Energy Flow in Organisms

In this unit we learned about enzymes, the digestive system and cell respiration. I learned that enzymes are proteins that have active sites to let certain subunits come in and transform into a product. Enzymes have a specific ph level and optimal temperature. Some are most active in basic environments and some in acidic environments. When an enzyme is in a different environment, such as too much heat, it can denature and change its form.

We also learned about the digestive system and its function from the mouth to the rectum and out the body. We did an activity where we got a bagel and put it through the digestive system. Each person in the class was an organ, enzyme or another important part of digesting food. We went step by step through every part of the digestive tract until we wee at the rectum to find that the bagel was mushed and digested into a wet mess (thank god it was in a zip lock bag). We learned about digestive enzymes such as salivary amylase which digests carbohydrates such as starch, pancreatic amylase, lipase and nucleases digesting food in the small intestine, and pepsin that digests protein.

We also learned about cell respiration. Cell Respiration is the process by which chemical energy of food molecules is released and partially captured in the form of ATP. Carbohydrates, fats, and proteins can be used as fuels for cell respiration. Glycolysis,  and if oxygen is available, Krebs cycle and electron transport chain (oxidative phosphorolation). If oxygen is not available fermentation begins after glycolysis. Glycolysis occurs in the cytoplasm and does not need oxygen. The 6 carbon molecule glucose is broken down in the investment and pay off phase into two, three carbon molecules called pyruvate. Glycolysis uses 2 ATP's to produce 4ATP's. the net gain of ATP's is 2. An NADH + H is formed in glycolysis (substrate level phosphorolation). The intermediate step before reaching Krebs cycle occurs after glycolysis and oxidizes the pyruvate molecules. A carbon from each pyruvate releases a CO2 and forms 2, 2 carbon molecules called Acetyl CoA. An NAD+ is reduced to form NADH for each molecule. This occurs in the matrix of the mitochondria. The next step is the Krebs cycle which is substrate level phosphorolation and occurs in the matrix. Also known as the Citric Cycle, the cycle generates a pool of chemical energy from the oxidation of pyruvate. The 2 carbon molecule from the intermediate step joins a free floating 4 carbon molecule created through evolution and makes a 6 carbon molecule called citrate (enzyme catalyzed reaction). Citrate goes through the cycle and loses 2 carbons releasing as CO2 making a 4 carbon molecule. During this cycle, NAD+ reduces to NADH three times for each molecule. 1 ATP is made and 1 FADH2 is made for each molecule. A total of 6 NADH + 6H, 2 ATP and 2FADH2 is made in Krebs Cycle. From glycolysis, int. phase and krebs cycle, a total of 10 NADH, 2FADH2 and 4ATP are created. The next 34 ATP are produced in the ETC and Chemiosmosis. The cristae contain protein complexes where the electron carriers, NADH and FADH2 drop off and release a pair of electrons. Each electron pair in transferred from a high level of energy to a low energy level. In this process, energy is released during the redox reactions to make ATP. Electrons provide the energy to pump protons across the membrane into the inter membrane space creating a H+ gradient. The matrix becomes more basic while the inter-membrane space becomes more acidic. The protons want to diffuse back into the matrix going from a high concentration to a low concentration. Chemiosmosis occurs as the hydrogens act as a generator and move through the enzyme ATP synthase into the matrix. ATP synthase has a rector that spins and creates electrical movement joining ADP and Phosphate substrates to make an end product of ATP. For each NADH, 3ATPS's are made. For each FADH2, 2 ATP's are made. This makes an average of 34 ATP's made in chemiosmosis. A total amount of ATP's made from all steps average to 38 ATP's. Electrons join with oxygen in ETC and attract protons to form H2O or water. As shown, oxygen drives this process.  

   

Forensics

             In this unit we learned about forensics and how to diagnose a case. We learned different organs and anatomy of the body. We did exercises where we are given information of how the carcass was found and as scientific thinkers, we find how the person died and what happened in his body that caused the person to stop functioning. We had visual aids such as a plastic body with organs and bones to guide us to where the body was hit. You can see my Forensic Quiz on my website for an example of a case done. 

Cancer!

This week we started a new unit on cancer! We were assigned a six page research paper on a specific type of cancer of our choice and watched some videos giving background on how cancer forms and spreads. 

         Cancer results from a series of molecular events that fundamentally alter the normal properties of cells. In cancer cells the normal control systems that prevent cell overgrowth and the invasion of other tissues are disabled. These altered cells divide and grow in the presence of signals that normally inhibit cell growth; therefore, they no longer require special signals to induce cell growth and division. As these cells grow they develop new characteristics, including changes in cell structure, decreased cell adhesion, and production of new enzymes. These heritable changes allow the cell and its progeny to divide and grow, even in the presence of normal cells that typically inhibit the growth of nearby cells. Such changes allow the cancer cells to spread and invade other tissues.

