Post #1:

Quote:

"Some researchers believe that Type 1 diabetes is an autoimmune disease -- the body's natural defense system incorrectly identifies certain cells as outside invaders and sets out to destroy them. In the case of Type 1 diabetes, the cells that fall victim to this biological friendly fire are the precise cells in the pancreas responsible for insulin production."

Connection:

This quote mentions several different topics that were covered in the AP biology curriculum this year. First, it talks about Type 1 diabetes as an autoimmune disease. An autoimmune disease is one in which the immune system attacks "self" cells. Normally, the antigen receptors on the B-cells and other cells of the immune system distinguish between foreign andibodies and the body's own cells. In a normally functioning immune system, the varying antigen receptors in the plasma membranes of the body's B-cells each match a specific antigen that is found in a foreign invader. Once an antigen receptor comes across a matching antigen in, it triggers the B-cell to multiply and create two different types of cells; Memory B-cells, and Plasma cells. The plasma cells produce and release many copies of the antibody which cooresponds to the detected antigen. These antibodies then attach to the antigens on the invader's surface and can, among other things, "weigh down" or clumbing together the invading enemies so that it is easier for macrophages to engulf them, act as "warning flags" to encourage endocytosis by macrophages, or the antibodies can simply incapacitate the invader by overwhelming and "smothering" it and not allowing anything to reach its surface. The Memory B-cells come into play when the invader tries to infect the body in the future. The presence of Memory B-cells means that there are more antigen receptors for a given invader. Therefore, the invader can more quickly be identified, and the immune response can occurr much more rapidly upon later infection by the invader. This is the Humoral Immune response.

Normally, antibodies are only produced to attack foreign invaders. However, "Patients with autoimmune diseases frequently have unusual antibodies circulating in their blood that target their own body tissues."(1). In other words, the immune system, which normally differentiates foreign organisms from the body's own cells has an immune response that targets specific cells of the human body. Such autoimmune diseases can wreak havok on the body, and in the case of Type 1 diabetes, the attack destroys the cells responsible for insulin production, the Pancreatic Beta Cells. This leads to the second topic mentioned in the quote, and ties back to the overall theme of regulation; the endocrine system, specifically the regulation of blood glucose levels by pancreatic hormones. It is the job of the pancreas to ensure that blood glucose levels remain relatively constant. To do this, it releases the hormones insulin and glucagon to, respectively, lower or raise blood glucose levels. When blood glucose levels dip below or rise above a certain level, the pancreas releases the apropriate hormone to address the issue. For example, "After a meal, the blood glucose level rises. In response to the increased glucose level, the pancreas normally releases more insulin into the bloodstream to help glucose enter the cells and lower blood glucose levels after a meal."(2). Besides facilitating the uptake of glucose by the cells of the body, insulin also triggers cells in the liver and muscles to store the glucose as glycogen. This lowers overall blood sugar levels. Glucagon has the opposite effect. It stimulates the storage cells in the liver to release stored glycogen as glucose into the bloodstream in order to raise blood glucose levels when they dip too low. Through this process, the pancreas normally keeps the blood glucose level in the blood relatively consistent. However, in the case of Type 1 diabetes, the body's immune system has attacked the beta cells that produce the insulin in the pancreas, and without a means to produce insulin, the pancreas can no longer regulate the levels of glucose in the blood.

This loss of Regulation can have serious health complications, including blindness, kidney failure, heart disease, and many more,(2). However, as Dr. Sharon Moalem discusses, there may have been some evolutionary advantage for having what is now a trait that causes disease in the past because it allowed previous generations to survive a more severe evolutionary pressure that no longer applies. I find this notion to be very interesting, and it makes what would seem to be very illogical (evolutionary pressure for a dammaging trait) make perfect sense evolutionarily. This idea that Dr. Moalem puts forward also makes me wonder what other genetic diseases might have experienced a similar situation which would explain why they evolved dispite their apparent lack of benifits.

