Miss Napolitano & Mrs. Haas
CP Biology

• All living things are composed of matter
• Matter: anything that takes up space and has mass
• Matter is made up of elements
• Elements: substance that cannot be broken down into other substances
• A substance consisting of 2+ elements in a fixed ratio is called a compound
• Ex: NaCl, C
6
H
12
O
6
• Essential elements of life: CHNOPSCaK
(carbon, hydrogen nitrogen, oxygen, phosphorus, sulfur, calcium, potassium)

• Atoms : smallest unit of matter
• Made up of subatomic particles
• Protons: positive charge <-- in nucleus!
• Neutrons: neutral (no) charge <-- in nucleus!
• Electrons: negative charge
• Atomic number : number of protons
• Mass number : number of protons + number of neutrons

• Shows nucleus (with P + and N o ) as well as energy levels with electrons
• 1 st energy level can hold 2 electrons
• 2 nd & 3 rd energy levels can hold 8 electrons each
• Electrons are paired when 4+ in a shell

• Valence shell: outermost shell, contains valence electrons
• Valence electrons: electrons involved in chemical bonding

• Shows the chemical symbol for the element with valence electrons
• Electrons are drawn in a circle around the symbols
• Electrons are paired if there are 4+ in its valence shell

• Isotopes: Atoms of the same element with different numbers of neutrons
• Radioactive isotopes occur when the nucleus decays and gives off particles & energy
• When protons are lost, new elements are formed
• Useful in fossil dating & PET scans

• Chemical bonds: attraction between 2+ atoms
• Driving force – full valence shells
• 3 types for this class:
• Covalent bonds
• Ionic bonds
• Hydrogen bonds

• Sharing of a pair of valence electrons to create a molecule
• Example: CH
4
• 2 types of covalent bonds:
• Nonpolar covalent: electrons are shared equally throughout the molecule
• Molecules are usually symmetrical, such as CH
4
• Polar covalent: electrons are not shared equally throughout the molecule due to differences in electronegativity
• Molecules are usually asymmetrical, such as H
2
O

• In ionic bonding , the electronegativity is so strong in one atom that it “takes” an electron from the other
• Create either positive cations or negative anions (types of ions ), and opposite charges are attracted to one another
• Form salts such as NaCl

• Hydrogen bond: weak attractions between H and O or N of different molecules
• Remember! H
2
O is an example of a polar covalent molecule, so H and O have partial positive & negative charges!
• Partial negative charge of O ( δ ) attracts partial positive charge ( δ + ) of H of a different water molecule

• Chemical reaction (rxn): the making or breaking of chemical bonds leading to changes in matter
• Reactants: starting materials
• Products: end result
• Coefficients: the number of molecules involved
• Some reactions are reversible
• A reaction becomes stable when it reaches equilibrium

• Endothermic reactions: absorb energy
• Exothermic reaction: release energy

• 71% of Earth’s surface is water!
• Up to 60% of an adult human body is made up of water!
• Water is polar (unequal distribution of charges)
• Water molecules are held together by covalent bonds
• Water molecules are held to one another by hydrogen bonds

• Cohesion: Water “sticks” to itself
• Ex: drops of water on wax paper
• Adhesion: Water “sticks” to other substances
• Ex: meniscus in a graduated cylinder
• Capillary action: moves against gravity
• Ex: water movement in plants
• Surface tension: difficult to break the surface of water
• Ex: Water strider on top of a pond

• Moderate temperature
• Freezes at 0 o C, boils at 100 o C
• Body temp = 37 o C
• High specific heat – amount of heat absorbed or lost for
1g of a substance to change 1 o C
• Water: 1 cal/g/ o C due to H bonds
• Therefore, resists changes in temperature (ex: ocean)
• Evaporative cooling – prevents organisms from overheating

• Expansion upon freezing
•
•
• Less dense as a solid than a liquid
Water condenses until 4 o C, then expands
Ice floats & insulates water beneath it, allowing for life to thrive
• Versatile solvent
• Solute: substance being dissolved
•
• Solvent: substance doing the dissolving
•
Solution: homogenous mixture of 2+ substances
Aqueous solution: water is the solvent
• Water forms a hydration sphere around ionic compounds and dissolves polar compounds
• Hydrophilic: mixes well with water
• Hydrophobic: repels water (nonpolar)

• Due to the dissociation of water
• Hydrogen ion (H + ) is transferred to another molecule
•
•
Left with hydroxide ion (OH )
Process is reversible!
• Acids: increase H + concentration
• Ex: Hydrochloric acid (HCl)
• Bases: reduce H + concentration
• Ex: Sodium hydroxide (NaOH)
• Strong acids & bases dissociate completely when mixed with water

• In any aqueous solution at 25 o C, [H + ][OH ] = 10 -14
• pH = -log [H + ]
• Ex: For pure water, [H + ] = 10 -7 so –log [10 -7 ] = 7 therefore pH = 7
• pH declines as H + increases

• Internal pH of most cells is about 7
• Changes in pH can be harmful to cells
• Buffers: minimize changes in concentrations of H + and
OH in a solution
• Work by accepting excess H + in acidic solutions or donating H + in basic solutions
• Most contain a weak acid & a corresponding base