        The abnormalities in cancer cells usually result from mutations in protein-encoding genes that regulate cell division. Over time more genes become mutated. This is often because the genes that make the proteins that normally repair DNA damage are themselves not functioning normally because they are also mutated. Consequently, mutations begin to increase in the cell, causing further abnormalities in that cell and the daughter cells. Some of these mutated cells die, but other alterations may give the abnormal cell a selective advantage that allows it to multiply much more rapidly than the normal cells. This enhanced growth describes most cancer cells, which have gained functions repressed in the normal, healthy cells. As long as these cells remain in their original location, they are considered benign; if they become invasive, they are considered malignant. Cancer cells in malignant tumors can often metastasize, sending cancer cells to distant sites in the body where new tumors may form.  
               Alterations in the same gene often are associated with different forms of cancer. These malfunctioning genes can be broadly classified into three groups. The first group, called pro to-oncogenes produces protein products that normally enhance cell division or inhibit normal cell death. The mutated forms of these genes are called oncogenes. The second group, called tumor suppressors makes proteins that normally prevent cell division or cause cell death. The third group contains DNA repair genes, which help prevent mutations that lead to cancer.

              Proto-oncogenes and tumor suppressor genes work much like the accelerator and brakes of a car, respectively. The normal speed of a car can be maintained by controlled use of both the accelerator and the brake. Similarly, controlled cell growth is maintained by regulation of proto-oncogenes, which accelerate growth, and tumor suppressor genes, which slow cell growth. Mutations that produce oncogenes accelerate growth while those that affect tumor suppressors prevent the normal inhibition of growth. In either case, uncontrolled cell growth occurs. Oncogenes are altered versions of the proto-oncogenes that code for these signaling molecules. The oncogenes activate the signaling cascade continuously, resulting in an increased production of factors that stimulate growth. RAS is an oncogene that normally functions as an “on-off” switch in the signal cascade. Mutations in RAS cause the signaling pathway to remain “on,” leading to uncontrolled cell growth. About thirty percent of tumors — including lung, colon, thyroid, and pancreatic carcinomas — have a mutation in RAS.
 
 

We also learned about the suppressor gene P53. Upon cellular stress, particularly that induced by DNA damage, p53 can arrest cell cycle progression, thus allowing the DNA to be repaired; or it can lead to apoptosis. These functions are achieved, in part, by the transactivational properties of p53, which activate a series of genes involved in cell cycle regulation. In cancer cells bearing a mutant p53, this protein is no longer able to control cell proliferation, resulting in inefficient DNA repair and the emergence of genetically unstable cells. The most common changes of p53 in human cancers are point missense mutations within the coding sequences of the gene.

Immune System Quiz

An important defense against disease in vertebrate animals is the ability to eliminate, inactivate, or destroy foreign substances and organisms. Explain how the immune system achieves all of the following.

1. Provides an immediate nonspecific immune response
2. Activates T and B cells in response to an infection
3. Responds to a later exposure to the same infectious agent
4. Distinguishes self from nonself 

 The immune response is how your body recognizes and defends itself against bacteria, viruses, and substances that appear foreign and harmful.The immune system protects the body from possibly harmful substances by recognizing and responding to antigens. Antigens are substances (usually proteins) on the surface of cells, viruses, fungi, or bacteria. Nonliving substances such as toxins, chemicals, drugs, and foreign particles (such as a splinter) can also be antigens. The immune system recognizes and destroys substances that contain antigens.Your own body's cells have proteins that are antigens. These include a group of antigens called HLA antigens. Your immune system learns to see these antigens as normal and usually does not react against them. 

1. 

The immune system protects you from dying from infection with layered defenses of increasing specificity. 

Physical barriers prevent pathogens such as bacteria and viruses from entering the body. 

If a pathogen breaches these barriers, the innate immune system provides an immediate, but non-specific response. Innate, or nonspecific, immunity is the defense system with which you were born. It protects you against all antigens. Innate immunity involves barriers that keep harmful materials from entering your body. These barriers form the first line of defense in the immune response. Examples of innate immunity are cough reflex, enzymes in tears and skin oils, skin, and stomach acid. Innate immunity also comes in a protein chemical form, called innate humoral immunity. Examples include the body's complement system and substances called interferon and interleukin-1 (which causes fever). If an antigen gets past these barriers, it is attacked and destroyed by other parts of the immune system.

2. The immune system includes certain types of white blood cells. It also includes chemicals and proteins in the blood, such as antibodies, complement proteins, and interferon. Some of these directly attack foreign substances in the body, and others work together to help the immune system cells.

Lymphocytes are a type of white blood cell. There are B and T type lymphocytes.

• B lymphocytes become cells that produce antibodies. Antibodies attach to a specific antigen and make it easier for the immune cells to destroy the antigen.

• T lymphocytes attack antigens directly and help control the immune response. They also release chemicals, known as cytokines, which control the entire immune response.

