Cellular Respiration Lab - An Experimental Design printable pdf download

Cellular Respiration Lab

Observations, Interpretations, and Experimental Design

Each partner is responsible for their own write-up

DO NOT WRITE ON THIS LAB HANDOUT!! PLEASE RETURN

Enzymes in mitochondria

C 6 H 12 O 6 + O 2

CO 2 + H 2 O + ATP

→

(cellular energy)

(glucose)

(oxygen)

(carbon dioxide)

Chemical reactions used in determining rate of cellular respiration

PHTH

Pink

CO 2 + H 2 O

!! H 2 CO 3

NaOH + H 2 O

→

(Clear)

Acidic

Basic

I. Initial Observations:

Working with your partner, familiarize yourself with the equipment and the procedures

for using the phenolphthalein indicator (PHTH) with the sodium hydroxide (NaOH).

See procedures and equipment below for determining CO

production.

MATERIALS

• A clock that measures seconds

• Phenolphthalein solution (PHTH)

• Two-250-milliliter flasks

• 0.6 percent NaOH in a dropping bottle

• Water

(6 grams NaOH/1 liter)

• Soda straw

• A white sheet of paper

Measuring CO

production:

Fill two 250-milliliter flasks with 150 ml of tap water. Add three drops of

phenolphthalein to each flask. Add sodium hydroxide (NaOH) to the water drop by

drop until you obtain a light pink color in both flasks; label ONE flask “control”. Label

the second flask “experimental”. Insert a straw into the experimental flask, and blow

gently into the water for 1 minute. (You may need to take one or two breaths; the total

exhalation time should be 1 minute.) Exhaled carbon dioxide dissolves in water to

create an acidic solution. (Water and carbon dioxide react to form carbonic acid.) As

the pH of the solution drops below 8, the PHTH in the solution loses its pink color.

Add NaOH to the experimental flask, drop by drop, and swirl gently to mix. Count

the number of drops it takes to restore the original pink color, comparing the color of

the experimental flask to the control flask. The total number of NaOH drops needed

to restore the original pink color will be your quantitative measurement of the amount

of CO

produced by you!

Measuring Breathing rate:

Visually count the number of breaths taken in 30 seconds. Convert this to the number

of breaths per minute.

A. FIVE Observations:

(Label your paper with this subheading)

Working with your partner and using the equipment and procedures above, record five

good observations with respect to CO

production, breathing rate per minute.

Make no interpretations!

Cellular Respiration Lab - An Experimental Design

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