Works Cited:

  1. "Autoimmune Disease Definition - Medical Dictionary Definitions of Popular Medical Terms Easily Defined on MedTerms." MedicineNet.com. Web. 03 June 2010. <http://www.medterms.com/script/main/art.asp?articlekey=2402>.
  2. "Diabetes (Diabetes Type 1, Diabetes Type 2) Causes, Symptoms, and Diagnosis on MedicineNet.com." MedicineNet.com. Web. 03 June 2010. <http://www.medicinenet.com/diabetes_mellitus/article.htm>.



Post #2:


Quote:

"Folic acid or folate, depending on its form, is just as important to human life. Folate gets its name from the Latin word for 'leaf' because one of the best sources for folate is leafy greens like spinach and cabbage. Folate is an integral part of the Cell growth system, helping the body to replicate DNA when cells divide."

Connection:

This quote connects to several topics in our AP biology curriculum. For example, folic acid, (also known as vitamin B 9), is an essential nutrient, and vital for human health and growth. Like any vitamin, folic acid is needed in small ammounts by the body in order to function normally, and because most vitamins cannot be produced in the body, they must be obtained through diet. There are many vitamins that are crucial to human life, and they come in two main catagories; fat soluble and water soluble vitamins. Fat soluble vitamins include vitamins A, D, E, and K. Water soluble vitamins include B and C vitamins, such as folate,(2). (see fig.1).

