If you have been teaching for at least a week, you have heard it. That dreaded phrase, always in a whiny tone, “why do we need to know this?” Of course, there is a reason, but being put on the spot can make it hard to come up with legitimate real world examples. This article is going to help you give students reasons for learning about cell transport and osmosis!
According to the CDC, there was an more than 9,800 heat-related deaths between 2004 and 2018. Dehydration is a contributing cause to heat-related injuries and death. Drinking enough water can help us stay hydrated, but understanding osmosis can help us understand which drinks are best. Strangely enough, water is not the best thing to drink when you are trying to get hydrated. Straight water will readily move into cells because it is hypotonic to our cells, but solutions that are isotonic (meaning they have the same solute concentration as our cells) work best. According to this study milk and oral hydrating solution work best. Water, soda, tea, and other beveraes are still okay options, but because they have different solute concentrations as our cells they do not work as well. Obviously there is way more to this answer than just osmosis. The different ion channels and active transport play a roll in how quickly each liquid hydrates our cells. But if we want to understand why water isn’t the best hydrating solution, we need to have a solid understanding of osmosis.
You know the IV bags they give patients at the hospital? That isn’t straight water. Doing that would cause cells to burst (aka lyse). Instead, the IVs have salt added to them to make them isotonic to cells, preventing lysis. It is important that anyone who is making IV bags gets it right. A life could be lost if it is wrong.
Many methods of preserving food rely on osmosis to work. Raisins, salted peanuts, and other dry foods want to stay dry. Being dry means they have little water and will be hypertonic to most fungi, bacteria, and other food spoiling organisms. Any organism that lands on the dryed food loses water and becomes dehydrated causing them to be disabled or die.
It’s not just dry foods that benefit from an understanding of osmosis. Keeping fruits and vegetables fresh requires the opposite approach. Cells are constantly losing wate to the environment, so they need to gain water. The misters in grocery stores help to keep vegies nice and full of water (aka tirgid). No body wants a mealy celery stalk (some people don’t even like celery at all). Keeping celery hydrated helps make them crunchy.
Most fish live exclusively in fresh water or exclusively in salt water. Some are able to bridge the gap (looking at you salmon). Fish are adapted to the waters they live in. Salt water fish remain isotonic with the water around them, while fresh water fish must pump excess water out of their cells. If a fish cannot pump excess water out fast enough, they die. This is why salt water fish cannot live in fresh water tanks. Anyone who wants to keep a pet fish needs to understand osmosis to help them stay healthy.
Fun fact: there is only one species of shark lives exclusively in fresh water: the Ganges shark (Glyphis gangeticus)
Our skin provides a barrier to the outside world. Unlike reptiles, we secrete oils that help coat our skin and keep the moisture inside. Dry scaly skin (aka being ashy) is the result of too few oils on our skin. We can replace those oils by using topical creams that have lipids in them. The lipids are hydrophobic, meaning they repel water. At first glance you might think this would be bad, but really that means it stops the water from leaving your skin. Leaves have a similar coating called a cuticle. This allows leaves to be wide and thin, and still retain water.
This one may not be one you want to share with your students, especially if you have squeamish or dastardly students. Forensic scientists can determine how long a body has been in the water. This means they can figure out when a victim was dumped into a body of water based on how much water their body has logged. They can do this because they understand osmosis and how fast water passes into cells.
Every single organism has water as its major component in all of their cells. Every single one has to regulate the amount of water going in lest their cells srivle or pop. Honestly, unless students plan on going into forensic science or the medical feild, they will not likely be diong any kind of osmosis calculations. However, understanding the basic principals of osmosis will help them keep their pets, plants, and themselves alive. That makes learning about osmosis a good lesson for everyone. If you want some extra resources to help you teach osmosis, check out this FREE osmosis worksheet.
