Lab Respiration

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Slide 6

CELL RESPIRATION

Experimental procedure for comparison of photosynthesis and respiration (cont.)

Step 4: Place two tubes, one with Elodea and one without between the lights on the counter.

Slide 7

CELL RESPIRATION

Introduction to fermentation

Fermentation is a pathway for the oxidation of glucose that produces ATP in the absence of oxygen. Fermentation is similar to respiration because it begins with glycolysis. Fermentation differs from respiration because it does not involve the Krebs cycle or an electron transport chain.

Fermentation yields waste products other than CO2 and H2O. In humans, fermentation yields lactic acid and in yeast fermentation yields ethyl alcohol in addition to CO2.

Since fermentation lacks a Krebs cycle and an electron transport chain, the only energy products come from glycolysis. The 2 NADH are used to produce the alcohol or lactic acid. The total amount of ATP produced from one molecule of glucose is 2.

Slide 8

CELL RESPIRATION

Experimental procedure for fermentation

Tests performed by the Instructor:

Test for carbon dioxide (CO2)production: The instructor will demonstrate the reaction between CO2 and barium carbonate by using a straw to breath into a tube of barium carbonate. Note the reaction when the instructor performs this activity. Students will not perform this activity because barium carbonate is toxic.

The instructor will then place a tube from a beaker containing yeast in a sucrose solution into a second tube of barium carbonate to test for CO2 production by the yeast.

Slide 9

CELL RESPIRATION

Experimental procedure for fermentation (cont.)

Tests performed by the Instructor (cont.):

Test for ethyl alcohol production: The instructor will assemble a distillation apparatus to collect alcohol from both flasks. The flasks will be heated to separate the alcohol from the water. The distillate will be tested for the presence of alcohol as described in the lab manual.

This flask contains

sucrose alone.

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This flask contains

yeast and sucrose.

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Slide 10

CELL RESPIRATION

Experimental procedure for fermentation (cont.)

Tests performed by the Student:

Controls for alcohol production: You will prepare two tubes (Tube 1 and Tube 2) that will be used as controls for the presence of alcohol.

Tube 1 will be a negative control because it will not contain alcohol. This tube will give a negative result for the presence of alcohol.