Discover the tiny living systems that build every plant, animal, fungus, and many microorganisms.
Cell biology studies the basic units of life. Scientists examine how cells are built, how they move materials and energy, how they use genetic information, and how many cells work together in larger organisms.
Organelles perform specialized jobs that keep cells functioning.
Learn MoreMembranes control what enters and leaves a cell.
Learn MoreCells transform energy to power growth, repair, and movement.
Learn MoreGenetic information helps direct cell activities and protein production.
Learn MoreCells reproduce through carefully organized processes.
Learn MoreDifferent cell types are shaped for different jobs.
Learn MoreMany cells contain specialized structures called organelles. The nucleus stores most of a eukaryotic cell's DNA, ribosomes build proteins, mitochondria help release usable energy from food molecules, and other organelles sort, transport, recycle, or store materials. Plant cells also contain chloroplasts for photosynthesis and usually have a rigid cell wall outside the cell membrane.
The cell membrane forms a flexible boundary between the cell and its surroundings. It is selectively permeable, which means some substances can cross more easily than others. Water, nutrients, gases, ions, and wastes may move by diffusion, osmosis, transport proteins, or energy-requiring transport depending on the substance and the cell's needs.
Cells need energy for nearly every activity. In many organisms, cellular respiration breaks down energy-rich molecules and transfers some of that energy into ATP, a molecule cells can use directly. Plants and algae also capture light energy during photosynthesis, producing sugars that can later be used in cellular respiration.
DNA stores hereditary information in sequences of chemical building blocks. Genes are sections of DNA that contain instructions used to make functional molecules, often proteins. Cells regulate which genes are active, helping different cell types perform different jobs even though most cells in one organism contain the same basic genetic information.
Cell division allows organisms to grow, replace damaged cells, and reproduce. Before many eukaryotic cells divide, they copy their DNA. Mitosis separates duplicated chromosomes into two nuclei, and the cell then divides its contents. Another form of division, meiosis, produces reproductive cells with half the usual chromosome number.
In multicellular organisms, cells become specialized for particular functions. Nerve cells can carry electrical signals over long distances, muscle cells can contract, red blood cells transport oxygen, and leaf cells may contain many chloroplasts. Tissues and organs form when specialized cells cooperate in organized groups.