ACID AND BASE

1. Block 3 case 2 (biochemistry)
PBL:G5

2. Objectives
❏ Acidity and Basicity.
❏ Definition and Reaction of Acidity and Basicity.
❏ Relationship between the Acidity and Basicity.
❏ Where we have acid and base in our bodies (general).
❏ Definition of the PH and Levels of it.
❏ How we can calculated the PH?
❏ How we can measure PH (indicators).

3. ❏ How does the blood maintain PH?
❏ Definition of the Buffer system in the human body.
❏ The buffer capacity.
❏ Different types (levels) of the buffer.
❏ What happen if we have more acid or base in our bodies ?
❏ Bicarbonate buffer system

4. ACIDITY
Acid
​
​​

5. Basicity
A basic solution has a low H+​ concentration, less than that of
pure water. Solutions are classified as acidic or basic based on
their hydrogen ion concentration relative to pure water. Basic
(alkaline) solutions have a lower H+
​concentration than acids. A
base raises pH by providing hydroxide (OH​−
​​) or another ion or
molecule that scoops up hydrogen ions and removes them from
solution. Strong bases like sodium hydroxide (NaOH) completely
dissociate in water, releasing hydroxide ions (or other types of
basic ions) that can absorb H+
​.

6. What is pH?
The concentration of hydrogen ions in a solution is usually denoted by the
term pH, which is the negative log10
of the hydrogen ion concentration
expressed in moles per liter (mol/L)
pH = -log[H+
]
The pH value is an expression of the ratio of [H+ ] to [OH‐] (hydroxide ion
concentration). Hence, if the [H+ ] is greater than [OH‐ ], the solution is acidic.
Conversely, if the [OH‐ ] is greater than the [H+ ], the solution is basic.
Since pH is a logarithmic value, it doesn’t have any unit.

7. Importance of maintaining pH.
● Most living things depend on a proper pH level to sustain life
● The blood flowing through our veins must have a pH between 7.35 and
7.45. Exceeding this range by as little as one‐tenth of a pH unit could
prove fatal.
● To attain high crop yields, farmers must condition their fields to the
correct pH value
● Rain is typically around 5.6 pH but, in some areas, it increases to harmful
levels between 4.0 and 5.0 pH due to atmospheric pollutants resulting in
acid rain.

8. Calculate pH
To calculate the pH of an aqueous solution you need to know the
concentration of the hydronium ion in moles per liter (molarity). The pH
is then calculated using the expression:
pH = - log [HзO ].
similarly, pOH is the negative of the logarithm of the OH-
ion
concentration.
pOH = - log [OH-
]
pH + pOH = 14

9. Examples:
Example1: Calculate the pH of 0.06 mol/L HCl.
pH = − log0.06 = 1.22
Example 2: Calculate the pH of 0.02 mol/L H2SO4 .
pH = − log0.04 = 1.3979 = ~ 1.4
What is the pOH of a solution that has a hydroxide ion concentration of
4.82 x 10-5
M?
pOH = - log [4.82 x 10-5
] = - ( - 4.32) = 4.32

12. PH SCALE
The ion product of water,is the basis for
the pH scale .It is a convenient means of
designating the actual concentration of
H+ (and thus of OH− ) in any aqueous
solution in the range between 1.0 M H+
and 1.0 M OH−
Because pH is equal to –log [H+], the
greater the [H+], the lower the pH. A
solution with a pH of 7 is neutral, a
solution with a pH <7 is acidic, and a
solution with a pH >7 is basic.

13. Buffer system in the human body
Buffer systems play important roles in nature and in laboratory settings. In nature, they
offer protection to living organisms, while in labs they're used to create an environment
with a stable pH.
Buffer : A solution that resists change in pH when limited amounts of an acid or a base are
added to it; an aqueous solution containing a weak acid and its conjugate base

14. Buffer capacity
◄
◄

15. →
→

16. •

17. •
→

18. Buffer and types of buffer system.
Types of buffer.
There are two types of buffer:
● Acidic buffer.
● Basic buffer.

19. Acidic buffer.
A buffer solution containing large amounts of a weak acid, and its salt with a strong
base, is termed as an acid buffer. Such buffer solutions have pH on the acidic side A
solution containing equimolar quantities of acetic acid and sodium acetate maintains its pH
value around 4.74.The pH of an acid buffer is given by the equation. CH3
COOH and
CH3
COONa.
Where Ka is the acid dissociation constant of the weak acid

