To everything there is a time and a purpose

So this is the end of the semester, and the end of my time with you in AP Biology. There is so much more that I would have liked to have covered, but unfortunately time is of the essence and we just didn't have enough together. I hope that you feel more confident in your ability to problem solve, more connected to your fellow organisms, and above all, have a new sense of awe at the miracle that is life. Above all, I hope you have lots of questions that will continue to steer you in the quest for new answers. Life is a quest that should never end. Lift your heads up from your technology long enough to see some of it.

I found out on Friday that you will also be my last AP Biology classes at Magna Vista. I will not be teaching any additional AP Biology classes in the spring, and the odds are that I won't be teaching any in the future. I do not completely know the reason why, but it is unimportant. What is important is that you were a great group of students and fantastic human beings. I count myself lucky to have met you and I won't abandon you in the spring as your actual AP test looms. I will be holding voluntary weekend review sessions at the Ridgeway Public Library. Complete this form if you are interested in either being contacted for the review sessions or joining a Google review group. Much peace and happiness to you and if you need a letter of recommendation, please feel free to drop by my classroom!

To Life!

Genetics - your own personal code

Deep inside the nuclei that are found in most of the cells of your body is a long strand of a molecule that is the chemical blueprint for your entire physical form. While external influences may affect what parts of this code are read, or may even change the code, this code is still copied every cellular generation. When these copies, found in discrete units called chromosomes, are expressed, they tell a tale of you - blue eyes, brown hair, PTC taster, tongue roller, lactose intolerant you...

The study of genetics is where we are now - we are looking at how the specific traits that collectively comprise you are inherited and expressed. The traits that you inherit come as a split set - half from your mom and half from your dad, divided from their own original code by a process called Meiosis, which results in the formation of gametes or sex cells. In the male, these cells containing only half of the chromosomes of a body cell will be carried by the sperm. In the female, the mother's half of the chromosome pool is laying, waiting, inside a round, expectant egg. Once fertilization occurs, it is only a short matter of time before the two sets of DNA are recombined, homologous pairs joining up to once again create a new living being. There are many ways to make a baby, but the code is still entirely new each time. Variation is the spice of life.

From simple Mendellian genetics or royal sex linked traits to complex incompletely dominant trihybrid crosses and epistatic inhibitors, you are gonna become genetic pros. This is cool stuff, and the power of probability becomes very real. Forget those poker cards and dice - this is the ultimate game of chance!

Thoughts and Suggestions for Cellular Energetics...Cellular Respiration

Just Breathe......

Everyone knows we breathe in Oxygen and exhale Carbon Dioxide that was released from our cells. But most people don't understand just why we need that Oxygen for life. It's primary role can be found deep inside the Mitochondria, in one of the critical stages of Cellular Respiration.

Glucose produced from the process of Photosynthesis will be come an essential reactant to accompany Oxygen in the energy-releasing phase of the our metabolism. Remember, it's not energy creation - it's energy release from a chemical storage unit constructed by the autotrophs. The beginning stage of cellular respiration is Glycolysis, and it tells an ancient tale of the struggle for energy. Since Glycolysis occurs in the cytoplasm, a region of the cell found in all living things, this represents the most likely source of energy for even the most primitive of organisms billions of years ago. Glycolysis is the breakdown of a 6-Carbon Glucose molecule into two 3-Carbon Pyruvate molecules. Some energy is given off during this breakdown, and a very small contribution is made to the energy fund for the body.

 

Following this process, the Pyruvate will either move to the Krebs Cycle (aerobic respiration) or down the anaerobic pathway that leads to fermentation and the buildup of lactic acid or alcohols. If we're lucky and have done our breathing exercises, the Krebs Cycle will happily accept the Pyruvate, which have conveniently been converted to Acetyl Co-A right before they enter the cycle. The Krebs Cycle itself does not generate much energy in the form of ATP, however it creates some wonderfully powerful molecules of NADH+ and FADH2+ which will slide on down to the Electron Transport Chain. 

Here's where the big money can be found. The Electron Transport Chain functions much like that seen in Photosynthesis (hmmmmmmm, verrryyy interesting! I wonder why...). Electrons are passed along the chain, creating a strong negative force which helps to pull Protons to one side of the membrane. Because the protons create an imbalanced gradient, they will move passively down the gradient through a fantastic protein structure known as an ATP synthase. This little molecule spins like a water wheel, happily slapping Phosphate groups onto ADP molecules, and in the process, making a total of about 32 ATP per molecule of Glucose. What a bargain!

 So why do we need Oxygen again? It turns out that as all of those protons (H+) are being shuttled around, some of them must come out of the system to keep the gradient effective. These H+ bind to the Oxygen we breathe in and make water, which will then exit our cells. So, the water we drink comes from the air we breathe, and the air we breathe comes from the water we drink. Cool, huh?

Thoughts and Suggestions for Cellular Energetics...Photosynthesis

I recognize that Cellular energetics was quite the wild ride for you guys. Based on the results of the recent Cellular Respiration test you took, I believe that you need to wade back into it some more on your own to be sure you really understand and grasp how Cellular Respiration is conducted and how it connects to Photosynthesis. Remember, the two processes are linked in a great cycle, and if you stop one long enough, the other will stop as well. The reactants and the products are the links that tie these two together, so let's quickly touch on that before I recommend some sites to review with. We'll start with Photosynthesis in this post.

Remember that Photosynthesis is a two stage process. The light dependent reaction is essential for creating energy for the second stage. The light dependent reaction converts solar energy into chemical energy in the form of NADPH+ and ATP. It does this through the use of light capturing pigments, and the movement of excited electrons through the electron transport chain embedded in the membrane of the thylakoids.  These two sources of energy are going to move into the open space in the Chloroplast, the Stroma, to power up the Calvin Cycle - the sugar production phase.

 The Calvin Cycle occurs in the open stroma of the Chloroplast, and is the site of Carbon Fixation. Carbon Dioxide (CO2) is taken in through the stomates of the plant and moves to the chloroplasts, where it is captured by a molecule of that ever prevalent 5 Carbon molecule of Rubisco. This new 6-Carbon molecule will be split into two 3-Carbon molecules, which are molecules reduced using the energy carried by the NADPH+ and ATP into G3P. One of these molecules of G3P will be used as a building block for Glucose, while the other G3P will combine with the 2-C remains to form a regenerated molecule of Rubisco. It will take 6 cycles of this process to make one Glucose molecule.

In the earliest stages of Photosynthesis, H20 is split to free up electrons needed for the electron transport chain and to create a Proton gradient to drive ATP synthase. The Oxygen will be released as that happy byproduct needed by most cells for respiration. The electrons will move on down the road on the ETC. The Oxygen will reappear as the reactant in the next system: Cellular Respiration. Thus the cycles are linked and you should be able to describe the inputs and outputs of both stages.