Laboratory Investigation # 4
Photosynthesis and Respiration
Description of the Lab
Metabolism of plant is the process of photosynthesis. This lab will take about 1-
1.5 hours. Preparation should begin a week before the lab time.
Outline of Investigation
1. Requirements for photosynthesis
A. Potted Pelargonium (geranium) plant that has been placed in dark for
72 hours.
Black paper- put on portions of leaves and place plant in light for 24
hours.
2. Reactants for photosynthesis
Elodea (1 sprig per group) 1 sprig has been placed in dark before lab for
24 hours
OPTION
Measure oxygen concentration of dark-adapted and light-adapted Elodea
3. Products of photosynthesis (DEMONSTRATION)
Elodea sprig,
4. Products and substrates of Respiration
A. Four 100 mL beakers
250 mL beaker
Yeast
200 mL of warm tap water (per group)
C. Barley seed (2 batches) soaked overnight with aeration (DEMO)
1 batch of seeds is sealed in a flask contain pyrogallol overnight
1 batch of seeds is sealed in a flask contain distilled water overnight
Laboratory Materials and Equipment for Student Use
Materials and Equipment
Per
Student
Per Pair of
Students
Per Lab
Group
Per Room
Four 100 ml beakers
4
One 250 ml beaker
1
Two 1 liter flasks
2
Stoppers for the flasks
2
Hot plates
5
2
4
1
2
1
cm diameter, 6.5 cm length) small test
tube (10 mL capacity), and bent glass
pipette with stopper
Fresh live materials
Variegated Coleus—preferably green
and white
1
Preparation of laboratory Materials and Reagents
Reagents
1% Phenol Red solution
1. Weigh 1 gram of phenol red and put in a beaker.
One week prior to the lab
1. Make sure you have enough potted plants. Plant were growth at the beginning of
the semester
2 days prior to the lab
Barley seeds soaked over night with
aeration
Reagents
Questions for Lab #4 Photosynthesis & Respiration
Use the knowledge you acquired in this lab exercise, along with information from your
textbook, to answer the following questions.
1. The First Law of Thermodynamics states “Energy cannot be created or destroyed,
although it can be transformed from one form to another” (Berg p. 40). What is the
energy transformation that occurs in photosynthesis?
2. What are the two products of photosynthesis? How are both these products important
to other organisms in the biosphere?
Oxygen – utilized by aerobic organisms
3. The carbon dioxide concentration is increasing in the Earth’s atmosphere due to
accelerated burning of fossil fuels. Considering the photosynthetic process how might
increased carbon dioxide concentration affect plants? Explain.
4. Albino (white) plants may arise when a mutation prevents the synthesis of
chlorophyll. What is the consequence of this mutation for the plants? Explain
5. Geranium and Coleus, used in the photosynthesis experiments, were first put in the
dark to deplete the starch. What process is responsible for starch depletion and what is
the function of that process? Can the plants be maintained indefinitely in the dark?
The process responsible for starch depletion is aerobic cellular respiration. This
6. The overall equation for respiration is the same as that for combustion. However, the
amount of heat energy released in combustion is far greater than that released from
respiration. How do you explain this, considering the First Law of Thermodynamics
(question 1 above)?
Respiration is a controlled series of reaction whereas combustion is like an
7. Table sugar was used as a starting material for respiration of yeast. Describe an
experiment you would do to find out if other sugars can be used in respiration.
1. Obtain a yeast culture solution and pipette 1 mL into 4 test tubes.
2. Pipette 1 ml of the following sugars to the test tube
a. Sucrose to test tube 1
d. Water to test tube 4 as a control
3. Mix the solution in each test tube
8. When spring rains flood farmlands that have just been seeded, the farmers often have
to reseed the fields later in the spring. What does flooding do to hinder the germination
process?
Flooding cause depletion of the oxygen in the environment surround the seed.