Category: 1st Semester

Energy in food

 

 

The Heat is On – The Energy Stored in Food
Introduction:

Plants utilize sunlight during photosynthesis to convert carbon dioxide and water into glucose (sugar) and oxygen. This glucose has energy stored in its chemical bonds that can be used by other organisms. This stored energy is released whenever these chemical bonds are broken in metabolic processes such as cellular respiration.

Cellular respiration is the process by which the chemical energy of “food” molecules is released and partially captured in the form of ATP. Cellular respiration is the general term which describes all metabolic reactions involved in the formation of usable energy from the breakdown of nutrients. In living organisms, the “universal” source of energy is adenosine triphosphate (ATP). Carbohydrates, fats, and proteins can all be used as fuels in cellular respiration, but glucose is most commonly used as an example to examine the reactions and pathways involved.

Marathon runners eat a large plate of pasta the night before a competition because pasta is a good source of energy, or fuel for the body. All foods contain energy, but the amount of potential energy stored will vary greatly depending on the type of food. Moreover, not all of the stored energy is available to do work. When we eat food, our bodies convert the stored energy, known as Calories, to chemical energy, thereby allowing us to do work. A calorie is the amount of heat (energy) required to raise the temperature of 1 gram (g) of water 1 degree Celsius (°C). The density of water is 1 gram per milliliter (1g/ml) therefore 1 g of water is equal to 1 ml of water. When we talk about caloric values of food, we refer to them as Calories (notice the capital “C”), which are actually kilocalories. There are 1000 calories in a kilocalorie. So in reality, a food item that is listed as having 38 Calories has 38,000 calories. Calories are a way to measure the energy you get from the food you eat.

Just as pasta can provide a runner energy to run a marathon, a tiny peanut contains stored energy that can be used to heat a container of water. For this lab exercise, you will indirectly measure the amount of Calories in couple of food items using a calorimeter. A calorimeter (calor = Latin for heat) is a device that measures the heat generated by a chemical reaction, change of state, or formation of a solution. There are several types of calorimeters but the main emphasis of all calorimeters is to insulate the reaction to prevent heat loss. We will be using a homemade calorimeter modeled after a constant-volume calorimeter. A particular food item will be ignited, the homemade calorimeter will trap the heat of the burning food, and the water above will absorb the heat, thereby causing the temperature (T) of the water to increase. By measuring the change in temperature (∆T) of a known volume of water, you will be able to calculate the amount of energy in the food tested

 

Objective:

 

In this experiment, you will measure the amount of energy available for use from three types of nuts, a plant product. This process of measuring the energy stored in food is known as calorimetry.

Materials:
large paper clip, oC thermometer, soft drink can, soft drink can with openings cut into the side, mixed nuts, matches, water, electronic balance, pencil & paper, 100 ml graduated cylinder, calculator

Procedure:

  1. Carefully, cut out two openings along the side of a soft drink can. This will serve as your support for the second drink can that will contain water & sit on top.

  1. Bend a large size paper clip so that a nut can be attached on one end and the other end will sit flat inside the cut-out soft drink can.

 

  1. Use the graduated cylinder to accurately measure 100g (100ml) of water. Pour this water into the uncut soft drink can.
  2. Place the thermometer in the uncut can and measure the water temperature after 3 minutes.  Record this temperature on  data table 1.

  1. Mass the nut (g) that you will burn and record this mass on  data table 1.
  2. Attach the nut to the bent end of your paper clip and carefully set the clip & nut into the cut-out soft drink can on bottom. Make sure the cans are sitting on a flat, nonflammable surface!

  1. Carefully light the nut from the bottom using a match and record the change in water temperature as the nut burns (thermometer in the can during burning). Immediately after the nut finishes burning, record the final (highest) water temperature on data table 1.
  2. Measure the mass (g) of the remaining nut & record this in the data table 1. (Mass the burned nut and paper clip together and then subtract the mass of the nut to get the mass of the nut alone.)
  3. Complete the data table1 by calculating the change in mass of the nut.
  4. Repeat this experiment with the other two types of nuts .
  5. When all three nuts have been burned, complete the analysis on data table 2.

Results:

 

 

Table 1 – Results of Burning
PECAN WALNUT ALMOND
oC  H2O temperature Before burning
oC  
oC  H2O temperature After burning
oC
Difference in oC H2O temperature
oC
Mass of Paper Clip
g
Mass of Nut Before Burning
Mass of Paper Clip and Nut After Burning
g
Mass of Nut ALONE After Burning
(Subtract paper clip mass from mass of nut & paper clip after burning)
g (Subtract paper clip mass from mass of nut & paper clip after burning)
g  

 

 

Table 2 – Data Analysis from Nut Calorimetry

PECAN WALNUT ALMOND
Mass Difference of Nut Before & After Burning

(Subtract mass of nut after burning from Mass of nut before burning)
g
Temperature Difference of H2O Before & After Burning
(Subtract original water temp. from final water temp.)
oC
Calories Required to Change the Temperature of 100 g of H2O
(Multiply temperature change by 100)Cal
Average Calories per gram in the Nut
(Divide the total calories by the mass difference of the nut before & after burning)Cal/g
Average kilocalories or food calories per gram
(Divide the calories per gram by 1000)kcal/g

