Inorganic Coordination Chemistry in Biology

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What is the primary focus of this chapter in relation to metal ions?

Their physical properties

Their electronic structural features

Their Lewis acid characteristics

Their roles in biology (correct)

What do metal ions in biology frequently bind to?

Nucleic acid acids

Donor ligands (correct)

Other metal ions

Protein backbones

What is a characteristic of 'hard' species in the hard-soft theory of acids and bases?

They are found only in organic cofactors

They are large and highly polarizable

They are always Lewis bases

They are small and less easily polarized (correct)

What is the term for species that are large and fairly polarizable?

Soft Signup and view all the answers

What do ligand atoms coordinate to in a biological medium?

Metal centers Signup and view all the answers

What is the purpose of understanding the special properties of metal ions?

To understand the functions of metal centers Signup and view all the answers

What is the general rule regarding hard acids and hard bases?

Hard acids bind preferentially to hard bases and soft acids to soft bases. Signup and view all the answers

What type of metal ions tend to bind to cysteine sulfhydryl groups or methionine thioether linkages?

Soft metal ions like Pt(I1). Signup and view all the answers

What is the primary function of metallothionein proteins?

To protect cells against the toxic effects of metal ions. Signup and view all the answers

What is the term used to describe the coordination of two or more donor atoms from a single ligand to a central metal atom?

Chelation. Signup and view all the answers

What is the purpose of adding EDTA to buffer solutions in biological research?

To reduce the concentration of free metal ions. Signup and view all the answers

What type of metal ions are typically coordinated by carboxylate oxygen atoms?

Hard metal ions like Ca2+. Signup and view all the answers

What is the name of the ligand used in medicine to chelate metal ions that might be present in toxic excess?

EDTA. Signup and view all the answers

What is the term used to describe the stability of metal-chelate complexes resulting from the favorable entropic factor?

The chelate effect. Signup and view all the answers

What is the name of the macrocyclic molecules that have four nearly coplanar pyrrole rings with their nitrogen donor atoms directed toward a central metal ion?

Porphyrins. Signup and view all the answers

What is the biological function of metallothionein proteins?

To protect cells against the toxic effects of metal ions. Signup and view all the answers

What is the effect of adding bulky R groups to Cu(R-sal) complexes?

It raises the redox potential. Signup and view all the answers

What is the preferred coordination geometry of divalent copper(II) complexes?

Square-planar Signup and view all the answers

What is the general order of binding preference for divalent first-row transition-metal ions?

Ca2+ < Mg2+ < Mn2+ < Fe2+ < Co2+ < Ni2+ < Cu2+ > Zn2+ Signup and view all the answers

What is the effect of the positive charge on most metal ions in biology on protic ligands bound in the coordination sphere?

It stabilizes the acid anion (conjugate base) of protic ligands. Signup and view all the answers

What is the effect of soft ligands such as RS- or R2S on the Cu(I)/Cu(II) reduction potential?

It raises the potential. Signup and view all the answers

What is the effect of coordinating multiple metal ions to a protic ligand on the pK, value?

It decreases the pK, value. Signup and view all the answers

What is the role of noncoordinating residues in proteins?

They contribute to local hydrophilicity or hydrophobicity and stereochemistry. Signup and view all the answers

What is the redox potential of the Cu(I)/Cu(II) couple affected by?

The ligand donor atom and stereochemistry at the metal center. Signup and view all the answers

What determines the thermodynamic stability of a metal center in a biological environment?

Both the inherent preferences of the metal and the ability of the biopolymer to control the stereochemistry and ligands available for coordination. Signup and view all the answers

What is the significance of the Irving-Williams series?

It is a series of metal ions in order of their tendency to bind to hard donors. Signup and view all the answers

What is the preferred coordination geometry of copper(I), a closed-shell d10 ion?

Tetrahedral four-coordinate or trigonal three-coordinate. Signup and view all the answers

What is the general term for the study of the principles governing the formation of complexes of metal ions with biological molecules?

Bioinorganic chemistry. Signup and view all the answers

What is the effect of the protein environment on the redox potential of metal ions?

It can either raise or lower the potential. Signup and view all the answers

What is an example of a metalloprotein that has a strong and specific metal-binding site?

Superoxide dismutase Signup and view all the answers

What is the deprotonation of coordinated water to form a hydroxo ligand related to?

Metalloenzyme catalysis. Signup and view all the answers

What is the function of the chelate effect in bioinorganic chemistry?

To provide a specific and strong metal-binding site. Signup and view all the answers

What is the effect of divalent metal ions on the pK, values of protic ligands compared to trivalent metal ions?

Trivalent metal ions have a greater effect. Signup and view all the answers

What is the effect of the local dielectric constant on the redox potential of metal ions?

It can either raise or lower the potential. Signup and view all the answers

What is the structure of the [Fe(H2O)5OH]+ complex?

Octahedral with a hydroxo ligand. Signup and view all the answers

What is the function of EDTA (ethylenediaminetetraacetic acid) in bioinorganic chemistry?

It is a metal chelating agent. Signup and view all the answers

What is the phenomenon referred to as the alteration of energy levels of d-orbitals in a metal ion due to the surrounding ligands?

Ligand-field splitting Signup and view all the answers

What determines the strength of the ligand field at a metal center?

The set of ligand donor atoms Signup and view all the answers

What is the spectrochemical series used to determine?

The ability of ligands to split d-orbitals Signup and view all the answers

What can be used to highlight a very localized region of a metalloprotein?

