Some Questions from Students before Exam 1, October 1, 2015

Joseph Dixon ♦ October 1, 2015 ♦ Leave a comment

I’ve had quite a few students drop in for office hours and another bunch have emailed me questions.

Q:  Can you further clarify what chemical score is and how your derive it.  Specifically can you explain the practice question (#18) on the exam practice test. Why is is about 70% as good as egg protein?

Answer:  Thank you for the questions:  I don’t have the practice exam in front of me but I think the full answer will help:  The chemical score is a method that uses the amino acid profile of a test protein to predict whether it is high quality protein (support maximal growth in children for example).  It is one of many methods (I can think of 5 or 6).  You derive the chemical score by knowing what the amino acid composition of the test protein is. You take the essential amino acid in lowest relative amount in the test protein and compare it to that same amino acid in egg protein (the highest quality protein).

Test protein (ex: Algal protein) = tryptophan is 3 grams/100 grams protein
Egg protein =                              tryptophan is 5 grams/100 grams protein

Chemical score is 3/5 x100 = 60%;  The algal protein is 60% as good as egg protein!
A good thing about chemical score –  it demonstrates that the protein requirement is really a requirement for essential amino acids.  And it is simple, I think.
A bad thing – chemical score doesn’t account for other factors like digestibility!

Q:  Also why is fructose digested differently (diffusion) than glucose and galactose?

Answer:  You mean absorbed differently!  I don’t know why!  Sorry!  It is one of those things!

Q:  “I have a general question about the exam. I  have been reviewing the powerpoint presentations and trying to look over the textbook since Monday and I still feel overwhelmed with the amount of information. I am following the review guide but I realize there is a lot of additional information in the book and slides not mentioned in the review guide. I am not a science major and all this information is new for me as I have not taken a science related class in years. Do you recommend we mainly use the review as a guide to prepare and study the other info on the slides in less detail? Grasping everything seems almost impossible but yet I don’t want to miss out on important concepts for the exam. Thank you.”

Answer:  Thank you for your question!  I have received this same question from many students.  The best way to study is to print out the study guide and go through the Powerpoint slides and cross reference the information you see on the slides with the study guide.  I did say a few times that you should read the book but do not study all the terms that are defined.  You do not have to know structures beyond the fact that polysaccharides are long chains of glucose.  And proteins are chains of amino acids. You do not have to regurgitate the diagrams (except for the Progression to Type 2 diabetes, for which there is an example in the practice exams Folder). You should try to get the basic messages from the diagrams.  Good luck!

Q:  Is the RDA for protein the same as the protein requirement?   I know the RDA for protein is 0.8 grams of protein per kg body weight. 

Answer:  This is explained in the PowerPoint slide that gives the method how they went from the EAR for protein to the RDA for protein.  The protein requirement is an average, and the RDA is for 98% of all healthy people–so they are not the same!