This article gives a brief history/overview of what endosymbiosis is. So, there is this preconceived notion that the first photosynthetic organisms were single-celled bacteria. About 1.5 million years ago, something phenomenal occurred. Non-photosynthetic plants (way back in the day), took in tiny green bacteria. They maintained a mutual relationship. The host cell provided a healthy/safe environment for the bacteria; and the bacteria provided energy for the cell that was harvested from sunlight. Eventually these two became so dependent on each other that they pretty much got to a point where one couldn't live without the other. Plastids are remnants of organisms inside a cell. Chloroplasts are the green plastids inside plant cells.
More recently amoebas also decided to take advantage of the sunlight. Now, amoebas are usually not photosynthetic but, there is a species that has plastids that are closely related to cyanobacteria. This leads scientists to suggest that this new species must be relatively new.
Endosymbiosis can actually happen again and again with the same organism. For example, Hatena arenicola (a unicellular organism) hosts algae; which itself is a product of endosymbiotic events. There are also some red and green algae that have been used by other cells to become plastids.
This article also mentions a couple other organisms that have been trying to "go green" such as the: green sea slug and the photosynthetic salamander!
This article is about how protein synthesis accounts for many components necessary to the cell. But along with protein synthesis compartmentalization is necessary. This article talks about how proteins know where to go in a cell, how they get to their specific destinations, how there is a chance for errors, and what diseases those errors might cause. The article mentions a couple of diseases that arise from defective protein folding, and failures of the cell's quality control center. One disease that may result from conformational errors is Alzheimer's Disease. Conformational diseases arise when a protein changes size or shape and tissue disposition occurs as amyloid fibrils. Alzheimer's specifically results when a specific protein undergoes a conformational rearrangement that results in aggregation and deposition within tissues. Alzheimer's has occasional patterns such as appearing later in life and causing neuronal loss and synaptic abnormalities. Alzheimer's itself is the most common form of dementia. You gradually lose your memory, and your brain functions and behavior start to deteriorate. Relating to trafficking, what causes Alzheimer's is extracellular plaques and intracellular neurofibrillary tangles. Extracellular plaques are primarily made up of amyloid-β-peptide and tangles are made of cytoskeleton proteins. Another disease and second most common neurodegenerative disorder is Parkinson's Disease. Parkinson's is the degeneration of dopaminergic neurons in the substantia nigra. Parkinson's will give you muscular rigidity, postural instability, and a resting tremor. It is caused by deposition in brain cells of intracytoplasmic inclusion bodies, Lewy bodies.
This article is about Tay-Sachs Disease. Tay-Sachs is a genetic disorder that usually occurs in children. It is caused by the absence of hexosaminidase-A (hex A). Without this enzyme, a lipid accumulates abnormally in cells, specifically in nerve cells of the brain. The excessive accumulation will eventually start to damage cells. This is why/how Tay-Sachs progressively destructs the nervous system.
Babies with Tay-Sachs appear normal until about 6 months, which is when their development slows. By the time they turn 2 years old they may experience seizures and their mental state starts to degress. They will forget how to crawl, reach, sit... and death usually results by the age of 5, if not earlier. :'( Tay-Sachs babies develop a "cherry-red" macula (spot) in the back of their eyes (retina). Eventually they lose their ability to see altogether. This is a picture of their retina, seen through an opthalmoscope:
Tay-Sachs results from a defect on chromosome 15 and can be identified through a simple blood test.
A common misconception is that this disease is limited to people of jewish decent. This is not true, although it is most common amongst people of Eastern (Ashkenazi) Jewish decent, anyone can be a carrier. There is no cure or treatment for Tay-Sachs. Researchers are in the process of finding a cure but, none so far. Scientists have looked at enzyme replacement therapy to provide for the Hex-A that Tay-Sachs' babies are lacking. Bone marrow transplants have been attempted, but did not slow down or reverse the symptoms of Tay-Sachs. Scientists still have hope on gene therapy. Hopefully the cure will show up in the near future!!!
