Unicellular organisms consist of one cell only that performs all vital functions including metabolism, excretion, and reproduction. They are responsible for obtaining nutrients, producing energy, and making proteins.
The three main ideas of cell theory are that:
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1. All living things are made up of one or more cells. </span>
<span>2. Cells are the basic units of life in which activities of life occur. </span>
<span>3. Living cells come only from other existing and living cells. </span>
The bronchi (singular: bronchus) are the airways that lead from the trachea into the lungs, and then branch into smaller bronchioles. Structurally, the bronchi are made up of cartilage that gives them stability and prevents their collapse.
