Life Sciences lab classes explained

Dilutions   tend to worry first years! These come up a lot in 107 and 109. I think a lot of you just don't get along with the terminology that is used when people talk about dilutions.  Let me try to clarify things a little... Sometimes, dilutions are talked about in terms of  ratios . i.e. a  1:2 dilution  or a  1:3 dilution .  Remember that  ratios   tell you  how much of one thing there is in comparison to another thing .  So, for a   1:2 dilution   (which could also be written as a  '1 to 2 dilution' ) , this means that there will be one 'part' of one thing and two 'parts' of a second thing, and therefore three 'parts' in total.  Example: If you were asked to make a  1:2 dilution  of a   60 mM NaCl   solution, and the final volume required was  180 mls ,  then you would take   60 mls   of your   60 mM NaCl  solution and mix it with   120 mls  of...

Struggling with the Cytochrome C question in your 109 workshop 2.... Then this post is for you! Let me show you how I would do this question: The Question: A lot of information followed by... The Biochemist prepared 2.5 ml of cytochrome c (Mr = 12000) in water (solution A). It was then diluted by addition of 1.0 ml solution A to 9.0 ml water to give solution B. Finally 2.0 ml solution B was diluted 20-fold (i.e. the ratio of the final volume to the initial volume is 20) with water to give a final solution C which was determined to have a concentration of 0.15 mg/ml. Before I even look at the questions, I would draw out the information provided in a kind of flow diagram: Ok, now I have a clear idea of what I have been told, I will look at the questions: 1)  What volume of water was added to give the 20-fold dilution of cytochrome C in the preparation of solution C? So, we know that we are talking about the second dilution step, where 2.0 ml of solution B was taken and dilu...