Calculating Percentage Solutions

For some reason, percentage solution calculations cause students some problems. However, hopefully, once you have read this blog post, you should have a good understanding of percentage solutions and how to do the calculations.

If you want to practice your 'science maths', then have a look at Maths4Biosciences

What are percentage solutions?

A percentage solution is an amount or volume of something per 100 ml or 100 g of a solution. It is as simple as that. It is a percentage.

Why are they used?

Percentage solutions are a convenient and easy way to record solution concentrations. One advantage is that you don’t need to know anything about the compound in terms of molecular weight; all you need is the percentage of the required solution.

Why are there three types of percentage solutions?

This is slightly difficult to explain. However, there are three types of percentage solutions:

• Percentage weight by volume (w/v)
• Percentage volume by volume (v/v)
• Percentage weight by weight (w/w)

The percentage weight by volume (w/v) is the number of grams of compound per 100 ml of solution. This type of percentage solution is used when describing the amount of powder in a solution. For example, 5 g of powder made up to a final volume of 100 ml would be a 5% (w/v) solution. Likewise, 2.5 g of powder made up to 50 ml would also be a 5% (w/v) solution, as you would have 5 g in 100 ml.

The percentage volume by volume (v/v) is the number of ml of some liquid per 100 ml of the solution. This type of percentage solution is usually used to describe a solution made by mixing two liquids. For example, 5 ml of a liquid made up to a final volume of 100 ml would be a 5% (v/v) solution. Likewise, 2.5 ml of a liquid made up to 50 ml would also be a 5% (v/v) solution, as you would have 5 ml in 100 ml.

Finally, the percentage weight by weight (w/w). This one is more difficult to understand, but the principles, as explained above, are still valid. A percentage weight by weight (w/w) solution can be the weight of a powder or a liquid made up in a solution to the final weight of the solution. So, for example, 5 g of a powder (or a liquid) made up in a solution with a final weight of 100 g would be a 5% (w/w) solution. Likewise, 2.5 g of a liquid or powder made up to give a solution that weighed 50 g would also be a 5% (w/w) solution, as you would have 5 g of the powder or liquid in 100 g of a solution.

 

If you would like to support my blogging efforts, then please feel free to buy me a coffee at https://www.buymeacoffee.com/drnickm

Additional Resources

•  📗 - Maths and Chemistry Refresher for Life and Biomedical Scientists - Google Play Book Store
•  📗 - Catchup Maths and Stats - (affiliate link)
•  📗 - Catchup Chemistry - (affiliate link)
•  🌎 - You can practice your lab calculations at: https://maths4biosciences.drnickmorris.com/

3d Structure of the GDP G-protein alpha subunit

The movie below shows the 3d structure of a guanosine diphosphate (GDP) bound G protein alpha-subunit.

The small green molecule in the middle is the bound GDP.

https://www.rcsb.org/structure/1TAG

If you would like to support my blogging efforts, then please feel free to buy me a coffee at https://www.buymeacoffee.com/drnickm

Additional Resources

• 📗 - Biochemistry (Stryer) (affiliate link)
• 📗 - Principles of Biochemistry (Lehninger) (affiliate link)

Bovine Rhodopsin

The structure of a G-protein coupled receptor is often shown as:


However, the crystal structure of bovine rhodopsin shows that the seven transmembrane-spanning domains actually form a tight core


J. Mol. Biol. (2004) 342, 571–583 https://www.rcsb.org/structure/1U19

If you would like to support my blogging efforts, then please feel free to buy me a coffee at https://www.buymeacoffee.com/drnickm

Additional Resources

• 📗 - Biochemistry (Stryer) (affiliate link)
• 📗 - Principles of Biochemistry (Lehninger) (affiliate link)

3d Structure - β2AR-T4L

The structure of a G-protein coupled receptor is often shown as:


Which shows a receptor with the N-terminal outside the cell, seven transmembrane-spanning domains, 3 exoloops, 4 cytoloops and a C terminal inside the cell.

However, it is actually more compact, with the seven transmembrane spanning domains forming a tight core.


Lower part = T4-lysozyme in place of cyto 3 Small green molecules = cholesterol; can just make out bound ligand in pocket
Science. 2007 318(5854): 1258–1265. https://www.rcsb.org/structure/2RH1

If you would like to support my blogging efforts, then please feel free to buy me a coffee at https://www.buymeacoffee.com/drnickm

Additional Resources

• 📗 - Biochemistry (Stryer) (affiliate link)
• 📗 - Principles of Biochemistry (Lehninger) (affiliate link)

⍺Gs and Adenylyl Cyclase

The following animation shows αGs interacting with adenylyl cyclase.

The animation is also available as a slightly larger video....

If you would like to support my blogging efforts, then please feel free to buy me a coffee at https://www.buymeacoffee.com/drnickm

Additional Resources

• 📗 - Biochemistry (Stryer) (affiliate link)
• 📗 - Principles of Biochemistry (Lehninger) (affiliate link)

GPCR movement of TM3 and 6

I have been asked for access to a number of the movies I used in the lectures.

The following animation shows the proposed movements of transmembrane spanning domains 3 and 6 for rhodopsin and β2 adrenergic receptors.

It should be noted that other GPCRs may use different methods.

If you would like to support my blogging efforts, then please feel free to buy me a coffee at https://www.buymeacoffee.com/drnickm

Additional Resources

• 📗 - Biochemistry (Stryer) (affiliate link)
• 📗 - Principles of Biochemistry (Lehninger) (affiliate link)

Back to Basics: How do you study?

I have just read a really interesting paper in Science¹, which has a very good write-up in the New York Times (New York Times: "To Really Learn, Quit Studying and Take a Test" - link) on how to study.

I am not going to discuss the findings of the paper here, but instead, I will just mention the major findings of the work.

Basically, Karpicke and Janell¹ looked at how students learn. They have used a scientific approach to look at this with some carefully designed experiments. The authors looked at:

1. Just reading
2. Repeat reading
3. Reading and drawing a concept map whilst consulting the text
4. Reading and then drawing a concept map from memory (no consulting the text)
5. Reading and then writing what you have read (without consulting the original text)

The findings, put in simple terms (as judged by testing the students a week after carrying out the original exercise), was that method 4 and 5 produced the best results. That is, read the text, and then test yourself.

I strongly recommend reading the write-up in the New York Times (link) and then tackling the original paper at Science.

If you would like to support my blogging efforts, then please feel free to buy me a coffee at https://www.buymeacoffee.com/drnickm

Reference:

1. Jeffrey D. Karpicke and Janell R. Blunt "Retrieval Practice Produces More Learning than Elaborative Studying with Concept Mapping" Science 1199327 Published online 20 January 2011 [DOI:10.1126/science.1199327] link