Chemistry
Biochemistry
4,992 words, 10 sections
Biochemistry is the branch of science that studies the biomolecules found in living cells and organisms together with the chemical reactions they undergo, which is why the federal book calls it a hybrid science rather than one subject. It has no place of its own in the official PMDC syllabus table, and its measured examination weight is zero: no question in the paper bank carries a topic tag for this chapter, so there are 0 distinct questions across 0 official papers, with no years recorded and no boards recorded. The practice bank holds 1 active question on the chapter. The material still belongs on the page because it is textbook content attached to the official organic and biological chemistry units, and everything written here is the foundation the biological molecules and enzymes elsewhere are built on. A student who has it can name the four macromolecule classes, follow glucose into glycogen, explain how an amino acid becomes a peptide and how a protein folds, tell a fat from an oil, and keep DNA and RNA apart.
Biochemistry is the study of the biomolecules occurring in living cells and the reactions they take part in, and a living organism transforms matter and energy, responds to changes in its surroundings, and grows and reproduces. Behind each of those abilities sit very large organic compounds, and the compounds that carry those functions are called macromolecules. Four classes of them run almost everything in the body: carbohydrates, proteins, lipids and nucleic acids.
The four classes are best kept apart by what they are made of and what they do. Carbohydrates are the sugars and starches, built from carbon, hydrogen and oxygen, and their business is energy supply and structure. Proteins are chains of amino acids and they do the work of catalysis, transport, storage and regulation. Lipids are the fats, oils and related compounds, esters of fatty acids and alcohols, and they store energy and insulate. Nucleic acids carry and pass on genetic information. Each class has its own vocabulary in the pages that follow, and a question that names a molecule and asks for its class is answered by recognising which of the four building patterns it fits.
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