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11.1 Morphine: A Molecular Imposter
Morphine is derived from opium.
The effects of opium have been known for thousands of years, but it wasn't until the early 1800s that morphine was isolated from opium.
Morphine acts by binding to nerve cells.
The transmission of nerve signals is altered when morphine is binding to an opiate receptor.
The body's natural painkillers are endorphins.
During periods of pain, our bodies produce an opiate called endorphins.
The so-called runner's high is a feeling of well-being that often follows an athlete's intense workout.
Morphine is able to bind to the opioids because it fits into a pocket on the opioid receptor that is normally bound to the opiate.
Even though they are not the original key, certain parts of the morphine molecule fit the lock.
The revolution that has occurred in biology over the last 50 years is largely due to our ability to determine the shapes of key biological molecules.
We look at ways to account for the shapes of the molecule.
The same principles apply to both the smaller and larger molecule we examine.
They account for the properties of the molecule.
The electron groups are attracted to the nucleus, but the repulsions are the focus of the theory.
The number of electron groups around the central atom and how many of them are bonding groups are two factors that affect the geometry of the atom.
The five basic shapes of molecule are repulsions between electron groups etries.
We look at how these basic determine geometry.
In this structure, beryllium forms incomplete about the central atom: octets.
The theory predicts that the molecule is linear.
The same geometry is observed in all molecules with two electron groups.
The Lewis structure of CO2 has two electron groups around the central carbon atom.
Experiments show that CO2 is a linear molecule.
The B structure confirms the predictions of the theory.
The bond angles should be 120 degrees.
The HCO bond angles are 121.9 and the HCH bond angles are 116.2.
The bond angles reflect the differences.
There isn't enough information to determine the geometry of the molecule.
To solve the problem, you need to know how many electron pairs are on the other two atoms.
There are two-dimensional and easy to represent geometries on paper for molecules with two or three electron groups around the central atom.
Molecules with four or more electron groups around a central atom are more difficult to imagine and draw.
We are able to understand these shapes by analogy to balloons tied together.
When two balloons are tied together, they assume a linear arrangement.
The linear geometry is created by the repulsion between two electron groups.
Three electron groups adopt a trigonal geometry.
Each electron group around a central atom is like a balloon.
The bulkiness of the balloons causes them to spread out as much as possible, as the repulsion between electron groups causes them to position themselves as far apart as possible.
The maximum separation among the groups can be achieved by using the three-dimensional shape of the tetrahedron.
The molecule assumes the shape of a triangle.
When we write the Lewis structure of CH4 on paper, it may seem that the molecule should be square.
The balloon analogy shows that the electron groups can get farther away from each other by forming the tetrahedral geometry in three dimensions.
There are different angles in the trigonal bipyramidal structure.
The three chlorine atoms are separated by bond angles, while the two chlorine atoms are separated by bond angles.
The angles are all 90 degrees.
All six bonds of this molecule are equivalent.
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