How much does a single cell weigh?

10 January 2017

Question

Tony asks: Having heard a segment on your recent Q&A show in which it was estimated that the human body makes 5 million cells a second, I started to wonder how much a cell would weigh and how I might work it out. I then realised different types of cells might have different weights and sizes and would be renewed at different rates. Any ideas?

Answer

Chris Smith put Tony's question to Cambridge University's Maud Borensztein...

Maud - The body is made up of very different types of cells. If you think about a red blood cell, for example, that is a very tiny cell compared to nerve cells. Nerve cells can reach lengths over a metre so it’s a bit difficult to do an approximation of the weight of a single cell.

Chris - Shall we have a straw poll? James - how much do you think a cell weighs?

James - It depends which cell you’re talking about Chris, I suppose.

Chris - What cell would you like to estimate?

James - Red blood cell.

Chris - Okay, how much does a red blood cell weight?

James - I would say about… a thousandth of a gram.

Chris - One milligram. James is going for a milligram. What do you think Stuart - does that sound within the realms of of possibility?

Stuart - Well, you said 3.7 trillion earlier so I’ll try and divide that by…

Maud - Yeah. In between 3.7 and 30 trillion.

Stuart - I’m going to go for a bit less than a gram. Round it to one - physicist approach.

Chris - Maud, put us out of misery then.

Maud - We can more or less do an approximation of under one nanogram.

Chris - A nanogram?

Maud - Yes, a nanogram. So we can imagine…

Chris:: So, James is a millionfold out then?

Maud:: Yeah, exactly. We can imagine to do a gram of cells we would need nearly a billion.

Chris:: Wow! That quite light isn’t it?

Maud - Yeah.

Chris - But you did say, and James was crafty he said which sort of cell are talking about because some cells, like you say, are muscle cells - a big muscle cell. Some of them are a foot long aren’t they?

Maud - A muscle cell will be a lot easier. Even like an adipose cell, fat cells for example. There’s a question of size but also a question of weight. A fat cell will be lighter than muscle cells even if both are quite big.

James - Because I imagine, as you say Chris, the muscles of your quadriceps or your hamstrings - a foot long - got to be up there 10 or 20 grams, probably more isn’t it?

Chris - I would think probably because that’s one of the biggest muscles you’ve got apart from you gluteal muscles in your bum. They are, I think, the ‘king’ muscle, aren’t they?

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