On a brighter note, and mildly off-topic, but nonetheless interesting, this article talks about how there may be a Jewish gene for intelligence! Like Tay-Sachs and Gaucher's, there are certain things that are common, if not limited to, Jews. In my opinion, it sounds a bit ludicrous, but Gregory Coch-ran has teamed up with anthropologists and they have proposed that Ashkenazi Jews are more intelligent because of genetic mutation. After much assessment these researches concluded that genetic diseases are linked to a tendency to having greater intelligence. I don't know how accurate these researchers are but, I think we should keep in mind that Coch-ran was also the one who proposed that homo-sexuality is caused by an infectious disease... yeah!
I. Summary Proteins
Proteins are what allow a cell to carry out most of it's functions. Proteins play a structural role, they maintain cell shape and provide support. They are catalytic and this is why some proteins (enzymes) speed up reactions. Cells communicate with their environments by regulation through membrane proteins. Proteins also allow cells mobility. For example, sperm cells have flagellum (protein) that helps them move. Cells respond to their environment through regulatory and receptor proteins. They allow cells to respond to stimulus. Hormone proteins carry regulatory signals between cells. Antibody proteins defend against invading molecules and organisms. Storage proteins store substances for later use.
Proteins have four different levels of structure. Primary Structure is the sequence of amino acids that characterize a specific protein. The amino acids are joined together by peptide bonds (formed through dehydration synthesis). Proteins differ based on their primary structure, the sequence of their amino acids. Not all amino acids are hydrophilic. To protect the hydrophobic ones, the linear chain may fold, which leads us to the secondary structure. Secondary Structure is where amino acids interact with other amino acids around them. They might twist or bend, forming hydrogen bonds. It can form an alpha-helix or a beta-strand, which are essentially zig-zags in a flat plane. Beta-strands continue to form beta-sheets. Hydrogen bonds are what help stabilize secondary structures. Tertiary Structure is the overall conformation or three-dimensional shape of a protien. As the structures progress, they become more globular and compact. Now that the structure is more spherical and compact, we see that the hydrophobic regions can easily be protected from any aqueous solution because they can hide on the inside of the structure. Tertiary structures are stabilized by their R-groups. Of all the interactions (hydrogen, ionic, hydrophobic, and disulfide linkages) disulfide linkages are the strongest because they are covalent. Denaturation is the loss of protein structure and function. Folded proteins are functional and unfolded proteins are inactive. In this sense, primary and secondary structured proteins are not functional, only tertiary and quaternary are. Denaturation occurs at high heat, change in pH, and addition of salt. Quaternary Structure represents the interaction between two or more protein chains.
In sum, these structures are important because they determine the function and it is the sequence of the linear chains of amino acids that determine that function. Primary structures are stabilized by peptide bonds, secondary are stabilized by hydrogen bonds, tertiary are stabilized by ionic, hydrogen, hydrophobic interactions, and disulfide linkages. Of these, disulfide linkages are the most stable. Nucleic Acids
Nucleic acids are long polymers of nucleotide building blocks. DNA (deoxyribose nucleic acid) stores all the information for proper cell function. DNA information is what determines the primary structures of proteins. RNA (ribose nucleic acids) is used in various forms to help assemble proteins. Nucleotides are made of a five-carbon sugar, nitrogenous base, and three phosphate groups. The general structure is numbered. One way to differentiate between DNA and RNA is that DNA has H on its 2' (that's why it's called deoxy... without oxygen). Meanwhile, RNA would have OH on its 2'. Nucleoside is the term used when referring to the sugar and nitrogenous base only. Nucleoside monophosphate is the sugar, nitrogenous base, and one phosphate. Diphosphate and triphosphate would have two or three phosphates respectively.
There are 20 amino acids used to make a protein. Of those, there are 4 nucleotides used to construct DNA and 4 to construct RNA. DNA uses A, T, C, G and RNA uses A, U, C, G. Nucleotides vary in sugar and nitrogenous bases. Two categories of nitrogenous bases are pyrimidines (one ring) and purines (two rings). DNA has a double helical structure because the partially negatively charged oxygen molecules form hydrogen bonds with the partially positively charged hydrogen molecules.
