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Methods of Studying Cells

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Biology

Cells come in many different shapes and sizes. Prokaryotes are cells without a nucleus or organelles. There are endless subtypes of prokaryotes when looking at all the bacteria, all with unique features and many different eukaryotic cells that can specialise in having a specific function.

So how do we know about all of these features, functions, and subtypes? That's where different methods and techniques of studying cells comes in. Depending on what question we want to answer about a cell, various methods are needed. There is one method nearly everyone knows: cell microscopy. Here we look at cells and cell parts to gather information about them. Depending on those features, the cells work with different types of stains. For example, a different stain is used with fat cells than muscle cells.

Did you know that the biggest unicellular organism is an alga called Caulerpa taxifolia? Its cells can grow to a whopping 15 to 30 cm! A naked eye cannot see most other cells, so this is a giant!

Let's cover some safe laboratory working techniques first.

Safe laboratory working practices

Before starting to work: Prepare or read an existing risk assessment with potential hazards of the experiment outlined. Report any damage to the equipment you are about to use and make sure you have all the personal protective equipment (PPE) required for the experiment.

Depending on the experiment's nature, PPE includes safety goggles, a laboratory coat, boots, face shields, and others.

When experimenting, follow the correct procedure.

Emergency procedures: In an emergency, you must be able to quickly locate emergency eyewash stations and showers, as well as a first aid kit. You will be supervised by your teacher or a lab technician who will advise you on these.

Good housekeeping: Avoid direct contact with potentially hazardous chemicals, do not eat or drink in the lab, wash your hands regularly, tie your hair back and use relevant PPE.

There may also be others; your teacher will guide you and read over the experiment carefully.

Cell biology lab techniques

Labs use many different techniques to study various cells, so let us take a closer look at some of them. First, we will briefly look at microscopy and how cell cultures work.

If you want to learn more about microscopy, we have a whole article about it!

Cell microscopy

There are many different types of cell microscopy. The most notable are light microscopy and electron microscopy. Light microscopy is used to view tissues and cells, while electron microscopy is used to view cell organelles in detail.

Within the realm of light microscopy, many subtypes are used to improve the resolution of light microscopes, such as working with fluorescent dyes and radioactive markers.

Growing cell cultures using the streaking technique

The most common cell cultures are microbial cultures. These are done to detect bacteria in a sample or replicate a specific bacteria. The most well-known method for growing distinct bacterial colonies is the streaking technique. The working environment must be sterile, i.e. using an aseptic technique.

Aseptic technique: using appropriate equipment and procedures to prevent pathogens contamination, i.e. sterile environment.

Equipment

  • An isolated culture of bacteria
  • Inoculation loop
  • Bunsen burner (+ lighter/match to ignite)
  • Agar plate (or any other sugar-based media suitable)

Procedure

  1. Turn on your bunsen burner and turn the flame to a blue flame to start the process.
  2. Sterilise the inoculation loop in the blue flame until it appears bright red. Let it cool.
  3. Pick up some of the isolated colony with the loop and streak around 3 or 4 times in a parallel motion to cover about a quarter of your petri dish.
  4. Put the loop under the flame again and when it cools, extend the streaks on the plate into the next quarter of the plate.
  5. Repeat in the next two-quarters of the petri dish.

Techniques in cell and molecular biology

While cell biology looks at cells as a whole and their organelles, molecular biology looks at smaller parts within the cell, such as Chromosomes and DNA. Specific techniques are needed to find out more about these molecules. The main methods you should know are polymerase chain reactions (PCR) and gel electrophoresis.

Polymerase chain reaction (PCR)

This technique is used to copy small fragments of DNA so that there is enough DNA and can be further studied or used in tests that detect DNA, the Covid-19 PCR tests, for example.

To understand a PCR, you first need to understand DNA replication; if you need to refresh your memory, look at our article on DNA replication.

Steps of PCR:

  1. DNA denaturation - DNA sequence is denatured into single strands.
  2. Annealing - DNA primers, nucleotides and Taq polymerase (heat stables) are added to the solution. DNA primers attach to the target nucleotide sequence.
  3. Elongation - Taq polymerase binds to the DNA primers, and the strand is copied.
  4. The cycle is repeated, and millions of DNA fragments are made.

Taq polymerase is a heat resistance enzyme widely used in PCR to replicate a specific DNA sequence.

DNA primers: A short, single-stranded DNA sequence.

Taq polymerase is extracted from a heat resistant bacteria called Thermus aquaticus.

Gel electrophoresis

Gel electrophoresis is used to separate molecules, including DNA, RNA and proteins, by molecular size. The molecules investigated are put in a gel that makes the molecules move using electrical currents. The gel contains small pores. The molecules differ in molecular sizes and will move at different speeds. Smaller molecules will generally travel faster than bigger ones because smaller molecules will pass through the pores in the gel more easily.

