Unit 1: Water and Life

does everything have water in its composition? why is it important?

yes, everything is tied to water

why is water a polar molecule?

bonded together by two polar covalent bonds.

aproximate number of water in animals/humans

animals 60-70%

humans 80-90%

75% infant, 65% children, 55% women, 60% men

hypertonic vs hypotonic

hypertonic: not enough water cause cells to shrink

hypotonic: too much water cause shells to swell up

stay in the middle, neutral, isotonic, normal

what happens during dehydration? hypertonic

loss of water from body, body fluids become hypertonic, thrist, dark urine, small volume of urine, lagargy, raised pulse, low bp, extreme brain damange, seizure, death

what happens during over hydration? hypotonic

extra intake of water, body fluids become hypotonic, clear large volumes of urine, confusion, drowsiness, delirium, nausea, extreme seizures, coma, death

characteristics of O-H molecule

covalent bond bc sharing of one electrons

single bond bc one pair of electrons is shared between O and H

polar bond bc unequal sharing of electron pair; oxygen more electromagnetic & has stronger pull on electron pair

explain

there is one oxygen atom and two hydrogen atoms.

the oxygen atom is bonded to two hydrogen atoms via covalent bonds which means the atoms share electrons. sharing is unequal

oxygen is more electromagnetic than hydrogen meaning it pulls the shared electrons closer to itself resulting in a partial neagtive charge on the oxygen atom and a partial positive charge on the hydrogen atoms.

the molecule is not linear but it is bent. due to the repulsion between the pairs of unshared electrons on the oxygen atom which pushes the hydrogen atoms closer together.

unequal sharing of electrons so it is a polar molecule.

the oxygen end of the molecule is slightly negative, and the hydrogen ends are slightly positive. this polarity allows water to interact strongly with other polar substances and gives it unique properties like high surface tension and the ability to dissolve many substances.

why is earth habitable?

the abundance of water

where does the metabolism occur?

water medium

cytoplasm is

water based

a molecule is

2 or more molecules connected by bonds

what holds dna together?

hydrogen bonds

water molecules can

form hydrogen bonds with themselves/with other molecules

characteristics of the O-H bond in a water molecule

H-O-H bonded together by 2 polar covalent bonds. therefor water is polar.

covalent bond bc electrons are shared

single bond bc 1 pair of electrons is shared between H & O

polar bond bc unequal sharing of electron pair so oxygen is more electronegative and has a stronger pull on the electron pair

delta negative charges on oxygen

delta positive charges on hydrogen

water molecule is neutral (net charge=0) bc the delta negative and elta positive cancel each other out

hydrogen bond is a weak attraction between

delta negative and delta positive

bonds from strongest to weakest

covalent, ionic, h-bond

h-bonds in water

holds water molecules together

bc h-bonds are weak attractions, they break and reform with great frequency in liquid water.

bc of their large numbers in water, the h-bond determines many properties of water

why is the h-bond important in biology?

plays an important role in holding water molecules together/solubility of water

found in proteins, nucleic acids…

shape of dna, proteins & water determined by h-bonds

the polar nature of water contributes to earth’s

suitability for life

waters life supporting properties

cohesion, adhesion, crucial solvent of life, frozen water floats, high specific heat

cohesion

holding hands together, cling to one another, can form large bodies

surface tension

surface of water body: stronger bonding enable us to float things on water

resistance of water to spill from glass, formation of water droplets

adhesion

water molecules cling to other polar surfaces: plants

water climbs up because of , clings together by __

adhesion, cohesion

for all life the dissolving agent is

water, water is the solvent of life

solute

dissolves in water

sugar, salt

solution

homogenous mixture of solvent & solute

2 types of sulute

hydrophilic: love water, dissolve easily, ionic compounds NaCl, polar molecules sugar

hydrophobic: dislie water, does not dissolve in water, nonpolar molecules - fats, oils, O2

hydration shell

water molecules form a sphere around ions & polar molecules as they dissolve

hydrophilic material _ while hydrophobic materials _ absorb water

absorb, do not

is water attracted to molecules with no charge?

no, only charged molecules

is ice denser than water?

less dense, has to do with h-bonding

liquid water

water molecules tightly packed in liquid water making it more dense

heaviest at 4 degrees celcius

h-bonds constantly break & reform in liquid water

density

mass over volume: mass/volume

why does ice expand?

water molecules expand (spread out) & locked in place by stable hydrogen bonds as water molecules freeze at 0 degrees celcius

most dense water all the way at the bottom because

more dense so it is heavier

what would happen if ice was heavier than water?

ponds, lakes, oceans would freeze solid killing life

specific heat

amount of heat energy required to raise the temperature of. a substance by 1 degree Celcius (or 1 Kelvin).

a substance with high specific heat requires more heat to change its temperature compared to a substance with lower specific heat.

why does water have high specific heat?

due to its molecular structure & strong hydrogen bonds between water molecules

high specific heat of water

water molecules held together by h-bonds

when you add heat to water, instead of the energy increasing the motion of the molecules (which raises the temperature), the energy goes towards breaking/weakening these h-bonds

bc of the h-bonds water can absorb a lot of heat without significant rise of temperature. this gives water a specific heat of 4.18 J/g degree celcius

why is high specific heat of water important?

