57 terms

Ch 3: Water and Life

General Biology Campbell Biology 9e
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Water
The biological medium on Earth required by all living organisms more than any other substance.
70-95%
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?
Polar molecule
Opposite ends have opposite charges
Polarity
Allows water molecules to form hydrogen bonds with each other
Cohesion
Collectively, hydrogen bonds hold water molecules together, a phenomenon called ________.
transport; gravity
Cohesion helps the _______ of water against ________ in plants.
Adhesion
An attraction between different substances, for example, between water and plant cell walls.
Surface tension
A measure of how hard it is to break the surface of a liquid
Related to cohesion
What is surface tension related to?
warmer; cooler
Water absorbs heat from ______ air and releases store heat to ______ air.
Water
What can absorb or release a large amount of heat with only a slight change in is own temperature?
Kinetic energy
The energy of motion
Heat
A measure of the total amount of kinetic energy due to molecular motion
Temperature
Measures the intensity of heat due to the average kinetic energy of molecules
Specific heat
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 _____ _________ _______.
Hydrogen bonding
What water's high specific heat can be traced to?
Heat is absorbed
When hydrogen bonds break, _____ ___ _________.
Heat is released
When hydrogen bonds form, ______ ____ _________.
temperature fluctuations
What does the high specific heat of water minimize to within limits that permit life?
Evaporation
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.
Evaporative cooling
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?
Solution
A liquid that is a homogeneous mixture of substances.
Solvent
The dissolving agent of a solution
Solute
The substance that is dissolved
Aqueous solution
One in which water is the solvent
Polarity (versatile)
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 ______ _______
Hydrophilic
A substance that has an affinity for water
Hydrophobic
A substance that does not have an affinity for water
relatively nonpolar bonds
Oil molecules are hydrophobic because they have _________ _________ ________.
Hydrogen ion
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 ________.
Hydronium ion
The molecule with the extra proton in now a _________ _____, and is often represented at H+
Hydroxide ion
The molecule that lost the proton
Dynamic equilibrium
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.
Pure water
Concentrations of H+ and OH- are equal in _______ _______.
Acids and bases
Adding what solutes modifies the concentrations of H+ and OH-?
pH scale
Biologists use something called what to describe whether a solution is acidic or basic (the opposite of acidic).
Acid
Any substance that increases the H+ concentration of a solution
Base
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.
pH
A solution is defined by the negative logarithm of H+ concentration
Acidic
Solutions have pH values less than 7
Basic
Solutions have pH values greater than 7
6 to 8
Most biological fluids have pH values in the range of ___ to ____.
Colloid
A stable suspension of fine particles in a liquid.
Reaction
The higher the concentration the higher the _________.