DNA and RNA polynucleotide chains are formed by linking the phosphate group of one nucleotide to the sugar of the next one. These are linked together by phosphodiester bonds which are covalent bonds specifically found in nucleic acids. Dehydration reactions link nucleotides. Just like how proteins have N and C termini, DNA has opposite ends, 5' and 3'. DNA is anti-parallel because one strand runs 5' to 3' and the other runs 3' to 5'. Two strands of DNA are joined by hydrogen bonds between the nitrogenous bases following base-pairing rules: A-T and C-G. A-T forms two hydrogen bonds and C-G forms three hydrogen bonds. Bonding of these purines-pyrimidines gives ideal spacing for hydrogen bonding.
RNA usually exists as a single strand. It uses a ribose sugar, instead of deoxyribose and Uracil instead of Thymine. The difference is just the Thymine has a methyl group and Uracil doesn't. It also follows same base-pairing rules as DNA. II. Useful Materials
This websiteprovides interactive flashcards and can help you memorize the 20 amino acids. It keeps track of how many you get correct and incorrect. Then, when you're ready you can take a test and the website will generate different kinds of questions to test your knowledge on the topic!
This video shows DNA and RNA bonding. It explains the components of nucleotides, base pairing specificity, and the main differences between DNA and RNA.
III. Article
Thisarticleis about thalidomide. Kevadon, which is known today by it's generic name thalidomide was meant to be a sedative. When William S. Merrell Co. applied for this drug to be approved by the FDA, they declined. Dr. Frances Kelsey was the one who was assigned to this drug, and she automatically declined it. She had always been very cautious about taking drugs while pregnant.
When articles began to pop up about women who took thalidomide during their pregnancy giving birth to severely deformed babies, America had Dr. Kelsey to thank. The only Americans who were exposed to the drug were travellers taking it while travelling the seas, and people who took part in experimental studies. This close encounter with thalidomide caused congress to pass the Kefauver Act, which required more in-depth documentation and careful review of drug safety.
In 1957 a drug, thalidomide, was introduced to help relieve pregnant women of morning sickness. It turns out, this drug had some major side-effects that caused sever malformations in developing fetuses. These "thalidomide babies" had many defects including shortened upper limbs; as shown below:
The drug was finally discontinued in 1961.
In the 1990s, the FDA approved the use of thalidomide for multiple myeloma and some complications of leprosy. The drugs powerful anti-inflammatory and anti-angiogenic effects actually will help you feel better, but they have horrible side-effects. There is still study going on about whether it can be used for arthritis, breast cancer, and more than 30 other diseases.
Recently Tokyo Institute of Technology have been conducting experiments on zebra fish and chick embryos to see why exactly thalidomide causes birth defects. Previous studies suggest that the side-effects are caused by thalidomide's therapeutic effects on inflammation, blood vessel formation, and cell stress.
Despite the past with thalidomide, and with ongoing research, it is surprising to see that the FDA actually has approved supervised, modicum use of the drug.
Atoms
Biology is the study of life, and to understand it, we have to know a little bit about chemistry and physics; as they help us understand how atoms and molecules interact. All living organisms are composed of matter, anything that takes up space and has mass. Matter is made up of atoms, which are the smallest functional units of all living things. Atoms are made up of tiny little particles. Atoms can also bond together to create molecules. Examples of some atoms are Hydrogen, Carbon, Nitrogen, and Oxygen. These specific types of atoms are called elements, pure substances of only one kind of atom. Protons, neutrons, and electrons can be found within an atom. The protons and neutrons can be found within the atomic nucleus and the electrons occupy orbitals around an atom's nucleus. Orbitals are the regions around the nucleus where the electrons are most likely to be found. They are almost like rings around the nucleus. Orbitals occupy energy shells, or energy levels. The electrons in the outermost shell are called valence electrons. These are the most important electrons that we need to know for this chapter. They determine whether an atom can bond with other atoms.
