8 Cell-cell interactions How cells communicate with each other (article) Khan Academy PDF

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Cell-cell interactions: How cells communicate with each other (article) | Khan Academy

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Can you imagine what it would be like if your brain couldn’t tell your leg muscles to contract so you could walk? Or your bladder couldn’t tell your brain that you had to use the bathroom? Or what if you had contracted an infecon and your immune system had to deal with it? Cells need to be able to communicate with each other to do these things, and so much more! There are a few different types of cell-cell interacons. Some of these interacons are meant for big molecules that enter and exit the cell called, endocytosis (entering the cell) and exocytosis (exing the cell). For smaller parcles like amino acids, water, ions and other solutes there are different types of direct contact between the cells called gap juncons.

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Exocytosis is a process used by the cell to take out its trash and to incorporate proteins into the cell membrane. During exocytosis, the phospholipid bilayer of the cell membrane surrounds the waste proteins, creang a bubble-like structure called a vesicle. Vesicles are frequently used in the cell for transportaon of molecules across the cell membrane.

Waste proteins A slightly different process occurs for waste products being ejected out of the cell, instead of proteins being incorporated into the cell membrane. Once the vesicle has enclosed the waste proteins on the inside of the cell, it moves towards the cell membrane. The vesicle merges with the cell membrane, opening the bubble-like structure and ejecng the contents in the environment surrounding the cell.

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Proteins desned for the cell membrane Exocytosis is also used to integrate new proteins into the cell membrane. In this process, the new protein is formed inside the cell, and migrates to phospholipid bilayer of the vesicle. The vesicle, containing the new protein as a part of the phospholipid bilayer, fuses with the cell membrane. This allows the protein to be directly integrated into the cell membrane when the vesicle, in the same way as with waste proteins, fuses and opens with the cell membrane.

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Endocytosis is the opposite process of exocytosis. Endocytosis brings molecules into the cell. These molecules are important for the survival of the cell, such as glucose. There are three different styles of endocytosis: 1) phagocytosis, 2) pinocytosis, and 3) receptor-mediated endocytosis.

Phagocytosis Phagocytosis is the process similar to eang, where the cell engulfs a molecule in order to move it to the interior of the cell. The process starts by the molecule binding to specific receptors on the surface of the cell membrane, triggering the cell membrane to reshape, surrounding the molecule. The receptors allow this process to be specific, controlling what can enter the cell. Then, the two ends of the cell fuse, creang a vesicle that surrounds the molecule. Eventually the membrane around the molecule will be digested and its contents will be used! For example, white blood cells recognize pathogens, such as viruses or bacterial cells, outside of the cell and will use phagocytosis to bring it in to destroy it!

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Pinocytosis If phagocytosis is how the cell eats, then pinocytosis is how the cell drinks. Pinocytosis engulfs dissolved ions and other solutes in the liquid medium surrounding the cell. This is different than phagocytosis, which brings full, undissolved or insoluble molecules into the cell. The distoron of the cell membrane to engulf the dissolved solutes is similar to that of phagocytosis. Another important disncon is that pinocytosis is not specific to what is carried into the cell, whereas phagocytosis can be highly specific. The liquid medium outside the cell is always filled with dissolved parcles and solutes that are handy for the cell, so the cell doesn’t need this process to be specific.

Receptor-mediated endocytosis Receptor-mediated endocytosis is very specific with respect to what is imported into the cell. It’s actually a bit like a lock-and-key system. There are receptors embedded in the cell membrane that, when bound by molecules with an exact match in shape, size, or other physical aribute, will allow the https://www.khanacademy.org/test-prep/mcat/cells/cell-cell-interactions/a/cell-cell-interactions-how-cells-communicate-with-each-other

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molecule to enter into the cell through the same engulfment process as phagocytosis or pinocytosis.

Cell juncons There are many different ways that cells can connect to each other. The three main ways for cells to connect with each other are: gap juncons, ght juncons, and desmosomes. These types of juncons have different purposes, and are found in different places.

Gap Juncons Gap juncons are essenally tubes that join two cells together. These tubes create a connecon that allows for the transport of water and ions to and from the connecng cells. The tubes also help to spread electrochemical signals that are produced by acon potenals that occur in the nervous

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system (neurons) and in cardiac cells that make your heart beat. Gap juncons have a prey important job!