temperature regulation: water can act as a buffer, absorbing/releasing heat with small changes in temperature. important for stable environments for organisms. large bodies of water (like oceans) help moderate earth’s climate by absorbing heat during the day and releasing it at night

human & animal bodies: our bodies mostly composed of water, high specific heat helps us maintain stable internal temperature. crucial for homestasis: process of keeping our bodies functioning properly despite changes in environment

climate & weather:weather paterns, stabilizes coastal climates preventing extreme temperature fluctuations. between day & night

what is waters high specific heat mainly due to?

h-bonds between molecules which require a lot of energy to break before temperature can rise

evaporative cooling

evaporation of water from the surface of the body, leaving the body cooler

as sweat evaporates it removes excess heat, helps mamals from over heating

importance of ph

plants depend on soil to have right ph level for proper growth

our bodies must maintain proper ph level to function properly

soft drinks, medicine, cosmetics are “ph balanced”

ph informs us of

the power of hydrogen in life

stomach acid

ph of 2 or 3, very acidic, lots of hydrogen ions H+

most living things can not live in the presence of strong acid so it is important stomach acid stays in the stomach

the cells in stomach lining replace themselves continually bc it is a rough environment in which to live.

chemical composition of water

H2O

H3O+ (H+) ion

OH- ion

naturally undergoes a dossiciation (ionization) producing hydorgen ions (H+) and hydroxide ions (OH-) in equal amounts.

neutral ph of 7, 10^-7 mol/L with an equal concentration of of H+ and OH- ions

H+ and OH- are very reactive

H+ acidity

OH- alkalinity (basic)

acidity

acidic content in solution, determined by concentration of H+ ions or protons in that solution

high concentration of H+ ions

ph less than 7

more H+ ions more acidic

alkalinity

ability of a solution to neutralize acids

measure of a solutions capacity to resist changes in ph when acids are added

considered alkaline (basic) if it has high concentration of OH- ions

ph greater than 7

often associated with the precense of substances like bicarbonate ions (HCO3-), carbonate ions (CO3²-) and hydroxide ions (OH-) which can act as buffers to neutralize acids

acids

H+ (proton) donors

increase H+ concentration

hydrolic acid HCL ~ H+ + Cl-

acidosis

high levels of free H+

stop cell reactions, denature proteins, nucleic acids, coma, death

bases

H+ (proton) acceptors

OH- donors

decrease H+ when added to water

stronger the base, greater decrease in H+

acids & bases

when added to water, change the concentrations of H+ and OH-

ph scale

ranges from 0-14

ph stands for

potential hydrogen

a measure of H+ concentrations in moles per litr

calculate ph of distilled water

ph = -log[H+] -log[10^-7]= -[-7] =7

ph is 7

calculate pOH- of distilled water

pOH= -logOH-] -log[10^7] = -[-7] = 7

pOH is 7

ph scale

classifies substances as neutral, acidic, alkaline 0-14

ph 7 neutral

ph 0-6.9 acidic

7.1-14 alkaline

2 important constants on the ph scale

ph + pOH = 14

[H+] x [OH-] = 10^-14

change in ph vs change in [H+]

if ph drops by 1 unit more acidic; [H+] is 10-fold higher

if ph rises by 1 unit less acidic; [H+] is 10-fold lower

each unit change on ph scale represents a 10-fold change in [H+]

buffers

helps maintain constant ph ph by neutralizing acids or bases

minimize changes in ph when acid or base is added

minimizes [H+] and [OH-]

weak acid + conjugate acid

weak acid: neutralizes alkalinity; H+ donor

conjugate acid: neutralizes acidity; H+ acceptor

buffers are crucial for

normal cell function, metabolism, homeostasis

bicarbonate buffer system in the blood is one of the most important examples of how buffers maintain a stable internal environment in organisms.

what is the ph of pure water

7

if water has the ability to buffer it should

resist change even if you add acid or base to it

ph should resist change

ph should be maintained for a good buffer/resist change

if ph goes down it is now a good buffer

the composition of buffer is

acid and conjugate base

you can neutralize acid and base if

buffer is present

if something is very alkaline

ph level will be above 7, more OH- ions, low H+ proton (inverse so acidic is the opposite)

how does the acid neutralize the base

raise H+ levels

buffer capacity

once it gets used up the system will no longer buffer

in the human, tissue fluid and blood what is the common buffer

carbonic acid, sodium bicarbonate system HCO3

if it does not have an H+ it will pick up another positively charged ion

base neutralizes

acid

human buffer system as a ph regulator

carbonic acid - bicarbonate buffer

H.HCO3 (back and forth) Na.HCO3

buffer capacity

once weak acid or conjugate base of buffer is depleted solution can no longer buffer and rapid changes in ph occur

how many bonds hold the atoms of a water molecule together? What type of bonds?

2, 2 polar covalent bond

what element is more electronegative and has a partial negative charge in water

oxygen

anything with high specific heat

can not change the temperature easily

why is it hard to change the temperature in water

the kinetic energy does not increase bc the water molecules are held together by the h-bonds, so break the h-bonds

when removing h-bonds

involves removal of heat

acids are

H+ donors, raise H+ levels (associated with acidity)

bases are

OH- donors, lower H+ levels (associated with alkalinity)

H+ acceptors

OH- + H+ =

H2O