The atomic number is the number of protons an atom contains. The atomic mass is an atom's mass relative to other atoms. This is usually confused with weight, which is the the gravitational pull on a given mass. The atomic mass is measured in daltons. A Dalton, also known as atomic mass unit, is equivalent to 1/12 the mass of a carbon atom. A mole of any substance contains the same number of particles as there are atoms in exactly 12g of carbon. <------ this is something that I'm still a little iffy about!
Traditionally, the number of neutrons are the same as the number of protons, in any given atom. However, variations of an element in their numbers of neutrons, can exist; these are called isotopes. An isotope found in nature that is inherently unstable and usually does not exist for long periods of time is called a radioisotope. They decay and emit energy in the form of radiation.
Oxygen, Nitrogen, Carbon, and Hydrogen make up the majority of atoms in all living organisms. Hydrogen and oxygen we know form water, carbon is the building block of all living matter, and nitrogen is vital in proteins. Trace elements are also necessary for normal function in all living organisms, but is only needed in small quantities. Iron and copper are examples of trace elements. Chemical Bonds and Molecules
A molecular formula is a representation of a molecule that consists of the chemical symbols for all of the atoms present and and subscripts that indicate how many of those atoms are present. A molecule that is composed of two or more different elements is called a compound. Water is a compound as it contains two hydrogen molecules and one oxygen molecule. Chemical bonds are what hold atoms in molecules together.
Covalent bonds are where atoms share electrons. This is the strongest type of chemical bond.
For most atoms, 8 electrons are needed to fill their outer most shells. The octet rule states that atoms are stable when they have 8 electrons in their outermost shell. Keep in mind, this rule doesn't always apply (hydrogen only needs 2 electrons to fill its valence shell).
A double bond is when the atoms of a molecule share two pairs of electrons, rather than one. An atom's ability to attract electrons, electronegativity, is not the same for each atom. In a covalent bond, although the two atoms are sharing electrons, they don't always necessarily share electrons evenly. Sometimes one atom's electronegativity is greater than the other and the shared electrons spend more time around one atom than the other. This phenomenon is called a polar covalent bond. Water is a great example of a polar covalent bond. Although hydrogen is sharing its electrons with oxygen, oxygen has a greater electronegativity and therefore hydrogen's two electrons spend more time orbiting oxygen's nucleus than they do their own. Nonpolar covalent bonds are where the electrons shared in a covalent bond, are shared equally because the electronegativity of the two atoms are similar. A single molecule can have areas with nonpolar bonds and areas with polar bonds. When the bonds in a molecule are predominantly nonpolar, it is called a nonpolar molecule. Vice versa is referred to as a polar molecule. Hydrogen bonds are the weakest bonds and form when a hydrogen atom from one polar molecule is electrically attracted to an electronegative atom in another polar molecule. The strength of hydrogen bonds increases relative directly as the number of bonds increase. AKA 3 hydrogen bonds are stronger than 2 hydrogen bonds. A good example is DNA; it takes considerable amount of energy to pry the two strands apart because of the amount of hydrogen bonds. Enzymes are proteins that either facilitate or catalyze chemical reaction in a cell. Van der Waals forces are attractive forces between molecules in close proximity of each other, caused by the variations in the distribution of electron density around individual atoms. <------ another unclear topic!
An ion is when an atom or molecule gains or loses electrons, giving it a net electric charge. Cations are ions that have a net positive charge and anions are ions that have a net negative charge. What helps me remember that cations are the positive ones and anions the negative is that cations has a t which kind of looks like a +, for positive. Yes, every time I read cation I read it like ca+tion! Ionic bonds occur when a cation bonds to an anion. Essentially one atom is giving electrons and the other is recieving. This exchange of electrons will change it's charge.
A free radical is an atom that only has one valence electron. Free radicals steal electrons from other atoms until their valence shell is full.
