22 topics with concise breakdowns: definitions, key facts, and classroom questions.
In this chapter, we examine the molecular foundation of life—the most important classes of bioorganic compounds. You will study the chemistry of living organisms, starting with the structure and cyclic forms of carbohydrates (glucose, fructose, pentoses, disaccharides, and cellulose) and ending with triacylglycerols and the chemical properties of fats.
Special attention is paid to the structural and functional components of cells. We will analyze in detail the chemical properties of amino acids, the physicochemical characteristics and levels of organization of proteins, as well as the structure of peptides and the function of enzymes. A separate section is devoted to the storage and transmission of information: purine bases, nucleotides, and the role of DNA in protein synthesis.
During seminars and colloquia, instructors most frequently ask about the chemical properties of glucose and amino acids, the mechanisms of peptide bond formation, and the spatial structure of enzymes and nucleic acids. A firm grasp of this material is absolutely essential for successfully mastering biochemistry in senior years.
Where does the bulk of oxygen in abiotic natural reactions come from?
The primary source of molecular oxygen ($O_2$) on Earth is the vital activity of organisms, specifically the process of photosynthesis in plant cells containing chlorophyll.
What is the difference between aldoses and ketoses?
In aldoses, the carbonyl group is located at the end of the carbon chain (aldehyde group), whereas in ketoses, it is located within the chain (ketone group).
What are carbohydrate anomers?
These are optical isomers ($\alpha$- and $\beta$-forms) that differ in configuration solely at the hemiacetal (anomeric) carbon atom. This asymmetric center arises only during the ring-closure process.
Between which atoms does the furanose ring of fructose close?
In the fructose molecule, the ring is formed due to the establishment of a bond between the keto group at the second carbon atom ($^2\text{C}$) and the oxygen atom located at the fifth carbon atom ($^5\text{C}$).
Why do glycosides lose their reducing ability?
Tautomerism is absent in glycoside molecules. The substituting group rigidly fixes the cyclic structure, preventing the molecule from transitioning into an open-chain form with the generation of a free aldehyde group.
Why does sucrose not exhibit reducing properties?
The hemiacetal hydroxyl groups of both glucose and fructose participate in bond formation. No free hemiacetal hydroxyl remains, so the molecule cannot transition into the open form and exhibit aldehyde properties.
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