biology EXAM #1 pt. 3 Flashcards
Water is
the molecule that supports all life
All living organisms require _______ more than any other substance
_________________ of the Earth’s surface is submerged in water
the main reason the Earth is habitable:
water
Three-quarters
The abundance of water
properties of water
Polarity of water and hydrogen bonding
The polarity of water molecules results
The water molecule is a
in hydrogen bonding
polar molecule
the polarity of water molecules allow for
About 15% of the molecules are bonded to four partners in short–lived clusters at any instant in liquid water at 37ºC (human body temperature),.
Allows them to form hydrogen bonds with each other
Contributes to the various properties water exhibits
Four emergent properties of water contribute to Earth’s fitness for life:
-Cohesion
-Moderation of temperature
-Ice – less dense than liquid form of water, insulation of bodies of water by floating ice
-Solvent of life
cohesion is:
due to :
helps:
Is the bonding of a high percentage of the molecules to neighboring molecules
Is due to hydrogen bonding
Helps pull water up through the microscopic vessels of plants
adhesion:
what is it:
in plants it is:
Adhesion is an attraction between different substances, for example, between water and plant cell walls
the clinging of one substance to another, also plays a role. Adhesion of water to the walls of the cells helps counter the downward pull of gravity
water transport
Evaporation from leaves pulls water upward from the roots through water–conducting cells, in this case located in the trunk of a tree. Cohesion due to hydrogen bonding helps hold together the column of water within the cells. Adhesion of the water to cell walls helps resist the downward pull of gravity. Because of these properties, the tallest trees can transport water more than 100 meters (m) upward—approximately one–quarter the height of the Empire State Building in New York City.
entender
surface tension:
is related to
The result is
Is a measure of how hard it is to stretch or break the surface of a liquid
Is related to cohesion
collective strength of its hydrogen bonds
moderation of temperature
Water moderates air temperature by:
Specific heat of water
-absorbing heat from air that is warmer and releasing the stored heat to air that is cooler
-Water is effective as a heat bank – it can absorb or release a relatively large amount of heat with only a slight change in its own temperature.
Kinetic energy is:
The kinetic energy associated with random motion of atoms or molecules is called
Is the energy of motion
-thermal energy
Heat:
Is a measure of the total amount of kinetic energy due to molecular motion. It is the thermal energy in transfer from one body of matter to another
Temperature:
represents the:
Measures the intensity of heat
represents the average kinetic energy of the molecules in a body of matter
The specific heat of a substance:
The specific heat of water is
Water resists changing its temperature because
Is the amount of heat that must be absorbed or lost for 1 gram of water to change its temperature by 1ºC. Much energy compared to alcohol and other compounds
1 cal/(g * ºC)
of its high specific heat
Water has a high specific heat, which allows it to:
Heat is absorbed when
Heat is released when
-minimize temperature fluctuations to within limits that permit life
hydrogen bonds break
hydrogen bonds form
Evaporation:
Is the transformation of a substance from a liquid to a gas
Heat of vaporization:
It takes about ____ calories of heat to evaporate: (nearly double the amount needed to vaporize 1 gm of alcohol or ammonia)
-Is the quantity of heat a liquid must absorb for 1 gram of water to be converted from a liquid to a gas
-580; 1 gm of water at 25oC
As a liquid evaporates, its remaining surface cools, a process called
This helps:
this is due to-
it allows-
evaporative cooling
- stabilize temperatures in organisms and bodies of water
-Is due to water’s high heat of vaporization
-Allows water to cool a surface
Solid water, or ice is less:
and it:
why is it less ___?
In ice, each molecule is _________________________. Because __________________, ice has fewer molecules than an equal volume of liquid water.
in liquid water:
Is less dense than liquid water
Floats in liquid water
The hydrogen bonds in ice are more “ordered”and stable than in liquid water, making ice less dense
-hydrogen–bonded to four neighbors in a three–dimensional crystal
-the crystal is spacious
-Hydrogen bonds constantly break and re-form
Since ice floats in water:
Many scientists are worried that global warming is having a profound effect on icy environments around the globe
The rate at which glaciers and Arctic sea ice are disappearing poses an extreme challenge to
Life can exist under the frozen surfaces of lakes and polar seas
-animals that depend on ice for their survival
Water is a versatile solvent due to :
The solvent is the
The solute is the substance that
It can form:
The different regions of the polar water molecule can interact with
Water can also dissolve :
Even large polar molecules such as __________ can dissolve in _____ if they have :
Water can also interact with polar molecules such:
-its polarity
-dissolving agent of a solution
-that is dissolved
-aqueous solutions
-ionic compounds called solutes and dissolve them
-compounds made of nonionic polar molecules
-proteins ; water if they have ionic and polar regions.
