Cell Membrane

Potato Experiment       Hypertonic 

                          Hypotonic 

                           Isotonic 

Osmosis!!

It was another day of biology with Dr. Cleveland. 

"Today we're learning about the cell membrane!" exclaimed Dr. Cleveland. "Put away your notes. We won't need those. We're going on a field trip!" 

"Where are we going?" asked a student.

"We're going inside these potatoes! Follow me outside!" 

The students looked at each other, confused, but they shrugged and followed her outside. 

They came outside and found a bus waiting for them. They all climbed on and took a seat. 

" so how are we getting into the potato?" questioned a student. 

Dr. Cleveland laughed

"Did I not mention that this is a magic school bus? Here we go!!" As she spoke the bus began to shrink. They soon became small enough to enter the potato but they continued to shrink till they could see the cells in the potato. 

"We're here!!" 

Fun Fact

The Phospholipid bilayer has water-loving (hydrophilic) heads, and water-fearing (hydrophobic) tails that work together to create a barrier!   

Fun Fact 

Different proteins help larger substances pass through the barrier 

"Welcome to the plasma membrane! It plays the vital role of controlling what comes in and out of the cell. As you can see there are many different structures that make up the membrane. Which is why they call it the fluid mosaic model.  Lets take a look at the different parts! First lets look at the phospholipid bilayer! They are the building blocks of the barrier that protects the cell! next lets look at the proteins! They help the substance that cannot pass through the bilayer get through!"

" How do substances get through the membrane?" asked a student.  

" Good question! Substances can move in and out of the membrane through a process called diffusion! Over time, the molecules in the substance with more molecules will move with the gradient  so that both have the same amount of molecules!" 

" Oh, like when you put food dye into water, and they gradually blend together!" Exclaimed a student. 

"Exactly!" said Dr. Cleveland. "Another form of diffusion is osmosis, which is the movement of water from high to low concentration.  Lets take a look at how water moves in different solutions."

"Let's leave the potato to look at potatoes in different saltwater solutions! The first solution we will look at is an isotonic solution. In an isotonic solution, salt molecules have the same concentration in the solution and the cells. This is the ideal solution because the cells will remain intact." 

" Oh, I see! We want the substances to be at equilibrium! What happens if there is more salt in the solution than in the cells?" Asked a student 

" Ah, that's a hypertonic solution. Let's fly over to the next potato and take a look!" 

"This is a hypertonic solution. This means there is more salt outside the cells than inside. As you can see the water is leaving the potato and it is becoming soft and squishy." 

"Oh, so the water leaves the cells to return the concentration of salt to equilibrium!" Exclaims a student.

" Exactly!" Shouts Dr. Cleveland. "Now we have one more solution to look at. Hypotonic solutions."

" We have arrived at our final potato! As you can see, there are very few salt molecules in the solution, but when you look inside the cell, the salt concentration is very high. Do you all notice something different about this potato?" 

"It looks like the potato is swollen!" Point out a student. "Does that mean the water is flowing into the cell?"

"Correct, as you can see in all the solutions we've looked at, the water moves from high to low concentrations! Now that we've learned about how water moves through the membrane, let's talk about different types of transport! We'll need to head back into the cells!

Fun fact: Did you know that Passive Transport is an exergonic reaction? This means it does not require energy to assist in transporting  molecules across the cell.  

The students slowly made their way back into the cell where Dr. Cleaveland was ready to teach the next lesson.

Passive Transport allows molecules or substances to move from an area of high concentration to an area of low concentration on the gradient. 

There are two key types of passive transportation known as diffusion and osmosis. 

"Osmosis is when water molecules move through the cell membrane on a gradient " exclaimed a student. "I remember learning that earlier on in the field trip."

"Class, we are entering  through the channel protein now." "Everybody needs to grab on to a buddy, it is going to be a tight squeeze".

When a substance moves against the gradient, it is not moving to the more highly concentrated area of solute in the cell