Question Video: Arranging Biological Structures by Size Biology

Put the following structures in the order in which they are organized in the human body, from largest to smallest: cells, molecules, atoms, organelles.

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Video Transcript

Put the following structures in the order in which they are organized in the human body, from largest to smallest: cells, molecules, atoms, organelles.

This question is asking us to compare the size of biological structures in the human body. To answer this question, we’ll review key facts about the name, structures, and the levels of organization within the human body.

Many complex organisms, like humans, have a high degree of organization. So to understand how the body functions, it can be helpful to consider the levels of organization, that is, how the smallest parts of the organism are assembled into the larger structures. Let’s review the levels of organization in the human body in hierarchical order, starting with the smallest structure, the atom, and ending with the largest structure, the organism.

Atoms are the smallest unit of matter. At the most basic level, your body is made up of atoms like oxygen. Oxygen atoms are the most abundant atom by mass in the human body. Groups of atoms can be organized into larger structures called molecules. A molecule is two or more atoms joined by chemical bonds. For example, a water molecule is made from one oxygen atom bonding with two different hydrogen atoms.

Through the process of polymerization, single molecules can be joined together to form larger structures called macromolecules. The most common macromolecules found in the human body are lipids, proteins, carbohydrates, and nucleic acids.

Macromolecules that play the same function can be aggregated into a larger structure called an organelle. Organelles are functional subunits found within a cell. Examples of organelles include the nucleus, mitochondria, and the endoplasmic reticulum. Organelles carry out specialized functions like releasing energy for the cell or storing genetic information.

Groups of organelles that work together to carry out a common function form larger structures called cells. A cell is the smallest structural and functional unit of an organism. Cells consist of a flexible cell membrane that encloses cytoplasm, which surround a variety of organelles. Groups of cells that work together to carry out a common function create larger structures called tissues.

After cells, the hierarchical order continues and includes tissues, organs, organ systems, and organisms, like a human. So to summarize, groups of atoms join together to form molecules. Many molecules with the same function form organelles. And many organelles working together form a cell. With this knowledge, we can answer our question. The correct order of the structures from largest to smallest is cells, organelles, molecules, atoms.

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