As lymphocytes develop, they normally learn to tell the difference between your own body tissues and substances that are not normally found in your body. Once B cells and T cells are formed, a few of those cells will multiply and provide "memory" for your immune system. This allows your immune system to respond faster and more efficiently the next time you are exposed to the same antigen. In many cases it will prevent you from getting sick. For example, a person who has had chickenpox or has been immunized against chickenpox is immune from getting chickenpox again. 

Here you can watch a video on Immune Response! 

The immune system includes specialized white blood cells, called lymphocytes that adapt themselves to fight specific foreign invaders. These cells develop into two groups in the bone marrow.

From the bone marrow, one group of lymphocytes migrates to a gland called the thymus and become T lymphocytes or T cells. Within the thymus, the T cells mature under the influence of several hormones.

The T cells mature into several different types, including helper, killer and suppressor cells. T cells are responsible for cell-mediated immunity. This type of immunity becomes deficient in persons with HIV, the virus that causes AIDS, because HIV attacks and destroys helper T cells.

The other group of lymphocytes, B lymphocytes or B cells, mature and develop within the bone marrow itself. In that process, they achieve the ability to recognize specific foreign invaders. From the bone marrow, B cells migrate through the body fluids to the lymph nodes, spleen and blood. B lymphocytes provide the body with humoral immunity as they circulate in the fluids in search of specific foreign invaders to destroy.

3. The immune system creates memory B cells that remember the foreign substance and it begins immune responses to fight off the infectious agent. These memory cells are able to recognize the threatening pathogens and are able to quickly and easily attack and kill. A primary immune response happens the first time that the body encounters a specific antigen. It takes several days to begin and one or two weeks to reach maximum activity. A secondary immune response occurs if the body encounters the same antigen at a later time. It takes only hours to begin and may peak within a few days. The invader is usually removed before it has a chance to cause disease. This is because some of the cloned T _C cells and B cells produced during a primary immune response develop into memory cells. These cells immediately become activated if the antigen appears again. 

4.  At the heart of the immune response is the ability to distinguish between "self" and "non-self." Every cell in your body carries the same set of distinctive surface proteins that distinguish you as "self." Normally your immune cells do not attack your own body tissues, which all carry the same pattern of self-markers; rather, your immune system coexists peaceably with your other body cells in a state known as self-tolerance. This set of unique markers on human cells is called the major histocompatibility complex (MHC). There are two classes: MHC Class I proteins, which are on all cells, and MHC Class II proteins, which are only on certain specialized cells. 

Any non-self substance capable of triggering an immune response is known as an antigen. An antigen can be a whole non-self cell, a bacterium, a virus, an MHC marker protein or even a portion of a protein from a foreign organism. The distinctive markers on antigens that trigger an immune response are called epitopes. When tissues or cells from another individual enter your body carrying such antigenic non-self epitopes, your immune cells react. This explains why transplanted tissues may be rejected as foreign and why antibodies will bind to them.

Erythropoietin Hormone Podcast

Erythropoietin 

https://soundcloud.com/user605460877/erythropoietin-hormone

Here is my podcast on EPO

Hormone Podcast

Erythropoietin, also known as EPO, is a glycoprotein hormone that controls erythropoiesis, or red blood cell production. It is a protein signaling molecule for red blood cell precursors in the bone marrow. 

It is produced by interstitial fibroblasts in the kidney. It is also produced in perisinusoidal cells in the liver. While liver production predominates in the fetal and perinatal period, renal production is predominant during adulthood. In addition to erythropoiesis, erythropoietin also has other known biological functions. For example, it plays an important role in the brain's response to neuronal injury. EPO is also involved in the wound healing process.

Erythropoietin is an essential hormone for red cell production. Without it, definitive erythropoiesis does not take place. Under hypoxic conditions, the kidney will produce and secrete erythropoietin to increase the production of red blood cells by targeting CFU-E. Erythropoietin has its primary effect on red blood cell progenitors and precursors (which are found in the bone marrow in humans) by promoting their survival through protecting these cells from apoptosis. EPO is water soluble.

The burst-forming unit-erythroid (BFU-E) cells start erythropoietin receptor, encoded by the EPOR gene, expression and are sensitive to erythropoietin.

Erythropoietin levels in blood are quite low in the absence of anemia,  However, in hypoxic stress, EPO production greatly increases. EPO is produced mainly by peritubular capillary lining cells of the renal cortex, which are highly specialized, epithelial-like cells. It is synthesized by renal peritubular cells in adults, with a small amount being produced in the liver. Regulation is believed to rely on a feedback mechanism measuring blood oxygenation. Constitutively synthesized transcription factors for EPO, known as hypoxia-inducible factors , are hydroxylated and proteosomally digested in the presence of oxygen.

Works Cited

Erythropoietin, http://www.medicinenet.com/erythropoietin/article.htm

Erythropoietin Test, http://www.nlm.nih.gov/medlineplus/ency/article/003683.htm