Consider Two Solution Chambers of Equal Volume Divided by a Dialysis

question 30

Short Answer

Consider two solution chambers of equal volume divided by a dialysis membrane that is impermeable to antibody molecules but permeable to small antigens. Starting with an antigen concentration of 4.8 nM in both chambers, you add its specific IgG antibody to one of the chambers at 1 nM concentration. You then measure the concentration of the antigen in the other chamber after equilibrium is reached, which turns out to be about 4 nM. What is the association constant (K_a) for the binding of the antigen to each antigen-binding site of IgG? Assume independent antigen-binding sites in each antibody molecule. Write down your answer in liters per mole, in scientific notation with one decimal place, e.g. 5.0 × 10² liters/mole).

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Definitions:

Nuclear Receptor

A class of proteins within cells that, upon binding with a ligand, can act as transcription factors to regulate gene expression.

G Protein

A type of protein that acts as a molecular switch inside cells, involved in transmitting signals from stimuli outside the cell to its interior.

Neural Inhibition

A process in the nervous system where certain neurons suppress the activity of other neurons, helping to control and refine neural circuits.

Sympathetic Activity

Part of the autonomic nervous system that prepares the body for 'fight or flight' response by increasing heart rate, constricting blood vessels, and raising blood pressure.