My notes and thoughts from Biology 111, for Friday, September 19, 2008. The entire series can be found here.
As we took our first exam on Wednesday, September 17, there was no lecture for that day.
We took the first part of class to go over the exam results. I had left the exam feeling very good, figuring I was unsure about and may have missed two or three questions. Turns out, I missed eight.
Out of 64 students in 3 sections, the highest score was a 91, the lowest a 29, and the median 67. I scored an 88.
Doc said not to sweat it too much, as the first exam is the one everyone does a little less well on, unfamiliar territory, etc., and he drops the lowest exam score.
I was rather surprised at about 5 of my 8 incorrect answers, thinking to myself, “What the hell were you thinking???? You know better than that!!!” I really pulled some dumb answers from out of my butt to very simple answers.
One of my incorrect answers though, was the molecular formula of maltose (two glucose molecules bonded together). Now, without thinking, I simply answered with double the formula of glucose, stupidly forgetting to subtract the water molecule from the hydrolysis synthesis that is required to form maltose from two glucose molecules (or any disaccharide from two monosaccharides).
Hence the unforgettable graphic I made subsequently. After making that animation, I will never repeat that mistake.
After going over the exam, we moved on to Chapter 6 – A Tour of the Cell.
Notes for that brief lecture are below the fold.
All living things are composed of one (unicellular organisms) or more (multicellular organisms) cells.
Since a unicellular living thing is made up of just one cell (duh), it means that a cell is a living thing.
The cell is the basic unit of structure and function of all living things.
What is a cell?
Robert Hooke gave us the term “cell”. Looking at the bark of a dead oak tree under a microscope, he observed that the structure he saw looked like little rooms, or cells.
A cell is defined by its plasma membrane, the outer bound that separates the non-living extracellular fluid (ECF – mostly water) from the intracellular fluid (ICF – also mostly water) inside the living cell. The ICF is made up of cytosol, a thick syrupy water solution containing proteins etc.
A cell must exist in ECF, or it will die. As an example, Doc pointed out that the upper layer of skin cells on the body are dead cells, as they are exposed to the air.
Way back in the beginning of the class, one of the properties we said helped to define living things was the need for nutrients and the production of waste. The cell, being a living thing, does indeed require nutrients and produces waste, in an exchange across the plasma membrane between the ECF and the ICF.
A cell must have operating instructions. Those instructions are in the form of a chromosome, and a cell must have at least one chromosome. (Humans have 23 pairs of them.) The instructions are instructions for making proteins. Those proteins are made by ribosomes (though I’m not entirely sure I caught exactly what the doc was saying here, and may have muffed that – corrections welcome).
Doc then drew up our tree again, labeling domains and pointing out how we know that the cell nucleus came after the split off of Bacteria and Archaea.
We ran out of time and had to pick up the differences between Prokarya and Eukarya on Monday.
From whence came the art:
The first image is of our textbook, Biology, Eighth Edition, by Campbell & Reese et al.
Other images by me and are licensed under the Creative Commons Attribution- NonCommercial- Share Alike 3.0 License.