Question

With this new concept in your students' minds, you can now begin discussing how cells can utilize dehydration synthesis and hydrolysis reactions to build macromolecules consisting of thousands of smaller molecules. these macromolecules will play important roles in the cell's metabolic functions. the first group of macromolecules to be discussed with your students is the lipids. lipids are characterized by long chains of carbons and hydrogen atoms linked by nonpolar bonds. these hydrocarbon chains are nonpolar, hydrophobic (hydro- meaning "water" and -phobic meaning "afraid of") macromolecules, which is the causal factor responsible for many of the important functional characteristics of lipids. these long chains can be differentiated from one another by the number of carbons present, the degree of saturation (every carbon atom in the fatty acid chain has two hydrogen atoms bound to it), and the terminal carboxyl group, which is used to classify lipids into different classes of fatty acids. triglycerides and phospholipids are two types of lipids with similar configurations and important biological roles. triglycerides are formed by a series of dehydration reactions that join three fatty acid chains to a three-carbon molecule of glycerol. alternatively, a phospholipid is formed when a glycerol molecule is bound to two fatty acid chains and a phosphate group. since triglycerides and phospholipids are similar in construction and structure, they also share many functional properties. in both molecules, the glycerol "head" is hydrophilic and the fatty acid "tails" are hydrophobic, which gives the macromolecule an amphipathic nature--that is, the presence of opposing properties within one molecule.

Answer 1

The biosynthesis of fatty acids and lipids meets two imperatives in the

cell :

- supply of fatty acids necessary for the synthesis of structural lipids;

- storage of energy.

The synthesis of fatty acids goes through a dehydration step during its synthesis. and its catabolism goes through a hydration stage, which shows the importance of H2O molecules to build lipids (even cholesterol).

Synthesis of the fatty acid:

firstly, acetyl-ACP and malonyl-ACP were condensed, followed by reduction of acetoacetyl-ACP to β-hydroxybutyryl-ACP, followed by dehydration of β-hydroxyacyl-ACP, and finally reduction of the double bond by NADPH + H

Catabolism:

The reverse steps will occur: a beta oxidation, a hydration of the molecule, and finally another oxidation.