METABOLIC PATHWAYS Objective.- The objective of this activity is to measure the
ID: 224583 • Letter: M
Question
METABOLIC PATHWAYS
Objective.- The objective of this activity is to measure the products of two basic metabolic pathways : Cellular Respiration and Photosynthesis. The students will measure the rate of carbon dioxide production as respiration occurs in bean seeds and the rate of photosynthesis in plants as a function of different light conditions.
Introduction.-
Cellular Respiration and Photosynthesis are two important metabolic pathways that are essential for life. During Cellular Respiration, organisms use oxygen and other compounds to obtain energy from food. In Photosynthesis, autotrophic organisms capture energy from the sun to produce food and support themselves and the other organisms above the food change.
Both pathways are essential for life and the reactants and products of them are complementary. Plants use energy from light, carbon dioxide (CO2) and water (H2O) to produce sugars and oxygen. Organisms (including plants) use the sugars and the oxygen produced during photosynthesis to obtain energy and store it in the form of ATP (Adenosine Triphosphate). In addition, cellular respiration produces CO2, which is needed in photosynthesis.
Thus, both metabolic pathways are needed to support life in our planet. Photosynthesis occurs in the chloroplasts of plants and cellular respiration occurs in the cytosol of cells and in mitochondria of plants and animals. It is possible to represent the products and reactants of these pathways using chemical equations.
1) Cellular Respiration Activity
In this activity we will measure the rate of cellular respiration using bean seeds. Seeds contain a plant embryo and all the necessary nutrients for plant growth. When seeds germinate, the stored sugars are used in cellular respiration to produce ATP needed for plant development. In this lab activity, you will germinate bean seeds to measure cellular respiration.
We know from the equation above that cellular respiration produces carbon dioxide. Carbon dioxide is also a compound that has the ability to change the pH of a solution. So if we place beans in solution and measure any change in pH, we will be measuring carbon dioxide production and as a consequence respiration. In order to have a reference point, you will first manipulate the pH of a solution using Sodium Bicarbonate and then perform the cellular respiration experiment using beans.
Materials:
1) Small bag of Lima Beans
2) Paper cups
3) Grape Juice
4) Sodium Bicarbonate
5) Plastic Wrap
Experimental Procedure:
1) Take a small paper cup and add grape juice (3/4 of the volume).
2) Add 1 tablespoon of sodium bicarbonate and mix.
(Note: The purpose of this activity is to change the pH of the solution which will result in a color change).
OBSERVATIONS.
Describe your observations below (what was the color of the juice before and after mixing carbon dioxide? Can you give any tentative explanation to this?):
Explanation / Answer
Grape juice contains organic acids like tartaric, malic and citric. For this reason, the color of the acidic juice before mixing of carbon dioxide through sodium bicarbonate was reddish-purple. After addition of sodium bicarbonate, the color of the juice became bluish-purple or black.
Sodium bicarbonate is a base.It also forms carbon dioxide gas. For this reason, sodium bicarbonate reacts with the acidic grape juice to form neutral salt and water by the process of neutralization. This reaction is indicated by change in color of the grape juice. Here color of grape juice acts as the indicator.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.