Experiment 2: The Neuromuscular Junction

Each skeletal muscle is connected to the nervous system be motor end units. When the neurotransmitter acetylcholine is release at this site, the muscle fiber depolarizes. Calcium ions are released from stores in the sarcoplasmic reticulum. The presence of Ca2+ triggers the ratcheting of actin and myosin filaments and the contraction of the myofiber as all of the myofibrils contract simultaneously.

Materials Neuromuscular Junction Digital Slide Images Neuromuscular Junction (Longitudinal Section) Digital Slide Images

Procedure

1. Examine the digital slide images of the neuromuscular junction.

Neuromuscular junction 100X.

Neuromuscular Junction (Longitudinal Section) 1000X.

Post-Lab Questions

1. Identify the axon, terminal branches, and muscle fibers in the slide image below. If possible, trace the fiber to its terminus. 

2. Are there few or many nuclei at the end plate?

3. What is a motor unit?

4. How is a greater force generated (in terms or motor unit recruitment)?

5. What types of sensors are present within the muscle to identify how much force is generated?

Experiment 3: Muscle Fatigue

Muscle contractions are essential for muscles to function properly. The inability of a muscle to maintain tension is muscle fatigue. Failure to contract may occur because of the accumulation of lactic acid, a lack of ATP, or decreased blood flow. In this exercise, you will investigate the correlation between repeated movements and muscle fatigue.

Materials Rubber Band

Stopwatch

Note: If you suffer from a medical condition that does not permit you to perform this activity, please ask a partner to volunteer for you.

Procedure

1. Hypothesize how many times you can stretch a rubber band between your thumb and pinky finger in 20 seconds. Record your predictions in the table below.

2. Using your dominant hand, count the number of times you can completely stretch a rubber band between the thumb and pinky finger in 20 seconds. Be sure to stretch the rubber band as far as possible each time and do not take a break in between trials.

3. Record your count for each trial in Table 1.

Table 1: Experimental Counts
	Trial 1	Trial 2	Trial 3	Trial 4	Trial 5
Predicted Value
Actual Value

Post-Lab Questions

1. How did the predicted results compare to the actual results?

2. Did you notice any changes in the number of repetitions you could perform, or how your hand felt after each of the trials?

3. Explain the actions that were occurring at the cellular level to produce this movement. Include sources of energy and any possible effect of muscle fatigue.

4. Hypothesize what would happen if blood flow was restricted to the hand when this experiment is performed.

Experiment 4: Gross Anatomy of the Muscular System

Muscle actions are often described as a departure of the from the anatomical position of the body. In performing the next exercise, you will understand how muscles act to affect motion.

Materials *Participant (can be yourself) *Heavy Object (approximately 5 pounds)

*You must provide

Procedure

1. Begin by examining muscles found in the upper limbs. First, extend your forearm so you have a clear view of your hand. What muscle is required to perform this extension? Extend your fingers out so they are straight and splayed apart. Then, retract your fingers into a tight fist. Repeat this motion several times, observing the wrist and hand muscles as the flex and relax. What muscles are used to complete this action? Record your observations in Table 2.

Note: It is helpful to palpate the area being flexed to better identify which muscles are being used.

2. Moving up the limb, extend your forearm out until it is parallel to the ground. Have a partner press down on your forearm. Flex your forearm to provide resistance as your partner pushes down. Observe the forearm and identify which muscles are being used. Record your observations in Table 2.

3. The partner should stop pushing down on your forearm, but keep it extended. Curl the forearm upward, creating a bend at the elbow. Observe which muscles are being used to complete this action, and record your observations in Table 2.

4. Find a heavy object, and pick it up. Keeping your arm straight, raise the object out to the side until it is parallel to the ground. What muscles does this require? Continue holding the object, and extend your arm back behind you. What muscles does this activate? Record your observations in Table 2.

Note: Be sure the heavy object is not too heavy before you lift it. This item should be approximately 5 – 10 pounds. This object should never be raised above your head!

5. Move down to the lower limbs, and determine what motions are needed to view the lower limb muscles in action. For example, you may want to walk, jump, sit, point your toes, etc. Engage at leave seven different muscles and indicate what motion was used to engage each muscle in Table 2.

