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Studying Cells

Studying Cells

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:

  1. The plasma membrane separates the contents of the cell from its external environment.

  2. The cytoplasm is a jelly-like fluid that fills the inside of a cell.

  3. Ribosomes are the site of protein production.

  4. 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

  1. Zedalis, Julianne, et al. Advanced Placement Biology for AP Courses Textbook. Texas Education Agency.
  2. 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/.
  3. “Stem Cell.” Genome.gov, https://www.genome.gov/genetics-glossary/Stem-Cell.
  4. “Cell Biology.” Cell Biology | Biochemistry, https://www.bumc.bu.edu/biochemistry/research/cellbiology/.
  5. “Cytology.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., https://www.britannica.com/science/cytology.
  6. “Studying Cells.” PressBooks, OpenStaxCollege, 22 Aug. 2012, https://pressbooks-dev.oer.hawaii.edu/biology/chapter/studying-cells/.
  7. 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.
  8. “About Sickle Cell Disease.” Genome.gov, https://www.genome.gov/Genetic-Disorders/Sickle-Cell-Disease.
  9. “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.

Frequently Asked Questions about Studying Cells

The study of the structure and function of cells is called cytology.

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 is called cell biology.

Scientists are studying stem cells because it 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. Stem cells can also serve as a renewable supply of donor cells for transplantation.

Because individual cells are so small they are invisible to the naked eye, researchers use microscopes to study them.

The microscope was first used to study cells in 1667 by scientist Robert Hooke. He coined the term 'cell' in his observation of cork cells. 

Final Studying Cells Quiz

Question

How do we quantify cell mass?

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Answer

Picobalance

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Question

How do we measure cell size?

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Answer

Light microscope

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Question

What is hematocrit?

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Answer

Red blood cell volume

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Question

Eukaryotic cells are larger than prokaryotic cells

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Answer

True

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Question

The ovum is the smallest human cell

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Answer

False

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Question

Cells are different sizes depending on their different functions

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Answer

True

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Question

Why are prokaryotic cells smaller than eukaryotic cells?

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Answer

They have fewer organelles

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Question

Bacteria size depends on the species

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Answer

True

Show question

Question

What is cell confluency?

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Answer

A percentage of a given area covered by cells 

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Question

What happens if a patient has a low hematocrit? 

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Answer

A low hematocrit count indicates an abnormally low percentage of red blood cells and that the patient may be experiencing:


  • Hemorrhage
  • Anemia  
  • Bone marrow defects

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Question

What happens if a patient has a high hematocrit? 

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Answer

A high hematocrit indicates an abnormally high percentage of red blood cells and that the patient may be experiencing:


  • Dehydration
  • Polycythemia vera

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Question

What do a pipette scratch and transwell invasion assay help with?

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Answer

Measuring cell migration

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What is cell density?

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Answer

Mass to volume ratio

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What is cellular metabolism? 

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Answer

Sum of all biochemical processes occurring inside the cell

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Question

What limits cell size?

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Answer

  • Surface area to volume ratio: the larger the cell the more nutrients it will need (you can see this in the figure below)
  • Nucleo-cytoplasmic ratio: the nucleus can only manage so much cytoplasm/cell space at once
  • Cell membrane strength: larger cells have a higher chance of damaging their cell membrane
  • Mechanical structures: structures such as a cell wall make cells stronger and able to grow in size, cells without a cell wall will not be able to be as large

Show question

Question

The study of cell structures and functions is called ___.

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Answer

Cytology

Show question

Question

Describe the work of a cytotechnologist.

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Answer

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. 

Show question

Question

How is sickle cell disease identified?

Show answer

Answer

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.

Show question

Question

Cells of the same kind that assemble and perform similar functions comprise ____.

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Answer

tissues

Show question

Question

This is the capacity of a microscope to make a thing look larger.

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Answer

Magnification

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Question

This is the capacity of a microscope to discern between structures that are close to each other.

