Tutorial:Basic Chemistry Topics: Difference between revisions
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The polarity of an amino acid is dependent on the difference in electronegativity and the asymmetry of the compounds structure, discussed previously. For example, Arginine is a polar amino acid and Glycine is a nonpolar amino acid. As we learned earlier, an amino acid’s structure consists of a carboxylic acid, an amine, hydrogen, and a functional group. Look at the structures of <scene name='Tutorial:Basic_Chemistry_Topics/Polar_nonpolaraa/1'>arginine and glycine</scene>. Arginine has the amine group, carboxylic acid and hydrogen located towards the bottom of the representation, and the functional group is the large extension of atoms upward. You can see from this image that the functional group has a greater density/electronegativity compared to the core of the amino acid (carboxylic acid, amine and hydrogen), hence making this amino acid polar. In contrast the structure of glycine, located next to arginine, has little polarity. The functional group attached to glycine is only a methyl group (CH3). A methyl group has low density/electronegativity compared to the rest of the structure, making glycine a nonpolar amino acid. Neutral amino acids have functional groups that are similar in electronegativity compared to the core, so the electrons are not pulled in one direction more dominantly then another. In other words, there is no increase in density to one side. When an amino acid is neutral, it is less reactive then a polar amino acid. It is less reactive because the structure is stable. A polar amino acid is pulling electrons yielding a slight positive and negative charge within the amino acid structure, making it less stable. Those charges want to react with other atoms, yielding the higher reactivity. | The polarity of an amino acid is dependent on the difference in electronegativity and the asymmetry of the compounds structure, discussed previously. For example, Arginine is a polar amino acid and Glycine is a nonpolar amino acid. As we learned earlier, an amino acid’s structure consists of a carboxylic acid, an amine, hydrogen, and a functional group. Look at the structures of <scene name='Tutorial:Basic_Chemistry_Topics/Polar_nonpolaraa/1'>arginine and glycine</scene>. Arginine has the amine group, carboxylic acid and hydrogen located towards the bottom of the representation, and the functional group is the large extension of atoms upward. You can see from this image that the functional group has a greater density/electronegativity compared to the core of the amino acid (carboxylic acid, amine and hydrogen), hence making this amino acid polar. In contrast the structure of glycine, located next to arginine, has little polarity. The functional group attached to glycine is only a methyl group (CH3). A methyl group has low density/electronegativity compared to the rest of the structure, making glycine a nonpolar amino acid. Neutral amino acids have functional groups that are similar in electronegativity compared to the core, so the electrons are not pulled in one direction more dominantly then another. In other words, there is no increase in density to one side. When an amino acid is neutral, it is less reactive then a polar amino acid. It is less reactive because the structure is stable. A polar amino acid is pulling electrons yielding a slight positive and negative charge within the amino acid structure, making it less stable. Those charges want to react with other atoms, yielding the higher reactivity. | ||
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''Nonpolar amino acids'' | ''Nonpolar amino acids'' | ||
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[[Image:PH scale.png| thumb | center | 600px ]] | [[Image:PH scale.png| thumb | center | 600px ]] | ||
An Example of a pH scale is located above. A pH scale ranges from 1-14, 1 being the most acidic and 14 being the most basic. An acidic pH has a value below 7, a basic pH is greater than 7, and a pH of 7 is considered neutral (ex: water). Some common acidic functional groups are alcohols (OH) and carboxylic acids (COOH). Some basic functional groups are amines (NH3) and ethers (CH2OCH2). | An Example of a pH scale is located above. A pH scale ranges from 1-14, 1 being the most acidic and 14 being the most basic. An acidic pH has a value below 7, a basic pH is greater than 7, and a pH of 7 is considered neutral (ex: water). Some common acidic functional groups are alcohols (OH) and carboxylic acids (COOH). Some basic functional groups are amines (NH3) and ethers (CH2OCH2). | ||
You can predict if an amino acid will be acidic or basic according to its structure. For example, <scene name='Tutorial:Basic_Chemistry_Topics/Glu/1'>glutamic acid</scene> contains a carboxylic acid functional group, which was stated previously to be an acidic functional group that lowers the pH of the amino acid. On the other hand, | You can predict if an amino acid will be acidic or basic according to its structure. For example, <scene name='Tutorial:Basic_Chemistry_Topics/Glu/1'>glutamic acid</scene> contains a carboxylic acid functional group, which was stated previously to be an acidic functional group that lowers the pH of the amino acid. On the other hand, arginine is classified as a basic amino acid. The functional group of arginine contains a guanidine group. A guanidine group contains amine groups, increasing the pH of the amino acid. | ||
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