Biochemistry Flashcards
Ch. 2, 3, 4, 5 (53 cards)
What is electronegativity
The attraction of a particular atom for the electroms of a covalent bond
A nonpolar covalent bond is:
A covalent bond where the electrons are shared equally
A polar covalent bond is:
A covalent bond in which one atom is more electronegative than the other, resulting in an unequal distribution of electrons
Explain why H2O is considered to be polar even though it does not have a negative charge
Oxygen is more electronegative than hydrogen, meaning electrons are pulled toward oxygen. This creates partial negative charges at the oxygen end and 2 partial positive charges at each hydrogen end
What are hydrogen bonds
The partial positive charge in hydrogen resulting from polar covalent bonds allows the hydrogen to form bonds with other electronegative atoms
This accounts for water’s great suitibility for life
What are Van der Waal interactions
Electrons may accumulate in polar & nonpolar bonds by chance. This causes fluctuating positive and negative regions, allowing molecules to bind together
What are the 4 emergent properties of water
- Cohesive behavior
- Ability to moderate temperature
- Expansion upon freezing
- Versatility as a solvent
Cohesive behavior
What is cohesion in water
Water molecules will stay close together and bonded due to polar nature and hydrogen bonds
This accounts for structure seen in water vs other liquids
Cohesive behavior
What is adhesion in water
Hydrogen bonds in water help form bonds with other molecules
Cohesive behavior
What is surface tension in regards to water molecules and explain how it relates to cohesion
Surface tension in water is a measure of how difficult it is to stretch or break the surface
Water is not hydrogen-bonded to the air above but to itself. Water therefore does not want to ‘break’ until it is stretched past the point of no return
Moderation of temperature
How does water moderate air temperature
Water absorbs heat from air when warm and releases stored heat when cold
Water stores heat in H-bonds and C-bonds
Moderation of temperature
What is the difference between thermal energy and temperature
Thermal energy reflects the total kinetic energy of atoms in a body of matter and is therefore dependent on volume
Temperature is the average kinetic energy of a molecule in a body of matter, regardless of volume
Moderation of temperature
What is a specific heat capacity
The amount of heat that must be absorbed of lost for 1 gram of substance to change temperature by 1°C
Moderation of temperature
Define heat
Thermal energy in transfer from one body of matter to another
Moderation of temperature
What is heat of vaporization
Quantity of heat a liquid must absorb for 1 gram of substance to go from a liquid to a gas
H-bonds must break before molecule can go from liquid to gas
Moderation of temperature
What is evaporation cooling
As a liquid evaporaties, the surface of the remaining liquid begins to cool because the ‘hottest’ molecules have already left
Expansion upon freezing
Water ____ as it warms and ____ as it cools
expands, contracts
Expansion upon freezing
Between 0-4°C, water begins to freeze, breaking which type of bonds
Hydrogen bonds
Expansion upon freezing
True or False:
At 1°C, water locks into a crystaline lattice form
False
This happens at 0°C
Versatility as a solvent
Solutes placed in water dissociate as they are surrounded by:
Hydration shells
What is a buffer
A substance that minimizes changes in [OH-] and [H3O+] in a solution
Accepts H+ when in excess and donates H+ when depleted
What is an isomer
A variation in structure of an organic molecule
What is a structural isomer
An isomer differing in covalent arrangements
Ex. 2, 2-dimethyl propane vs 2-methyl butane
What is a cis-trans isomer
A double-bonded isomer with R groups on the same side or opposite side
*inflexible due to double bond
Ex. Cis-but-2-ene vs. Trans-but-2-ene
