our stomach is an amazing organ, how does it protect itself from its own digestive enzymes?

Name:

Date:

Graded Assignment

3.15 Lab Report- Digestion Activity

What is the best environment to digest eggs?  That is the question you will be investigating in this lab.

Directions Day 1 – Set up test tubes and measure pH:

1. Open the virtual lab using the link on slide 2 of 3.13 Laboratory: Human Digestion Actions 1, or copy this web address into your internet browser to enter the virtual lab:

k12.http.internapcdn.net/k12_vitalstream_com/CURRICULUM/329465/CURRENT_RELEASE/BIO_VL_Human_Digestion.html

1. Click on “Tutorial”.  The tutorial will show you how to set up the first 2 test tubes.
2. Continue on your own to set up Tubes 3 -6.  Follow the chart below.
3. Don’t forget to rinse the graduated cylinder when changing chemicals.
4. Use a stirring rod to mix each of the test tubes.  Don’t forget to use a new stirring rod for each tube!
5. If you need to restart, click the home button, reset the lab, and click the Begin the Lab button.

Place the following in each test tube.  1 and 2 are part of the tutorial.

Test tube number	Substance Added
1	10mL water
2	10 mL pepsin
3	10 mL hydrochloric acid (HCL)
4	10 mL sodium bicarbonate
5	5 mL pepsin + 5 mL sodium bicarbonate
6	5 mL pepsin + 5 mL hydrochloric acid

 

1. Using the forceps, pick up a pH test strip and determine the pH value for each test tube. Hover over each test tube and click to “dip” the strip in the tube.  If it remains green, that is not necessarily an error.  It might be a neutral solution, pH of 7.  Use a new pH strip for each test tube. Place the “used” test strips on the bulletin board above the ph Chart.  Record the pH values in the chart below.
   

(6 points)

Score

1. List the pH color and number you measured for each test tube. In column 3, identify the environment in each tube as acidic, basic, or neutral according to the pH levels measured.

Answer:

Test Tube	Color of pH strip/ph number	Environment: Acidic, basic or neutral?
1
2
3
4
5
6

 

1. Set the forceps back on the work station. Place a stopper on each test tube.
2. Click START on the timer.

(1 point)

1. Copy and paste the exact code you are given onto your lab report so that you can easily retrieve it.  Remember to save your lab report after pasting your code!
   • Code: _________________________________
2. For the reactions to take place, wait an entire 48 hours. After 48 hours have passed, enter the code in the space provided on the opening screen. The program will bring you back to your lab where the reactions will have taken place.
3. Answer questions 2-4 below on Day 1.

(2 points)

2. Write a hypothesis: Which test tube do you think will show the most digestion?  Please write an “If….then statement”.

Here is an optional sentence frame that you can use, by filling in the blanks, to help you write your hypothesis.  You can also write your own hypothesis not using this sentence frame.

If the stomach contains __________________________, then test tube #___ will show the most digestion because __________________________.

 

(2 points)

3. What are the variables in this lab?
   1. Independent Variable (This is what we change on purpose, or what is different about each test tube.):

 

1. Dependent Variable (This is what we measure or observe in each test tube.):

 

(2 points)

4. What things are remaining constant? (These are the same about each test tube.)

Directions Day 3 – Collecting and Analyzing the Results:

1. Return to the virtual lab and enter your code that you recorded above under letter J.
2. Observe the results of digestion in the protein tubes.

(1 point)

1. Insert a screenshot showing the results of the 6 test tubes below:

Analysis questions:  Please write in full sentences with complete answers.

(2 points)

5. Which test tube showed the most digestion?

(2 points)

6. Did this match your hypothesis

(4 points)

7. Consider the three test tubes that contained pepsin. Tubes 2, 5 and 6.  What do the results tell you about the environment (neutral, acidic, or basic pH) pepsin requires for digestion to occur

(5 points)

8. Think about what you have learned about digestion in the human stomach from Lesson 3.13. In which test tube was the digestion most like that of a real human stomach? Explain your answer based on what you know about the chemicals present in that test tube.

 

 

(3 points)

1. Your stomach is an amazing organ, how does it protect itself from its own digestive enzymes?

 

Score

 

Your Score

___ of 30

Grading Rubric.  Refer to this rubric when you are writing and proofreading your answers.  Make sure your answer to each question meets all of the grading criteria in the rubric.  I will use this when grading your lab report to give you your score and feedback.  As always, use the feedback to revise your answers and then resubmit your lab report to be regraded for a new score.

Grade Criteria	Score & Feedback
Question 1 (6 points total): Correct pH color and number, and correctly identified acidic basic or neutral environment: 1 point: Test Tube 1 1 point: Test Tube 2 1 point: Test Tube 3 1 point: Test Tube 4 1 point: Test Tube 5 1 point: Test Tube 6	/6 points
Code: 1 point: Day 1 lab Code copy/pasted onto lab report under Directions Day 1 letter J.	/1 point
Question 2 (2 points total): 1 point: Hypothesis is reasonable. 1 point: Hypothesis written as an “If…Then…” statement.	/2 points
Question 3 (2 points total): 1 point: Correct Independent Variable. 1 point: Correct Dependent Variable.	/2 points
Question 4 (2 points total): 2 points: All constants are identified.	/2 points
Screenshot: 1 point: Screenshot showing correct results for all 6 test tubes is inserted into the lab report under Directions Day 3 letter C.	/1 point
Question 5 (2 points total): 1 point: Written in complete sentences with correct grammar, spelling and punctuation. 1 point: Correct Answer	/2 points
Question 6 (2 points total): 1 point: Written in complete sentences with correct grammar, spelling and punctuation. 1 point: Correctly stated if results matched hypothesis.	/2 points
Question 7 (4 points total): 1 point: Written in complete sentences with correct grammar, spelling and punctuation. 3 points: Explained correct environment pepsin requires for digestion.	/4 points
Question 8 (5 points total): 1 point: Written in complete sentences with correct grammar, spelling and punctuation. 1 point: Identified the correct test tube with digestion most like a real human stomach. 3 points: Complete and accurate explanation.	/5 points
Question 9 (3 points total): 1 point: Written in complete sentences with correct grammar, spelling and punctuation. 2 points: Complete and accurate explanation.	/3 points
TOTAL SCORE	/30