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BIOLOGY
Ch-2 Chemistry of life
Nature of matter
An __________is the smallest unit of matter that cannot be broken down by chemical
means.
Subatomic particles:

Protons –

Electrons –

Neutrons –
Draw the model of an Atom.
An _________________is a pure substance made of only one kind of atom.
Number of known elements now is ____________
e.g.
Atoms of an element that contain different numbers of neutrons are called
__________________.
e.g.
CHEMICAL BONDING
Atoms can join with other atoms to form stable substances through a _____________
________.
A _____________ is a substance made of the joined atoms of two or more different
elements.
e.g.
Covalent Bonds
A , molecule is a group of atoms held together by covalent bonds.
e.g
Covalent bonds form when two or more atoms share electrons to form a molecule.
e.g.
Hydrogen bonds
Molecules with an unequal distribution of electrical charge, such as water molecules,
are called __________ molecules. This attraction between two water molecules is an
example of a hydrogen bond—a weak chemical attraction between polar molecules.
Ionic Bonds
Sometimes atoms or molecules gain or lose electrons. An atom or molecule that has
gained or lost one or more electrons is called an _______.
An atom that has lost electrons is _____________charged, whereas an atom that has
gained electrons is ___________ charged.
Ions of opposite charge may interact to form an _________ bond.
e.g.
Water and Solutions
Properties of water:
 Storage of heat –

Cohesion –

Surface tension –

Adhesion –
Aqueous Solutions
A _____________ is a mixture in which one or more substances are evenly distributed in
another substance.
What is Polarity?
Give an example of a polar substance.
Give an example of a non polar substance.
Acids and Bases
H2O
--------------- H+ + OH–
Pure water always has a low concentration of hydrogen ions and hydroxide ions, which
are present in equal numbers.
Compounds that form hydrogen ions when dissolved in water are called
______________.
When an acid is added to water, the concentration of hydrogen ions in the solution is
increased above that of pure water.
Compounds that reduce the concentration of hydrogen ions in a solution are called
__________. Many bases form hydroxide ions when dissolved in water.
pH scale
Carbon Compounds
Organic compounds contain _________ atoms that are covalently bonded to other
elements—typically hydrogen, oxygen, and other carbon atoms.
Four principal classes of organic compounds are found in living things:
Carbohydrates, lipids, proteins, and nucleic acids
CARBOHYDRATES
Properties and uses:
Made of carbon, hydrogen, and oxygen atoms in the proportion of 1:2:1
Key source of energy, and they are found in most foods—especially fruits, vegetables,
and grains
Classification:
LIPIDS
Properties and uses:
They are nonpolar molecules that are not soluble in water.
They include fats, phospholipids, steroids, and waxes.
They are an important part of the structure and functioning of cell membranes.
Phospholipids make up the lipid bilayer of cell membranes.
Steroids include cholesterol, which is found in animal cell membranes.
Other lipids include some light-absorbing compounds called pigments, such as the plant
pigment chlorophyll.
Fats are lipids that store energy
Fat = Glycerol + 3 fatty acids
Classification:
PROTEIN is a large molecule formed by linked smaller molecules called amino acids.
20 types of amino acids are found. They may be polar, non polar or electrically charged.
Proteins tend to fold into compact shapes determined by how the protein’s amino acids
interact with water and one another.
Uses:
Some proteins are enzymes and they promote chemical reactions
Structural functions Antibodies help fight infections
Help muscle contraction Carry oxygen in blood -
NUCLEIC ACIDS are long chain of smaller molecules called nucleotides. A has three
parts: a sugar, a base, and a phosphate group, which contains phosphorus and oxygen
atoms.
There are two types of nucleic acids—
DNA and RNA—and each type contains four kinds of nucleotides.
DNA - ________________________ consists of two strands of nucleotides that spiral
around each other. Chromosomes contain long strands of DNA, which stores hereditary
information
RNA - _____________________ consists of a single strand of nucleotides. RNA plays
many key roles in the manufacture of proteins. RNA can also act as an enzyme,
promoting chemical reactions that link amino acids to form proteins.
Other important compounds
ATP _____________________________ is a single nucleotide with two extra energy-storing
phosphate groups.
Energy and chemical reactions
__________________ is the ability to move or change matter. Energy exists in
many forms—including light, heat, chemical energy, mechanical energy, and electrical
energy—and it can be converted from one form to another.
A _____________ ______________is a process during which chemical bonds between
atoms are broken and new ones are formed, producing one or more different substances
Reactants --------
e.g.
ENERGY AND CHEMICAL REACTIONS
(Refer to figure ___ in textbook)
 Energy releasing reactions
e.g. When water freezes, the process that leads to the formation of ice crystals
causes heat energy to be released.
 Energy absorbing reactions
e.g. When you remove ice cubes from the freezer, the ice begins to melt. When ice
melts, it absorbs heat from the environment.
________________ is the term used to describe all of the chemical reactions that occur
within an organism
Activation Energy
The energy needed to start a chemical reaction is called _______________ __________.
Activation energy is simply a chemical “push” that starts a chemical reaction
Enzymes –
Enzymes are catalysts, which are substances that reduce the activation energy of a
chemical reaction
Enzymes help organisms maintain homeostasis. Without enzymes, chemical reactions
would not occur quickly enough to sustain life.
(Refer to figure ___ in textbook)
e.g.
Enzyme Specificity
A substance on which an enzyme acts during a chemical reaction is called
a_________________.
Enzymes act only on specific substrates.
e.g. starch------------
e.g. 2H2O2 ----------------- 2H2O + O2
An enzyme’s shape determines its activity. Typically, an enzyme is a large protein with
one or more deep folds on its surface. These folds form pockets called_______ ________
An enzyme acts only on a specific substrate because only that substrate fits into its active
site.
(Refer to figure ___ in textbook)
Factors in Enzyme Activity



Temperature
pH
Chemicals