Download Page 1 of 3 Chapter 2 Essential Chemistry CONTENT I. Basic

Bio100’15 Medina
Chapter 2
Essential Chemistry
Objectives: You will be able to:
1. Explain the importance of basic chemistry in Biology and provide definitions for all new terms.
2. Sketch an atom based on the atomic number and show its sub-atomic particles and their charges. Locate valence electrons.
3. Using a table, compare and contrast 3 types of chemical bonds.
4. Using a sketch, compare and contrast non-polar and polar molecules, as well as dissociation of hydrophilic substances.
5. List and describe the properties of water and provide an example of their impact to life.
6. Using a pH scale, identify acids and bases, provide examples, and define the term acid and base based on their relative
hydrogen concentration.
CONTENT
I. Basic Chemistry
Life is carried on through chains of chemical reactions. We study chemistry to understand how these chemical
reactions are involved in the living world, that is, how elements combine with other elements.
Chemistry: Greek “chemeia”  “cast or pour together”, chemistry deals with science of matter at the atomic to
molecular level. Chemistry deals mostly with collections of atoms. The subject of chemistry is matter and its
transformations.
• Matter: anything that occupies space and has mass.
• Mass is the quantity of matter in an object  mass of an object = space and density
II. Fundamental forms of matter: elements
• Element: pure substance that cannot be separated into a simpler component substance through
chemical processes.
Each element is defined by the number of protons = atomic number in its nucleus; i.e. carbon is
composed of identical atoms each with 6 protons in their nucleus, chlorine has 17 protons. What elements
are found in our bodies? 4 Most abundant:_________,_________,__________, & __________
Checkpoint:
We study chemistry because___________________________________________________________________________________________
_____________________________________________________________________________________________________________________
Matter is defined as ____________________________________________________________________________________________________
An element is a ________substance. Elements are separated & identified by their number of _________________
III. The Atom: Greek: “indivisible”
The atom is an indivisible component of matter: i.e. 100 million carbon atoms fit end to end in 3 cm.
Sub-atomic particles:
• Nucleus (center, heavier):
o Protons: _________charge
o Neutrons: ________charge or neutral
• Orbitals or shells (lighter):
o Electrons: ________charge, “cloud”
http://commons.wikimedia.org/wiki/Image:HAtomOrbitals.png
More basic concepts:
• Atomic mass = number of protons (identifies the element)
• Usually, number of protons equals number neutrons
• Stable atom: outermost shell is filled to capacity (2 or 8), otherwise unstable
• Electrons on outermost shell are called valence electrons
• Electronegativity: capacity of an atom to pull electrons towards itself.
• Isotope: form of an element with difference in mass due to different number of neutrons
• Radioactive isotope: nucleus decays spontaneously, giving off particles and energy.
Draw and label an atom, atomic # 3:
Draw and label an atom, atomic # 4:
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Bio100’15 Medina
Why is the atom, atomic# 4, more stable than the atom with an atomic # 3?______________________________________________________
What provides most of the atom’s weight? Orbitals / Nucleus
What is electronegativity?
What differs between an element and its isotope?
What are the uses of radioactive isotopes?
Why are radioisotopes dangerous?
(Valence / All)_________________electrons in an atom form bonds because they are readily accessible on the outermost shell.
IV. Chemical Bonding and Molecules matter gets transformed
• Process of chemical combinations and rearrangements to achieve stability by interactions between
electrons.
• Stability: having a full outer shell (2 or 8 electrons).
• Nonreactive elements, such as Helium, have full outer shells and will not react. Reactive elements
(unstable) have unpaired valence electrons (i.e. N, H)
• Three types of bonds: covalent, ionic, and hydrogen bonds:
1) Covalent bonds- electrons are shared to have a full outer shell. Atoms share
electrons based on their electronegativity and receive a name based on polarity:
a. Nonpolar covalent bond, equal sharing (example, hydrogen gas: H - H)
b. Polar covalent bond: unequal sharing (examples, water molecule: H-O-H).
2) Ionic bonds- electrons are lost or gained (example, table salt: sodium + chloride,
Ions = charged atoms after losing or gaining one electron: cation ( ), anion ( )
Ionic compounds stay together due to the attraction of opposite charges= salts.
3) Hydrogen bonds- attraction between H and O or N, this weak attraction occurs
between different molecules or within the same molecule (example, interaction
between water molecules, interactions within a DNA or protein molecules).
Partial negative end of one water molecule is attracted to the partial positive end
of another water molecule.
Checkpoint:
In Covalent bonding, electrons are ___________. A nonpolar covalent bond is formed by equal / unequal sharing, whereas a polar
covalent bond is formed by equal / unequal sharing of electrons between 2 atoms.
