We started off this week learning about the signal transduction pathway. The basic gist of the signal transduction pathway is that it starts with a ligand that floats on the outside of the cell. That is the first step to the four step process. The next step, reception, occurs when the ligand bonds perfectly to the receptor protein which is located in the cell membrane. Once the ligand is fitted into the receptor protein, transduction is activated. (Step 3). This all now happens in the cytoplasm. A relay protein was activated during reception, and now activates other relay proteins. The activating of multiple proteins, one after another is called amplification. The fourth step is the response. Below is an image of the signal transduction pathway.


The next thing we learned was the phosphorylation cascade. This process is slightly longer with 7 total steps. The phosphorylation cascade starts off with the ligand attaching to the receptor protein, just like it did in the signal transduction pathway. Also like the signal transduction pathway, the second step is the activation of the relay protein. The third step is when the relay protein enters the cell and finds an inactive protein kinase and activates it, rather than another relay protein. The activation of the protein kinase causes it to undergo the process of developing ADP from ATP, which is the fourth step. During this process a phosphate group joins with the protein kinase, which is called phosphorylation. It continues to under go phosphorylation until it reaches the nucleus. (Step 4 and 5). Once the active protein kinase reached the nucleus it activates and inactive transpiration factor which creates the response. This is the last step. Below is an image on the phosphorylation cascade. Screen Shot 2017-01-15 at 3.19.27 PM.png

Our packet also briefly touched on this concept of secondary messengers. This particular pathway starts off just like the signal transduction pathway and the phosphorylation cascade, with the ligand connecting to the receptor protein, followed by the activation of the relay proteins. But,  in step 3, the active relay protein comes in contact with a transport protein, unlike the first two pathways. So now any molecules that comes through the transport protein is acting as a secondary messenger because they are caring messages from relay proteins. The fourth step is when the secondary messengers come in contact with active relay proteins. The fifth step is when the response happens.

Once we could wrap our heads around the ideas of the signal transduction pathway, the phosphorylation cascade, and secondary messengers, we focused back in on cellular respiration. Cellular respiration is basically how lots of energy is created. Cellular respiration occurs in the mitochondria and produces around 32 ATP. The process of cellular respiration is basically just extracting the glucose from the food you eat and digest. Glycolysis, which is the break down of glucose in the cytoplasm, starts off the process. This process creates pyruvate. Next, the pyruvate molecules are transported into the mitochondria. Once the pyruvate enters the mitochondria, it becomes a part of the Kreb cycle. In the Kreb cycle, pyruvate converts its energy into FADH2, ATP and NADH. The product of this cycle is the creation of CO2. In this next step, FADH2 and NADH are used to generate ATP. This part of the process is called electron transport chain. Now the FADH2 and NADH pump protons out of the thylakoid, and then move back to the the thylakoid through facilitated diffusion. ATP is made by adding inorganic phosphate to ADP. This process can also have a similar pathway, but have different results when it is occurring in anaerobic conditions, which is when there is a lack of oxygen. During anaerobic conditions, only two ATP are generated but other byproducts are created, such as lactic acid and alcohol.


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