A biology student lists four bonds: peptide, glycosidic, ester and phosphodiester…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A biology student lists four bonds: peptide, glycosidic, ester and phosphodiester. (a) Which bond joins the glucose units of starch? (b) Which bond holds a fatty acid to glycerol in a fat? (c) Which bond joins the amino acids of a protein? (d) Which bond makes the backbone of a strand of DNA? (e) What do the four reactions that make these bonds have in common?
Need a reminder? The key ideaShow
Joining two monomers removes a molecule of water. Peptide bond: amino acids, between the carboxyl group of one and the amino group of the next. Glycosidic bond: monosaccharides. Ester bond: glycerol and fatty acids; a triglyceride has three. Phosphodiester bond: nucleotides, a phosphate that makes two ester bonds, linking the 3' carbon and the 5' carbon of neighbouring sugars. A chain of n monomers has n minus 1 bonds. Hydrolysis breaks a bond by adding water, as in digestion.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Matching. Starch: glycosidic. A fat: ester. A protein: peptide. The backbone of DNA: phosphodiester.
Step 2. What they share. In each reaction a molecule of water is given off. These are dehydration, or condensation, reactions. Each bond can be broken again by hydrolysis, which adds water.
Answer: (a) glycosidic; (b) ester; (c) peptide; (d) phosphodiester; (e) each gives off a molecule of water.
Discussion (0)
Log in to join the discussion.
Loading…