell
- Exists in complexes with ADP and ATP, and is the central atom of chlorophyll
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Description
This quiz covers the chemistry of methylcobalamin, its involvement in methane-producing bacteria metabolism, and its role in converting elemental mercury into toxic methylmercury ion.
