If this is not your first time encountering the term “cells,” you may know by now that cells are the basic unit of life, and that they make up all organisms, big or small.
But have you ever asked yourself if studying cells served any purpose beyond letting us know that they make up all organisms? Or that they are usually too small to be seen by the naked eye?
- Here, we will discuss what the field of cell biology and cytology are and why we study cells.
- We will also talk about cell structure and function, and what tools and methods we use to study cells.
Study Of Cell Structure And Function
Cell biology is the study of the structure and function of cells, their interactions with the environment, and their relationship with other cells to form living tissue and organisms. Within the discipline of cell biology is a more specific discipline called cytology which focuses only on the structure and function of cells.
Why is it important to study cells? Learning about cell structure and function helps us understand the biological processes that sustain life. It also helps us identify abnormalities and diseases. To give you a better picture of the purpose of studying cells, we'll discuss examples of how the study of cells is used in diagnosing and treating diseases.
Specialist In The Study Of Cells
Cytotechnologists are specialists that study cells by doing laboratory experiments and microscopic exams. When studying cells, they discern between normal and potentially pathological changes in the cell.
For example, cytotechnologists studying red blood cells are trained to identify C-shaped cells that indicate sickle cell disease. Or when studying skin cells sampled from an irregularly-shaped mole, they can also identify skin cancer cells among other skin cells.
Case Study About Sickle Cell Anemia
The shape of healthy red blood cells is called biconcave, which means that they are round with an indented center. When they have an abnormal C-shape, this may be a sign of sickle cell disease.
Sickle cell disease (SCD) is a group of hereditary red blood cell disorders that causes their red blood cells to become stiff, sticky, and resemble a sickle (a C-shaped farm tool). Sickle cells die rapidly, causing anemia in people with SCD. This is why SCD is also called sickle cell anemia.
A blood test that looks for hemoglobin S, an abnormal type of hemoglobin, helps doctors look out for sickle cell disease. A blood sample is analyzed under a microscope to look for a lot of sickle red blood cells, which are the disease's defining feature, to confirm the diagnosis.
Why Scientists Study Stem Cells
The loss or dysfunction of particular cell types in the body gives rise to a number of degenerative illnesses that are currently incurable. Although damaged or defective organs and tissues are frequently replaced with donated ones, there are not enough donors to cover the demand. Stem cells may offer a renewable supply of donor cells for transplantation.
A stem cell is a type of cell that has the capacity to develop into other cell types in the body. When stem cells divide, they can generate either new stem cells or other cells that perform specific functions. While adult stem cells can only generate a limited number of specialized cell types, embryonic stem cells are capable of forming an entire individual. And as long as the individual lives, their stem cells will keep on dividing.
While mired in controversy, the study of stem cells holds out considerable promise for a deeper understanding of the fundamental processes behind human development. There is also a potential for using these cells to cure a variety of illnesses and disorders.
What We Know About Cell Structure And Function: A Short Study Guide
The cell is the smallest unit of life: from bacteria to whales, cells make up all living organisms. Regardless of origin, all cells have four common components:
The plasma membrane separates the contents of the cell from its external environment.
The cytoplasm is a jelly-like fluid that fills the inside of a cell.
Ribosomes are the site of protein production.
DNA are biological macromolecules that store and transmit genetic information.
Cells are typically classified as prokaryotic or eukaryotic. Prokaryotic cells do not have a nucleus (membrane-bound organelle that contains DNA) or any other membrane-bound organelles. On the other hand, eukaryotic cells have a nucleus and other membrane-bound organelles that carry out compartmentalized functions:
The Golgi apparatus receives, processes, and packages lipids, proteins, and other small molecules.
The mitochondria produce energy for the cell.
Chloroplasts (found in plant cells and some algae cells) carry out photosynthesis.
Lysosomes break down unwanted or damaged cell parts.
Peroxisomes are involved in the oxidation of fatty acids, amino acids, and some toxins.
Vesicles store and transport substances.
Vacuoles perform different tasks depending on the type of cell.
In plant cells, the central vacuole stores various substances such as nutrients and enzymes, breaks down macromolecules, and maintains rigidity.
In animal cells, vacuoles assist in sequestering waste.
Besides their organelles, prokaryotic and eukaryotic cells also differ in terms of cell size. The size of prokaryotic cells range from 0.1 to 5 μm in diameter, while eukaryotic cells range from 10 to 100 μm.
To give you an idea of how small cells usually are, the average human red blood cell has a diameter of around 8μm, whereas the head of a pin has a diameter of about 2mm. This means that the head of a pin could hold roughly 250 red blood cells!
Cells may be small but they are fundamental to life. Cells of the same kind that assemble and perform similar functions comprise tissues. Likewise, tissues make up organs (like your stomach); organs make up organ systems (like your digestive system), and organ systems make up organisms (like you!).
Tools in and Methods of Studying Cells
Because individual cells are so small they are invisible to the naked eye, researchers use microscopes to study them. A microscope is a tool used to magnify an object. Two parameters are important in tackling microscopy: magnification and resolving power.