Fill in the missing information on the following table:
Bond Name
Electrons are
How are electrons shared?
Name of bond
a.
a.
Covalent
b.
b.
Ionic
N/A
N/A
__________ or ___________
Hydrogen Opposite charges from H and
N/A
N/A
_________________attract each other
V. Chemical Reactions
Rearrangement of molecules by breaking existing bonds and making new ones:
Write down the chemical reaction for water &
Label the Reactants and Products:
A molecule’s shape gives it unique characteristics.
Three-dimensional molecular shape determines the capacity to bind with one another. Shape determines
function. Example: How something tastes depends on the shape of its molecule. Specific receptors bind specific
molecules, a signal is sent to the brain and it is detected as salty, sweet, sour or bitter.
Shape determines:__________________
What quality of the molecule insulin allows glucose to enter the cell? Circle one: color / size / shape.
http://mol-biol4masters.masters.grkraj.org/html/Cellular_Signal_Transduction3-Signal_Transduction_Pathways.htm
http://www.youtube.com/watch?v=OYvav8aDGCc
VI. Water has features that enable it to support all life.
• 71% Earth’s surface, 66% human body weight water is required or generated by cellular
reactions. Example: saliva breaks down maltose into glucose units.
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•
•
•
•
•
Cohesion and adhesion work together and create capillary action.
Due to great amounts of H-bonding, water molecules are more stable when they stay close to
each other; it takes energy to break those bonds. Terms:
1. Cohesion: tendency to stay together: H2O-H2O
2. Adhesion: tendency to adhere to a solid: H2O-surface area
Surface tension: water molecules have a specific fluidity and support pressure acting as an elastic
material, without surface tension the smallest particle would sink to the bottom  keeps healthy
ecosystems, keeps cell membrane from collapsing on itself, for transport of water and blood.
Specific heat is high large heat capacity (0°C to 100°C at sea level) to moderate temperature on
land=buffer. Oceans absorb enormous amounts of heat from the sun and release it when
temperatures go down; water also cools down land-dwelling creatures by evaporative cooling.
Low density as a solid  Insulator (i.e. in aquatic environments fish are protected by the top ice
layer). Ice is less dense than liquid water  it floats because molecules are more rigid and spaced
farther apart.
Important solvent for hydrophilic compounds universal hydrophilic solvent. Does not dissolve
hydrophobic compounds and thus allows for compartmentalization (creation of compartments by a
membrane). Solvent: ____________agent; solute: dissolved substance; solution: solute dissolved in
solvent. H, as partially charged end, bonds with polar or charged molecules
 Hydrophobic = repels water, nonpolar (nonpolar covalent bonds)
 Hydrophilic = attracts water, polar (polar covalent / ionic / H-bonds)
 A single molecule may have both polar and nonpolar sides
Checkpoint: Water is essential to all living organisms due to its properties. Connect the properties in the left column to their corresponding
benefits in the right column:
About 70% of earth is water
means it’s a buffer to keep stable temperature on land
Universal solvent of hydrophilic compounds
allow for transportation of nutrients through capillary action
Ice has low density
indicates that it’s required or generated by cellular reactions
Large heat capacity
means it dissolves polar/charged molecules
Cohesion & adhesion
allows for “compartmentalization” (formation of a cell membrane)
Inability to dissolve hydrophobic molecules
this serves as a temperature insulator in large bodies of water
VII. Acids, Bases, and pH
A. pH Scale: a measure of hydrogen ion concentration in a solution. 10-fold change. H2O  H+ + OH0 ______________________________________7______________________________________14
Acid
Neutral
Base/Alkaline
Accepts H+
Releases H+
B. Living organisms are sensitive to pH:
 Enzymes can be denatured at low pH
 Organisms develop buffering systems to keep pH within normal limits:
Homeostasis: capacity to keep a stable, constant internal environment (human blood pH
is7.4). Breathing in a balanced way maintains proper pH levels. If the system fails=
hyperventilation: exhaling > inhaling
CO2 + H2O  H2CO3 (carbonic acid)
1. CO2 leaves blood so pH becomes basic
2. Symptoms: lightheaded, slight numbness hands & feet, may pass out
2. An acid___________(yields or accepts) hydrogen ions. A base ___________(yields or accepts) hydrogen ions.
3. Place the following substances on the appropriate side of the pH scale above: oven cleaner, human blood, bleach, water, vinegar,
battery acid, ammonia, and baking soda.
4. Why is pH important for living organisms?________________________________________________________________
Answer Questions 1-10, 12 & 13 on page 35 of your textbook.
________________________________________________END____________________________________________
HOMEWORK: Chapter 3 (1 pt) DUE NEXT MEETING
Make a list of the 4 Biological Molecules, define, provide their main function and one specific example of each.
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