Diffusion & Osmosis



Cellular Respiration

Key Concepts:

Cell Respiration*: C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (ATP)

In this lab, the respiratory rate (O2 production) of germinating and nongerminating (dry) peas was investigated using a respirometer. Germinating peas respire and need to consume oxygen in order to continue to grow. Nongerminating pea seeds do not respire actively.

In this lab, the amount of oxygen consumed was measured – the lab was conducted at 2 temperatures: 25°C and 10°C, because peas consume MORE oxygen at HIGHER temperatures.

In the Lab:

Control: glass beads

Use of KOH: consumes CO2 – ensures that the change in volume of gas is due to the oxygen consumed and not the CO2 that is produced during cell respiration.

Results: germinating seeds consume most oxygen.

Effect of Temp on Respiration: peas at room temperature respired at a higher rate than those in ice water.

BE SURE YOU CAN CALCULATE THE RATE OF O2 CONSUMPTION FROM THE GRAPH OR DATA!!! ALSO...THIS SAME LAB SET UP CAN BE USED TO CALCULATE O2 CONSUMPTION BY A SMALL ORGANISM...CRICKET, ETC.

The Essay:

The results below are measurements of cumulative oxygen consumption by germinating and dry seeds. Gas volume measurements were corrected for changes in temperature and pressure.

|Cumulative Oxygen Consumed (mL) |

|Time (minutes) |0 |10 |20 |30 |40 |

|22° C Germinating Seeds |0.0 |8.8 |16.0 |23.7 |32..0 |

|Dry Seeds |0.0 |0.2 |0.1 |0.0 |0.1 |

|10° C Germinating Seeds |0.0 |2.9 |6.2 |9.4 |12.5 |

|Dry Seeds |0.0 |0.0 |0.2 |0.1 |0.2 |

a. Using the graph paper provided, plot the results for the germinating seeds at 22° C and at 10° C.

b. Calculate function the rate of oxygen consumption for the germinating seeds at 22° C, using the time interval between 10 and 20 minutes.

c. Account for the differences in oxygen consumption observed between:

i. germinating seeds at 22° C and at 10° C

ii. germinating seeds and dry seeds

d. Describe the essential features of an experimental apparatus that could be used to measure oxygen consumption by a small organism. Explain why each of these features is necessary.

NOTE: Parts A, B, and C together…8 points MAX!

| (A) GRAPHS – 4 possible points |Possible Points |

|correct orientation of x (independent) and y (dependent) axes |1 |

|scale and label axes |1 |

|curves plotted (both lines drawn and identified as 100/220) |1 |

|graph appropriately titled |1 |

|(B) RATE CALCULATION – 2 possible points |Possible Points |

|set up (16 – 8.8) / (20 – 10) or number 7.2 or 0.72 |1 |

|rate concept – units (volume/time) |1 |

|7.2mL/10min or 0.72mL/min | |

|(C) EXPLANATIONS – 7 possible points |Possible Points |

|Temperature Variation | |

|seeds show no temperature regulation (at environmental temperature); do not increase O2 consumption to maintain preset temperature |1 |

|temperature increase causes increased activity (or increased respiration or metabolism) | |

|extended explanation of respiratory enzyme reaction rate, rate increases (to limit) with increased temperature |1 |

|220 v/s 100 rates reversed in cold hardiness (genetically determined) seeds |1 |

| | |

| |1 |

|Germinating Seeds v/s Dry Seeds |1 |

|dry seeds dormant and/or germinating seeds metabolically active | |

|extended explanation of dormancy and/or metabolism |1 |

|explanation of water based chemistry of respiratory enzyme reactions |1 |

|(D) EXPERIMENTAL APPARATUS – 7 possible points (3 points MAX) |Possible Points |

|Method to separate O2 consumption v/s CO2 release |1 |

|i.e. something (KOH) to remove CO2 (gas ->solid) | |

|Closed system |1 |

|Method to measure pressure/volume change = graduated tube/pipet, containing bubble/water/etc |1 |

|Method to control temperature (water bath) |1 |

|Method to control volume (glass beads or some other inert material v/s seeds) |1 |

|Timing device |1 |

|Equal numbers of organisms in experimental and control |1 |

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download