Ch.2 The Chemical Basis of Life

WHAT HAPPENS IF WE ARE LACK OF TRACE ELEMENTS?
If you are lack of trace elements, it means that you are not getting enough nutrition for your body. You always need enough trace elements and minerals in your body. They have three important functions.
1) Structural components of body organs and tissues.
2) Constituents of body fluids and tissues as electrolytes concerned with body fluid balance, acid-base balance, membrane permeability, tissue irritability.
3) Catalysts in enzyme and hormone systems.
Those functions will stop working in your body. To prevent making those functions stop working, trace elements are needed in your body.

WHY DO WE USE RADIOACTIVE ISOTOPE IF IT COULD HARM US?
Since minute traces of radioactive isotopes can be sensitively detected by means of the Geiger counter and other methods, such as they use in medical therapy, diagnosis, and research. In therapy, they are used to kill or inhibit specific malfunctioning cells. There are many ways to use radioactive isotopes in our lives.


HOW CAN WATER STRIDERS WALK ON WATER? WHAT DOES IT HAVE TO DO WITH SURFACE TENSION?
Surface tension is a measure of how difficult it is to stretch or break the surface of liquid. Hydrogen bonds give water unusually high surface tension, making it behave as though it were coated with an invisible film. It is composed of thousands of molecules of water. They bond together, but it is also easy to break the bond. Therefore, when people try to walk on the water, we break the bonds and we sink in the water. However, water striders are too light to break the bonds. Therefore they are able to walk on the water without breaking them.


KEY TERMS
-Matter: anything that occupies space and has mass
-Element: a substance that cannot be broken down to other substances by ordinary chemical means
-Trace Elements: essential elements, but only in minute quantities
-Compound: a substance consisting of two or more different elements combined in a fixed ratio
-Isotopes: atoms that have the same numbers of protons and electrons and behave identically in chemical reactions, but they have different numbers of neutrons
-Ion: an atom or molecule with an electrical charge resulting from a gain or loss of one or more electrons
-Covalent Bond: when two atoms share one or more pairs of outer-shell electrons
-Polar Covalent Bond: the bonds of molecules that are sharing electrons unequally. In this bond, the pulling of shared, negatively charged electrons closer to the more electronegative atom makes that atom partially positive
-Cohesion: the tendency of hydrogen-bonded molecules stick together
-Adhesion: the clinging of one substance to another

SUMMARY
This chapter talks about chemistry the most because studying the structures and functions of living organisms is necessary to learn about life. Living organisms are all composed of matter, which is anything that occupies space and has mass. Matter is composed of elements which are substances that cannot be broken down to other substance by ordinary chemical means. All discovered elements are on periodic table. Trace elements are essential but only in minute quantities. For example, we need one of trace elements, iodine, for our bodies. If you do not take any, you will get goiter. Therefore people add iodine purposely to table salt to improve health. Chemicals are added to food to make it more nutritious, or simply make it look better. Elements also can combine to form compounds, such as H2O. H2(hydrogen) and O2(oxygen) combine and form H2O(water).
Atom is the smallest unit of matter. It consists of protons, electrons, and neutrons. protons and neutrons are tightly packed and electrons are around it. This packed protons and neutrons are called nucleus. The number of protons is called atomic number, and the sum of the protons and neutrons in nucleus is called mass number. Atomic mass is approximately equal to its mass number. Radioactive isotopes are useful as tracers in research on the chemistry of life because organisms incorporate radioactive isotopes of of an element into their molecules just as they do non-radioactive isotopes, and researchers can use special scanning devices to detect the presence of the radioactive isotopes, but it also can be harmful.
Electrons occur only at certain energy levels, called electron shells. For example, hydrogen only has 1 electron, so first shell holds it. However neon has 10 electrons so first shell cannot hold all of them. Thus it has second shell that holds the rest. When two ions with opposite charges attract each other, it is called ionic bond. Salt, NaCl, is an example. When two or more atoms share outer shell electrons, it is called covalent bond. For example, two hydrogen atoms share their electrons, it will turn H2, hydrogen. When hydrogen bonds some other elements, it is called hydrogen bond. It is a weak bond, but it is important in the chemistry of life. There are two types of conditions in the chemistry of life. Acidic and basic conditions. If the number is between 0 to 6 on pH scale, it is acid. If the number is between 8 to 14, it is base. If the number is 7, it is neutral, water.

Mass of ice is lighter than mass of liquid water as you can tell from the diagram. In liquid water, they do not have bonds, so it is easy to change shape. However they have stable bonds in ice, so it does not change shape easily. Also there are not many molecules in the ice so it is lighter than liquid water, which means it flows in the water.

5 FACTS:
1) Living things are all composed of matter.
2) We need 25 essential elements, trace elements, in our bodies always. Such as iron. They prevent disease.
3) An atom is composed of neutron, proton, and electron.
4) Chemical bonds occur depending on number of electrons on the outer shell.
5) Water has more dense than ice. This is because atoms in the ice do not move. They are stuck in the ice.