A chemical reaction is the formation and breaking of chemical bonds, resulting in a change in the composition of substances. This can be when two elements combine to form a compound, or when a compound is broken down into elements. Chemical reactions require energy, which is partly provided through heat. Heat energy allows atoms and molecules to move and vibrate; this is known as Brownian motion. Chemical reactions also need to be catalyzed. Chemical reactions proceed in a particular direction and will eventually reach a state of equilibrium unless something happens to prevent equilibrium. A reactant is something that participates in a chemical reaction and becomes changed by that reaction and a product is the end result of the reaction. Chemical equilibrium is a state in the chemical reaction where the rate of formation of products equals the rate of formation of reactants. Properties of Water
A substance dissolved in a liquid is a solute and a solvent is the liquid in which a solute is dissolved. A solution is a liquid that contains one or more dissolved solutes. Aqueous solutions are solutions made with water. Ions and molecules that contain polar covalent bonds and WILL dissolve in water are known as hydrophilic. Molecules that don't have partial charges and are not attracted to water molecules are hydrophobic. They are composed of carbon and hydrogen and are relatively insoluble in water. Cohesion is when water molecules are attracted to each other and adhesion is when water adheres to a surface that is not electrically charged. Water also has a very high specific heat which is the amount of heat energy needed to raise the temperature of 1g by one degree Celsius. DON'T GET THIS CONFUSED WITH heat capacity which is the amount of heat energy needed to raise the temperature of an entire object or substance.
The colligative properties of water are dependent on the number of dissolved solutes and allow water to function as an anti-freeze in certain organisms. Water's high heat of vaporization and high heat of fusion help it be very stable while in liquid form. Hydrolysis is the breaking down of large molecules into smaller units and a dehydration reaction combines smaller molecules into a larger one.
The pH of a solution refers to it's concentration of hydrogen ions. The pH scale is from 0-14. 0 is acidic and contains the most H+ ions, whereas 14 is basic, or alkaline, and has more OH- ions. PH balance can be regulated by using a buffer. A buffer is a compound that minimizes pH fluctuations in fluids of living organisms; they can raise or lower pH, as needed.
II. Useful Materials
Above, I mentioned how the concept of a mole was still a little unclear to me. This song demonstrates how to find a mole, gives the definition, and helps remember everything. Its super catchy, LISTEN TO IT!!!
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I also mentioned how I didn't quite understand the van der Waals force. Here's a video that actually explains and clarifies it. He digresses a little but, in the end he actually helped! He pretty much said that the van der Waals force is a weak attractive force between atoms of nonpolar molecules caused by a temporary change in dipole moment from a brief shift of orbital electrons to one side of an atom or molecule, creating a similar shift in adjacent atoms/molecules.
III. Article
Thisarticleis about physicists that came about creating the heaviest isotope of magnesium. While experimenting, however, an isotope of aluminum also showed up. How exciting! This could help us come closer to understanding occasional X-ray emissions from neutron stars that are growing in mass.
On the 5th day of a 7-day-long experiment in Michigan State University, an isotope of aluminum appeared unexpectedly. Most theories predicted that aluminum-42 wouldn't exist; this is why it's appearance was so shocking. In sum, the discovery of aluminum-42 suggested that even heavier aluminum isotopes could exist and maybe even other elements, that are higher in the periodic table, would be able to accommodate more neutrons than expected.
In the past, scientists believed that the moon was bone dry; but, during recent missions, some rocks were brought back, and showed considerable traces of hydroxyl which is a compound formed by the breakdown of water. Thus, scientists believed that the Moon contained significant amounts of water. A new study, however, by geochemist Zachary Sharp, measured chlorine isotopes and found that the chlorine isotope values were almost 25 times more than Earth's. Since chlorine is strongly attracted to hydrogen, and when they are both present in molten rock, they tend to form hydrogen chloride gas. Sharp concluded that when the rocks cooled 4.5 billion years ago, they were low in hydrogen because instead of becoming mostly hydrogen chloride gas, the chlorine bonded with other elements (leading to more chlorine isotopes). Basically, if moon rocks lack hydrogen, they must lack water.
In essence, this article shows how much isotopes can prove and how important they are in research. A prior notion was that the Moon contained a lot of water but recent study on chlorine isotopes showed how the Moon is actually very dry and contains very little water. Study is still going on about water existing on the Moon but, perhaps this means living on the Moon could actually be possible in the future?
