biogeno.us

Today, October 2, 2008, in AP Biology we took notes on the cell cycle. We focused mainly on the phases of cell division. I took my notes on a laptop in order to inject some much needed technology into my otherwise old school day. The class got through all of the phases of cell division, with minimal delays from the slower note takers. The phases of cell division are broken down into two main sections: interphase and mitotic phase. Interphase consists of a first growth phase, a synthesis phase (where the cell duplicates its DNA), and a second growth phase (the cell prepares for division). The mitotic phase consists of prophase, metaphase, anaphase, and telophase. During prophase, the chromatin condenses and appears as sister chromatids. The nuclear envelope breaks down and the centrioles move to opposite poles. The nucleus disappears and the next transitional step, prometaphase, occurs. Prometaphase consists of the mitotic spindle, made of microtubules, attaching to a structure at the centromere of each chromosome called the kintochore.

**A sketch of cell division by falsestartjunkyard on flickr.com

During metaphase the replicated chromosomes line up on the metaphase plate, or the middle line of the cell. The next step is anaphase, in which the sister chromatids separate. The sister chromatids then move to opposite poles of the spindle. The cell begins to lengthen. The next phase of cell division is telophase. The chromosomes go to opposite poles, the daughter nuclei form, and the chromosomes spread out. At that point, the cell division processes are no longer visible under the light microscope. The next step is cytokinesis in which microfilaments condense in the center of the lengthened cell. Cleavage furrows form and the cell splits in two.

What happens when cell division doesn’t work like its supposed to? Malignant cancer cells spread throughout the body because their cell division is unregulated. Cancer cells continue to divide, forming abnormal cells. Cancer is an example of what happens when cell division goes wrong.

cancer cells invading a mouse's cells by mearse on flickr.com

the-cell-cycle-notes-pdf

No Comments »

Today, the class’ objective was to finish the notes of the remaining organelles which consisted of  the cytoskeleton. The teacher intricately discussed the three major protein fibers, microtubules, microfilaments, and intermediate filaments and the class analyzed the structure and the function of these different fibers.

Firstly, the class went over the details of microtubules, which are the thickest of the three fibers, measuring at about 25nm. They are also composed of protein tubulin. They are significant because they are responsible for a cell’s structure and a cell’s movement. They also move chromosomes during cell division with the use of centrioles, which organizes microtubules by guiding these chromosomes. Microtubules are also are able to move through the use of cilia and flagella. Although cilia and flagella both create movement, they function in very disparate ways. For example, cilia moves with an oar-like movement with alternating power and recovery strokes. Flagella has an undulatory movement and it allows small organisms to propel themselves through water. Also, it its important to know that the bending of cilia and flagella is a result of motor proteins such as dynein.

Another similar structure to the microtubules are the intermediate filaments which are quite smaller measuring about 8-12nm. These filaments are built from keratin proteins. Some of their functions are that they are specialized for bearing tension, and they are able to holding things in place within cells.They also reinforce the shape of the cell and they fix the organelle locations. Last of the main protein fibers are the microfilaments which are about 7nm in diameter, making them the thinnest of the three. They are often referred to as actin filaments because they consist of twisted double chains of actin subunits. They are quite essential in muscles cells and by interacting with myosin filaments, the actin filaments create muscle contraction. Actin filaments also constantly form and dissolve which makes the cytoplasm liquid or stiff during movement.

Lastly, the class watched a video that concerned the functions and the actions that occur within a cell. This video elaboarate on the true structre and movement of these organelles within cells and what functions they perform within the body. This really helped to piece together and eplain how sophicated a cell really is with the use of a visual aid.

No Comments »

     Today in class, we began by jotting down our observations for day 7 of our Seed Germination Lab.  At this point the mold is starting to bug us, but we will live with it.  Then we began to login to our email accounts and access the new blog site set up by our genious of a teacher.

    By this point, we WOULD have been eating quesadillas if Miss “Penguin” had brought cheese and tortillas. Therefore, we snacked on “Winnie the Pooh” animal crackers, which were pretty stinking delicious. Thus, quesadilla day will be tomorrow.  As we accessed our new bolg page, we had some difficulties in choosing a general topic for our individual blog names, so we decided on animal species to fit our Biology theme.

     As we got everything set up, our teacher brought up our new set of notes, and it was time to learn. The notes were on Carbon, and more specifically carbon compounds. We learned how Carbon atoms are versatile building blocks that assemble like “Tinker Toys.”

     We also learned about Hydrocarbons and how they differentiate, from methane to cyclohexane. You see, when carbons form together, they can either make straight lines, adding no prefix (ex: ethane/hexane); branches, adding the “iso” prefix (ex: isoheptane); or rings, adding the “cyclo” prefix (ex: cyclohexane). We aslo learned that hydrocarbons are: bound to 4 Hydrogen atoms at most, nonpolar, not soluble in Water, stable, and gases at room temp. Once we finished this short section, the bell rang…. 

No Comments »