The basic unit of all living organisms, from bacteria to humans, is the cell. Robert Hooke first described the cell in 1665, when he used a microscope to examine a piece of cork. To his eyes, he saw an orderly pattern of “a great many little boxes,” or holes separated by thin walls much like a honeycomb. A few years later, and with a more sensitive microscope, Antoni Van Leeuwenhoek visualized the first living cells darting around water droplets, which he called “very little animalcules.” This was likely the first description bacteria and protists, which we can observe in a drop of pond water today.
Nowadays, we know that living things are made of cells. However, not every cell is the same. Bacterial cells differ from protists, which differ from animal cells. Some organisms consist of one cell (unicellular), and others consist of multiple cells (multicellular). Furthermore, within a multicellular organism, there can be many types of cells working together in structures like tissues and organs to build a complex organism.
So how can we learn more about these amazing building blocks of life? Using microscopy and techniques from biochemistry, physiology, and molecular biology, cell biologists investigate the structure and function of the cell and its components, and how the distinct parts of a cell work together. Let’s explore cells in your classroom laboratory!
Membranes and Transport:
At its simplest, a cell is essentially a drop of a thick, watery substance (cytoplasm) surrounded by a layer of fats (cell membrane) that form a barrier between the inside of the cell and the outside environment. The cell membrane consists of two layers of lipids embedded with proteins that move ions and other molecules into and out of the cell.
- EVT-043: Osmosis and Diffusion
- S-74: What is Osmosis?
- AP04: Diffusion and Osmosis
- AP11: Transpiration
Contained within a cell is the genetic material (DNA), and the cellular machinery necessary to create proteins (ribosomes). However, that is where the similarities between all cells end. Through their experiments, scientists identified two distinct types of cells – prokaryotes and eukaryotes. Contained within eukaryotic cells are a diverse collection of membrane-bound compartments (organelles) that each have a specific biological function. In contrast, prokaryotic cells do not have organelles; instead all biological materials are present in the cytoplasm.
Nucleus: Contains DNA, acts as a cell’s control center.
Ribosome: Links amino acids together to form proteins.
Mitochondria: Cell’s powerhouse, converts food to energy.
- AP06: Cellular Respiration
- 332: The Mother of All Experiments: Exploring Human Origin by PCR Amplification of Mitochondrial DNA
- EVT-027: Mega Mitochondria Model
Chloroplast: Uses sunlight to create food for plants.
- 284: Plant Pigment Chromatography and Photosynthesis
- EVT-002: Cool Chloroplasts Model
- AP05: Photosynthesis
Cell morphology refers to the shape, appearance, and structure of a cell. The structure of a cell relates to the functions of the cell, whether it is prokaryotic or eukaryotic. In prokaryotes, researchers observe the shape and arrangement of cells to identify the species of bacteria. In higher organisms, the morphology of cells relates to the tissue from which they originated. Changes in a cell’s morphology indicate diseases like sickle cell anemia or cancer.
- 160: Identification and Characterization of Bacteria
- 986: Analysis of Mammalian Cell Types
- 990: Morphology of Cancer Cells
- 116: Sickle Cell Gene Detection
All cells divide in order to create more cells. In most cases, one parent cell will split into two identical daughter cells. This allows an organism to grow, to develop, and to replace old cells. In order for a cell to divide, the cell must increase in volume, duplicate its DNA, and then split all of the cellular components into two separate cells. This process must be carefully regulated to ensure that the cell divides at the right time and in the right place. Rapid, unregulated cell division can result in a group of diseases called cancer. Cancer changes the nature of the cells, which can be identified using biomedical tests.
- EVT-036: Mitosis and Meiosis Model
- 1001: Eukaryotic Cell Biology
- AP07: Cell Division – Mitosis and Meiosis
- 141: Blood-based Cancer Diagnostics