Lectures 1 & 2 Flashcards
Mass Number
number of protons + neutrons
Atomic Number
number of protons
Covalent Bond
- Made of 2 electrons
- Those 2 electrons are shared (i.e. one electron comes from each atom)
- Atoms can form bonds until their outermost shell is filled
Polar Covalent Bonds in water molecules
electrons are not shared equally (O is more electronegative than H), so partial charges exist on the O and H atoms
Increasing positive electrical charge in nucleus
H < C < N < O < F
Hydrogen Bond
A hydrogen bond is an electrostatic attraction between two polar groups that occurs when a hydrogen (H) atom, covalently bound to a highly electronegative atom such as nitrogen (N), oxygen (O), or fluorine (F)
Meniscus
forms where water meets a solid surface, as a result of two forces. Adhesion: Water molecules that adhere to the glass resist the downward pull of cohesion Cohesion: Water molecules at the surface experience a net downward pull from hydrogen bonds with water molecules below
High Surface Tension
Property of Water - Because of surface tension, light objects do not fall through the water’s surface
Ice
Water molecules form a crystal lattice.
Liquid water
- No crystal lattice forms.
- Denser than ice. As a result,
ice floats.
Ionic Bond
- Electrostatic attraction between positive and negative charge
- Forms ions
Hydrophilic
Water loving
a) Polar molecules and ions dissolve readily in water
- partial negative and positive charges of water interact with the positive and negative ions
ex. salt dissolved in water, ions separate then dissolve
Hydrophobic
Water Fearing
b) Nonpolar molecules do not dissolve in water.
cannot interact with water, so they stay away
ex. Water and oil
Hydrophobic interaction
Water forces nonpolar molecules together, because doingso minimizes their disruptive effects on the hydrogen-bonded water network
- important for protein folding
Van der Waals interaction
Nonpolar molecules are also attracted to each other via relatively weak attractions called van der Waals forces (transient dipoles).
Bond Energy
Amount of energy needed to separate two bonded or interacting atoms under physiological conditions
Chemical bonds in order of strength in biology
Covalent > H bond > Ionic Bond > Hydrophobic interaction > LDF
Chemical Reactions
A chemical reaction can be written as an equation. The equation must balance because matter is neither created nor destroyed.
Molarity
A 1 molar (1 M) solution is one mole of a compound dissolved in water to make one liter.
Example: One mole of NaCl is the atomic weight of Na (23) plus the atomic weight of Cl (35.5), or 58.5, in grams. When 58.5 grams of NaCl are dissolved in water to make one liter, the solution is 1 molar.
Mole
- amount of a substance in grams whose weight is equal to its molecular weight.
Acids
release/donate H+ ions in solution.
If the reaction (dissociation) is complete, it is a strong acid, such as HCl.
The carboxyl group (—COOH) is common in biological compounds. It functions as a weak acid because it dissociates partially and reversibly
—COOH —COO– + H+
Bases
- accept H+ in solution (release OH–). (takes protons from water)
- NaOH ionizes completely to Na+ and OH–. The OH– absorbs H+ to form water. It is a strong base.
- The amino group (—NH2) is an important part of many biological compounds; it functions as a weak base by partially and reversibly accepting H+:
—NH2 + H+ —(NH3)+
pH
defined as the negative logarithm of the H+ concentration in moles/liter
1 (very acidic) -14 (very basic)
7- neutral (water)
