69: Liver and gall bladder
1) DRAWING LESSON
95 minutes
This lesson is really long (about an hour and a half). You might want to do it in two or three sessions. (And if it is too much information for you, don’t worry about it, just enjoy marveling at how amazing the liver is!)
There are three parts: 1) General anatomy, plus blood supply to the liver, 2) Microscopic views of liver tissue, 3) List of major functions of the liver. You can take a break after each section if you need to.
2) ACTIVITIES
Activity 69-1: Do a catalase experiment
Catalase is one of the many enzymes that the liver makes. Catalase’s job is to break down hydrogen peroxide, H2O2. You may recognize this substance as something that is used to clean wounds. The reason it is used to clean wounds is that it quickly breaks down into H20 (water) and O2 (oxygen), and oxygen is toxic to germs. Hydrogen peroxide is also toxic to your body, however. The peroxisome organelles inside the hepatocytes produce H2O2 as a by-product of the process of breaking down fats. The fats must be broken down into small pieces that can be sent to the Krebs cycle and burned for energy, but as a result, H2O2 is produced. The peroxisomes can’t let the H2O2 get out into the cell or into the rest of the body. So the peroxisomes also make an enzyme called catalase that can immediately get rid of the H2O2 and turn it into harmless water and oxygen that can be used by the cell. (Two molecules of H2O2 will be turned into 2 molecules of water, H2O, and 1 molecule of oxygen, O2.)
There are a number of ways to perform experiments using catalase. Some labs ask you to provide things like test tubes and beakers. If you don’t have test tubes and beakers, you can use small glass jars. Don’t let the recommendations of lab glassware scare you off. Just use containers and equipment you have available. You can find many variations of this lab by typing key words (liver, catalase, lab, experiment, hydrogen peroxide) into a search engine. You can find videos, web pages, and printable pdfs. Here are a few ideas to get you started:
- COLLECT OXYGEN produced by the catalase reaction: Chop up a bunch of liver and put it into a bottle or test tube. Pour some H2O2 over the liver. You will see bubbles forming. You can prove this is oxygen by relighting an extinguished wooden splint (use a wooden coffee stir stick). The glowing ember will re-light in the presence of oxygen. Here is a school video that might help you: https://www.youtube.com/watch?v=4nOCR_vwV7U
- USE YEAST INSTEAD OF LIVER: You can soak small pieces of paper (use coffee filters) in yeast solutions and then put them into a glass of H2O2. The more yeast in the paper, the more O2 will be produced, causing the papers to float to the top at a measurable rate. Here is a video explanation by Craig Anderson of “Bozeman Science”: https://www.youtube.com/watch?v=hs75JmgGW5Y
- ADD (ACID/BASE) AND (HEAT/COLD) VARIABLES INTO THE EXPERIMENT: Here is a slightly more complicated version of the experiment that uses acids and bases and hot and cold water to see what happens to the speed at which the enzyme can react. https://www.scientificamerican.com/article/bring-science-home-liver-helping-enzymes/
- A PRINTABLE LAB that is designed to be used with AP level classes. (It asks you to provide HCl (hydrochloric acid) and NaOH (sodium hydroxide) but you can substitute vinegar for the HCl and baking soda for the NaOH.) https://www.biologycorner.com/worksheets/enzyme_lab.html
3) VIDEOS
Liver anatomy and function, medical video (4 min.)
What is bile and what does it do?
