Facts from ECB CH2, Chemical Components of Cells

• Chemical Bonds
• Small Molecules in Cells
• Macromolecules in Cells

Here are facts I found interesting from the second chapter of Essential Cell Biology.

Chemical Bonds

• C, H, N, and O constitute 96% of any organism’s weight.
• Typical covalent bonds are stronger than thermal energies by a factor of 100.
• In living organisms, covalent bonds are only broken when in the presence of enzymes.
• In an aqueous solution, ionic bonds are 10-1000 times weaker than the covalent bonds.
• Cell interiors are kept close to neutral pH by the presence of buffers.

Small Molecules in Cells

• Molecules with a backbone of carbon are called organic molecules.
• Cells contain four major families of small organic molecules: sugars, fatty acids, amino acids, and nucleotides.
• Here is a table summarizing the chemical composition of a bacterial cell
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• Fatty acids can produce six times the number of energy per gram as glucose.
• 20 types of amino acids are commonly found in proteins.
• Proteins are 1/2 of a cell’s dry mass.

Macromolecules in Cells

• Macromolecules are 80% of a cell’s dry mass.
• Early chemists didn’t think that large molecules could exist. With its purported 700 carbon atoms, the existence of hemoglobin was deemed “very improbable” by leading chemists. Centrifuging hemoglobin revealed a single sharp band with molecular weight of 68k daltons, confirming its size.
• Enzymes recognize their substrates via noncovalent interactions.
• Proteins bind together into multiprotein complexes with noncovalent bonds.