Cellular Respiration

AP Biology Lab #3

Janice Chan

Period 2

Partners: Kevin Ta,

Janice Chan

Dr. Fuller

AP Biology – Period 2

30 September 2010

AP Biology Lab #3 – Cellular Respiration

I. Pre-lab Questions1. What are the mechanisms of diffusion and osmosis and their importance to

cells? Diffusion is known as the movement of molecules from a higher concentration to

a lower concentration. Osmosis is a special type of diffusion in which the action occurs, “in water separated by a selectively permeable membrane, with different solute concentrations on either side of the membrane… In osmosis, the water moves from a region of low solute concentration to a region of high solute concentration.” The mechanisms are important to cells because they allow for many life functions of the cell, including the transportation of “vitally important nutrients and compounds without expenditure of excess metabolic energy.” Osmosis and its impact on plant cells allows for, “the absorption and early transport of water into the root system of plants, and, with transpirational pull, helps transport water in the xylem.

2. What are the effects of solute size and concentration gradients on diffusion and osmosis between two solutions separated by the membrane? The solute size does not affect the diffusion of the membrane, but the

concentration gradient does. The higher the concentration, the faster the water will flow through the membrane.

3. What are the effects of a selectively permeable membrane on diffusion and osmosis between two solutions separated by the membrane? When you have a membrane that separates two solutions, it restricts certain

materials from passing freely through the membrane. With diffusion and osmosis, the membrane allows certain, “small, neutrally charged molecules, such as oxygen, carbon dioxide, water, and glucose to pass freely.”

The selectively permeable membrane has different cellular concentrations on either side, so the osmosis moves the solution from lower concentration to higher concentration.

4. What is water potential? A solute’s relative concentration; Water always moves from an area of higher

water potential to an area of lower water potential.5. What is the relationship between solute concentration, pressure potential, and

the water potential of a solution? Pressure potential and osmotic potential assist water potential in reaching

equilibrium.

Solute concentration equals water potential, and when the pressure potential is equal to the osmotic potential, water potential is 0, and equilibrium has been reached.

6. What is the relationship of molarity to osmotic concentration? As molarity increases, so does osmotic concentration.

Cellular Respiration Lab

I. Titlea. Cellular Respiration

II. Objectivea. To measure the conditions that affect the rate of cell respiration.

III. Hypothesisa. If peas are made to leave dormancy and germinate, then their respiration will

increase.b. If germinating peas are cooled from room temperature to 10 degrees C, then their

respiration will decrease.c. If there is light coming from a heat lamp shining down on the peas, their cellular

respiration will increase.

IV. Materials

1. PASCO Xplorer GLX with CO₂ sensor and temperature sensor

2. 25 dry pea pods

3. 25 soaked [germinating] pea seeds

4. 500 ml beaker

5. Ice

V. Procedurea. Part A

i. Place 25 dry peas into CO₂ bottle, insert CO₂ sensor into bottle, be sure that jar is sealed by stopper on sensor. Place temp sensor next to bottle.

ii. Press start button on Xplorer to begin data display. Record concentration of CO₂ every minute for 15 minutes.

iii. Remove dry peas from bottle, invert open bottle and shake for several seconds. Rid all CO₂ that may be present.

iv. Place 25 soaked peas into bottle, replace CO₂ sensor.v. Press start button twice, restart data collection. Record again, every minute

for 15 minutes.vi. Remove sensor, remove soaked peas [place on paper towel] and invert and

shake open bottle, drain CO₂ again.vii. Fill 500 ml half beaker half full with water and add ice while stirring, until

temp reaches 10AC.

viii. Place open bottle into beaker with ice water, let sit for 5 minutes. Place temp sensor into beaker.

ix. Return soaked peas to bottle, Replace CO₂ sensor in bottle, press again twice to restart data collection. Record again every minute for 15 minutes. [Concentration & temp] Add ice as needed to keep temp as close to 10AC as possible.

x. Using germination and dry peas, create and carry out own experiment to explore conditions that affect respiration.

VI. Dataa. Key

i. Black = Original.ii. Red = Soaked.

iii. Blue = With ice, regulating temperature at 10 2C.iv. Orange = With light.

Time [ Minutes] - 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Concentration [PPM]

407 543 543 544 543 546 541 542 545 546 551 552 544 543 540 545

Temp [2C] 24.7 25 25 25 24.8 24.8 24.7 24.6 24.8 24.7 24.8 24.5 24.3 24.2 24.3 24.2

Concentration [PPM]

507 7321029

1280

1509

1711

1900

2048

2168

2286

2389

2506

2604

2714

2818

2923

Temp [2C] 23.222.6

22.9 22.6 22.8 22.4 22.9 22.9 23.2 23.3 23.6 24 24 24 24.2 24.3

Concentration [PPM]

336 484 565 655 741 791 833 903 450 9971020

1071

1091

1142

1181

1223

Temp [2C] 9.810.3

10.6 9.2 10.7 10.9 10.5 10.0 10.0 10.0 10.3 10.0 9.6 9.8 10.0 10.0

Concentration [PPM]

417 530 656 805 9641147

1370

1611

1870

2080

2286

2607

2870

3115

3372

3645

Temp [2C] 22.723.6

26 28.8 30 30.9 31.0 32.1 33 33.6 33.4 34 33 34 33.4 31.8

VII. Post-Lab Questions1. In Part A, what molecules could diffuse through the dialysis tubing and

which stayed inside? Why? The glucose was able to diffuse through the tubing because of its smaller

molecular structure and its lower density.2. In Part B, why did the mass of the bags change? The mass of the bags changed because of the bag’s higher concentration. The

solution naturally moved from the water in the cup to the bag due to osmosis, which adds mass to the bag.

3. If the bags in Part B were placed in .4 M sucrose instead of distilled water, what would the results be?

The results would change, because everything below .4 M would decrease in mass, while the bags above .4 M would increase in mass. The .4 M bag would not change at all, because it is at equilibrium with the solution.

4. Why is measuring the temperature an important part of the calculation of osmotic potential?

Without the temperature, the potential could be too varied for the experiment. The heat or cold would change the data.

5. If the potato cores in Part C were allowed to dry out before use in this experiment, how would the results be affected?

They would gain more water if they were allowed to dry out before use. More water would be absorbed when you placed the potato core into the water solution.

VIII. Conclusion