Archive for September, 2011
Biology Chapter 4: Inside the Cell
The cell is the smallest structural and functional unit of an organism, consisting of cytoplasm and a nucleus surrounded in a membrane. Cells are microscopic in size. Cells must remain small in order to have an adequate amount of surface area per cell volume.
All cells have a plasma membrane, cytoplasm, and genetic material. Prokaryotic cells do not have a membrane-bound nucleus. Eukaryotic cells have a membrane-bounded nucleus and also do various membranous organelles. Bacteria are representative of the prokaryotes. They have a cell wall and capsule, in addition to a plasma membrane. Their DNA is in the nucleoid. They have many ribosomes and three possible appendages.
The plasma membrane of both prokaryotes and eukaryotes is a phospholipid bilayer. The phospholipid bilayer regulates the passage of molecules and ions into and out of the cell. The fluid-mosaic model of membrane structure shows that the embedded proteins form a varying pattern. The types of embedded proteins include channel, transport, cell recognition, receptor, enzymatic proteins.
Biology Chapter 2
In chemistry and physics, atomic theory is a theory of the nature of matter, which states that matter is organized into discrete units called atoms. The Greek word rendered “atom” meaning ‘indivisible’ was applied to the basic particle that constituted a chemical element, because the chemists of the era believed that these were the fundamental particles of matter. Not until around the turn of the 20th century, through various experiments with electromagnetism and
radioactivity, did physicists discover that the so-called “indivisible atom” was actually a conglomerate of various particles called subatomic particles- electrons, protons and neutrons- which can exist separately from each other. Since atoms were found to be actually divisible, physicists later invented the term “elementary particles” to describe subatomic particles. The electron is a subatomic particle with a negative electric charge. It is generally thought to be an elementary particle. The periodic table is a tabular display of the 118 known chemical elements organized by selected properties of their atomic structures. Elements are presented by increasing atomic number, the number of protons in an atom’s atomic nucleus. Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation of the atom as a particular element. A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges between electrons and nuclei. Covalent bonding is a common type of bonding, in which the electronegativity difference between the bonded atoms is small or nonexistent. Bonds within most organic compounds are described as covalent. Ionic bonding is a type of electrostatic interaction between atoms which have a large electronegativity difference. A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. The hydrogen must be covalently bonded to another electronegative atom to create the bond. A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. The substances initially involved in a chemical reaction are called reactants. Chemical reactions are usually characterized by a chemical change, and they produce one or more products, which usually have properties different from the reactants. Reactions often consist of a sequence of individual sub-steps, the so-called elementary reactions, and the information on the precise course of action is part of the reaction method. Chemical reactions are described with chemical equations, which graphically present the starting materials, end products, and sometimes intermediate products. Water is a chemical substance with the chemical formula H2O. Its molecule contains one oxygen and two hydrogen atoms connected by covalent bonds.
Chapter 20 Review: America in the Twenties
For most Americans, the decade of the 1920s was a time of wealth. It was a time of rapid growth in American industry, with the construction, automobile, and public utilities industries leading the way. New methods of mass production made American workers more productive than ever before. The result was a higher standard of living for most workers and much higher profits for business and corporations. Profits were also increased by the tax and tariff policies of three successive Republican presidents. The administrations of Warren G. Harding, Calvin Coolidge, and Herbert Hoover pursued a foreign policy designed to extend and protect American overseas investments and trade.
The twenties were an era of dramatic social change in the United States. Women won the right to vote and went on to gain a greater measure of economic dependence. Although European immigration declined with the passage of restrictive acts, migration of rural Americans to the cities continued. African Americans migrated from the rural South to northern Industrial cities in large numbers. They were confined to low-paying jobs and to housing in the poorest neighborhoods. Racial discrimination made movement out of these ghettos nearly impossible. Cities grew upward and outward. Skyscrapers and suburban neighborhoods became common features of the landscape.
Many Americans were disturbed by the changes of the 1920s. They were alarmed that young people were rebelling against the Victorian standards of morality. Some Americans felt traditional values were being eroded as society was becoming culturally diverse. The resurgence of nativism made groups like the Ku Klux Klan more popular.
Chapter 19 Review: Progressive Era Diplomacy
After 1900, whether Americans liked it or not, the nation could no longer avoid playing an important part in world affairs. The progressive presidents clearly understood the new role. Yet each had different ideas about how to go about playing it.
These three presidents also brought very different styles, interests, and values to their handling of international relations. Their specific policies reflected these differences. Roosevelt’s balance-of-power diplomacy differed greatly with Taft’s dollar diplomacy and Wilson’s missionary idealism. Of the three, Roosevelt was probably most successful in completing his foreign policy goals. Taft’s dollar diplomacy had little success. Wilson was probably least successful overall, because idealism and vision exceeded what he could practically accomplish. How the progressive presidents’ foreign policies were judged depends mostly on a definition of national interests and how best to handle them. Americans continue to argue about this.
