6. Cell Energy (photosynthesis and respiration)

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Here you will find a toolbox full of inquiry investigations on photosynthesis and respiration. Rather than the detailed lesson plans provided elsewhere at My Science Box, each experiment only contains a short background, materials, procedure, and going further section. It is up to you to decide which of the many experiments you wish to try with your students and how to sequence them. You will find everything from descriptions for how to extract chlorophyll, discover that plants “breathe”, recreate the experiments of Priestly and Ingenhousz, detect carbon dioxide production, and measure the rate of yeast respiration. None of these experiments require expensive equipment such as metabolism chambers or oxygen meters although those are great tools if you can afford them.

Briefly, photosynthesis occurs in the chloroplasts of plants as a means of turning solar energy into chemical energy in the form of glucose, the primary food/energy source of cells. Through a series of biochemical reactions, sunlight energy transforms carbon dioxide and water into glucose and oxygen.

6CO2 + 6H2O + light → C6H12O6 + 6O2

Respiration releases the chemical energy stored in glucose and turns it into energy that can be used by the cell in the form of ATP (adenosine 5’triphosphate). ATP may be considered the standard currency of the cell, much as the dollar is the standard currency in American society. Nearly all cellular processes depend on ATP as their energy source. The chemical equation for respiration using glucose is the mirror image of the chemical equation for photosynthesis.

C6H12O6 + 6O2 → 6CO2 + 6H2O + energy

Can recognize that all living things metabolize and thus require nutrients, take advantage of chemical reactions to release energy, and produce wastes.
Can describe the general process of photosynthesis and respiration.
Can recognize the reciprocal relationship between photosynthesis and respiration.
Can explain the jobs of chloroplasts and mitochondria and their importance to cells.
Can design, conduct, and interpret experiments on plants and animals related to photosynthesis and respiration.

Chemical reaction
Carbon dioxide
Bromthymol blue
Carbonic acid

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