# Liberal Arts Blog — Human Body Composition — Three Perspectives

Liberal Arts Blog — Wednesday is the Joy of Science, Engineering, and Technology Day

Today’s Topic: Human Body Composition — Three Perspectives (elemental, molecular, cellular)

So what are we made of? How much of us is muscle? bone? fat? water? carbon? Today, three perspectives. There is a metaphor here. Three highlights: 34% of you is extracellular! Red blood cells are 85% of cells by number but only 4% by mass. You have 10X more RNA than DNA by mass and 1,000,000X more by number. Best visualization you ever saw of human body composition? Or of any other marvel of nature for that matter? Say the universe, for example? Or the earth? Experts — please chime in. Correct, elaborate, elucidate.

BY ELEMENT: OXYGEN — 65% BY MASS, 24% BY NUMBER OF ATOMS

1. Carbon: 18% by mass, 12% by number of atoms.

2. Hydrogen: 12% by mass, 62% by number of atoms

3. Nitrogen: 3.2% by mass, 1.1% by number of atoms

NB: Calcium 1.5% by mass, .22% by number of elements, Phosphorus 1.0% by mass, .22% by number of elements.

BY MOLECULES: WATER — 65% BY MASS, 99% BY NUMBER

1. Protein: 20% by mass, .01% by number.

2. Lipids: 12% by mass, .47% by number

3. RNA: 1% by mass, 3X 10 to the minus fifth by number

DNA: .1% by mass, 3X 10 the minus 11th by number

NB: Other inorganics: 1.5% by mass, .74% by number

BY CELL TYPE: RED BLOOD CELLS: 85% BY NUMBER, 4.2% BY MASS

1. Muscle Cells: 29% by mass, .001% by number

2. Fat cells: 9.5% by mass, .2% by number

3. Other cells: 14.3% of mass, 14.8% by number

NB: Extra cellular components: 34% of mass !!!!!!

Composition of the human body

A LINK TO THE LAST THREE YEARS OF POSTS ORGANIZED BY THEME:

Please share the coolest thing you learned this week related to science, engineering, or technology. Or, even better, the coolest or most important thing you learned in your life related to science and engineering.

This is your chance to make someone else’s day. Or to cement in your mind something that you might otherwise forget. Or to think more deeply about something dear to your heart. Continuity is key to depth of thought.

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