Show answer

Answer

Resolving power

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The higher the resolution of a microscope, ____.

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Answer

the more detailed and distinguishable are the parts of the specimen

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How does a light microscope work?

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Answer

light microscope works by allowing visible light to bend and pass through the lens system so that the user can view the specimen.

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Question

How does an electron microscope work?

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An electron microscope uses a beam of electrons, which increases both magnification and resolving power.

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Question

What is the difference between a scanning and a transmission electron microscope?

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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. 

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Question

Why is cell staining done?

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Answer

Cell staining improves the visibility of cells and their constituent parts when viewed under a microscope.

Show question

Question

This substance interacts chemically with the stain to create an insoluble, colored precipitate

Show answer

Answer

Mordant

Show question

Question

Why is permeabilization done prior to cell staining?

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Answer

Permeabilization is done to dissolve the cell membranes so that bigger dye molecules can enter the cell. 

Show question

Question

Describe the process of cell staining.

Show answer

Answer

Cell staining can be done by dipping the specimen in a dye solution, 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.

Show question

Question

Which of the following are dyes commonly used in cell staining?

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Answer

Hematoxylin

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Question

What is a microscope?

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Answer

microscope is an instrument that’s used to optically magnify objects. Microscopes are made up of lenses that make small objects appear larger when looked through them. 

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The images taken with the aid of a microscope are called ___.

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Answer

Micrograph

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Who coined the term "cell" after observing cork cells under the microscope?

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Answer

Robert Hooke

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What are lenses and how do they magnify objects?

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Answer

Lenses are clear pieces of glass or plastic that are curved in a way that bends the light passing through them, effectively magnifying an object’s appearance.

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Compound microscopes are microscopes with at least two ___.

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Answer

Lenses

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Question

Compare and contrast light and electron microscopes.

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Answer

Light microscopes use visible light to illuminate subjects. Said light is reflected off the sample to then be bent by a lens system and optically magnify the image. On the other hand, electron microscopes use accelerated electrons to illuminate samples. Electron microscopes have a much higher resolving power.

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Question

What makes the resolving power of electron microscopes different from light microscopes?

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Answer

Accelerated electrons used in electron microscopes have a shorter wavelength than visible light photons do, so their resolving power is significantly higher.

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Question

What is the purpose of cell staining?

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Answer

Cell staining helps the viewer distinguish between the different parts of a specimen by brining in some color and therefore increasing the contrast of the sample.

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Question

Why must a sample be studied under a vacuum when using an electron microscope?

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Answer

Samples must be studied while under a vacuum, so as to not interfere with or disperse the beam of electrons being fired - something that air alone can do. This process implies that no cells can be observed while alive, and steps such as drying and freezing are part of a necessary procedure. 

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Question

____ are mainly used to study the internal structures of specimens under study.

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Answer

Transmission electron microscopes

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___ are mainly used to study the external morphology of specimens under study.

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Answer

Scanning electron microscopes

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Question

Which of the two types of electron microscopes require thin samples?

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Answer

Transmission electron microscopes

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Question

What is the purpose of the condenser in a light microscope?

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Answer

Condenser lenses are used to concentrate the light coming from the illuminator and properly direct it onto the specimen. Their use allows for a greater resolution of the final images, particularly when using high magnification lenses.

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Question

Both transmission and scanning electron microscopes use electrons to study a sample. Why do they produce different images: one showing the internal structure of the specimen and the other showing its external morphology?

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Answer

The difference lies between how the electron beam is used. For transmission electron microscopes, the electron beam is transmitted directly through the sample, whereas for scanning electron microscopes, the  electrons  are reflected off of its surface.

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Question

Describe how we see objects through a light microscope.

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Answer

Once the subject is well-illuminated, its light passes through an objective lens, which first magnifies it. The image that results from this process is then passed through an eyepiece lens, which magnifies it again. It is by looking at said eyepiece lens that the final picture is ready to be seen by the human eye.

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