(fig.1) Essential Nutrients; vitamins and minerals (1)
Nutrient
RDA
UL*
Experimental high dose
Potential toxic effects
Main function
Best food sources
Vitamin A
Men: 3,000 IU
Women: 2,300 IU
10,000 IU
3,000-10,000 IU
Liver toxicity, dry rough skin and cracked lips, irritability, headache, birth defects
Healthy immune barriers and epithelial tissue, growth, reproduction, bone and red blood cell formation, vision
Foods high in beta carotene, fortified foods, liver
Beta carotene (as mixed carotenoids)
N.D.
N.D.
5,000-25,000 IU
Possibly increased lung cancer in smokers, harmless orange skin colour
Antioxidant, source of vitamin A, immune booster, possible cancer prevention, vision
Orange, yellow, red and green vegetables and fruits
Vitamin D
9-50 years: 200 IU
51-70 years: 400 IU
  • 70 years: 600 IU
Osteopenia or osteoporosis: 1,000 IU
2,000 IU
1,000 IU
Heart/liver/kidney toxicity, hypercalcemia (excess calcium in the blood)
Calcium metabolism, bone mineralization, possible cancer prevention
Fortified milk, fatty fish
Vitamin E
22 IU
1,500 IU
200 IU
Possible increase in heart disease, excess bleeding
Antioxidant, anticoagulant, protection from heart disease, possible cancer prevention
Wheat germ, vegetable oils, nuts
Vitamin K
M: 120 mcg
W: 90 mcg
N.D.
N.D.
Interaction with blood thinners
Bone mineralization, blood clotting
Green leafy vegetables
Vitamin C
M: 90 mg
W: 75 mg
smokers add 35 mg
2,000 mg
500-2,000 mg
Pro-oxidant, excess iron absorption, diarrhea
Antioxidant, immunity, antiviral in test-tubes, cancer prevention, increases iron absorption
Fruits and vegetables, especially peppers and citrus fruits
Thiamine (B1)
M: 1.2 mg
W: 0.9 mg
N.D.
30-100 mg
Very high doses may promote tumour growth
Energy metabolism, mood, nervous system
Whole grains, brown rice, fortified foods, legumes, pork, oysters
Riboflavin (B2)
M: 1.3 mg
W: 1.1 mg
N.D.
30-100 mg
N.D.
Energy metabolism, antioxidant, possible migraine prevention
Dairy products, leafy greens, oysters
Niacin (nicotinic acid)
M: 16 mg
W: 14 mg
35 mg
500-1,000 mg
Itching, skin flushing,
Liver toxicity, insulin resistance
Energy metabolism, lowers LDL cholesterol and triglycerides, raises HDL cholesterol
Poultry, red meat, fish, legumes, peanut butter, nuts
Vitamin B6
M: 1.3-1.7 mg
W: 1.3-1.5 mg
100 mg
100 mg
Nerve damage (neuropathy)
Protein metabolism, immunity, neurotransmitter synthesis (e.g. serotonin and dopamine), treats peripheral neuropathy and PMS
Meat, fish, poultry, eggs, potatoes, fortified cereals, peanuts, soybeans
Folate
0.4 mg
1 mg
0.4 -1.0 mg
High dose can mask B12 deficiency leading to nerve damage
Cell division, prevents neural tube defects and perhaps other birth defects, lowers homocysteine, possible cancer prevention
Leafy greens, legumes, oranges, broccoli, cauliflower
Vitamin B12 (cobalamin)
2.4 mcg
N.D.
1,000 mcg weekly or monthly for deficiency
Rare cases of eye damage
Cell division, amino acid metabolism, nervous system, mental function
Fish, shellfish, meat, fortified soy and rice milk, fermented soy products
Calcium
1,000-1,200 mg
2,500 mg (from food and supplements)
1,000-1,500 mg
Calcium deposits in soft tissues
Bone mineralization, muscle contraction
Dairy products, fortified soy and rice milk, fish bones
Magnesium
M: 400 mg
W: 320 mg
350 mg
350 mg
Diarrhea, decreased calcium absorption
Bone mineralization, active in more than 300 chemical reactions in the body
Whole grains, nuts, green vegetables, legumes
Iron
M: 8 mg
W: 18 mg
45 mg
Use only to treat iron-deficiency anemia
Iron overload disorders, heart disease, liver cirrhosis
Makes hemoglobin which carries oxygen, makes energy in the mitochondria
Meat, legumes, tofu, leafy greens, breakfast cereals
Zinc
M: 11 mg
W: 8 mg
40 mg
40 mg
Immune suppression, nausea, metallic taste, copper deficiency
Growth, immunity, wound healing, taste, sperm production, antioxidant, prostate health
Oysters, meat, poultry, fish
Selenium**
55 mcg
400 mcg
100-400 mcg
Brittle hair and nails, irritability, garlic breath, fatigue, nausea
Antioxidant, immunity, possible cancer prevention, viral infections
Whole grains from selenium-rich soils, poultry, meat, dairy
RDA: recommended daily allowance (from all sources); UL: upper tolerable limit (from supplements only); N.D.: not determined; IU: international unit; mg: milligram; mcg: microgram
  • Caution should be exercised when taking doses above the UL.
    • There is little to no evidence of efficacy for these doses. Discuss your options with your physician and dietitian.

Folic acid is needed durring cell growth and DNA replication,(3). This leads to the second connection to the AP biology curriculum; DNA replication. DNA replication begins at the origins of replication. The DNA double helix is unwond by the helicase enzyme, and topoisomerase attaches above the split DNA strands in order to reduce stress on the double helix. Then, single strand binding proteins bind to the exposed strands of DNA in order to stabilize the unwound DNA and to prevent it from re-coiling. RNA primase enzymes then attach RNA primers to the exposed DNA strands, allowing DNA Polimerase III to attach DNA nucleotides to the RNA primer. The RNA primer is needed because DNA polymerase III can only attach nucleotides to the 3' end of the growing DNA molecule. This also means that a leading strand and lagging strand are present in the replicating DNA molecule. In the leading strand, nucleotides are added in the same direction as the unzipping of the DNA, and can therefore be replicated with only one primer. However, because DNA polymerase III can only attach nucleotides to the 3' end of the primer, many primers must be placed on the lagging strand. Then, DNA polymerase III can add DNA nucleotides to the Many primers, forming Okazaki fragments. Then, DNA polymerase I replaces the RNA nucleotides in the primer with DNA nucleotides. DNA ligase then connects the Okazaki fragments, completing replication of the lagging strand. I have included a video below that highlights the main steps in this process.



