in this video, we're going to begin our lesson on a cellular infectious agents, including viruses, viral Roids and Pry ins now recall from our previous lesson videos that the term a cellular or non cellular is just a term that means not consisting of or containing cells or cellular structures. And so anything that is a cellular is not going to be made of cells. And that includes these, a cellular infectious agents, viruses, viruses and prions. Now by definition, anything that is a cellular and is not made of cells is also not going to be considered living because recall that the smallest and most fundamental unit of life is the cell. And so if it's not consisting of cells, it's not technically by definition considered alive. And so all of these a cellular infectious agents are not technically considered alive because they lack many of the features of life, including not being uh, cellular. And so these a cellular infectious agents once again are non cellular or a cellular, not composed of cells. And so they're non cellular objects that will contaminate and affect living cells. And once again, this includes viruses, viral roids and prions are the three groups of a cellular infectious agents. And so if we take a look at our image down below at our map of the microbial world, recall that in our previous lesson videos, we already introduced the cellular organisms including the pro carry out such as bacteria and archaea, as well as the microscopic eukaryotes, including fungi, the protests, algae and protozoa, as well as helmets. And so this green region that I've highlighted here on the map represents the living aspect of the microbial world, the living cellular components, the living cellular organisms. But then notice over here, on the right hand side, is where the a cellular infectious agents fall that are not composed of cells and are not technically considered alive. And this once again includes the viruses, viral roids and prions. And as we move forward in our course, we're going to talk more about each of these groups, but for now, this year concludes our brief introduction to a cellular infectious agents, and we'll be able to talk more about them as we move forward. So I'll see you all in our next video.
2
concept
Viruses
Video duration:
3m
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in this video, we're going to begin our introduction to viruses. But later in our course in a different video, we're going to talk a lot more details about the structure and function of viruses. This video here is just an introduction and so a virus can be defined as an obligate intracellular parasite that is made of DNA or RNA but not both. And this DNA or RNA will be packed into a protein coat and sometimes the DNA and RNA can be packed into a lipid envelope. Now we said that a virus is an obligate intracellular parasite. And so to define an obligate intracellular parasite, we can define as substances that can only replicate inside of a host that they infect or harm. And so this virus, it can only replicate and reproduce when it is on the inside of a host that it infects and harms. Now all forms of life can actually be affected or infected by different types of viruses. And this includes bacteria, Archaea and you Correa. All forms of life can be infected by different types of viruses. Now frequently viruses will kill the cells that they infect. However, they can also silently remain inside of the host without killing them. And so this is an idea that we'll get to talk more about later in our course. But if we take a look at our image down below at our introduction of viruses, notice over here on the left hand side, we're showing you one type of virus that's known as a bacterial fage, which is a type of virus that infects bacteria. And so notice that it has on the perimeter and pink color a protein coat. And then on the inside there is genetic material either DNA or RNA. And so this is a micrografx of an escort rekia virus, T four bacteria fage. Uh Then over here on the right hand side what we're showing you is a human virus, which notice takes on a different structure. However, it still has a protein coat and it still is going to have genetic material. And of course, uh we're all familiar with the SARS Kobe to virus that caused Covid 19, the Covid 19 pandemic. And so here is a visual a depiction of the SARS COv two virus that caused Covid disease in humans. And so this year concludes our brief introduction to viruses, these obligate intracellular parasites. But again, once again. Later in our course, we're going to talk a lot more details about the structure and function of viruses. For now, I'll see you all in our next video.
3
Problem
Problem
Viruses:
A
Contain both protein and nucleic acids.
B
Infect only eukaryotic cells.
C
Can grow in the absence of living cells.
D
Are generally the same size as prokaryotes.
E
Always kill the cells they infect.
