Table of Contents
Roles of Four Major Biomolecules in Living Cells Exam Guide
Identify biomolecules and functions: Carbohydrates for energy, lipids for storage/membranes, nucleic acids for genetics, proteins for catalysis/structure—not vitamins/enzymes as listed—essential classification for General Biology certification.
Question
Identify the main types of biomolecules and their functions in living organisms.
A. Carbohydrates – Provide energy
B. Lipids – Store energy and form cell membranes
C. Nucleic acids – Encode genetic information
D. Proteins – Catalyze reactions and support cellular structure
E. Vitamins – Catalyze cellular reactions
F. Enzymes – Act as transport molecules
Answer
A. Carbohydrates – Provide energy
B. Lipids – Store energy and form cell membranes
C. Nucleic acids – Encode genetic information
D. Proteins – Catalyze reactions and support cellular structure
Explanation
Carbohydrates serve as primary energy sources through rapid breakdown into glucose for ATP production via glycolysis and act in structural roles like cellulose in plant cell walls or chitin in fungal exoskeletons, with polysaccharides such as starch and glycogen providing efficient storage in plants and animals. Lipids, including triglycerides, phospholipids, and steroids, function mainly in long-term energy storage (yielding over twice the ATP of carbohydrates per gram), form hydrophobic barriers in cell membranes via phospholipid bilayers, and include signaling molecules like hormones (e.g., estrogen from cholesterol). Nucleic acids—DNA and RNA—encode, store, and transmit genetic information as nucleotide polymers, directing protein synthesis through transcription and translation per the central dogma while enabling heredity and variation. Proteins exhibit diverse functions as enzymes catalyzing metabolic reactions by lowering activation energy, structural components like collagen or keratin, transporters (e.g., hemoglobin), and regulators (e.g., antibodies), folding into precise 3D shapes from amino acid chains linked by peptide bonds. Vitamins act as cofactors rather than primary biomolecules, and enzymes represent a protein subcategory, not transport molecules.