Works Cited:


  1. "A Practical Guide to Nutrition for People Living With HIV: The Big Chart of Vitamins and Minerals - The Body." The Complete HIV/AIDS Resource - The Body. Web. 07 June 2010. http://www.thebody.com/content/art46419.html.
  2. "Water-Soluble Vitamins." Colorado State University Extension. Web. 07 June 2010. http://www.ext.colostate.edu/pubs/foodnut/09312.html.
  3. WebMD - Better Information. Better Health. Web. 07 June 2010. [[http://www.webmd.com/vitamins-supplements/ingredientmono-1017-FOLIC%20ACID.aspx?activeIngredientId=1017&activeIngredientName=FOLIC ACID|http://www.webmd.com/vitamins-supplements/ingredientmono-1017-FOLIC ACID.aspx?activeIngredientId=1017&activeIngredientName=FOLIC ACID]].


Post #3:


Quote:

"Capsaicin is a sticky poison -- it adheres to mucous membranes, which is why your eyes burned if you ever rubbed them after handling peppers. It's also why the heat from a hot pepper sticks around so long -- and why water does nothing to cool the burn. its stickiness acts to prevent capsaicin from easily dissolving in water. You're much better off drinking milk (but this is one time to pass on the skim!) or eating something else with fat in it -- since fat is Hydrophobic, it helps to peel the capsaicin away from your mucous membranes and cool you down."

Connection:

This Quote talks about the properties of capsaicin, the chemical that puts the hot in hot pepper. This connects back to the begining of the year when we talked about chemical structures and properties. In the begining of the year, we learned about polar and non-polar molecules. Polar molecules had areas of positive charge and areas of general negative charge. For example, water is a polar molecule. Every water molecule consists of two hydrogen atoms covalently bonded to one oxygen atom. A covalent bond is when the two atoms "share" electrons. Because the oxygen atom has a higher electronegativity compared to the hydrogen atoms, it "hogs" the electrons, and because the two hydrogen atoms are oriented to one side of the molecule instead of evenly spread, the oxygen end of the molecule develops a generally negative charge and the hydrogen side develops a generally positive charge. Because water molecules develop this polar charge, they can form another type of chemical bond, the hydrogen bond. Hydrogen bonds form between the positively charged area of one molecule and the negatively charged area of another molecule. Because of this, water is a very good solvent because it can form hydrogen bonds with other polar, or Hydrophilic, molecules.

However, "Capsaicin is a nonpolar molecule, and is therefore hydrophobic."(1). In other words, because it is non-polar, it does not form hydrogen bonds as readily, meaning that it is hydrophobic. This also means that capsaicin does not dissolve easily in water. Capsaicin is therefore unable to be removed by simply washing the mouth out with water. On the other hand, by drinking milk or eating a fatty food, as Dr. Moalem suggests, the capsaicin can be removed. This is because the fat, which is a lipid, is also hydrophobic. Lipids are, by definition, hydrophobic molecules. They include phospholipids, which make up the plasma membranes of cells, fatty acids, which store large amounts of energy in their hydrocarbon "tails", and steroids, which can serve roles in regulation and the endocrine system (epinephrine and the fight or flight response), and can play a role in other parts of the body, (cholesterol in the cellular membrane),(2). Because lipids are hydrophobic, the fat in the milk can interact with the capsaicin, and can help clear it from the receptors in the mouth that it has binded to, thus stopping the pain.

As I sat on the couch, eating a jalapeƱo pepper, reading this quote, It made me stop and think about the chemistry behind things as simple as hot chile mouth. I also found it interesting how Dr. Moalem incorporates so many real life connections into the book that relate every day topics to biology.

Below is a link to a website where you can explore a 3D model of capsaicin.
http://www.edinformatics.com/interactive_molecules/3D/capsaicin_molecule.htm

Works Cited:

  1. Way, The. "Lipids." Other Information. Web. 08 June 2010. http://biology.clc.uc.edu/courses/bio104/lipids.htm.
  2. "Capsaicin -- the Active Ingredient in Chile Peppers." Edinformatics -- Education for the Information Age. Web. 08 June 2010. http://www.edinformatics.com/math_science/science_of_cooking/capsaicin.htm.




