Question

What is the largest organic molecule?

Answer 1

The largest organic molecule is probably DNA.

Explanation:

DNA is typically measured in the number of base pairs it contains.

For example the human nuclear genome consists of about `3.2×10^9` base pairs (bp) spread over 24 chromosomes.

The length of the chromosomes ranges from `50 ×10^6` to `260 × 10^6` bp, with an average of about `130 ×10^6` bp.

On average, a base pair is about 340 pm long and has a mass of about 650 u.

So, for the longest human chromosome, the length of the DNA molecule is

`"length" = 260×10^6 color(red)(cancel(color(black)("bp"))) × (340× 10^-12 "m")/(1 color(red)(cancel(color(black)("bp")))) = "0.08 m" = "8 cm"`

The genome of Paris japonica has more than 150 billion base pairs contained in 40 chromosomes.

(from en.wikipedia.org)

That makes it 50 times longer than the human genome!.

Its total length would be about 51 m, and an average DNA molecule would be about 1.3 m long.

The molar mass of 1 bp is about 650 g/mol, so 1 mol of a DNA molecule would have a mass of

`150× 10^9 color(red)(cancel(color(black)("bp"))) × "650 g"/(1 color(red)(cancel(color(black)("bp")))) = 9.8 × 10^13 "g"`

That's about one-fourth the mass of all humans alive!