Welcome to the third class on general microbiology and brewing microbiology, right? Brewing technician course here at our Federal Institute. South of Minas in Machado.
Let's see what we will cover today in the third class on cell biology. The content: prokaryotic cells or prokaryotes, eukaryotic cells or eukaryotes. The organelles present in these cells, plasma membrane, and cell wall.
Let's go to the next screen. We have two types of cells, prokaryotic cells or prokaryotes, right? And we will also address their structures and the function of each one.
So, we have here a prokaryotic cell, which is the case for bacteria, right? What is its characteristic? It does not have a nucleus individualized where it is stored.
The DNA and the RNA, right? It exists here in the cytoplasm, right? What?
DNA molecule. Here we have the structures that we are going to describe one by one. Ribosomes, cytoplasm, pili, flagella, the plasma membrane, which is just inside the cell wall, the capsule.
So, we have here the outermost capsule, the intermediate cell wall, and the plasma membrane, and here the DNA. So this is the structure of a prokaryotic cell and the organelles that are part of it. Recalling, it differs from eukaryotic cells because it does not have a nucleus where nucleic acids are stored.
Continuing, the prokaryotic cell. What is a prokaryotic cell? It is a very simple and primitive type of cell that does not possess—this is its main characteristic—it does not possess a true nucleus delimited by a membrane, having its genetic material free in the cytoplasm.
So, just going back here, genetic material, in this case DNA, is here in the cytoplasm of the prokaryotic cell. Having seen this, that is what is a prokaryotic cell and its definition, remembering that it does not possess a true nucleus where nucleic acid is stored. Prokaryotic cells, structures and functions.
So, the first structure, nucleoid, is not a nucleus. Nucleoid is a region of the cytoplasm where the main DNA is located ; it does not have RNA. Usually a single and circular molecule; there is no nuclear membrane.
Why is there no nuclear membrane? Because it does not have a nucleus as occurs in eukaryotic cells. The DNA present in the cytoplasm of prokaryotic cells has the basic function of providing genetic information essential to perform all cell activities, control metabolism, the entire working process of the cell, and ensure reproduction.
So, note well that the DNA of prokaryotic cells, besides storing genetic information, also has functions of controlling metabolism and ensuring cellular reproduction. the cytoplasm inside the cell, where the DNA is located, is a jelly-like substance that fills the interior of the cell. Back to this, here is the cytoplasm, right?
which fills the entire interior of the cell, where vital chemical reactions occur. So, it is fundamental to remember that it is in the cytoplasm of prokaryotic cells that vital chemical reactions occur. Then we now have the cell wall, which is more internal, wait, sorry, more external, a layer outside the membrane that gives shape and protection to the cell.
So, the cell wall of the prokaryotic cell, besides protecting the membrane, provides protection to the prokaryotic cell. More internal, the plasma membrane is a very thin layer that surrounds the cell . What is its specific function?
To control the entry and exit of substances. So it is a selective process. The capsule is an external layer of extra protection against the environment and the defense systems of other organisms.
So we have an order here, look. More internal, cell wall, intermediate, plasma membrane, and more external, protecting the cell in relation to the environment and acting as a defense system against other organisms, is the capsule. So we have more internal, intermediate, and more external.
Now we are going to talk about the organelles or structures within the prokaryotic cell. Ribosomes, okay? Uh, you have to emphasize and remember the function of each of these structures well.
Structures responsible for the manufacture of proteins. This here is the main point. They are the only organelles present, but they do not have a membrane, right?
So, remembering, keep the function in mind. Protein manufacturing, the attribution of ribosomes, plasmids, okay? Uh, they are not found in all prokaryotic cells.
There are specific groups. What are plasmids? They are small pieces of DNA, right?
Dispersed within the cell, separated from the main DNA, they do not carry vital genes. So we reach the conclusion that what carries vital genes is the RNA and DNA in eukaryotic cells, being resistant to antibiotics. So, that is why depending on the the disease a person has or something in that sense, antibiotics, certain types of antibiotics no longer work, you need a stronger medication.
Why? Because the plasmids gradually become very resistant to antibiotics. So, remembering, ribosomes, protein manufacturing.
