Practical+2

=Practical 2 (Cells)=

Affect of fluid movement and water freezing on cell structure.

 * ===HL: (1 hr, Aug 19), (0.5 hr, Aug 21)===
 * ===SL: (1 hr, Aug 20)===

Criteria to be assessed (D, DCP, CE):
[Design provided] Data collection & processing; conclusion & evaluation

Aim:
Students will make various salt (or sugar) concentrations in water then freeze "identical" size beet pieces in the solutions. After freezing, the solution surrounding beet pieces will be analyzed quantitatively to determine amount of betacyanin leakage (Davidson & Lee, 1998.) which will be an indirect measurement of cell damage.

//(adapted from Davidson & Lee, 1998)://

 * //Please record measurements and their error EVERY TIME you make the measurements. Don't leave this until later: you will certainly forget!// **
 * 1) Each student will make their own salt or sugar solutions as assigned: 0g/L, 0.1g/L, 1g/L, 10g/L and 20g/L.
 * 2) Place uniform volume or each solution into carefully labeled test tubes.
 * The amount solution in the test tube should be sufficient to completely immerse the piece of beet you place in each test tube (below).
 * 1) Cut beets pieces of identical dimensions. The pieces should be a size which can fit into test tubes easily and will be completely surrounded by the salt or sugar solution you made.
 * 2) Briefly rinse cut beet pieces before placing them into test tube so that any pigment (betacyanin) caused by the cutting will be removed and will not go into test tubes.
 * 3) Place beet pieces in test tubes containing salt or sugar solutions.
 * 4) Label test tubes and test tube rack.
 * 5) Place test tubes in freezer for at least 24 hours.
 * 6) Remove test tubes from freezer and thaw.
 * 7) Remove beets from each tube carefully, pat with towel to dry and mass them. Record quantitative and qualitative observations.
 * 8) Remove identical proportion or percentage of fluid from each test tube (in case they have different amount of liquid inside) and place the fluid in cuvettes.
 * 9) Use spectrophotometer or Vernier colorimeter to determine a quantitative measurement of relative amounts of betacyanin in each test tube.
 * 10) Record quantitative and qualitative observations.

Apparatus:
fresh beets, scalpel, knife, aluminum trays (for cutting), rulers (with mm), 25 mL and 250 mL graduated cylinders, Centigram balance

Data Collection:
Show the results in suitable tables. Include uncertainties where possible.
 * Note: in this lab you are welcome to use other students data as "replications" but clearly identify your own values as well.

Data Processing and Presentation:
Analyse your data and present it in an appropriate form. Include uncertainties where possible.

Conclusion and Evaluation.
Include in your write up, various ways to improve the investigation and possible errors that might have occurred.

References:
Davidson, Evelyn C. and Richard E. Lee. "When Cells Freeze Over". __The Science Teacher__. pp 28 - 31, 1998.