# how do you do this please explain steps

0 7. 3 Mice in Group Hwere injected with 2mg kg–1of monoclonal antibody. The monoclonal antibody was in a solution of concentration 500mg dm–3 Calculate the volume of antibody solution that the scientists would have injected into a 23g mouse. Give your answer in dm3 and in standard form. [2 marks

bio a level q
First, we should find how many mg we need for the mouse. We do this using our dose of 2mg/kg and our mouse’s bodyweight of 23g. We need to make sure our units are the same, so we can use 23x10-3kg for the mouse’s weight. Multiply the dose with the weight for total mg.

Now that we have total mg, we need to calculate what volume of the antibody we need. We do this by dividing the total mg by the concentration.

Hopefully this helps you follow it through - have a go and see what you get!
(edited 3 months ago)
Original post by TheVirtualPhoton
First, we should find how many mg we need for the mouse. We do this using our dose of 2mg/kg and our mouse’s bodyweight of 23g. We need to make sure our units are the same, so we can use 23x10-3kg for the mouse’s weight. Multiply the dose with the weight for total mg.

Now that we have total mg, we need to calculate what volume of the antibody we need. We do this by dividing the total mg by the concentration.

Hopefully this helps you follow it through - have a go and see what you get!

Thanks so much
Original post by sisterr
Thanks so much

I have a question
Why do we times the 23g and the 2mg/kg-1
Why do we use the mouses body weight.

This is the only step that still confuses me
A dose in mg/kg reflects how many mg of drug is given per killgram of bodyweight. This is often how drugs are given so that animals/people of different sizes are receiving the same dose, with a different total mg reflecting a different total amount of body tissue. So for example a 1kg rabbit would receive 2mg of antibody but a 5kg dog would receive 10mg, both at 2mg/kg.

I’m not sure I’ve explained that the best but hopefully it helps?
Original post by TheVirtualPhoton
A dose in mg/kg reflects how many mg of drug is given per killgram of bodyweight. This is often how drugs are given so that animals/people of different sizes are receiving the same dose, with a different total mg reflecting a different total amount of body tissue. So for example a 1kg rabbit would receive 2mg of antibody but a 5kg dog would receive 10mg, both at 2mg/kg.

I’m not sure I’ve explained that the best but hopefully it helps?

So helpful I understand it now.
Thank you again
I would urge anyone reading this to practice working with units. It saves you so much headspace!

Forget the numbers - just do a little algebra to work out which unit you need (dm3 in this case) and write down all the units you have to play with.

Original post by TheVirtualPhoton
First, we should find how many mg we need for the mouse. We do this using our dose of 2mg/kg and our mouse’s bodyweight of 23g. We need to make sure our units are the same, so we can use 23x10-3kg for the mouse’s weight. Multiply the dose with the weight for total mg.

Now that we have total mg, we need to calculate what volume of the antibody we need. We do this by dividing the total mg by the concentration.

Hopefully this helps you follow it through - have a go and see what you get!

Hi ! I would also want to ask why divide the mass of the antibody by 500 which is the concentration, how does it give you the dm3 needed ?
Original post by cantankerous-gai
Hi ! I would also want to ask why divide the mass of the antibody by 500 which is the concentration, how does it give you the dm3 needed ?

Because:

1/dm-3 = dm3