Gel electrophoresis allows scientists to distinguish between different lengths of DNA fragments.

DNA fingerprinting is a technique often used when trying to find a suspect in a criminal investigation. It links the evidence to the suspect.Why are there different sizes of DNA fragments amongst people? Well, every person has multiple repeated sections on their DNA. The number of repeats varies per person; the repeated sections are cut out of the DNA through specific reactions. If you look at five sections of DNA between two people, one person may have more repeats in section 1, and person two might have more repeats in section 4.

Methods of studying eukaryotic cell structure

Cells can be studied in many different ways depending on the aspect to be studied. Eukaryotic cells are often larger than prokaryotic cells, making them easier to see. The most well-known method of studying eukaryotic cells is through the light microscope. The cell is usually put between two glass/clear plastic slides - the microscope slide and the coverslip. Cells can be stained to accentuate organelles of interest.

A light microscope can see bigger organelles such as the nucleus, cytoplasm, and cell wall.

Organelles of interest can be isolated by breaking open the cell and isolating the different organelles for commercial use. This process is called subcellular fractionation.

Prokaryotes, like bacteria, are often grown in a laboratory to be studied; they have high division rates. Eukaryotic cells can also be grown in cell cultures like prokaryotic cells. However, this is more complicated since eukaryotic cells do not replicate in the same way as prokaryotic cells do. They will take more time to replicate.

Methods of Studying Cells - Key takeaways

  • Incorporating safe laboratory practices is essential before starting an experiment.
  • The two most frequently used types of microscopy is light microscopy and electron microscopy. Light microscopes are most often used in schools and universities to teach students.
  • The streaking technique is often used to grow isolated cultures of bacteria.
  • The polymerase chain reaction is used to determine the molecular weight of different lengths of DNA.

Methods of Studying Cells

The most well-known method of studying eukaryotic cells is through the light microscope. 

There are many different types of cell microscopy. The most notable are light microscopy and electron microscopy. Light microscopy is used to view tissues and cells, while electron microscopy is used to view cell organelles in detail. 


There are many techniques, common ones are microscopy and cell cultures.

Microscopic anatomy.

An alga called Caulerpa taxifolia.

Final Methods of Studying Cells Quiz

Question

What can be viewed with a light microscope?

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Answer

Cells and tissues.

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Question

What are microbial cultures used for?

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Answer

They are used to detect or replicate bacteria.

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Question

What is agar?

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Answer

It is a gel-like nutrient solution used in cell cultures.

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Question

What is molecular biology?


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Answer

It is the study of smaller fragments like DNA and chromosomes.

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Question

What does PCR sstand for?

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Answer

Polymerase chain reaction

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Question

What components are needed for a PCR?

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Answer

Taq-polymerase, DNA to be replicated, primers, nucleotides

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Question

How is a PCR done?

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Answer

1. The DNA is denatured to separate the DNA strands

2. Taq polymerase (heat stable), DNA primers and Nucleotides are in the solution

3. When the reaction cools down the primers bind to the single strands

4. the Taq polymerase can copy the strands by binding to the primers

The cycle is repeated and millions of DNA fragments are made

Show question

Question

What does a Gel electrophoresis do?

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Answer

Gel electrophoresis separates molecules by size. 

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Question

What can Gel electrophoresis be used for?

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Answer

Gel electrophoresis is used for identifying suspects based on DNA samples or paternity testing.

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Question

What makes DNA unique in size for gel electrophoresis?

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Answer

The amount of repeats of specific repetitions of DNA triplets makes DNA unique in size.

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Question

How are organelles from a eukaryotic cell separated?

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Answer

They are separated via subcellular fractionation


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Question

Why does subcellular fractionation work?

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Answer

Subcellular fractionation works because the organelles have different weights.

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Question

Explain the steps of subcellular fractionation.

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Answer

Step 1: The cell is membrane is broken so the organelles can be extracted. This is often done with a homogeniser. A homogeniser is similar to a blender. The resulting product is referred to as homogenate. 

Step 2: The homogenate can be filtered to remove any excess cells or big fragments.  

Step 3: The substance is centrifuged in an ultracentrifuge (a faster than normal centrifuge). Different speeds of the centrifuge then push fragments with different weights to the bottom of the tube, which is called sediment. At low speeds, heavy cell fragments like the nucleus and then mitochondria are found in the sediment. If done multiple times at different speeds all the organelles can be sorted.

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Question

Why is it more complicated to grow eukaryotic cells in a cell culture?

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Answer

They replicate in a different way than bacteria.

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Question

Where does Taq polymerase come from?

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Answer

A heat resistant organism called Thermus aquaticus.

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