Lab Questions….Expectations for Honors / IB Students

1. Lab Questions….Expectations for Honors / IB Students Work shall be NEAT Work shall be COMPLETE Work shall be WRITTEN IN COMPLETE SENTENCES Work shall include CORRECT SPELLING ……..ALL OF THE TIME 

2. Activity 2: Fully account for the difference in the color of the BTB between plants in Group A vs. Group B The plants in Group A were kept in the dark for 3 days. These plants produced energy through respiration, since there was no sunlight for photosynthesis. A product of respiration is carbon dioxide. Carbon dioxide becomes carbonic acid when dissolved in water. Since BTB is a pH indicator, it turns from a blue color to a yellow color when the pH has been lowered because of the production of an acid. The plants in Group B were in sunlight. They produced food through photosynthesis. The products of photosynthesis are glucose and oxygen – neither of which will cause a change in the pH of the water to affect the BTB, allowing it to remain a blue color.

3. Activity 5: Question 3: Why was it important that the water was a specific temperature? Yeast contains the enzyme zymase, which catalyzes alcoholic fermentation reaction. Like all enzymes, zymase is temperature specific, and can become denatured (and not work) if the temperature is too low or too high.

4. Activity 5: Question 5: Why didn’t the balloon inflate immediately after putting it on the test tube? The reaction between the yeast, sugar and warm water is an anaerobic one. Initially, there is oxygen in the test tube, which first had to be used up before the yeast converted from breaking glucose down aerobically, to breaking it down anaerobically in the process of alcoholic fermentation. Once the process of anaerobic respiration began, enough CO2 had to be produced before the balloon could inflate.

5. Activity 6: Question 2: For which product of fermentation are you testing? If the test is positive, explain how this happened. If the test is negative, explain your results. Offer at least 3 reasons why a negative result was obtained. The process that took place in this reaction is alcoholic fermentation, and the product we’re testing for is CO2. In water CO2 turns to carbonic acid. Since BTB is a pH indicator, it turns from a blue color to a yellow color when the pH has been lowered because of the production of carbonic acid. A negative result may be obtained by any of the following : ~ the tubing fitting improperly and allowing gas to escape ~ the water being too hot or cold and denaturing the enzyme ~ not enough CO2 being produced ~ the reaction not having enough time to take place

6. Genetics Vocab….yes, it will be on your test tomorrow! Genetics = study of heredity Allele = 1 variant of a gene. At least 2 alleles ‘code’ for a trait. 1 allele from mom, 1 from dad Gene = segment of DNA on a specific site on a chromosome which codes for a trait. Homozygous = both alleles for a trait are the same. aka pure Heterozygous = the 2 alleles for a trait are different. aka hybrid Dominant = when 1 allele is expressed over another allele Recessive = when an allele is not expressed unless it is homozygous Genotype = the actual gene combination of an organism; i.e., Tt Phenotype = the appearance of an organism because of its genotype; tall, green, widow’s peak, etc. Punnett square = shows the probability of the possible genetic combinations of offspring P1 = 1st parents to be crossed F1 = the first offspring of the P1 parent F2 = the offspring of the F1 generation; 2nd generation of the P1 parents