Magnification is the capacity of a microscope to make a thing look larger. The higher the magnification, the bigger the appearance of the specimen.
Resolving power is the capacity of a microscope to discern between structures that are close to each other. The higher the resolution, the more detailed and distinguishable are the parts of the specimen.
Here we will discuss two types of microscopes that are commonly used by people who study cells: light microscopes and electron microscopes.
What Are Light Microscopes?
If you’ve had the chance to use a microscope in the science lab while you were studying, chances are you used a light microscope. A light microscope works by allowing visible light to bend and pass through the lens system so that the user can view the specimen.
Light microscopes are useful for observing live things, but since individual cells are often transparent, it is difficult to tell which parts of an organism are which without the use of specific stains. More on cell staining later.
What Are Electron Microscopes?
Whereas a light microscope uses a light beam, an electron microscope uses a beam of electrons, which increases both magnification and resolving power.
A scanning electron microscope produces a beam of electrons that travels across a cell’s surface to highlight details on the cell surface. On the other hand, a transmission electron microscope produces a beam that passes through the cell and illuminates the interior of the cell to show its internal structure in great detail.
Because these require more sophisticated technology, electron microscopes are bigger and more expensive than light microscopes.
What Is Cell Staining?
Cell staining is the process of applying a dye to a sample to improve the visibility of cells and their constituent parts when viewed under a microscope. Cell staining can also be used to emphasize metabolic processes, distinguish between live and dead cells in a specimen, and count the cells for the measurement of biomass.
To prepare a specimen for cell staining it needs to undergo permeabilization, fixation, and/or mounting.
Permeabilization is where cells are treated with a solution–usually a mild surfactant–to dissolve the cell membranes so that bigger dye molecules can enter the cell.
Fixation usually involves the addition of chemical fixatives (such as formaldehyde, and ethanol) to increase the rigidity of the cell.
Mounting is the attachment of a specimen to a slide. A slide can either have cells grown directly on it or have loose cells applied onto it using a sterile procedure. Tissue samples in thin sections or slices may also be mounted on a microscope slide for examination.
Cell staining can be done by dipping the specimen in a dye solution (before or after fixation or mounting), washing it off, and then looking at it under a microscope. Some dyes call for the application of a mordant, a substance that interacts chemically with the stain to create an insoluble, colored precipitate. Once the extra dye solution is removed by washing, the mordanted stain will stay on or in the sample.
Stains can be applied to the cell's nucleus, cell wall, or even the entire cell. These stains can be used to reveal specific cellular structures or characteristics by reacting with organic compounds such as proteins, nucleic acids, and carbohydrates. Dyes that are commonly used in cell staining include:
Hematoxylin - when used with a mordant, this stains the nuclei blue-violet or brown.
Iodine - this is typically used to indicate the presence of starch in a cell.
Methylene blue - this is typically used to increase the visibility of nuclei in animal cells.
Safranin - this is typically used to counterstain the nucleus or indicate the presence of collagen.
Studying Cells - Key takeaways
- Cell biology is the study of the structure and physiological function of cells, their interactions with the environment, and their relationship with other cells to form living tissue and organisms.
- Within the discipline of cell biology is a more specific discipline called cytology which focuses only on the structure and function of cells.
- Because individual cells are so small they are invisible to the naked eye, researchers use microscopes to study them. There are two common types of microscopes: light microscope and electron microscope.
- A light microscope uses a light beam, while an electron microscope uses a beam of electrons.
- Cell staining is the process of applying a dye to a sample to improve the visibility of cells and their constituent parts when viewed under a microscope.
References
- Zedalis, Julianne, et al. Advanced Placement Biology for AP Courses Textbook. Texas Education Agency.
- Reisman, Miriam, and Katherine T Adams. “Stem Cell Therapy: A Look at Current Research, Regulations, and Remaining Hurdles.” P & T : a Peer-Reviewed Journal for Formulary Management, MediMedia USA, Inc., Dec. 2014, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4264671/.
- “Stem Cell.” Genome.gov, https://www.genome.gov/genetics-glossary/Stem-Cell.
- “Cell Biology.” Cell Biology | Biochemistry, https://www.bumc.bu.edu/biochemistry/research/cellbiology/.
- “Cytology.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., https://www.britannica.com/science/cytology.
- “Studying Cells.” PressBooks, OpenStaxCollege, 22 Aug. 2012, https://pressbooks-dev.oer.hawaii.edu/biology/chapter/studying-cells/.
- Bruckner, Monica Z. “Microscopy.” Microbial Life Educational Resources, Science Education Resource Center at Carleton College, 2 Feb. 2022, https://serc.carleton.edu/microbelife/research_methods/microscopy/index.html.
- “About Sickle Cell Disease.” Genome.gov, https://www.genome.gov/Genetic-Disorders/Sickle-Cell-Disease.
- “What Is Sickle Cell Disease?” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 7 June 2022, https://www.cdc.gov/ncbddd/sicklecell/facts.html.
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