The desire to build empires plus complicated political alliances pushed Europe into the greatest war the world had ever seen. The United States tried to keep neutral, but such factors as German interference with American shipping and strong cultural and economic ties with England forced the United States in the Great War (World War I). After the defeat of the Central Powers, the Allied powers imposed peace settlement that many historians believe helped to bring about World War II.
Chapter 18 Review: Progressive America
The reformers of the Progressive Era were the first generation of Americans to expand the role of the federal government into the affairs of everyday life. They looked to the federal government to solve problems too large for local and state governments. They voted for legislation that put federal meat inspectors in the packing plants and that forced food processors to label the contents of their products. At their insistence, Congress created the Federal Trade Commission to oversee the huge corporations. Out of the progressives’ belief in progress and social justice came the foundation for the modern regulatory state.
Aware that the presidency was the only elected office that represented all the people, Roosevelt and Wilson found new ways to expand the powers of the office. They used the visibility of the White House and the power of the press to mold public opinion and to shape legislation.
Although the Court took a traditional approach to most of the progressive legislation, some reform legislation was upheld, including the right to make laws limiting the numbers of hours that women could be made to work.
Passage of the Sixteenth Amendment finally answered the question of whether or not an income tax was constitutional. The direct election of senators, Prohibition, and universal women’s suffrage were other reformers that were created in this period by amendments to the Constitution.
The influence of progressives was also felt in literature and art. Writers criticized Social Darwinism and began to write fiction using realistic settings and characters. Painters began to experiment with abstract art forms that influenced people’s perception of reality.
Chapter 17 Review: Stirrings of Reform
The United States at the turn of the century was a rapidly changing society. The economy was surging ahead, the cities were growing, and many Americans had more leisure time than ever before; but it was also a society overwhelmed with problems. The industrial cities were troubled with widespread poverty, dangerous and unhealthy working conditions, and corrupt governments. Large corporations had attained vast economic power and political influence. To some, the future of American democracy itself seemed in danger.
While aware of the problems created by rapid industrialization, Americans of this generation firmly believed in the possibility of progress. They rejected the idea that big corporations were beyond their control or that American politics had become hopelessly corrupt. Most Americans seemed convinced that people of motivation together could reform American society. This idea was especially likable to members of the professional class, people trained and skilled in the techniques of management. All they needed to do was to apply those same skills to the nation’s social and political problems.
The result was a series of reform effort known as the progressive movement. Middle-class reformers reached out to the urban poor by establishing settlement houses in the slums. Reform mayors helped clean up community government in a number of cities. Other progressives worked to limit child labor and to regulate the working hours of women. Prodded by reformers, state legislatures enacted factory safety and worker’s compensation laws. Progressives also made government more democratic by introducing changes to election processes.
Although progressives achieved major reforms, women, African Americans, and American Indians still occupied a minority status in American society. Despite the efforts of organizations that fought for political rights and the hard work of heroic and dedicated minority leaders, the reform movement still had a long way to go.
Algebra II Day 1
An equation is a mathematical statement that asserts the equality of two expressions.
Equations often express relationships between given quantities, the knowns, and quantities yet to be determined, the unknowns. By convention, unknowns are denoted by letters at the end of the alphabet, x, y, z, w… while knowns are denoted by letters at the beginning, a, b, c, d… The process of expressing the unknowns in terms of the knowns is called solving the equation.
In an equation with a single unknown, a value of that unknown for which the equation is true is called a solution or root of the equation. In a set simultaneous equations, or system of equations, multiple equations are given with multiple unknowns. A solution to the system is an assignment of values to all the unknowns so that all of the equations are true.
One use of equations is in mathematical identities, assertions that are true independent of the values of any variables contained within them. For example, for any given value of x it is true
However, equations can also be correct for only certain values of the variables. In this case, they can be solved to find the values that satisfy the equality. For example, consider the following
The equation is true only for two values of x, the solutions of the equation. In this case, the solutions are x = 0 and x = 1.
If an equation in algebra is known to be true, the following operations may be used to produce another true equation:
- Any real number can be added to both sides.
- Any real number can be subtracted from both sides.
- Any real number can be multiplied to both sides.
- Any non-zero real number can divide both sides.
- Some functions can be applied to both sides. Caution must be exercised to ensure that the operation does not cause missing or extraneoussolutions. For example, the equation y*x=x has 2 solutions: y=1 and x=0. Dividing both sides by x “simplifies” the equation to y=1, but the second solution is lost.