Life Science: Session 8
What is the SPONCH CaFe?
In the video for Session 1, our host Dr. Doug Zook offered a simple mnemonic to remember the key elements that compose living things: the SPONCH CaFe. The letters are symbols for chemical elements: carbon (C), hydrogen (H), nitrogen (N), oxygen (O), phosphorus (P), sulfur (S), calcium (Ca) and iron (Fe). Although the symbols are not in order of relative abundance (that would be OCHNCaPSFe — hardly simple to say!), together these elements compose 99.8% of all living things.
What role do the various elements play?
You may recall from Session 1 that the molecules that compose living things are called organic molecules. Organic molecules are built from repeated subunits that are built from the elements in the SPONCH CaFe. Let’s take a look at some representative subunits to see where these elements are found.
C, H, O, N
(S in some)
Two linked amino acids:
C, H, O
(P and N in some)
Glycerol linked to three fatty acid chains
|Nucleic acid||Nucleotide||C, H, O, P, N||
Two linked nucleotides:
Carbohydrates store energy. The starch in a potato is a good example. They also act as structural components, such as the cellulose that makes a celery stalk stringy or the chitin that composes the outer skeleton of a beetle.
Proteins are what the cell uses to translate the information in DNA into cell products. Proteins act as enzymes, which are important in making chemical reactions happen in cells. There are also structural proteins. Hair and cartilage are good examples.
Lipids perform a variety of functions. Fats store energy. Cell membranes are made of a type of structural lipid. Sex hormones, such as testosterone and estrogen, are made of lipids. The pigment chlorophyll, which is important in photosynthesis, is a lipid.
Nucleic acids include DNA, which carries genetic information, and RNA, which translates that information into proteins.
What about the other elements?
The other elements in the SPONCH CaFe are calcium (Ca) and iron (Fe). Calcium is an important structural component. Bones and teeth contain calcium. It’s also critical in keeping body chemistry in balance. Iron is important in the synthesis of hemoglobin, which is responsible for carrying oxygen in blood.
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