Dopamine is a neurotransmitter—a chemical released by nerve cells to send signals to other nerve cells. Activities like sex and gambling increase the levels of dopamine released within the brain. The highly addictive drugs cocaine and methamphetamine mimic the effects of dopamine. Loss of dopamine releasing cells in parts of the brain can lead to Parkinson’s disease, a condition characterized by tremors and motor impairment.
(A) The Dopamine molecule is capable of making strong hydrogen bonds. Edit the dopamine molecule so it can no longer make strong hydrogen bonds.
(B) The Dopamine molecule cannot make ionic bonds. Edit the dopamine molecule so it now can make ionic bonds.
(C) The dopamine molecule has an intermediate hydrophobicity. Edit the dopamine molecule so that it is more hydrophobic.
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For (A) substitute the hydroxyl-groups with H and the amino-group with a methyl-group
For (C) substitute the hydroxyl-groups with chloride
For (D) Chloride
To modify the dopamine molecule to no longer make strong hydrogen bonds (A), we can replace or alter the functional groups that are responsible for forming hydrogen bonds. Dopamine contains hydroxyl and amine groups which are capable of hydrogen bonding. By replacing one or both of these groups, we can disrupt the ability of dopamine to form strong hydrogen bonds. For example, one hydroxyl group can be replaced with a methyl group or an aromatic ring, and the amine group can be substituted with a methyl or ethyl group.
To modify the dopamine molecule so it can make ionic bonds (B), we need to introduce charged functional groups into the structure. Dopamine itself is a neutral molecule and lacks charged groups. To add an ionic property, we can introduce a protonated amine group by reacting dopamine with an acid. This will result in the formation of a positively charged ammonium group, allowing for the formation of ionic bonds with negatively charged species.
To increase the hydrophobicity of the dopamine molecule (C), we can modify the functional groups to introduce more hydrophobic substituents. Dopamine already possesses a hydrophobic aromatic ring. However, we can increase the hydrophobicity by replacing the hydroxyl or amine groups with alkyl chains or other nonpolar groups. For example, replacing the hydroxyl group with an isopropyl group or substituting the amine group with a long alkyl chain would increase the hydrophobic character of dopamine.