 

Questions & Conclusion:

  1. Where did the energy stored in the nut originally come from?
  2. During what process was this energy stored in the nut, & where specifically was it stored?
  3. What simple sugar made by plants is a common source for stored energy?
  4. Which group of macromolecules would a nut contain — carbohydrates, lipids, or protein?
  5. What is the name for stored energy?
  6. Give some examples of how organisms would use this stored energy.
  7. In this experiment, discuss what happened to the energy stored in the nut.
  8. Why was the final mass of the nut less than the original mass of the nut? (Remember that matter can’t be destroyed in a chemical reaction.)

 
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DNA Quiz

DNA QUIZ QUESTIONS


1. What is the general name for chemicals like DNA and RNA
2. What general shape does the DNA molecule have?
3. List 4 differences between RNA and DNA
4. Describe the function of the mRNA in Protein Synthesis
5. What is the definition of a codon
6. What is the definition of an anti-codon
7. How many amino acids will result from the following strand of DNA?
A C G C C C A A A T A C
8. Name the two stages that make up protein synthesis
9. Where in the cell does replication take place?
10. Describe the function of the tRNA in Protein Synthesis?
11. Describe briefly the events that occur during transcription?
12. Name 2 common environmental mutagens
13. Describe briefly the events that occur during translation?
14. What is the definition of     a) translation       b) transcription
16. Define complementary base pairing and give an example?
17. Describe the function of the ribosome during protein synthesis
18. From a given strand of DNA. Show the results of Transcription or Replication
19. Make a drawing of DNA or RNA nucleotide and label the parts
20. Give 2 examples of     a) purines          b) pyrimidines
21. Name the 4 bases that make up DNA or RNA molecules
22. Describe how an environmental mutagen could cause a mutation
23. Describe briefly the events that occur during replication?
24. List 3 functions of DNA
25. Describe the function of the DNA in Protein Synthesis
26. What is the definition of a chromosomal mutation
27. What is the definition of a gene mutation
28. If the Nucleic acids are like ladders: What chemicals form the backbone of DNA or RNA molecules?
29. If the Nucleic acids are like ladders: What chemicals form the rungs of DNA or RNA molecule?
30. Briefly describe what occurs during Protein synthesis 

31. What is recombinanant DNA. Give two uses of recombinant DNA

 

DNA SUBJECTIVE QUESTIONS
1. Describe 2 differences between the following pairs of terms
a. codon and anti codon                  b. replication and transcription              c. RNA and DNA  

d. transcription and translation          e. chromosomal and gene mutation       f. mRNA and tRNA           

g. purine and pyrimidine                    h. complementary base pairing and joining of adjacent nucleotides
2. Describe complementary base pairing. Show an example. 

3. Explain the roles/function of the following during Protein Synthesis:
a. DNA in the nucleus       b. Transfer RNA (tRNA)            c. Messenger RNA (mRNA)             d. Ribosome
4. Name 2 environmental mutagens and describe how they could cause a mutation in an organism 

5. Explain the process of DNA replication 

6. Make a drawing of an RNA or DNA nucleotide and label the parts 

7. Compare DNA and RNA with respect to the following things:
a. shape         b. chemical makeup         c. function         d. abundance in the cell

8. Explain the process of translation

9. Explain the process of transcription

10. Describe in sequence, the process of protein synthesis. Include in your answer the names of the various steps, the organelles involved, and the names of the major molecules.

11. Describe how radiation or another such substance could cause mutations to occur. 

12. From a given strand of DNA be able to determine the sequence of mRNA codons, and the amino acid strand produced.

Diffusion and Osmosis

 

  Diffusion and Osmosis

Introduction:
In this exercise you will measure diffusion of small molecules through dialysis tubing, an example of a semi permeable membrane. The movement of a solute through a semi permeable membrane is called dialysis. The size of the minute pores in the dialysis tubing determines which substance can pass through the membrane. A solution of glucose and starch will be placed inside a bag of dialysis tubing. Distilled water will be placed in a beaker, outside the dialysis bag. After 30 minutes have passed, the solution inside the dialysis tubing and the solution in the beaker will be tested for glucose and starch. The presence of reducing sugars like glucose, fructose, and sucrose will be tested with Benedict’s Solution. The presence of starch will be tested with Lugol’s solution (iodine-potassium-iodide).