Plasmids, not in all cells, and what are they? Pieces of DNA that remain separate from the main DNA. So, what can we conclude?
That inside prokaryotic cells we have the main DNA and scattered fragments, which would be the plasmids. they do not carry vital genes. and are highly resistant to antibiotics.
Changing the image, we had prokaryotic cells where there was no individualized nucleus, examples like bacteria, fungi, etc. We now have eukaryotic cells, plant cell and animal cell. Here is the big difference from eukaryotic cells to prokaryotic, as these two types only exist in eukaryotes.
The big difference of it, eukaryotic compared to prokaryotic is exactly this here, see? An individualized nucleus protected by a membrane called the nuclear envelope. And inside here we have what?
DNA and RNA which are responsible for genetic traits. Scattered here we have the cytoplasmic organelles. Here around it is the cell wall.
Cell wall is characteristic only of plant cells. Here is an animal cell, right? The plasma membrane, the organelles.
Yes, like the plant cell, we have here the nucleus individualized, right, protected by a membrane. And here DNA and RNA. So, the basic difference between prokaryotic and eukaryotic cells is precisely that in prokaryotes there is an absence of an individualized nucleus, and the presence of only RNA in the cytoplasm.
In eukaryotic cells, we have the nucleus containing DNA and RNA protected by a membrane, right? This is the big difference. Individualized nucleus.
So here is a very clear diagram of the plant cell with its cell wall. And here is the animal cell protected by its characteristic membrane and the organelles that we are going to see here. Continuing, eukaryotic cells have a true nucleus where the DNA and RNA are located.
This true nucleus, right, is protected by a membrane called the nuclear envelope. Very well. And the structures inside eh inside the cell are called organelles.
So, coming back here, the organelles here, look. Look at the organelles here , look. Perfect.
Very well. Separated by a membrane called an organelle. Organized nucleus.
The DNA is kept inside a nuclear membrane separated from the rest of the cell. Returning, look at the nucleus here, look. totally wrapped by a layer, separating it from the other organelles, there is no contact.
Organized nucleus is kept separated from the rest of the cell. Linear DNA, linear means, like a ribbon . The genetic material is organized in linear strands associated with proteins called histones.
So, histones are a type of protein in eukaryotic cells. Membranous organelles are these organelles here, look. Right?
The cytoplasm contains small structures like mitochondria which are responsible for cellular respiration, energy production, Golgi complex, secretion of substances, endoplasmic reticulum, synthesis of substances for the cell. So, the cytoplasmic organelles are these here. Where are they?
Dispersed in the cytoplasm. Cytoplasm is all of this here. However, the cytoplasm has no contact with the nucleus, because the nucleus is protected by a membrane called the nuclear envelope.
Remember, mitochondria are the organelles responsible for cellular respiration. Golgi apparatus, substance secretion, and endoplasmic reticulum. There are two types of endoplasmic reticulum, the smooth and the rough, right?
We are going to put that in an activity for you, so you can tell one from the other . Greater complexity. They are larger and more complex than prokaryotic cells .
Why are they more complex than prokaryotic cells? Because it has a nucleus, the eukaryotic cell, it has an individualized nucleus. This individualized nucleus provides more complexity, besides having more organelles, varied organisms, eukaryotic cells, right?
We can have that single-celled type, called unicellular organisms, typical examples are protozoa, or multicellular like animals and plants with numerous cells. So unicellular eukaryotes with a typical example of just one cell. Protozoa like paramecia, or multicellular as in the case of animals and plants.
Eukaryotic cells. Structure and functions. The eukaryotic cell has three main parts, right?
The outermost one that protects the cell is called the plasma membrane. The interior, the cytoplasm. In this cytoplasm, cytoplasmic organelles are scattered.
And a well-defined nucleus, protected by the nuclear envelope, the membrane that stores the DNA. The plasma membrane is the outermost, a very thin layer that protects the cell. What is its function?
To control what enters and leaves the cell. That is the basic function. Cytoplasm, that core, that entire interior of the eukaryotic cell, patient.
It is formed by a gelatinous liquid called cytosol, right? Cyto- cytosol. It's right here.