Post #4:


Quote:

"Almost every human cell contains microscopic workhorses called mitochondria that function as dedicated power plants, producing the energy to run cells. most scientists now believe that mitochondria were once independent, parasitic bacteria that evolved a mutually beneficial relationship with some of our premammal evolutionary predecessors. Not only do these likely former bacteria live in almost all your cells, they even have their own inheritable DNA, called mitochondrial DNA or mtDNA."

Connection:

This Quote connects to several topics in our AP biology curriculum this year. First, this quote connects to the theory of endosymbiosis. This theory suggests that, "...mitochondria are descended from specialized bacteria (probably purple nonsulfur bacteria) that somehow survived endocytosis by another species of prokaryote or some other cell type, and became incorporated into the cytoplasm."(1). The incorporated cell's ability to cary out cellular respiration helped the host cell to survive by providing it with copius ammounts of ATP to run its cellular machinery. Therefore, cells with incorporated mitochondria were given an evolutionary advantage over cells lacking these "power houses" of the cell. This theory is supported by several facts. First, mitochondria have a double membrane, evidence of endocytosis. (the single membraned prokaryote forms the first membrane and the vacuole that formed around it durring endocytosis is the second membrane) Second, mitochondria have their own DNA, and more specifically, this DNA is sircular, like a bacterial chromosome. Also, mitochondria replicate in a process similar to binary fission, the processs used by bacteria to reproduce. This evidence, allong with much more, all support the idea that mitochondria were once seperate organisms that were incomperated into ancient cells and became an organelle through symbiosis and evolution. This same theory is also used to explain the development of chloroplasts, which also are double membrane bound and have their own DNA.

Another way that this quote connects to our AP biology class this year is the mention of the mitochondira's main role; mitochondria produce ATP through cellular respiration. ATP is the chemical energy source that fuels almost all cellular functions. This includes driving sodium potassium pumps or other mechanisms in the cell that regulate membrane potential, providing energy to build large organic molecules, or almost any other process that requires energy in the body. ATP is so versitile because of its structure. "The structure of ATP has an ordered carbon compound as a backbone, but the part that is really critical is the phosphorous part - the triphosphate."(2). The three phosphate groups contain many oxygen atoms. "Under the normal conditions in the body, each of these oxygens has a negative charge, and ... the negative charges repel each other. These bunched up negative charges want to escape - to get away from each other, so there is a lot of potential energy here." (2). Because of ATP's structure, it can function verry effectively in carying potential energy. This makes it the perfect fuel soruce for the cell, and its importance is also why the mitochondria are specialized just for the one task of maintaining a constant supply of ATP in the cell.
Diagram of ATP
Diagram of ATP

While reading this book, I noticed how well Dr. Moalem could summarize complex topics, which took us much class time to learn, in a few simple sentences that are easily understandable. Because he is able to introduce new topics to someone with little or no experience in the subject, Dr. Moalem is able to discuss more advanced subjects with the average person. However, when read from the viewpoint of an AP biology student, this simple explanation acts as an excellent summary instead of a dumbed down version of the topic, and given our prior knowledge on the subject, we can even better understand and appreciate the new connections that Dr. Moalem is creating in his book.

Below is a link to a website where you can explore a 3D model of ATP.
http://www.worldofmolecules.com/3D/atp_3d.htm

Works Cited:

  1. "Origin of Mitochondria - Endosymbiosis Theory." Rice University Web Calendar. Web. 15 June 2010. http://www.ruf.rice.edu/~bioslabs/studies/mitochondria/mitorigin.html.
  2. "Adenosine Triphosphate." Test Page for Apache Installation. Web. 15 June 2010. http://hyperphysics.phy-astr.gsu.edu/hbase/biology/atp.html.



Post #5:


Quote:

""

Connection: