Which statement correctly describes yeasts?

A. Fermentation: Fermentation is a metabolic process in which microorganisms, such as yeast and some bacteria, convert sugars (e.g., glucose) into alcohol (ethanol) and carbon dioxide under anaerobic conditions. This process is utilized in the production of alcoholic beverages, bread, and certain biofuels, and it also allows microorganisms to generate energy when oxygen is limited.

B. Pasteurization: Pasteurization is a heat-treatment process designed to reduce microbial load in food and beverages, such as milk and juice, to prevent spoilage and pathogen transmission. It does not involve the conversion of sugars to alcohol and is not a microbial metabolic process.

C. Tyndallization: Tyndallization is a method of sterilization using intermittent boiling to destroy heat-resistant bacterial spores over multiple cycles. It is a physical control technique and does not involve sugar metabolism or alcohol production.

D. Lyophilization: Lyophilization, or freeze-drying, is a preservation method that removes water from a substance by sublimation under vacuum. It is used for long-term storage of biological materials and does not include the microbial conversion of sugars to ethanol.

E. Alcoholism: Alcoholism is a medical condition characterized by chronic, compulsive consumption of alcoholic beverages. It is a behavioral and physiological disorder, not a microbial metabolic process.

A. Discovery of ribosomes as non-membranous organelles: Ribosomes are intracellular structures responsible for protein synthesis and are not surrounded by membranes. While their discovery expanded understanding of cellular components, it did not contradict classical cell theory, which focuses on cells as the basic structural and functional units of life.

B. Identification of multinucleated skeletal muscle fibers: Classical cell theory posits that a cell has a single nucleus and functions as an autonomous unit. The presence of multinucleated skeletal muscle fibers, also called syncytia, challenged this notion This observation revealed that some cells can deviate from “one nucleus per cell” concept, prompting refinement of the theory.

C. Observation that all living organisms metabolize ATP: While ATP metabolism is a universal feature of living cells, this observation supports rather than challenges cell theory. It reinforces the concept that cells are the basic functional units responsible for life-sustaining biochemical processes.

D. Recognition that membranes are composed of phospholipid bilayers: Identifying the phospholipid bilayer structure of membranes clarified how cells maintain compartmentalization and selective permeability. This structural insight complements classical cell theory and does not contradict the fundamental principles regarding cellular organization.