Chapter Two: The Chemical Basis of Life

Questions:

1.  What 25 chemical elements are living organisms composed of?

  A:  Oxygen (O,) Carbon (C,) Hydrogen (H,) and Nitrogen (N) make approximately 96% of the human body as well as most other living organisms.  Calcium (Ca,) Phosphorous (P,) Potassium (K,) Sulfur (S,) Sodium (Na,) Chlorine (Cl,) and Magnesium (Mg) make up most of the remaining 4%.  Trace elements of  Boron (B,) Chromium (Cr,) Cobalt (Co,) Copper (Cu,) Fluorine (F,) Iodine (I,) Iron (Fe,) Manganese (Mn,) Molybdenum (Mo,) Selenium (Se,) Silicon (Si,) Tin (Sn,) Vanadium (V,) and Zinc (Zn) are also found, but only in minute quantities (less than 0.01%.)

2.  Why is ice less dense than liquid water?

  A:  Because of hydrogen bonds.  When water freezes each molecule forms stable hydrogen bonds with four others, holding each at "arms length."  Whereas in water, the molecules are free to move and flow, making ice hold less molecules as water of the same mass.  Therefore, the ice is less dense, and able to float atop of liquid water.

3.  What is an Ionic bond?

  A:  When two ions of opposite chargers attract each other, this attraction holds them together forming an Ionic Bond.

Five Main Facts From The Reading:

1.  Water is the solvent of life.

2.  Hydrogen bonds are weak, but important to the chemistry of life.

3.  Living organisms are composed of approximately 25 chemical elements.

4.  Elements can combine to form compounds.

5.  Electron arrangement determines the chemical properties of an atom.

This chart shows the pH levels of different foods/commonly interacted with items.  The pH level in living organisms is very important, just a slight change and the human body can only survive several minutes before their body will shut down.  

Ten Key Terms:

Electron Shells- a grouping of electrons surrounding the nucleus of an atom.

Chemical Bond - an electrical force linking atoms.

Ion - an atom or molecule with an electrical charge resulting from a gain or loss of one or more electrons.

Covalent bond - in which two atoms share one or more pairs of outer-shell electrons.

Electronegativity - An atom's attraction for shared electrons.

Cohesion - the tendency for molecules to stick together.

Adhesion - the clinging of one substance to another.

Heat - the amount of energy associated with the movement of atoms and molecules in a body of matter.

Temperature - measure the intensity of heat/the average speed of molecules.

Aqueous Solution - a solution in which water is the solvent.

Covalent and Ionic Bond Video:  http://www.youtube.com/watch?v=628Hq-V0aBY

     This chapter is about chemistry and how it is important to the study of life.  For example: water.  Every living organism needs water to survive, but, what is water?  Water is the result of the chemical bond between two hydrogen particles and one oxygen particle.  Without this bonding of two elements, water would not exist, and therefore, neither would we.

     It also touched on the absolute frailty of life, as an example we can use the chart shown above.  The pH system.  The pH of human blood is almost exactly 7.4.  A human being will only survive up to a few minutes if the pH in the blood drops to 7 or rises to 7.8.  A human being will only last about 3 days without water.  This chapter covered the chemical happenings that result in life, and why they are important to the study of biology.