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Ch 3: Water and Life
General Biology Campbell Biology 9e
The biological medium on Earth required by all living organisms more than any other substance.
Most cells are surrounded by water, and cells themselves are about ___-___% water.
Abundance of water
The main reason the Earth is habitable.
Polar molecule (Water)
What type of molecule is a water molecule?
Opposite ends have opposite charges
Allows water molecules to form hydrogen bonds with each other
Collectively, hydrogen bonds hold water molecules together, a phenomenon called ________.
Cohesion helps the _______ of water against ________ in plants.
An attraction between different substances, for example, between water and plant cell walls.
A measure of how hard it is to break the surface of a liquid
Related to cohesion
What is surface tension related to?
Water absorbs heat from ______ air and releases store heat to ______ air.
What can absorb or release a large amount of heat with only a slight change in is own temperature?
The energy of motion
A measure of the total amount of kinetic energy due to molecular motion
Measures the intensity of heat due to the average kinetic energy of molecules
A substance is the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1 degree C.
High specific heat
Water resists changing its temperature because of its _____ _________ _______.
What water's high specific heat can be traced to?
Heat is absorbed
When hydrogen bonds break, _____ ___ _________.
Heat is released
When hydrogen bonds form, ______ ____ _________.
What does the high specific heat of water minimize to within limits that permit life?
Transformation of a substance from liquid to gas
Heat of vaporization
The heat a liquid must absorb for 1 g to be converted to gas.
A process by which as a liquid evaporates, its remaining surface cools. It helps water stabilize temperature in organisms and bodies of water.
ordered; less dense
Ice floats in liquid water because hydrogen bonds in ice are more "________," making ice _____ ________.
4 degrees C
Water reaches its greatest density at how many degrees Celcius?
If ice sank
What would eventually make all bodies of water freeze solid, thus making life impossible on earth?
A liquid that is a homogeneous mixture of substances.
The dissolving agent of a solution
The substance that is dissolved
One in which water is the solvent
What makes water a versatile solvent and allows it to form hydrogen bonds easily?
Hydration shell or sphere of hydration
When an ionic compound is dissolved in water, each ion is surrounded by a sphere of water molecules called a
Nonionic polar molecules
Water can also dissolve compounds made of what?
ionic and polar regions
Large polar molecules such as proteins can dissolve in water if they have _____ and ______ _______
A substance that has an affinity for water
A substance that does not have an affinity for water
relatively nonpolar bonds
Oil molecules are hydrophobic because they have _________ _________ ________.
The hydrogen atom leaves its electron behind and is transferred as a proton
Shift from one to the other
A hydrogen atom in a hydrogen bond between two molecules can ______ _______ ______ to the ________.
The molecule with the extra proton in now a _________ _____, and is often represented at H+
The molecule that lost the proton
Water is in a state of what in which water molecules dissociate at the same rate at which they are being reformed.
H+ and OH-
Changes in concentrations of _____ and _____ can drastically affect the chemistry of a cell.
Concentrations of H+ and OH- are equal in _______ _______.
Acids and bases
Adding what solutes modifies the concentrations of H+ and OH-?
Biologists use something called what to describe whether a solution is acidic or basic (the opposite of acidic).
Any substance that increases the H+ concentration of a solution
Any substance that reduces the H+ concentration of a solution
25 degrees C
In any aqueous solution at how many degrees is the product of H+ and OH- constant.
A solution is defined by the negative logarithm of H+ concentration
Solutions have pH values less than 7
Solutions have pH values greater than 7
6 to 8
Most biological fluids have pH values in the range of ___ to ____.
A stable suspension of fine particles in a liquid.
The higher the concentration the higher the _________.