These, these are organelles and this material that forms the cytoplasm here is called cytosol, right? The nucleus is very important, right? It is what mainly differentiates eukaryotic from prokaryotic cells.
It is the cell's command center. Why? Because that is where the genetic code is, right?
And it is protected by the nuclear envelope membrane and stores the genetic material for cell reproduction. DNA, deoxyribonucleic acid. Mitochondria is another organelle that is there in the cytoplasm of eukaryotic cells.
What is the function? To produce energy for the cell. To function through what?
Cellular respiration. So, basically, the main function of the mitochondria is cellular respiration. Endoplasmic reticulum, I told you, there are two types, smooth and rough.
We won't go into that detail. It is a network of channels that transports substances. So , the function of the endoplasmic reticulum, right?
Here, smooth or rough , right? Is to transport substances. The smooth one has a basic function, fat production, and the rough one is full of ribosomes that help make proteins.
So, there is a difference right here, look. The smooth one produces fat and the rough one, which has ribosomes attached to it, helps make proteins. Ribosomes, another cytoplasmic organelle.
So, you are seeing the complexity of eukaryotic cells in relation to prokaryotic ones. Ribosomes, small dots, are small fragments that manufacture the cell's proteins. Look at the complexity of the eukaryotic cell.
So, if the Golgi complex has as its main function the production of proteins for the cell. Look at how the process is. Interesting .
It packages and sends proteins and other substances out of or into the cell. According to the need of the function the cell is performing, it can be outward or inward, depending on the cell's need. Lysosomes.
The main function of lysosomes is the digestion of substances and they clean up waste inside the cell. Look how interesting, it digests substances inside the cell and then cleans up the cell's waste. Peroxisomes.
Basic function is to break down any toxic substance that could hinder the functioning of the eukaryotic cell, more specifically in our case, animal and plant cells. It eliminates toxic substances. This is a very explanatory diagram.
You have two types of cells: prokaryotic, eukaryotic , or prokaryotes and eukaryotes. The prokaryotic one, including the domain of bacteria. Bacteria as a typical example of prokaryotic.
Archaebacteria or archaea. Look at eukaryotes, look at the breakdown. Who has eukaryotic cells ?
Protists, fungi, animals, and plants. So, look at the diversity here in the prokaryotic, bacteria and archaebacteria. Here in eukaryotes there is a nucleus.
Individualized here , it does not. We have here, look, the protist kingdom, the fungi kingdom, the animal kingdom, and the plant kingdom. So, this is a very illustrative diagram for you to see who has prokaryotic cells and who has eukaryotic cells.
Here, a comparative table between prokaryotic and eukaryotic cells. Prokaryotic, nucleus absent. The DNA is free in the cytoplasm.
Eukaryotic, nucleus present, right? Separated from the cytoplasm, in addition to storing DNA, separated from the cytoplasm by a nuclear membrane. Size: the prokaryotic cell is smaller than 1.
5. micrometers. Just remembering that in 1 meter we have 1 million micrometers.
Here the eukaryotic is larger, about 10 to 100 micrometers. Organelles: it does not possess membrane-bound organelles. So the organelles inside the cytoplasm do not have a membrane.
It possesses several organelles, mitochondria, Golgi , etc. We refer to circular and free DNA called nucleoids. They are dispersed in the cytoplasm.
Not here. They are in the form of linear strands and organized into chromosomes. Chromosomes are responsible for the transmission, transmission of genetic traits.
Smaller, less complex ribosomes ; larger, more complex ones. Why are they more complex? Due to the functions they perform.
Organisms, examples of prokaryotic, bacteria and archaea. Eukaryotic, typical examples: animals, plants, fungi, and algae. Prokaryotic life type is only unicellular, one cell , and eukaryotic is unicellular or multicellular.
There are unicellular cases, but the majority are multicellular. The yeasts that interest us for brewing are beneficial unicellular fungi used to ferment the wort. What is the wort?
It is fresh grape juice added to give flavor and aroma to the beer. While contaminant bacteria are prokaryotic microorganisms that spoil the drink and create unpleasant flavors, right? So, normally , what we observe is that there are microorganisms here, okay, which are largely responsible for spoiling the drink and generating unpleasant flavors .