Table 2: Gross Anatomy Data
Movement	Muscle(s) Activated	Action(s) of Muscle(s)
1. Forearm Extended (Step 1)
2. Fingers Extended and  Splayed (Step 1)
3. Fingers Retracted (Step 1)
4.  Forearm Pressed Down Upon (Step 2)
5. Elbow Bent (Step 3)
6. Arm Raised to Side with Heavy Object (Step 4)
7. Arm Extended Back with Heavy Object (Step 4)
8. (lower limbs; student selects action…)
9. (lower limbs; student selects action…)
10. (lower limbs; student selects action…)
11. (lower limbs; student selects action…)
12. (lower limbs; student selects action…)
13. (lower limbs; student selects action…)
14. (lower limbs; student selects action…)

Post-Lab Questions

1. Label the human muscle diagram.

2. Which muscle(s) were used to extend your arm backwards?

3. Which muscle(s) were used to extend and splay your fingers outward?

Experiment 5: ATP and Muscle Fatigue

Muscles require energy to contract. Energy is released when biomolecules such as sugars and fats are broken down, and is stored in the form of ATP. ATP enables muscle contraction, but can only be stored in relatively small amounts. For this reason, the body must continually metabolize new ATP molecules.

Muscle fatigue occurs if the local ATP reservoir for a muscle becomes depleted. This is a common result of strenuous exercise in which ATP is consumed at a faster rate than it is produced. At this point, muscles may fail to contract and the intensity of an exercise must decrease. In this experiment, you will test how long it takes your muscles to fatigue.

Materials Stopwatch *Participant *Sturdy Wall to Stand Against

*You must provide

Procedure

1. To begin, find a wall that is strong enough for you to push against. A temporary wall (such as a partition panel) is not suitable.

2. Find the stopwatch and adjust the settings so it is ready to operate.

3. Stand with your back pressed up against the wall, and lower yourself into a “wall-sit”. To do this:

a. Align the backs of your heels, hips, and shoulders with the wall.

b. Keeping your back pressed against the wall, take a few small steps forward (your upper half will lower as you walk your feet out).

c. Lower yourself into a sitting position, keeping your back flat against the wall, until your knees form a 90 degree angle.

d. Steady this position by focusing the majority of your weight in your heels. Do not allow your lower back to pull away from the wall.

4. Start the stopwatch and time how long you are able to hold the wall-sit position. The amount of time will vary, but will likely fall within approximately 30 – 120 seconds. When you are tired, check the time on the stopwatch, and move out of the position by slowly lowering your body down to the floor or standing up.

5. Record how long you were able to hold the wall-sit in Table 3.

6. Allow your muscles to rest for approximately two minutes, reset the stopwatch, and repeat Steps 3 – 5.

7. Again, allow your muscles to rest for approximately two minutes, reset the stopwatch, and repeat Steps 3 – 5. You should have three trials of data.

Table 3: Muscle Fatigue Data
Trial	Time (seconds)
Trial 1
Trial 2
Trial 3

 

Post-Lab Questions

1. What happened to the time intervals between Trial 1 and Trial 3? What caused this change?

2. Identify three muscles which were engaged during the wall-sit.

3. Explain the biochemical reasoning behind muscle fatigue.

 

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This is the correct material for UMUC Biology 102/103 Lab 2: The Chemistry of Life. However, this is an Answer Key, which means, you should put it in your own words. Here are the questions that will be answered. Attached is the lab that is fully completed when purchased. Enjoy!

Pre-Lab Questions

1.    Nitrogen fixation is a natural process by which inert or unreactive forms of nitrogen are transformed into usable nitrogen. Why is this process important to life?

2.    Given what you have learned about the hydrogen bonding shared between nucleic acids in DNA, which pair is more stable under increasing heat: adenine and thymine, or cytosine and guanine? Explain why.

3.    Which of the following is not an organic molecule; Methane (CH₄), Fructose(C₆H₁₂O₆), Rosane (C₂₀H₃₆), or Ammonia (NH₃)? How do you know?

Experiment 1: Testing for Proteins

Data Tables and Post-Lab Assessment

Table 1: A Priori Predictions

Sample	Initial Color	Final Color	Is Protein Present?
1. Albumin Solution
2. Gelatin Solution
3. Glucose
4. Water
5. Unknown

 

Sample	Initial Color	Final Color	Is Protein Present?
1. Albumin Solution
2. Gelatin Solution
3. Glucose
4. Water
5. Unknown

Table 2: Testing for Proteins Results

Post-Lab Questions

1.    Write a statement to explain the molecular composition of the unknown solution based on the results obtained during testing with each reagent.

