Insulin & Aquaporin Case Study

Ribozyme

An rRNA molecule that catalyzes the formation of peptide bonds during protein translation.

How is mRNA synthesized and translated?

mRNA is synthesized from DNA in the nucleus and then transported to the cytoplasm, where it is translated into polypeptides.

Primary Protein Structure

The linear sequence of amino acids in a polypeptide chain, held together by peptide bonds.

Secondary Protein Structure

Local folding patterns, such as alpha-helices and beta-sheets, resulting from hydrogen bonding between the polypeptide backbone.

Tertiary Protein Structure

The full 3D shape of a polypeptide, stabilized by various interactions (ionic, hydrogen, hydrophobic, etc.) between amino acid side chains.

Quaternary Protein Structure

The assembly and interaction of multiple polypeptide subunits to form a functional protein complex.

Hydrophobic Effect

The phenomenon where nonpolar amino acid side chains aggregate in the interior of a protein to minimize contact with water.

How are the A and B chains of insulin connected?

They are connected together by disulfide bonds.

Ion-Ion Interactions

Non-covalent interactions that involve full charges and are generally strong and permanent.

Hydrogen Bonds

Interactions involving full or partial charges that are strong when permanent.

Van der Waals

The weakest of the non-covalent interactions; these are temporary forces.

Ion-Dipole Interactions

Interactions that occur between a charged molecule and a polar molecule.

2nd Law of Thermodynamics

A principle stating that the total entropy of a system and its surroundings always increases in a spontaneous process.

What is the formula for Gibbs Free Energy?

\text{ΔG} = \text{ΔH} - T\text{ΔS}

How is the spontaneity of a reaction evaluated in terms of Gibbs Free Energy?

Spontaneity is determined based on the relationship between temperature (T), enthalpy change (\text{ΔH}), and entropy change (\text{ΔS}).

What is the magnitude of the free energy difference between folded and unfolded protein states?

The free energy differences are modest, resulting from only a few non-covalent bonds.

Which environmental conditions can impact protein stability and folding?

Factors such as temperature and \text{pH} can impact protein folding and stability.

How do mutations affect the functionality of insulin?

Mutations can alter amino acid polarity, the ionization state at \text{pH 7.4}, and the resulting tertiary or quaternary interactions.

Aquaporins

Membrane proteins that facilitate rapid water transport across membranes, playing significant roles in kidney function and plant transpiration.

What is the primary composition of biological membrane molecules?

Phospholipid bilayers consisting of polar head groups and nonpolar tails, which define the membrane's physical properties.

Grotthuss Mechanism

A process where water molecules transport protons through hydrogen bonds in a chain reaction; aquaporins are structurally adapted to prevent this.

NPA Motif

Standing for Asparagine-Proline-Alanine, this motif is crucial for maintaining water selectivity and preventing proton conduction in aquaporin channels.

How do aquaporins maintain channel selectivity?

They facilitate water passage while repelling protons and other ions, such as Na^+ and Cl^-, through specific architectural adaptations and interactions.

Hula hoop analogy

An analogy used to explain how the disruption of hydrogen bonding within the channel allows for the selective passage of water molecules.

What determines the permeation characteristics of an aquaporin?

The specific 3D structure of the aquaporin protein is critical for its channel function and selective permeability.