Brewing yeasts. Brewing yeasts are fungi of the genus Saccharomyces, Saccharomyces cerevisiae, or also Saccharomyces pastorianus. So the important yeasts in beer production are the most known, most talked about, Saccharomyces cerevisiae, but we also have Saccharomyces pastorianus.
Function of the yeasts: consume sugar C6H12O6 to produce ethanol alcohol C2H5OH and carbon dioxide CO2 in a clean and controlled way, okay? So, function of the: consumes sugar in the form of glucose C6H12O6 and produces ethanol alcohol C2H5OH and carbon dioxide CO2 in a clean and controlled way. Physical characteristics of these yeasts: large cells, usually 5 to 10 micrometers, they are larger than other cells, right, than prokaryotic ones; they reproduce by budding, so buds grow in spaces on the fungus structure.
Sensory profile for the senses, right? They leave desirable profiles; esters are an organic compound and phenols are also organic compounds characteristic of beer, because there are esters and phenols that are not characteristic for this case here of the brewing yeast sensory profile. There are specific cases.
We talked about it and here it is, the main yeast for beer production: Saccharomyces cerevisiae. Here are some of its forms, right? some of its cells.
So this is our main yeast in beer production. We also mentioned that there is another type of Saccharomyces used in beer production. Saccharomyces pastorianus.
Look at its shape. Comparing it with the previous example. This is Saccharomyces cerevisiae, this is Saccharomyces pastorianus, okay?
It is good to visualize this here because just talking about it doesn't work, it seems a bit meaningless. So, showing some structures and how they are. Contaminating bacteria, contaminating microorganisms, in the case of beer production, microorganisms like lactobacillus, pediococcus, or acetobacter that enter the process through hygiene failures and raw materials.
So, every food and beverage manufacturing process must have its rigor. Any path that is not following what is determined will lead to contamination. So, these lactobacillus, pediococcus, right, and acetobacter, enter the process, okay, through hygiene failures, contaminating the beverage.
What do they do? They deteriorate the product being produced by competing for nutrients, trying to take nutrients and generating unwanted byproducts. So they deteriorate the nutrients, the nutrients take on another chemical composition and the byproduct will be unwanted, right?
Which is what is intended to be obtained. Physical characteristic. Prokaryotic organisms much smaller than yeasts, generally below 2 micrometers.
Recalling that a micrometer is 1 million times smaller than 1 meter. In the shape of rods, a stick, right? A small little rod or spheres.
Sensory profile. Produces off-flavors. Flavor means striking tastes like acidity.
So, the alteration can produce acetic acidity with a vinegar taste. Diacetyl is an organic radical, characteristic of excess butter or sulfurous aroma, smell of rotten egg. In the case of butter, it is that taste of rancid butter, right?
Acidity. That taste of vinegar and sulfurous, that odor of rotten egg. Here talking about off-flavors, flavors are aromas or unwanted and unexpected aspects.
It can arise during manufacturing, because you won't produce knowing there are no conditions for it. And in a product like beer, the first case where these unpleasant flavors can occur, production errors, failure in the manufacturing process or yeast fermentation, lack of equipment cleaning and sanitization. This will contaminate the final product.
Bad raw material, use of chlorinated water or altered ingredients. So, when one is going to make it, we know that 90 to 95 %of the beverage is water. So it has to be water of good quality, so a rigorous analysis must be done, otherwise, one or more batches of the product will be lost.
Incorrect storage. If you expose the beverage to light or oxygen for a long time, it will deteriorate the product. Common examples of diacetyl that I mentioned to you, common butter taste due to fermentation failure.
So, when fermenting, if you do not follow the recommended standards, okay? We will have the presence of the organic compound diacetyl. Oxidation, the product oxidizes and gets a cardboard taste caused by contact with air.
So excessive contact with air, right? Causes oxidation of the product and the beverage gets a cardboard taste. Acetic acid.
Acetic acid is nothing more than vinegar. So the drink gets a smell of vinegar caused by bacteria that proliferate in this medium. Isovaleric acid is an organic compound, or propanoic acid, is its name.
The drink gets a smell of stinky feet. Imagine opening the drink, right? And with that unpleasant smell of stinky feet.
