Cells and Chemical Reactions: Cellular Respiration

Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the third of four Science Objects in the Cells and Chemical Reactions SciPack. It explores the process of cellular respiration in chemical reactions involved.

Non-photosynthetic organisms obtain the energy necessary for cell growth and maintenance by decomposing large molecules into smaller molecules that have lower energy levels stored in their chemical bonds (thus, releasing some energy from bonds so that it can be used to do cellular work). These smaller molecules can enter or exit the cell to be synthesized into larger complex molecules necessary for growth and maintenance of the organism. Organisms unable to photosynthesize, such as animals and fungi, must take matter into their cells to provide the building blocks (chemical constituents) and energy needed for metabolism (both synthesis and decomposition processes). The matter and energy that is stored in the structures that are synthesized by photosynthetic organisms (for example, the stems, roots and leaves of plants) can be consumed and used by other organisms as an essential source of this matter and energy.

The chemical bonds in the molecules that are synthesized through photosynthesis and other synthesis processes contain energy that is needed by all cells (including plant cells). The energy stored in chemical bonds of the matter taken into the cells can be released and transferred into a form available for cellular work. This occurs when the bonds are broken through decomposition reactions and new compounds with lower energy bonds are formed. Cells capture some of the energy that is released during decomposition and usually store this energy temporarily in the phosphate bonds of a small high-energy compound called ATP. The energy stored in the bonds of ATP is then readily available for use by the cell for synthesis and other cellular work.


Elementary SchoolMiddle SchoolHigh School


Type Science ObjectStock # SCB-CCRX.3.1

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