2.    How did your a priori predictions from Table 1 compare to your actual results in Table 2? If there were any inconsistencies, explain why this occurred.

3.    Identify the positive and negative controls used in this experiment. Explain how each of these controls are used, and why they are necessary to validate the experimental results.

4.    Identify two regions which proteins are vital components in the human body. Why are they important to these regions?

5.    Diet and nutrition are closely linked to the study of biomolecules. Describe one method by which you could monitor your food intake to ensure the cells in your body have the materials necessary to function.

Experiment 2: Testing for Reducing Sugars

Data Tables and Post-Lab Assessment

Table 3: Testing for Reducing Sugars Results

Post-Lab Questions

1.    What can you conclude about the molecular make-up of potatoes and onions based on the test you performed? Why might these foods contain these substance(s)?

 

2.    What results would you expect if you tested ribose, a monosaccharide, with Benedict’s solution? Biuret solution?

Experiment 3: What Household Substances are Acidic or Basic?

Data Tables and Post-Lab Assessment

Table 4: pH Values of Common Household Substances

Post-Lab Questions

1.    What is the purpose of determining the pH of the acetic acid and the sodium bicarbonate solution before testing the other household substances?

2.    Compare and contrast acids and bases in terms of their H⁺ ion and OH^– ion concentrations.

3.    Name two acids and two bases you often use.

 

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INSTRUCTIONS:

·         On your own and without assistance, complete this Lab 4 Answer Sheet electronically and submit it via the Assignments Folder by the date listed in the Course Schedule (under Syllabus).

·         To conduct your laboratory exercises, use the Laboratory Manual located under Course Content. Read the introduction and the directions for each exercise/experiment carefully before completing the exercises/experiments and answering the questions.

         Save your Lab 4 Answer Sheet in the following format:  LastName_Lab4 (e.g., Smith_Lab4).

·         You should submit your document as a Word (.doc or .docx) or Rich Text Format (.rtf) file for best compatibility.

Pre-Lab Questions

1. How could you test to see if an enzyme was completely saturated during an experiment?
2. List three conditions that would alter the activity of an enzyme. Be specific with your explanation.
3. Take a look around your house and identify household products that work by means of an enzyme. Name the products, and indicate how you know they work with an enzyme.

Experiment 1: Enzymes in Food

Data Tables and Post-Lab Assessment

Table 1: Substance vs. Starch Presence

Post-Lab Questions

 

1. What were your controls for this experiment? What did they demonstrate? Why was saliva included in this experiment?
2. What is the function of amylase? What does amylase do to starch?
3. Which of the foods that you tested contained amylase? Which did not? What experimental evidence supports your claim?
4. Saliva does not contain amylase until babies are two months old. How could this affect an infant’s digestive requirements?
5. There is another digestive enzyme (other than salivary amylase) that is secreted by the salivary glands. Research to determine what this enzyme is called. What substrate does it act on? Where in the body does it become activated, and why?
6. Digestive enzymes in the gut include proteases, which digest proteins. Why don’t these enzymes digest the stomach and small intestine, which are partially composed of protein?

Experiment 2: Effect of Temperature on Enzyme Activity

Data Tables and Post-Lab Assessment

Table 2: Balloon Circumference vs. Temperature

Table 2: Balloon Circumference vs. Temperature
Tube	Temperature (°C)	Uninflated Balloon Circumference (cm)	Final Balloon Circumference (cm)	Difference in Balloon Circumference (cm)
1 – (Cold)
2 – (RT)
3 – (Hot)

 

 

Post-Lab Questions

1. What reaction is being catalyzed in this experiment?
2. What is the enzyme in this experiment? What is the substrate?
3. What is the independent variable in this experiment? What is the dependent variable?
4. How does the temperature affect enzyme function? Use evidence from your data to support your answer.
5. Draw a graph of balloon diameter vs. temperature. What is the correlation?
6. Is there a negative control in this experiment? If yes, identify the control. If no, suggest how you could revise the experiment to include a negative control.
7. In general, how would an increase in substrate alter enzyme activity? Draw a graph to illustrate this relationship.
8. Design an experiment to determine the optimal temperature for enzyme function, complete with controls. Where would you find the enzymes for this experiment? What substrate would you use?

