Chapter 6 NotesThe Chemistry of Life

Composition of Matter• Matter - Everything in the universe is

composed of matter

• Matter is anything that occupies space or has mass

• Mass – quantity of matter an object has

• Weight – pull of gravity on an object

Elements• Elements: Pure substance that consists of

one type of atom (oxygen), and cannot be broken down chemically into simpler kinds of matter

• More than 100 elements (92 naturally occurring)

• Only four of the elements – Carbon, Hydrogen, Oxygen, and Nitrogen – make up 96% of the mass of a human.

Section 2-1

An Element in the Periodic Table

Elements

Atomic Number: # of Protons (+)

Atomic Mass: # of Protons (+) and Neutrons (0)

To find the # of Neutrons (0): Atomic Mass – Atomic # = # of Neutrons (0)

Atoms: The Building Blocks of Elements

• Atoms: Basic unit of matter, is the smallest particle of an element that has the characteristics of that element, and is made of subatomic particles (protons “+”, neutrons “0”, and electrons “-”)

• Atoms contain equal #’s of electrons “-” and protons “+” (no charge)

Atoms: The Nucleus

• Nucleus: Central core of the atom – Contains the protons and the neutrons

(Protons “+” charge, Neutrons “0” charge)

Atoms: The Electron Cloud

• Electrons are found In the electron cloud around the nucleus (“-” charge)

1st level 2 electrons max

2nd level 8 electrons max

3rd level 18 electrons max

Atoms: The Electron Cloud• Ex.: Oxygen – Atomic #8 = 8 electrons

- 1st energy level (2 electrons)

- 2nd energy level (6 electrons)• Atoms contain equal numbers of electrons and

protons; therefore, they have no net charge.

ATOMS

Isotopes

• Isotopes: Atoms of the same element that have a different number of neutrons.

Ex: Carbon 12 6p and 6n

Carbon 13 6p and 7n

• To find the number of neutrons, subtract the number of protons from the Mass #

• 13 – 6p = 7n

Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14

6 electrons6 protons6 neutrons

6 electrons6 protons8 neutrons

6 electrons6 protons7 neutrons

Section 2-1

Figure 2-2 Isotopes of Carbon

Carbon Isotopes

Compounds

• Compound: substance formed by the chemical combination of two or more elements.

• Compounds form between elements so they can become stable. – An atom becomes more stable when its

outermost energy level is full, such as having eight electrons in the second level.

Bonding• Chemical Bonds

- Ionic Bond: when one or more electrons are transferred from one atom to another.

-Ions: positively and negatively charged atoms

Ex. Na(+) Cl(-) (table salt)-Covalent Bond: Forms when electrons are shared by atoms to become stable (water H20)

-A molecule is a group of atoms held together by a covalent bond

Ionic Bond

Covalent Bond

Chemical Reactions• Chemical reactions occur when bonds are

formed or broken, causing substances to recombine into different substances. (Examples: Metabolism and Photosynthesis)

Mixtures• Mixture: A material composed of two or

more elements or compounds, in which the individual components retain their own properties.- Ex. Salt and Pepper Mixture- Ex. Earth’s Gases

Solutions • Solutions: Is a mixture in which one or more

substances (solutes) are distributed evenly in another substance (solvent).

-Ex. Salt water ( Salt is the solute – substance that is dissolved, Water is the solvent – substance in which the solute dissolves)

Suspensions

• Suspensions: Mixtures of water and non-dissolved materials.

-Ex. Blood: transports un-dissolved particles throughout the body

Acids and Bases

• pH Scale: is a measure of how acidic or basic a solution is. (0 – 14)

• 0 – 6: Acids, higher number of hydrogen ions

• 8 – 14: Bases, higher number of hydroxide ions

• 7: Neutral, not acidic or basic• Buffer: Weak acids or bases, that can react

with strong acids or bases to prevent sharp sudden changes in pH

pH Scale

WaterWater

• A water molecule (H2O), is made up of threethree atoms --- one oxygen and two hydrogen.

O

H

H

Importance of Water• Water is perhaps the most important compound

in living things.• Water is polar. The electrons in water are not

shared equally – the electrons are attracted by the oxygen atom more strongly than by the hydrogen atoms. Water can dissolve many ionic compounds, such as salt, yet can also dissolve many other polar molecules such as sugar.

Importance of Water• Water molecules also attract other water

molecules. The attraction of opposite between hydrogen and oxygen forms a weak bond called a hydrogen bond.– Hydrogen bonds are important because they

help hold proteins together and moving water throughout plants.

Hydrogen Bonds• Cohesion: Attraction of molecules of the same

substance.

-Ex. Water droplets

-Ex. Insects walking on water

Hydrogen Bonds

• Adhesion: Attraction of molecules of different substances.

-Ex. Water in a glass container

Importance of Water

• Water resists temperature changes. It is like an insulator that helps maintain a steady environment when conditions fluctuate.• Because cells exist in an aqueous

environment, this property of water is extremely important to cellular functions as it helps cells maintain homeostasis.

Importance of Water• Water expands when it freezes. Water is

one of the few substances that expands when it freezes. This property of water breaks down rocks, which then helps form soil.

Importance of Water• The properties of water make it an

excellent vehicle for carrying substances in living systems. One way to move substances is by diffusion.

• Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration.

Carbon Compounds

• Carbon Atoms: In order to become stable, a carbon atom forms four covalent bonds that fill its outer energy level. This property makes a huge number of carbon structures possible.

• Macromolecule: Monomers join together to form polymers

• Four groups of organic compounds: Carbohydrates, lipids, nucleic acids, and proteins

Carbon Compounds

• Carbohydrates: Living things use carbohydrates as main source of energy, also can be used for structural purposes.-Ex. Starches and Sugars1. Monosaccharide: (Single sugars Ex. Glucose, Fructose, and Galactose)

2. Polysaccharide: Linked to monosaccharides (Ex. Glycogen or Animal starch, plants make cellulose)

Carbon Compounds• Lipids: Fats and oils, used to store energy,

insulation, and protective coating. Non-soluble (Ex. Water and oil)

Carbon Compounds• Nucleic Acids: Macromolecules that contain

hydrogen, nitrogen, oxygen, carbon, and phosphorous.– Nucleotides: 3 parts (5 carbon sugar,

phosphate group, and a nitrogen base)– Two types DNA and RNA

Carbon Compounds

• Proteins: Provide structure for tissues and organs and carry out cell metabolism; made of amino acids.

- 20 different amino acids

- Amino Acids combine to make proteins.

Chemical Reactions and Enzymes• Chemical Reactions: Process that

changes or transforms chemicals into other chemicals.– Reactants: Elements or compounds that start

the reaction– Products: The end result of the reactants

2.4 Enzymes• Catalyst: A substance that speeds up the rate

of a chemical reaction. (Enzymes and Energy are catalysts)

- Enzymes: Proteins found in living things that speed up chemical reactions that take place in cells, speed the reactions in digestion of food, affect synthesis of molecules, and storage and release of energy.