-as proteins
A hydrophilic substance:
Has an affinity for water
A hydrophobic substance:
Does not have an affinity for water
Oil molecules are hydrophobic because :
Hydrophobic molecules related to oils are:
they have relatively nonpolar bonds
the major ingredients of cell membranes
Since most ________________ occur in water:
-It is important to learn to :
-When carrying out experiments,
-biochemical reactions
-calculate the concentration of solutes in an aqueous solution
-we use mass to calculate the number of solute molecules in an aqueous solution
Molecular mass is
Number of molecules can be measured in _______. This represents an exact number of :
-the sum of all masses of all atoms in a molecule
-MOLES
molecules of a substance in a given mass
1 mole (mole) = _________ molecules or daltons (Avogadro’s number and the unit “dalton” for ___________ = ______ )
Molarity:
6.02 x 10^23
6.02x1023 = 1g
-Is the number of moles of solute per liter of solution
The dynamic equilibrium of water molecules:
Dissociation of water molecules leads to
the rate which water molecules dissociate is the same as the rate at which they are being formed.
acidic and basic conditions that affect living organisms
Water can dissociate into:
Changes in the concentration of these ions:
Changes in concentrations of ___and____ can drastically affect the :
Into hydronium ions and hydroxide ions
-Can have a great affect on living organisms
-changes in H+ and OH–
chemistry of a cell
An acid
A base
Is any substance that increases the hydrogen ion concentration of a solution
Is any substance that reduces the hydrogen ion concentration of a solution
In any aqueous solution at 25°C the product of H+ and OH– is constant and can be written as
[H+][OH–] = 10^–14
The pH of a solution is defined by the negative logarithm of H+ concentration, written as
pH = –log [H+]
For a neutral aqueous solution, [H+] is 10^–7, so
pH = –(–7) = 7
Concentrations of H+ and OH– are
Adding certain solutes, called ____________, modifies the :
Biologists use the pH scale to describe whether:
equal in pure water
-acids and bases
-concentrations of H+ and OH–
-a solution is acidic or basic (the opposite of acidic)
Acidic solutions have pH values:
less than 7
Basic solutions have pH values :
greater than 7
Most biological fluids have pH values:
in the range of 6 to 8
The pH of a solution is determined by
-the relative concentration of hydrogen ions
-Is low in an acid
-Is high in a base
The internal pH of most living cells
Must remain close to
pH 7
Buffers
Consist of an :
example of a buffer:
Are substances that minimize changes in the concentrations of hydrogen and hydroxide ions in a solution
acid-base pair that reversibly combines with hydrogen ions
Carbonic acid, an example of a buffer in human blood and other biological solutions
Acid precipitation refers to :
Is caused primarily by the
Acid rain is thought to be responsible for
Acid precipitation can damage:
rain, snow, or fog with a pH lower than pH 5.6
- mixing of different pollutants with water in the air lowering pH below 5.2; example: H2SO4 and
HNO3
-killing trees in many forests,
-life in Earth’s ecosystems
Acidification
Human activities such as______________ also threaten water quality
main product of fossil fuel combustion
- burning fossil fuels
-CO2
About ___% of human-generated CO2 is absorbed by
CO2 dissolved in____________ forms ____________; this process is called:
-25% of human-generated CO2 is absorbed by the oceans
- sea water; carbonic acid
ocean acidification
As seawater acidifies,
_______________ is required for calcification (production of calcium carbonate) by many marine organisms, including reef-building corals
H+ ions combine with carbonate ions to produce bicarbonate (HCO3)
Carbonate
Carbonic acid dissociates into hydrogen ions and bicarbonate
The added H+ combines with carbonate ions forming more bicarbonate ions
The remarkable properties of water support life on Earth in many ways
Astrobiologists seeking life on other planets are concentrating their search on
To date, more than 800 planets have been found outside our solar system; one or two of them contain water
In our solar system, _______ has been found to have water
-planets with water
-Mars
