GENERAL BIOLOGY - The Chemistry of Life

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Interactive periodic table

The story of biology begins in chemistry. We must have a basic understanding of chemistry to understand biology. This is because, everything that is made up of matter (from rocks to human beings) is made up of atoms.

The story of YOU is more beautiful and complex than you can ever image!    Many scientists believe that our universe started with a "BIG BANG" or a "BIG BANG-LIKE" event. The universe we live in was created by some type of BANG that contained all of the subatomic particles needed to make matter.  In the beginning, the early universe was too hot for atoms to form, but as the universe cooled the first atoms were able to form.
The first atoms to form were hydrogen and helium. Hydrogen is made up of only 1 electron and 1 proton. Helium is made up of 2 electrons and 2 protons. Stars are made up almost entirely of hydrogen and helium. All of the heavier elements are made when a star dies and explodes as a super nova. 

The matter that you are made of has been around since the beginning of the universe 13 billion years ago. All of the heavier elements required for life like you and I to exist, were form in the cauldron  of an exploding star. We are all made of stars!

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The Atom

Atoms are the fundamental unit of matter. That means that all matter is composed entirely of atoms.

Atoms are made up of a combination of subatomic particles, which are protons, electrons and neutrons. 

PROTONS are positively charged and are found at the nucleus (center) of the atom.

ELECTRONS are negatively charged and are found on the outer portions of the atom.

NEUTRONS have no charge and are found in the nucleus of the atom.

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The simplest and most abundant atom is the hydrogen atom. The hydrogen atom contains only one electron and one proton.

An atom, by definition, is neutral (uncharged). That means in an atom, the number of protons will equal the number of electrons.

     Atoms can either gain or lose electrons from their outermost shell and become charged. A charged atom is called an ION. An atom that gains 1 electron will become an ion with a -1 charge. An atom that gains 2 electrons will will become an ion having a charge of -2. An atom that gains 3 electrons will become an ion with a -3 charge... and so on.
     This works the other way too. When an atom loses 1 electron, it will become an ion with +1 charge. When an atom loses 2 electrons, it will become an ion with +2 charge. When an atom loses 3 electrons, it will become an ion with +3 charge... and so on.  

   Remember that electrons are negatively charged, so loosing an electron, means gaining positive charge.  Conversely, gaining an electron means gaining negative charge. 

The electron in the outermost shell determines an atom’s ability to create bonds with other atoms. A carbon atom has 4 electrons in a valence shell that holds 8. Carbon is able to completes its outer shell by sharing electrons with other atoms in four covalent bonds.

CARBON IS KEY!

   All life as we know it is carbon-based. ​The reason for this is that carbon is the most versatile element, since it is able to form 4 strong bonds. This allows for a vast array of carbon-based molecules (called organic molecules) to form. Carbon is able to form large complex molecules. Organic molecules tend to carry a number of hydrogen atoms as well. 

WATER

     The most important elements for life are carbon, oxygen, hydrogen and nitrogen. Surprisingly, our bodies (as well as all biological entities) is more that 98% carbon, oxygen, hydrogen and nitrogen.   

 Life and its chemistry are tied to water. Life began in water and evolved there for 3 billion years before spreading onto land. And all life, even land-dwelling life, is still dependent on water.  Your cells are 75% water. The composition of the water surrounding the cells (extracellular fluid) is similar to sea water. When life evolved to move out of the ocean, we had to take the ocean with us! Water is the most abundant compound on the surface of Earth.

Types of Bonding
- ionic
- covalent (polar and non-polar)
- hydrogen bonds

• hydrogen bonds  in water
• the positively charged atom in this type of attraction is always a hydrogen atom.
• each hydrogen atom of a water molecule can form a hydrogen bond with a nearby partially negative oxygen atom of another water molecule.
•  And the negative (oxygen) pole of a water molecule can form hydrogen bonds to two hydrogen atoms.

 
 The  Life-Supporting Properties of WaterHydrogen bonds between molecules of liquid water last for only a few trillionths of a second, yet at any instant, many molecules are hydrogen-bonded to others.
This tendency of molecules of the same kind to stick together, called cohesion, is much stronger for water than for most other liquids.The cohesion of water is important in the living world. 

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     Water is resistant to temperature change. Thermal energy is the energy associated with the random movement of atoms and molecules.          Thermal energy in transfer from a warmer to a cooler body of matter is defined as heat. Temperature measures the intensity of heat—that is, the average speed of molecules in a body of matter. 

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Water is considered a POLAR molecule Since it is slightly negative on one end, and slightly positive on the other end! The Polarity of water allows it to have the ability to dissolving a variety of different substances! This is why water is called the UNIVERSAL SOLVENT. Water can dissolve more substances than any other molecule!
Also, atoms have to get close enough to react in order to form molecules.... And, since ATOMS DON'T have legs... The atoms are able to find each other as they float around in water.  In water, atoms can easily travel and react!

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