Download Digestive System Gallery - Lab

Digestive System - Gallery
Name ______________
We will be taking a gallery tour of the digestive system in our lab today. You and your lab
partner(s) will be moving around the room to visit lab stations which offer many different mini
digestive system experiments. As you travel, you will use this lab packet to understand the
methods you will need to use for each experiment, to record your findings and to answer
questions.
Stations:
1. Peristalsis with ping-pong balls
• Methods
• Imagine the stocking as being the digestive tube (esophagus or LI) and the balloon
being a recently digested piece of food
• Place the ball in the stocking and squeeze the ball down the stocking
• Define peristalsis: ____________________________________________
_________________________________________________________
Bonus challenge: Hold the stocking vertically and pretend the person was hanging upside-down.
Put the ball in the ‘mouth’ opening and squeeze it to the ‘stomach’ opening. Was it easier or
harder to go upside-down than rightside-up? Why? ____________________________________
_____________________________________________________________________________
2. pH of the digestive system
• pH is a scale that we use to measure how acidic or basic things are. As we’ve talked about,
different parts of the digestive system have different pH ratings. We’ll investigate the pH of
different parts of the system.
• Methods
• Stomach: the stomach contains an acid called hydrochloric acid. Wearing gloves, obtain
a piece of pH paper and dip it into the beaker to test its pH
• remember a low number on the pH scale means more acidic, and a high number on
the pH scale means more basic
• Small intestine: Now test the pH of the beaker containing HCl and an antacid tablet and
the beaker containing a solution of sodium bicarbonate.
• Write down pH number of HCl __________
• Write down pH number of HCl and antacid ___________
• What does the antacid represent? ________________________________
• What is the purpose of the HCl in the digestive system? ________________
• Which part of the digestive system secretes HCl?______________________
• Later on in the digestive system this acidity needs to be neutralized, what is the base called
that is used to neutralize this acidity? __________________
• Write down pH number of the sodium bicarbonate __________
• Where does this baking soda come from? ___________________________
3. Digestion of proteins
• A form of pepsin, which is the protein digesting enzyme of the stomach, is often found in
laundry detergent. It is used to break down protein stains on clothes.
• Smear a small blob of ketchup on to a piece of cotton cloth. Rub it in, and let it dry for a
minute. Place the piece of stained cotton cloth into the beaker of water with the enzymatic
detergent. Wait one minute and pull the cloth out of the water.
• Record what happens: _________________________________________
_________________________________________________________
_________________________________________________________
• What part of the digestive system releases pepsin? ____________________
4. Digestion of fats
• Lipids are hard to dissolve due to their hydrophobic nature. Lipids must be coated to make
them soluble in water where the lipase enzymes can act on them to break them down.
• Beaker 1
• Fill the beaker with warm water
• Add several drops of cooking oil to the water in the beaker
• Add several drops of dishwashing liquid to the beaker
• Mix it
• Beaker 2
• Fill another beaker with warm water
• Add several drops of cooking oil to the water in the beaker
• Mix it
• Compare the status of the oil in both beakers. What do you observe? ______
_________________________________________________________
_________________________________________________________
• In the digestive system, which chemical is similar in function to the dishwashing liquid?
___________________
• From which part of the digestive system does this chemical come? _______
5. Bile salts, lipids digestion
• When lipids are broken down by lipases into fatty acids, the pH of the mixture lowers
(lower pH = more acidic).
• BTB is an indicator of acidity. It is blue in neutral or basic mixtures, but turns yellow in an
acidic mixture.
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Using the graduated cylinder, add 3 ml of heavy cream to a beaker.
Using the graduated cylinder, add 5 ml of water to the beaker
Add 3 drops of bile solution to the mixture.
Add 15 drops of sodium bicarbonate solution to the mixture.
Using the graduated cylinder, add 2 mL of BTB to the beaker.
Swirl the mixture to evenly distribute all the components.
Using the graduated cylinder, add 5 ml of lipase solution to the beaker
• What was the color of the mix before you added lipase? ______________
• What was the color after lipase was added?__________________________
• Attempt to explain your results: __________________________________
__________________________________________________________
__________________________________________________________
• What is the purpose of the bile solution in this experiment? ______________
__________________________________________________________
__________________________________________________________