In all organisms, the basic unit of structure and function is:
A.
The cell.
B.
The molecule.
C.
The atom.
D.
The macromolecule.
The Correct Answer and Explanation is:
The correct answer is A. The cell.
Explanation:
In all living organisms, the cell is the basic unit of structure and function. The cell theory, one of the fundamental principles of biology, states that all living things are composed of cells, and that the cell is the smallest unit of life that can perform all the necessary functions of a living organism.
Why the Cell is Fundamental:
- Structural Basis: Cells are the building blocks of all organisms, from single-celled bacteria to multicellular organisms like plants and animals. In multicellular organisms, cells group together to form tissues, which then combine to form organs, and eventually organ systems, each performing specific functions necessary for the organism’s survival.
- Functional Basis: Cells carry out the essential processes that sustain life, including metabolism, energy production, waste elimination, reproduction, and response to environmental stimuli. Within cells, organelles like the nucleus, mitochondria, and ribosomes work together to perform these tasks. For example, mitochondria generate energy through cellular respiration, while ribosomes synthesize proteins.
Comparison with Other Options:
- Molecule (B): Molecules, such as DNA, proteins, and lipids, are crucial for cell function, but they are not independently capable of life. Molecules are chemical compounds that form the structural and functional components within cells.
- Atom (C): Atoms are the smallest units of matter that retain the properties of an element. While atoms make up molecules and cells, they are not considered living and do not perform biological functions independently.
- Macromolecule (D): Macromolecules, such as proteins, nucleic acids, carbohydrates, and lipids, are large molecules essential for cellular structure and function. However, like molecules, they cannot independently sustain life outside the context of a cell.
In summary, while molecules, atoms, and macromolecules are critical components of life, it is the cell that represents the smallest unit capable of carrying out the full spectrum of life’s processes. This makes the cell the fundamental unit of both structure and function in all living organisms.