Tight Juncons Tight juncons are different from gap juncons because they are the connecons that form when cells are squished up against one another. In this case, the cell membranes are connected, but the contents of each cell are not connected in any way. There are no tubes here, but there is an impermeable layer in between the cells. These types of cell connecons are useful in places that need to contain certain fluids, like in the bladder, the intesnes or the kidneys. Imagine if you didn’t have a waterght seal in those connecons! Fluids like your urine would be circulang through your body! Yuck!

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Desmosomes Finally, desmosomes are quite different from gap juncons and ght juncons. With desmosomes, cell membranes are connected by thread like substances that connect the cells across the space in between cells. Much like ght juncons, desmosomes physically hold the cells together, but do not allow fluids or materials to pass from the inside of one cell to the next. These connecons are also aached to the scaffolding of the cell, called the cytoskeleton, to help with structural support. The space in between the cells allows for water and solutes to flow freely between each cell without compromising the connecon. This is convenient for areas of our body that experience high stress like in our skin or our intesnes because the space in between the cells offer flexibility that the other juncons can’t.

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Consider the following: What happens when cell juncons don’t work properly? Somemes there are mistakes in the genec blueprints of our body. Gap juncons are most commonly found in the skin, so mistakes in their funcons can lead to a variety of diseases that make up ectodermal dysplasia, a series of genec disorders affecng the development or funcon of the teeth, hair, nails and sweat glands. Addionally, errors in specific gap juncon genes called, Cx43 and Cx56.6, can lead to the breakdown of some of our brain ssue called white maer which makes up 60% of our brain. Diseases that include the breakdown of white maer include mulple sclerosis and Hunngton’s disease! Mistakes in our genes that produce desmosomes cause skin blistering.

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Want to join the conversaon? Log in

EW2000

Over all is understandable, but what is the slight difference between disposing waste and exocytosis?

tripleCherry001 Waste disposal is an example of exocytosis, the other example they give is when integrang proteins into the cell membrane.

ssweeney818

I'm confused. In this arcle, in the last paragraph, you say that gap juncons are most commonly found in skin cells, but in your video on cell juncons you say that desmosomes are most commonly found in the skin and gap juncons are more https://www.khanacademy.org/test-prep/mcat/cells/cell-cell-interactions/a/cell-cell-interactions-how-cells-communicate-with-each-other

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common in brain and cardiac cells. Which is right? It doesn't make much sense to me for gap juncons to be common in skin cells.

dhena008

In the arcle they menon that the space created with desmosomes is what gives the cells their flexibility, deducing from that statement you can imagine that the skin undergoes more stress and therefore desmosomes are most likely found on epithelial cells.

Arki

In the desmosomes paragraph,"This is convenient for areas of our body that experience high stress like in our skin or our intesnes because the space in between the cells offer flexibility that the other juncons can’t.";What does the term 'high stress' highlight?

Thien Vu

hps://www.ncbi.nlm.nih.gov/pmc/arcles/PMC4336551/ I believe the "high stress" refers to the mechanical stress (the stretch and https://www.khanacademy.org/test-prep/mcat/cells/cell-cell-interactions/a/cell-cell-interactions-how-cells-communicate-with-each-other

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movement) that certain areas of our body experiences throughout the day, e.g. in skin, intesnes, and heart.

Samuel God'sucess Adural…

can you please tell me the difference between desmosome and hemidesmosome

jennsusie

hemidesmosomes connect a cell to the extracellular matrix while desmosomes connect between 2 cells.

Jon

"The receptors allow this process to be specific, controlling what can enter the cell." Aer being confused about the difference between phagocytosis and RME, I searched up the differences online and every source said that phag. is not substance specific. Having the sentence I quoted at the top makes this lesson very confusing.

cha frank https://www.khanacademy.org/test-prep/mcat/cells/cell-cell-interactions/a/cell-cell-interactions-how-cells-communicate-with-each-other

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cha frank

if it is not specific at least to some degree ,then how does it know what to take up and what not to take up?

marco-xx97

What do you think about Biofield and the cellular communicaon throght photons? What do we know up to know?

Sophie

What is the most common type of juncon?

jennsusie

gap juncons

Mary A.

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Can you name cells in the body that are free-floang and do not form juncons with the neighboring cells?

Leah Vrolyk

What are the different ways cells communicate with one another and how might it vary between a plant and animal cell in close contact?

Grant Wilhelm

In pinocytosis, how does the cell membrane engulf the liquid? If it is not using membrane receptors to begin the pinocytosis process, what causes the vesicle to form around the liquid?

Cell-cell interacons quesons

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Cell Juncons

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