Cellular Respiration

Question 1

What is methyl blue used as in this experiment?

Answer 1

• artificial electron acceptor
  = outcompetes oxygen
  -> as a result, methyl blue becomes reduced when it accepts electrons and will change colour

Question 2

Design & conduct an experiment to test the release of carbon dioxide as a product of respiration

Answer 2

1. Place 5 fresh seeds in a test tube
2. Place 5 boiled seeds in another tube
3. Add 10ml distilled water to both test tubes
4. Add 4 drops phenol red solution into each of the test tubes
5. Cover each test tube with parafilm and invert each test tube to ensure mixing of the solution
6. Place the test tubes in the beaker filled with water (this will act as a temperature control) and leave in a dark room for a significant period of time
7. Observe and record any colour changes in a table
8. Repeat observations and write down results in table

Question 3

Why was one of the yeast solutions heat treated?

Answer 3

• to denature the proteins & enzymes within the yeast

= serves as a control

Question 4

Why was it important to record the time when the contents were initially mixed?

Answer 4

• Rxn starts to occur from that moment

= allows for accurate readings to be taken every 10 min => reference (starting time) remains accurate

Question 5

Do you think that temperature is a variable that could affect the rate of the reaction?
Explain.

Answer 5

Yes

• increase temp. = increase kinetic energy of particles = increase reaction rate -> more particles collide per unit time
• if temp. Too high = denature enzymes & proteins = decreases rxn rate

Question 6

What is the role of sodium citrate in the second test tube?

Answer 6

• 6 carbon compound that serves as a catalyst = increase rxn rate

Question 7

Why were the seeds boiled?

Answer 7

• denature enzymes and proteins in seeds

- allows seeds to be used as a control