4
concept
Viroids
Video duration:
2m
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in this video, we're going to begin our introduction to viral roids. Now, viral roids like viruses are also obligate intracellular parasites that must infect a living cell and be inside of the cell to replicate. Now, unlike viruses that are made up of D. N. A. Or R. N. A. As well as protein and sometimes lipids, virus roids are only made of a single short strand of RNA that forms a closed ring. Now Vie roids are only known to infect plants and cause plant diseases. They are not really known to infect other groups of life other than plants. And there's not really much known about how Bayreuth is originated or how they can cause disease and plants. And so they are under investigation and there is a lot of research to find out more about these viral roids. Now, if we take a look at our image down below the viral ads, which will notice is we're showing you this red structure here which is representing the circular single stranded RNA which we call the virus roid. And so notice that it is able to base pair with itself, but it is going to complete a circle here a closed ring and it can infect plants and cause plants to wilt and ultimately die. Now. Down below what you see right here is another example of a viral Lloyd, specifically potato spindle tuber Vier Oid or PS Tv, which is a virus that infects potatoes and so it can infect normal potatoes and cause the potatoes to become PS Tv, potatoes or potatoes that have been infected by the potato spindle tuber vier Oid. Um and so um this here concludes our brief introduction to Vie Roids, these single short strands of RNA that form a closed ring and are obligate intracellular parasites. And once again we'll be able to talk more about thyroids later in our course. This is just the introduction. And so I'll see you all in our next video
5
concept
Prions
Video duration:
2m
Play a video:
in this video, we're going to introduce prions. And so the term prions is actually derived from pro tenacious infectious agents. And you can see that with the bold in terms here to help create that word prions. And so by pro tenacious what this is referring to is that these infectious agents are made of proteins and only proteins. And these pry ins like viruses and viral loads are obligate intracellular parasites, which once again just means that they must infect a living cell and get inside of the cell in order to replicate themselves. And so unlike viruses and viral loads, these prions once again are made of only misfolded proteins. So they only consist of proteins and that's why they are pro tenacious. Uh and you can see that with the prions here Now prior ions again, they are misfolded proteins themselves. However, these misfolded prion proteins can cause normal proteins to misfold. And ultimately a misfolded protein is going to lose its function and that can cause disease. And Soap Ryan's are linked to several slow degenerative diseases, such as scrapie and mad cow disease. And so if we take a look at our image down below, over here on the left hand side, notice that we're showing you the structure of a normal protein whose uh structure were symbolizing like this. But you can see this is the actual detailed structure of the normal protein. And over here on the right, what we're showing you is the structure of the prion, which is going to be a misfolded protein itself. And so notice that the shape of this prion is different than the shape of the normal protein. And so over here, on the right hand side, we're showing you the brain of a healthy individual that's going to have normal proteins. However, if this individual is infected with a pry on then the prion can cause normal proteins to transform into prions. And so you can see that those normal proteins have transformed into prions misfolded proteins that have lost their function and that can lead to diseases. And so this represents the diseased brain. And so this year concludes our brief introduction to prions, and once again, we'll be able to talk more about prions later in our course. But for now, I'll see you all in our next video.
6
Problem
Problem
This type of acellular infectious agent is only known to infect plants and is a small, circular, single-stranded nucleic acid molecule.
A
Archaea.
B
Prion.
C
Virus.
D
Viroid.
7
Problem
Problem
An infectious protein is known to cause neurodegenerative diseases in humans such as Creutzfeldt-Jakob disease ('mad cow disease'). This type of acellular infectious agent is known as a _________.
A
Viroid.
B
Prion.
C
Virus.
D
Protozoan.
8
Problem
Problem
Which of the following statements about acellular infectious agents is FALSE?
A
Acellular infectious agents are non-cellular objects that contaminate and negatively affect living things.
B
Acellular infectious agents are obligate intracellular parasites and they cannot reproduce on their own.
C
Acellular infectious agents are considered the smallest forms of parasitic life.
D
Acellular infectious agents are known to infect all forms of life.
Additional resources for Acellular Infectious Agents: Viruses, Viroids & Prions
