What is the smallest structural and functional unit of the human body?
A. Tissue
B. Organ
C. Cell
D. Organ system
Answer (1)
The correct answer is C. Cell. The cell is the smallest unit of life in the human body. It is the basic structural and functional unit of all living organisms. Every organ, tissue, and system in the human body is made up of cells. Despite their microscopic size, cells carry out all the processes necessary for life — such as energy production, growth, reproduction, and waste removal.There are trillions of cells in the human body, and they vary in size, shape, and function. Each type of cell is specialized to perform specific tasks. For example:Muscle cells contract to create movement.Nerve cells (neurons) transmit signals.Red blood cells carry oxygen.Skin cells provide protection.Cells contain various structures called organelles, each with a specific role:The nucleus contains DNA and controls cell activities.The mitochondria produce energy (ATP).The ribosomes build proteins.The cell membrane controls what enters and exits the cell.Cells come together to form tissues (groups of similar cells), which then form organs (like the heart or liver). These organs work together in organ systems (like the circulatory or respiratory system) to maintain the body’s functions.Without cells, there would be no life. Even the most complex structures in the human body — such as the brain or the lungs — start as groups of specialized cells working together.
