Ch. 2 – The Chemistry of Life. I. THE COMPOSITION OF THE UNIVERSE A. Everything in the universe is...

Ch. 2 – The Chemistry of Life

I. THE COMPOSITION OF THE UNIVERSE

A. Everything in the universe is made of up atoms.B. An element is a pure substance that cannot be broken down chemically into other matter.

1. Examples of elements: Oxygen, Carbon, Hydrogen, Nitrogen, Phosphorous

2. More than 100 elements have been identified, but less than 24 are important to living things.

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3. Periodic Table of Elements:


4. The simplest part of an element is an atom.

5. Parts of an atom (a.k.a. sub-atomic particles):a. The “Central Core” or nucleus is made up of:

protons (+ charge)neutrons (neutral)


6. The electron energy levels move around the nucleus at a high speed in every levels.

a. Electron (- charge) – located outside the atomic nucleus

b. The number of electrons is equal to the number of protons an atom has. c. Electrons are tiny! Only 1/1840th of the mass of a proton.


7. How do you determine the Atomic Number? Atomic Mass?

a. Atomic Number = Number of protonsb. Atomic Mass = Sum of protons and neutrons


C. Building More Complex Substances1. Most elements combine with other elements in

nature. 2. A pure substance that is made up of a fixed number

of atoms of two or more elements is called a compound. a. Examples of compounds: NaCl, H2O, CO2,

C6H12O6

b. The properties of a compound are different than those of the elements that create it!


3. All atoms “want” to be stable; if their outermost energy level is not filled, then they will tend to undergo chemical reactions to find stability.

a. Bonds are then formed!


b. Two Important Biological Bonds:1. Covalent Bonds – share electrons Example: Water, Ammonia

** Covalent Bonds are usually found between non-metals and non-metals. **


2. Ionic Bonds – “Opposites” attract; “steal” or transfer electrons; Because of this, they have a charge.An atom or molecule with a charge is an ion. Example: NaCl

** Ionic Bonds are usually found between metals and non-metals. **


4. A molecule is the simplest form of a compound; when two or more atoms join.

a. Example of molecule:


5. van der Waals forces: slight attractions that form when oppositely charged regions of a

molecule are near each other. a. Not as strong as ionic or covalent bonds!b. Can help to keep larger molecules together.


Bond Review: Ionic or Covalent Bond?

a. CCl4 –

b.Li2O –

II. MIXING IT UP….Solutions!

A. A mixture is a material composed of two or more elements or compounds that are physically mixed together but not chemically combined.


B. A solution is a mixture in which one or more substances are evenly distributed in another substance.

1. Two major components: a. Solute – substances dissolved into the

solution b. Solvent – substance in which the solute is

dissolved (the dissolver)Examples of Solvent:Chocolate Milk – Solvent is the milkOcean water- Solvent is the water


2. How do we analyze the strength of a solution? Concentration – amount of solute dissolved in solution

III. Biology is “Burning” Up . . . (Acids, Bases, and pH)!

A. The acidity or basicity of a solution can be measured using the pH scale.

1. Range of the scale: 0-14


2. An acid has a pH of less than 7. It is a larger number of hydrogen (H+) ions than hydroxide (OH-) ions.

a. Example of acid: Milk – pH is 6.5, Stomach Acid – pH is 1.5


3. A base has a pH of greater than 7. It has a larger number of hydroxide (OH-) ions than hydrogen (H+) ions.

a. Example of base: Blood – pH is 7.4, Ammonia – pH is 11.5


4. Neutral pH = 7

a. Example of neutral: WATER!

5. Buffers neutralize acids or bases!

IV. The Chemistry of Water

A. The Polarity of Water

1. Remember . . . covalent bonds join the hydrogen atom and oxygen atom that make up water!

2. Though the electrons are shared, they are not shared equally.

a. Oxygen has 8 protons/positive charges to attract electrons.

b. Hydrogen only has 1 proton/positive charge.

IV. The Chemistry of Waterc. Because of its greater positive charge, the

nucleus of the oxygen atom pulls the shared electron towards its own nucleus and away from the hydrogen.

d. This makes the region of the water molecule where the oxygen is slightly negative (-) and the region where the hydrogen is slightly positive (+).

IV. The Chemistry of Water

e. This is why water is called a polar compound it has an uneven pattern in charge!f. A polar compound is good at dissolving other polar (sugar, proteins) substances and ionic compounds.

V. Hydrogen BondingA. The polarity of water causes water molecules to attract to each other or be “sticky”.

1. Hydrogen bond – attraction holding two (+) water molecules together

2. The region of one water molecule positive (H+) is attracted to the negative (O-) region of another.

3. These are weak bonds and can be broken easily.

V. Hydrogen Bonding

B. Why is hydrogen bonding important to life and biology?1. Creates cohesion of particles.

a. Cohesion – an attraction between molecules of the same substance.

b. Example of cohesion: Water “sitcks” allowing striders to move across water.

V. Hydrogen Bonding

c. Surface tension is created by cohesion.d. Surface tension is a force existing on the surface of a liquid, preventing the layer from being broken.

V. Hydrogen Bonding

2. Creates adhesion of particles. a. Adhesion – an attraction between molecules of different substances.b. Example of adhesion: Meniscus of a test tube.

V. Hydrogen Bonding

3. Adhesion + cohesion work together to create a property of water known as capillary action.

a. This allows water molecules to move upward through narrow tubes against the force of gravity. b. Example of capillary action: Water out of the roots of a plant and up the stem to leaves.

V. Hydrogen Bonding

4. Moderate temperature.a. Water must gain or lose large amount

of energy (heat) to break/form the hydrogen bonds for any temperature change.

b. Why is this important?1. Helps organisms maintain

homeostasis.2. Helps moderate

climate/ocean water temperature.

Ch. 2 – The Chemistry of Life. I. THE COMPOSITION OF THE UNIVERSE A. Everything in the universe is...

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