Procedure:

  1. Obtain a 30 -cm piece of 2.5-cm dialysis tubing that has been soaking in water. Tie off one end of the tubing to form a bag. To open the other end of the bag, rub the end between your fingers until the edges separate.
  2. Place 15 mL of the 15% glucose/ 1% starch solution in the bag. Tie off the other end of the bag, leaving sufficient space for the expansion of the bag’s contents. Record the color of the solution in Table 1.1.
  3. Test the 15% glucose / 1% starch solution in the bag for the presence of glucose. Your teacher may have you do a Benedict’s test. Record the results in Table1.1.
  4. Fill a 250 mL beaker or cup 2/3 full with distilled water. Add approximately 4 mL of Lugol’s solution to the distilled water and record the color in Table 1.1. Test the solution for glucose and record the results in Table 1.1.
  5. Immerse the bag in the beaker of solution.
  6. Allow your set up to stand for approximately 30 minutes or you see a distinct color change in the bag or the beaker. Record the final color of the solution in the bag, and of the solution in the beaker, in Table 1.1.
  7. Test the liquid in the beaker and in the bag for the presence of glucose. Record the results in Table 1.1.

 

Table 1.1

Initial Contents Initial Solution Color Final Solution Color Initial Presence of Glucose Final Presence of Glucose
Bag 15% Glucose & 1% starch
Beaker H2O + IKI

Analysis of Results:
1. Which substance(s) are entering the bag and which are leaving the bag? What experimental evidence supports your answer?

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2. Explain the results you obtained. Include the concentration differences and membrane pore size in your discussion.

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3. Quantitative data uses numbers to measure observed changes. How could this experiment be modified so that quantitative data could be collected to show that water diffused into the dialysis bag?

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4. Based on your observations, rank the following by relative size, beginning with the smallest : glucose molecules, water molecules, IKI molecules, membrane pores, starch molecules.

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5. What results would you expect if the experiment started with glucose and IKI solution inside the bag and only starch and water outside? Why?

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Osmosis:
In this experiment you will use dialysis tubing to investigate the relationship between solute concentration and the movement of water through a semi permeable membrane by the process of osmosis. When two solutions have the same concentration of solutes, they are said to be isotonic to each other. If the two solutions are separated by a semi permeable membrane, water will move between the two solutions, but there will be no net change in the amount of water in either solution. If two solutions differ in the concentration of solutes that each has, the one with more solute hypertonic to the one with the less solute. The solution that has less solute is hypotonic to the one with more solute. These words can only be used to compare solutions.

Procedure:
1. Obtain six 30-cm strips of presoaked dialysis tubing.

2. Tie a knot in one end of each piece of dialysis tubing to form six bags. Pour approximately 25 mL of each of the following solutions into separate bags:

  • Distilled water
  • 0.2 M sucrose
  • 0.4 M sucrose
  • 0.6 M sucrose
  • 0.8 M sucrose
  • 1.0 m sucrose

Remove most of the air from the bags by drawing the dialysis bag between two fingers. Tie off the other end of the bag. Leave sufficient space for the expansion of the contents in the bag.

3. Rinse each bag gently with distilled water to remove any sucrose spilled during filling.

4. Carefully blot the outside of each bag and record in Table 1.2 the initial mass of each bag.

5. Fill six 250 mL beakers 2/3 full with distilled water.

6. Immerse each bag in one of the beakers of distilled water and label the beaker to indicate the molarity of the solution in the dialysis bag. Be sure to completely submerge each bag.

7. Let them stand for 30 minutes.

8. At the end of 30 minutes remove the bags from the water. Carefully blot and determine the mass of each bag.

9. Record your group’s results in Table 1.2. Obtain data from the other lab groups in your class to complete Table 1.3: Class Data.

Table 1.2 Dialysis Bag Results: Individual Data

Contents in Dialysis Bag Initial Mass Final Mass Mass Difference % Change in Mass
a). Distilled Water  

 
b). 0.2 M  

 
c). 0.4 M  

 
d). 0.6 M  

 
e). 0.8 M  

 
f). 1.0 M  

 

To Calculate:

% change in mass = Final Mass-Initial Mass X 100
———————–

Initial Mass

Table 1.3 Dialysis Bag Results: Class Data

percent change in Mass of Dialysis Bags

 

Bag Contents Group 1 Group 2 Group 3 Group 4 Group 5 Group 6 Total Class Average
Distilled Water
0.2 M
0.4 M
0.6 m
0.8 M
1.0 M

10. Graph the results for both your individual data and class average on the following graph. For this graph you will need to determine the following:

a). the independent variable. __________________________________

b). the dependent variable. ___________________________________

Graph Title ______________________________________________

Analysis of Results:
1. Explain the relationship between the change in mass and the molarity of sucrose within the dialysis bag.

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2. Predict what would happen to the mass of each bag in this experiment if all the bags were placed in a 0.4 M sucrose solution instead of distilled water. Explain your response.

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3. Why did you calculate the per cent change in mass rather than using the change in mass?

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4. A dialysis bag is filled with distilled water and then placed in a sucrose solution. The bag’s initial mass is 20 g. and its final mass is 18 g. Calculate the percent change of mass, showing your calculations in the space below.

 

 

 

 

5. The sucrose solution in the beaker would have been ___________________ to the distilled water in the bag.