 

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Microscopy for Microbiology – Use and Function

Hands-On Labs, Inc. Version 42-0249-00-02

Lab Report Assistant

This document is not meant to be a substitute for a formal laboratory report. The Lab Report Assistant is simply a summary of the experiment’s questions, diagrams if needed, and data tables that should be addressed in a formal lab report. The intent is to facilitate students’ writing of lab reports by providing this information in an editable file which can be sent to an instructor.

Exercise 1: Getting to Know your Compound Microscope

Data Table 1. Microscope Components.

Letter	Component Name	Component Function
A
B
C
D
E
F
G
H
I
J
K
L
M

 

Data Table 2. Total Magnification.

Lens	Ocular Magnification	Objective Magnification	Total Magnification
Scanning
Low Power
High Power
Oil Immersion

Data Table 3. Field of View.

Lens	Total Magnification	Field of View (mm)	Field of View (µM)
Scanning
Low Power
High Power
Oil Immersion

 

Data Table 4. Letter e Viewing Results.

Lens	Photograph	Observations
Scanning
Low
High
Oil Immersion

 

Questions

A. Describe the details in the slides “Letter e” that become visible as the power changed from scanning power, to low power, to high power.

B. Why is it important to calculate the diameter of the field when first using the microscope?

Exercise 2: Viewing Prepared Microbe Slides

Data Table 5. Prepared Slide Viewing Results.

Slide	Photograph	Total Magnification
Amoeba
Penicillium
Yeast
Spirillium
Bacillus
Coccus

 

Questions

A. Using the field of view calculated in Exercise 1 for the high power lens, approximately how far across are each of the cells in the Bacteria Coccus Form slide in Data Table 5? Show your calculations.

B. Detail techniques you found helpful for focusing on the various slides in this exercise.

Exercise 3: Preparing Wet-Mount Slides

Data Table 6. Wet-Mount Viewing Results.

Slide	Photograph	Total Magnification
Cheek Cell Smear
Dental Tatar Smear

 

Questions

A. Describe the similarities and differences between the cheek cell wet mount and dental plaque wet mount.

B. How did the process of preparing wet-mount slides become easier as you prepared the second wet-mount slide of this exercise?

 

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Lab 2 Cell Structure and Function BIO101L

Student Name: Click here to enter text.

Access Code (located on the lid of your lab kit): Click here to enter text.

Pre-Lab Questions

1. Identify three major similarities and differences between prokaryotic and eukaryotic cells.

Click here to enter text.

2. Where is the DNA housed in a prokaryotic cell? Where is it housed in a eukaryotic cell?

3. Identify three structures which provide support and protection in a eukaryotic cell.

Experiment 1: Identifying Cell Structures

Post-Lab Questions

1. Label each of the arrows in the following slide image:

Structure	Identity
A	Click here to enter text.
B	Click here to enter text.
C	Click here to enter text.
D	Click here to enter text.

 

2. What is the difference between the rough and smooth endoplasmic reticulum?

3. Would an animal cell be able to survive without mitochondria? Why or why not?

4. What could you determine about a specimen if you observed a slide image showing the specimen with a cell wall, but no nucleus or mitochondria?

5. Hypothesize why parts of a plant, such as the leaves, are green, but other parts, such as the roots, are not. Use scientific reasoning to support your hypothesis.

Experiment 2: Create a Cell

Post-Lab Questions

1. What cell structures did you place in the plant cell that you did not place in the animal cell?

2. Is there any difference in the structure of the two cells?

3. What structures do cells have for support in organisms that lack cell walls?

4. How are organelles in a cell like organs in a human body?

5. How does the structure of a cell suggest its function? List three examples.

6. In the table below, list the items you used to represent the various organelles in your ANIMAL cell. Provide a brief rationale explaining why you selected each item.

Item	Organelle	Rationale
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Click here to enter text.	Click here to enter text.	Click here to enter text.

 

7. Insert picture of your ANIMAL cell with your name and access code handwritten in the background.

8. In the table below, list the items you used to represent the various organelles in your PLANT cell. Provide a brief rationale explaining why you selected each item.

Item	Organelle	Rationale
Click here to enter text.	Click here to enter text.	Click here to enter text.
Click here to enter text.	Click here to enter text.	Click here to enter text.
Click here to enter text.	Click here to enter text.	Click here to enter text.
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Click here to enter text.	Click here to enter text.	Click here to enter text.
Click here to enter text.	Click here to enter text.	Click here to enter text.

 

9. Insert picture of your PLANT cell with your name and access code handwritten in the background.

 

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