Lehninger Principles of Biochemistry 6th Edition

Published by W.H. Freeman
ISBN 10: 1-42923-414-8
ISBN 13: 978-1-42923-414-6

Chapter 1 - The Foundations of Biochemistry - Problems: 9


A) Use the differences in solubility to separate amino acids from fatty acids. Amino acids are more likely to be soluble in water, whereas the fatty acids will not dissolve but float to the top. B) Use a method to separate molecules based on charge, such as gel electrophoresis.

Work Step by Step

A) Fatty acids are composed of a carboxylic acid linked to a long aliphatic (many carbons) chain. While the carboxylic acid is hydrophilic (like water), the aliphatic chain is overwhelming hydrophobic (hates water), making the fatty acid separate from water. On the other hand, amino acids are much smaller than fatty acids and are more soluble in water. B) Nucleotides are composed of a pentose sugar bonded to a nitrogeneous base and a phosphate group. The phosphate group carries a negative charge, making the overall nucleotide charged. Glucose is a neutral molecule, thus behaving differently than the nucleotide when exposed to an electric field.
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