Cellular pH
*All matter has the ability to be dissolved
into a solution. A solution is a type of
liquid mixture in which a solid is
dissolved into a liquid.
*Two parts two a solution:
Solvent – the liquid part of a mixture
that does the dissolving.
Solute – solid substance being
dissolved into a solution.
Example Solutions:
salt water, blood, Sprite, coke
*Water is the most common solvent
in solutions.
*The most important chemical
property of a solution is its pH.
pH – is the measure of how acidic
or how basic a solution is.
*pH is an abbreviation for “potential
hydrogen”, which is created
when water breaks down matter
in a solution.
How does water determine the
pH of a solution?
*When water dissolves matter into a
solution, water actually dissociates
(breaks apart) into ions instead of
individual hydrogen and oxygen atoms.
An ion is one or more elements that are
charged due to the gain or loss of
electrons.
*Water breaks down into TWO types of
ions:
H2O > H+ + OH-
*H+ ion called hydronium ion and an OHion called hydroxide ion.
*As long as water is pure and nothing is
being dissolved, both of these ions will
be present in EQUAL amounts. Water
is said to be neutral. A neutral solution
is described as any substance that
contains an equal amount of H+ and
OH- ions in solution.
*However, if any other matter is
present and is dissolved into a
solution by water, an UNEQUAL
number of these ions are formed.
*The pH of a solution is a measure
of the H+ as water breaks matter
down. If there is an imbalance of
ions, the solution is either acidic
or basic (alkaline).
Acid – any type of solution that
contains a greater concentration
of H+ ions than OH- ions.
Base – any type of solution that
contains a greater concentration
of OH- ions than H+.
*Not all acids and bases are
created equal; some are
stronger and destructive;
others are weak and
harmless.
*The balance of the two ions
from water (H+ and OH-)
determine just how strong an
acid / base is and is
represented by a pH number
arranged on a pH scale.
The “Rule of Thumb” for acid
and base strength is
this….(meaning, you better
know this!!!!!)
The greater the concentration of
the ion that makes the acid or
base, the stronger the acid or
base is.
*The closer the ions are to
becoming balanced, the weaker
the acid and base.
*In other words, stronger acids
have more H+ than OH-;
stronger bases have more OHthan H+.
Characteristics of
Acids and Bases
Acids
Bases
*0 – 6.9 on pH scale.
*naturally sour in taste.
*good conductors of
electricity (used in
car batteries)
*H+ > OH*Stronger acids have
lower pH numbers;
weaker acids have
higher pH numbers.
*7.1 – 14 on pH
scale.
*naturally slimy in
texture.
*good conductors of
electricity (used in
alkaline batteries)
*OH- > H+
*Stronger bases
have higher pH
numbers; weaker
bases have lower
pH numbers.
The pH Scale
Weak Acids:
(pH 5 – 6)
*Acid Rain
Medium Acids:
(pH 3 – 4)
*Vinegar
*Colas
*Citrus Fruits
Strong Acids:
(pH 0 – 2)
*Toilet Bowl Cleaner
*Rust Remover
*Stomach Juices
*Battery Acid
Weak Bases:
(pH 8 – 9)
*Shampoos
*Body soaps
Medium Bases:
(pH 10 – 12)
*Heartburn Medication
(antacids)
*Cleaners
*Detergents
Strong Bases:
(pH 13 – 14)
*Ammonia
*Drain Cleaners
*Alkaline Batteries
*Acids and bases can only be
compared to each another as
“equals but opposites”…..one is
no more stronger or more
dangerous than the other.
*The strength of one acid can only
be compared to another
acid…not to a base (and viceversa).
*For each increase or decrease in
pH number on the pH scale, the
strength of an acid (or a base)
will change by the power of 10.
*For example, a base with pH = 11
is 10x stronger than pH = 10,
100x stronger than pH = 9 , and
1000x stronger than pH = 8.
*An acid with a pH of 5 is 10x
weaker than a pH of 4; 10,000
times weaker than pH of 1!!!
*General Formula To Determine
Comparison Strengths:
10n
(where n = # of spaces between two
solutions on pH scale)
Example Problems
1)
In a chemistry experiment,
Bertha’s solution had a pH of 1;
Agatha’s solution had a pH of
6? What is the comparative
strength of these two acids?
There are FIVE spaces between 1
and 6 on pH scale; therefore
use “105” power.
Final Answer: pH 1 is 100,000x
STRONGER than pH 6.
2)
Clifford tested his soil in his
garden and he determined that
the soil pH level was 10. Corn
prefers a neutral soil level.
a. In terms of pH, what type of
soil is Clifford’s corn growing
in?
Medium basic soil
b. How strong is a soil pH of 10
compared to 7?
103 = 1000x stronger
Neutralization
*Since acids and bases are “equals, but
opposites”, one has the capacity of
neutralizing the other.
Neutralization – the process of adding an
acid or base to a solution to achieve a
pH of 7.
