Cell Inclusions - Online Tutor, Practice Problems & Exam Prep

Cell Inclusions

In this video, we're going to begin our lesson on cell inclusions. And so inclusions are defined as cytoplasmic molecular aggregates, or in other words, aggregates of molecules in the cytoplasm. And they can be very diverse in both their structure as well as their function. And we'll be able to talk about some of the different types of inclusions down below in this table. Now, some inclusions are stored as insoluble granules, whereas others are enveloped by proteins, a lipid membrane, or both proteins and a lipid membrane. Now granules are defined as small particles that are barely visible by a microscope. And in many cases, granules are referring to vesicles, small little lipid bubbles. Now, down below in this table, once again, we have a bunch of different types of inclusions. This does not include all of the different types of inclusions. It only contains some of the more common types of inclusions that are usually tested on by microbiology professors. And so, notice that we have the inclusion type over here on the far left, and the function over here in the middle, and then a corresponding image on the far right. So the first type of inclusion that we have are the storage granules, which are granules that are used for storage purposes. Almost like a kitchen pantry in a way where you can store items in your kitchen pantry for use at a later time whenever you need it. And so, you can see here that storage granules are aggregates of large polymers that are in excess inside the cell. And so when the cell has a lot of a particular type of molecule, it can store it as these storage granules. And then later at a different time, if that molecule starts to get low, then they can use the storage granules as a source to be able to get more. And so there are many types of storage granules, including carbon granules, which are going to be storing carbon to be used later as an energy source. There are also polyphosphate granules, which are going to be storing phosphate groups, inorganic phosphate groups for later use in biosynthesis to make things like nucleotides and stuff like that. There are also sulfur granules, which are going to be storing sulfur in bacteria that actually use sulfur to generate energy. And so you can see over here, these little bubbles that are inside of the cells represent storage granules that can be inside of cells. Now the next type of inclusion that we have are carboxysomes. And carboxysomes have CO₂ fixing enzymes that are going to be enveloped by a protein shell. And carboxysomes serve as the location of carbon fixation in many bacteria. Now the next type of inclusion that we have are gas vesicles. And as their name implies, these are going to be gas particles enveloped by a protein shell, so they're going to contain gas. And these gas vesicles help to control the cell's buoyancy, which is really just the ability to float in aquatic environments. And so, this buoyancy control allows them to change their elevation within an aquatic environment to get to an area that has more light or more nutrients or less light and more nutrients. Gas vacuoles are basically just groups of gas vesicles in the cell. And so the gas vacuoles are a little bit larger than the gas vesicles themselves. And last but not least, the final type of inclusion that we have here in this table are the magnetosomes. And the magnetosomes are intracellular chains of iron-containing molecules that are enclosed within a membrane. And so, these magnetosomes are used by the cells to orient themselves with the earth's magnetic field. And so here in this image, you can notice there is this chain of these iron-containing molecules, and they help to orient the entire cell with respect to the earth's magnetic field so that the bacteria can have a sense of direction of what is up and what is down and things of that nature. And so this here concludes our brief lesson on cell inclusions. And we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.

Which of the following statements about gas vesicles is TRUE?

• A. Bacteria use them to align with the Earth's magnetic field.
• B. They store phosphate molecules as granules.
• C. They are used to control the cell's buoyancy in aquatic environments.
• D. They are the site of Carbon fixation.
• E. None of the above are true.

Which of the following inclusion bodies contain iron?

• A. Gas vesicles
• B. Magnetosome
• C. Storage granules
• D. Carboxysomes