The scores for Exam 1 are now posted on Canvas. There were some issues with the scoring that took a while to sort out – but those have finally been resolved.
You guys did GREAT! The mean was 52.53 (out of 56 points), and the standard deviation was 2.6.
There was one question that didn’t perform well – it was this one, about lipofuscin:
51. What is lipofuscin?
A. Melanin granules in neurons in certain brain regions
B. A microfilament present in axons
C. Brown granules that result from breakdown of blood
D. A harmless cellular pigment that accumulates with age
E. Oxidized fatty acids that accumulate when myelin is digested
The best answer is D – but only 49% of the class answered correctly, so either this point wasn’t stressed enough in lecture, or there was a problem with the question itself, or (most likely) both.
Lipofuscin was discussed on slide 16 of the Nerve Tissue ppt:
It’s is a brownish pigment (that’s the -fuscin part of the name) that contains undigested normal cellular breakdown products, some of which are lipid in nature (that’s the lipo- part). It’s totally harmless, and it accumulates with age.
I can see why you might have chosen E (Oxidized fatty acids that accumulate when myelin is digested), since fatty acids are lipids. However, myelin is only broken down and digested in certain disease states – so it wouldn’t make up the debris in lipofuscin (which is normal). Plus, lipofuscin is seen in all kinds of organs (so myelin can’t be its main component). We didn’t specifically cover those facts, though – so I can’t really hold you accountable for that.
I can also see why you might have chosen D (Brown granules that result from breakdown of blood), since lipofuscin is brown! However, red blood cells only break down and accumulate as a pigment when something is wrong (for example, there’s a big bleed and all that blood needs to be resorbed). However, in hindsight, that wasn’t something I should have expected you to know yet either!
So, since this wasn’t a great question, I added one point to everyone’s score (whether you got it wrong or right). I think this is the most fair way to handle these types of questions because it doesn’t penalize anyone: if you got the question wrong, you get that point back, and if you got it right, you get an extra point.
Let me know if you have any questions. Also, if you’d like to come take a look at your exam at any time, just let me know and we’ll set up a time.