*Only acids can neutralize bases; only
bases can neutralize acids.
*Each acid has an opposite base (called a
“conjugate base”) on the pH scale that
is equal in strength; each base has an
opposite acid (called a “conjugate acid”)
on the pH scale that is equal in
strength.
*Each acid or base conjugate is the direct
opposite (mirror image on the pH
scale) pH number.
*Ex: A base w/ pH of 9 will need a
conjugate acid w/pH of 5 to neutralize
it and bring the pH down to 7.
Why?
Both pH of 9 and pH of 5 are equally
distance from pH of 7 on pH scale.
Example Problems
1)
Sally’s swimming pool has
a pH of 11. What type of
solution and its pH would
Sally have to add to bring
her pool water back to a
safe pH of 7?
Since pH of 11 is a base,
Sally would have to add a
conjugate acid of 3 to
neutralize her pool (both
are four units away from pH
of 7 on pH scale).
2)
Billy Bob has severe heartburn,
with an estimated pH of 1.
Which of the following antacids
would be the most effective at
neutralizing his heartburn?
Which would be the least
effective?
Rolaids: pH = 10
Alka Selzter: pH = 8
Citricil: pH = 6
Tagamet: pH = 13
Answer: Most Effective =
Tagamet
Least Effective = Citricil (its an
acid!!)
pH Indicators
*You cannot tell the pH of a
solution just by looking at it.
*It is possible to determine a
solution’s pH by the use of a
pH indicator.
Indicator – a chemical that
turns a specific color in the
presence of an acid, base, or
neutral solution.
Types of pH
Indicators
Red Litmus
Blue Litmus
Phenylphthalein
Wide Range pH Indicator
Red Cabbage (natural
indicator)
. Enzyme Activity
*All living things are driven by
chemical reactions  respiration,
digestion, cell division,
glycolysis, protein production
are just a few of thousands of
chemical reactions that occur within
you right at this moment.
*Unfortunately, the natural rates of
chemical reactions within our body
are sooooo slooooow that they
cannot sustain life.
*All chemical reactions must require
“help” because the amount of
energy needed to get them started
(called activation energy) is too
high.
How do these chemical reactions
take place within us if they are
so slow?
*A catalyst is any type of
substance (natural or man-made)
that lowers the amount of
activation energy needed to start
a chemical reaction.
*Catalysts speed up chemical
reactions thousands of times
faster than those without
catalysts; they do NOT
increase the amount or the
quality of product made at the
end of the reaction!!
*Special types of proteins
called enzymes are the
catalysts used in living
things.
Enyzme – a type of biological
catalyst that is used to speed
up chemical reactions in
living things.
*Enzymes speed up chemical
reactions such as respiration,
cell division, and digestion by
lowering the amount of
activation energy needed to
get the reaction going.
Energy Diagram
*Enzyme Benefits:
1) Chemical reaction proceeds
faster.
2) Enzyme is reusable..... once
the enzyme speeds up reaction,
it is NOT used up in the process.
*Enzyme Cons:
1) Essential for life; many
illnesses and genetic disorders
are the result of missing or
malfunctioning enzymes.
2) Enyzmes are picky.....
meaning that each type of
enzyme can work only on certain
reactions; they are NOT
universal.
*The reactant or ingredient that
an enzyme works on in a
chemical reaction is called a
substrate.
*To speed up the chemical
reaction, the enzyme binds to
the substrate at its active
site.
*Because enzymes are picky
as to which substrate it will
work on, the active site is
shaped to fit the specific
enzyme. This prevents other
unnecessary enzymes from
working on the substrate.
*Notice the enzyme is shaped to
fit the substrate at the active
site. This phenomenon is called
the lock and key model
because it describes how
particular enzymes are
complementary to their
substrates just like keys are to a
specific lock.
How Enzymes Work
*Real-life examples of enzyme-substrate
complexes:
(FYI: most enzymes end in the suffix “-ase”)
Enzyme Name: Substrate:
1)
Amylase
Amylose
2)
Helicase
DNA
3)
Lactase
Lactose
4)
Lipase
Lipids
Reaction:
Digestion of
starch
Unwinds DNA
during replication
Digestion of
milk sugar
Breakdown
of fats
*Factors that affect enzyme function:
1) Temperatures – extreme
temperatures will denature (alter)
the shape of the enzyme, causing
it not to bind properly to substrate;
most human enzymes prefer
temperatures between 98-99F.
2) pH Levels – most living things
prefer pH levels between 6 – 8;
environments that are too acidic or
basic will denature the shape of
enzymes.
3)
Surface Area – enzymes
will work faster and are
more effective on
substrates that are already
broken into smaller pieces
instead of one huge chunk;
we chew are food into small
pieces so that digestive
enzymes can work faster at
breaking the food down.
4) Concentration – the more
enzymes present, the better
that they will work; higher
concentrations of enzymes
= faster chemical reactions.