Measuring the magnetic and spectroscopic properties Signup and view all the answers

What is the effect of metal ions on the reactivity of ligands?

Increase the acidity of coordinated ligands Signup and view all the answers

What is the term used to describe the energy separation between the lower and upper sets of orbitals in octahedral complexes?

Δo Signup and view all the answers

What is the shape of a coordination polyhedron with a coordination number of 5?

Square pyramidal Signup and view all the answers

What is the term used to describe the alteration of d-orbital energies due to the surrounding ligands?

Ligand-field splitting Signup and view all the answers

What is the purpose of ligand-field splitting diagrams?

To correlate physical properties with structure Signup and view all the answers

What is the effect of the positively charged metal center on the acidity of coordinated water?

Decrease the pKa value Signup and view all the answers

What is the primary reason for the kinetic inertness of metalloproteins?

The solvent inaccessibility to the metal coordination sphere due to steric shielding by the protein. Signup and view all the answers

What is the general trend for ligand exchange rates among metal ions?

Faster for M2+ than for M3+ metal ions. Signup and view all the answers

Which of the following metal ions is characterized by very inert ligand exchange rates?

Cr3+ Signup and view all the answers

What is the effect of multidentate chelating ligands on the metal-ligand exchange rates of first-row transition-metal ions?

They decrease the metal-ligand exchange rates. Signup and view all the answers

What is the typical coordination number of metal ions that undergo associative ligand displacement reactions?

2-4 Signup and view all the answers

What is the characteristic of inner-sphere electron transfer reactions?

The presence of one or more bridging ligands directly bonded to the coordination spheres of the reactants. Signup and view all the answers

Which of the following ligands is known to form a more inert M-L bond?

CO Signup and view all the answers

What is the effect of denaturing a protein on the metal ions bound to it?

The metal ions can be released. Signup and view all the answers

What is the characteristic of substitution reactions at metal centers bound to proteins or nucleic acids?

They are more complex due to interactions of the incoming ligand with other nearby groups. Signup and view all the answers

What is the typical feature of metalloporphyrins?

They are kinetically inert. Signup and view all the answers

What is the role of the chloride ion in the electron-transfer reaction between [CO(NH3)5CI]2+ and [Cr(H2O)5CI]2+?

It is transferred from the Co(III) to the Cr(I) center. Signup and view all the answers

What is the characteristic of the electron-transfer reaction between metal centers within and between metalloprotein molecules?

It is a long-range process that can occur over distances up to 30 Å. Signup and view all the answers

What is the prediction of the Marcus theory for outer-sphere electron-transfer reactions?

The rate of electron transfer has an optimal driving force. Signup and view all the answers

What is the d-electron configuration of the Fe(III) ion?

d5 Signup and view all the answers

What is the coordination geometry typically exhibited by metal ions in bioinorganic chemistry?

A variety of coordination geometries, including tetrahedral and octrahedral, are observed. Signup and view all the answers

What is the role of the precursor complex in outer-sphere electron-transfer reactions?

It is the initial step in the electron-transfer reaction. Signup and view all the answers

What is the characteristic of the inner-sphere electron-transfer reaction?

It involves the formation of a bridged binuclear complex. Signup and view all the answers

Why is the rate of electron transfer affected in the inverted region?

The driving force is too high. Signup and view all the answers

What is the term used to describe the correlation between the equilibrium and rate constants for outer-sphere electron-transfer reactions?

Marcus theory Signup and view all the answers

What is the purpose of understanding the special properties of metal ions in biology?

To understand the biological functions of metal ions Signup and view all the answers

What is the term used to describe the approach of forming a desired replica molecule by reacting a metal with the simplest ligands containing the known or suspected biological donor atoms?

Spontaneous self-assembly Signup and view all the answers

Why do the molecules formed between metal and ligands become major components of the mixture of compounds?

Because of the tactical skills of the synthetic inorganic chemist Signup and view all the answers

What is the characteristic of metal-ligand bonds in most bioinorganic centers?

They are labile Signup and view all the answers

What is the advantage of the spontaneous self-assembly approach in replicating metalloprotein core structures?

It is a simple and straightforward approach that mimics nature's strategy Signup and view all the answers

What is the criticism of the spontaneous self-assembly approach by some scientists?

It is just a matter of dumb luck Signup and view all the answers

What is the significance of the interaction between the geosphere and the biosphere in the development of bioinorganic chemistry?

It has led to the discovery of metal centers in biology Signup and view all the answers

What facilitates nucleophilic attack on the carbonyl group in the hydrolysis of amino-acid esters at neutral pH?

Coordination to a positively charged metal ion Signup and view all the answers

What is an example of a reaction that is facilitated by metal centers?

The hydrolysis of amino-acid esters Signup and view all the answers

Why is the uncatalyzed reaction of amino-acid ester hydrolysis essentially unobservable at neutral pH?

Due to the slow rate of the reaction Signup and view all the answers

What is the purpose of using model complexes in bioinorganic chemistry?

To replicate the physical and chemical properties of metal centers in biopolymers Signup and view all the answers

What is the term for the phenomenon in which the metal serves to organize reactive units in condensation reactions?

The template effect Signup and view all the answers

What is promoted by coordination of cupric ion to the leaving group in phosphate ester hydrolysis?

The hydrolysis of phosphate esters Signup and view all the answers

Why is it challenging to obtain high-resolution structural information about the metal coordination sphere in metallobiopolymers?

Due to the complexity of the molecule Signup and view all the answers