Chapter 6 Notes
The 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.
An Element in the Periodic Table
Elements
Section 2-1
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
Figure 2-2 Isotopes of Carbon
Section 2-1
Carbon Isotopes
Nonradioactive carbon-12
6 electrons
6 protons
6 neutrons
Nonradioactive carbon-13
6 electrons
6 protons
7 neutrons
Radioactive carbon-14
6 electrons
6 protons
8 neutrons
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 nondissolved 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
Water
• A water molecule (H2O), is made
up of three atoms --- one oxygen
and two hydrogen.
H
H
O
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 Sugars
1. 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.