20. Basic buffer
A buffer solution containing relatively large amounts of a weak base and its salt with a
strong acid is termed as a basic buffer. Such buffers have pH on the alkaline side e.g.:
NH4
OH and NH4
Cl. A solution containing equimolar quantities of ammonium hydroxide
and ammonium chloride maintains its pH value around 9.25.
The pH of a basic buffer is given by the equation:
Where Kb is the base dissociation constant of the weak base.
These equations are called Henderson Hasselbalch equations

21. How Acid relate with PH and Buffer
•
•
•
​

22. Bicarbonate buffer system
The pH of a solution ultimately depends on the concentration of H+ ions in the
solution. Changing the concentration, by the addition or removal of H+ ions,
can impact the pH of a solution. The bicarbonate buffering system is an crucial
buffer system in the acid-base homeostasis of all living things. The main role
of the bicarbonate system is to regulate and control the pH of blood and
counteract any force that will alter the pH. A buffer system exists to help
neutralize the blood if excess hydrogen or hydroxide ions are produced. An
acid-base buffer consists of a weak acid( H2CO),
CO2 (g) + H2O (l) ↔ H2CO3 (aq)↔ HCO3 –(aq) + H +(aq)

23. what will happen if we have high PH?
● Your body needs to maintain an optimum acid-base balance, or pH
level, to ensure the various processes within your body occur
without problems, according to the University of Maryland
Medical Center. When your body’s pH level becomes high, the
condition is known as alkalosis.

24. Arrhythmia
•

25. Coma
•

26. Where we have acid and base in our bodies?
Acids and bases are very essential to the human body. They function to balance
the pH levels in the body. Unbalanced acids and bases can cause many problems
in the body.
-Where we find them?:
1 - In lungs. (Our lungs regulate how much CO2 is in our blood).
2 - In kidneys (maintain homeostasis through the excretion of waste products)

27. -Role of the lungs
One mechanism the body uses to control blood pH involves the release of carbon dioxide from the
lungs. Carbon dioxide, which is mildly acidic, is a waste product of the processing (metabolism) of
oxygen (which all cells need) and, as such, is constantly produced by cells. As with all waste products,
carbon dioxide gets excreted into the blood. The blood carries carbon dioxide to the lungs, where it
is exhaled. As carbon dioxide accumulates in the blood, the pH of the blood decreases (acidity
increases).
-Role of the kidneys
The kidneys are able to affect blood pH by excreting excess acids or bases. The kidneys have some
ability to alter the amount of acid or base that is excreted, but because the kidneys make these
adjustments more slowly than the lungs do, this compensation generally takes several days.

29. What happen if we have more acid in our bodies?
● When your body fluids contain too much acid, this is known as Acidosis.
● Acidosis occurs when your kidneys and lungs cannot keep your body’s pH in
balance.
● The pH of your blood should be around 7.4. - According to the “American
Association for Clinical Chemistry”
● A lower pH means that your blood is more acidic.
● Acidosis is characterized by a pH of 7.35 or lower.

30. What happen if we have more acid in our bodies?
● There are two types of acidosis: Respiratory and Metabolic acidosis.
○ Respiratory acidosis occurs when too much CO2
builds up in the body.
“Normally the lungs remove CO2
while you breathe. However, sometimes your
body can’t get rid of enough CO2
.
○ Metabolic acidosis starts in the kidneys instead of the lungs. It occurs when they
can’t eliminate enough acid or when they get rid of too much base.

31. What happen if we have more acid in our bodies?
● Symptoms of Acidosis:
○ becoming tired easily.
○ confusion.
○ shortness of breath.
○ sleepiness.
○ headache.
○ lack of appetite.

32. References:-
● Introduction to organic and biochemistry,7th-edition, page 156
● http://study.com/academy/lesson/buffer-system-in-chemistry-definition-lesson-quiz.html
#lesson
● http://www.livestrong.com/article/317719-how-to-neutralize-acid-in-human-body/
● http://www.healthline.com/health/acidosis?m=2#Overview1
● https://www.google.com.sa/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ua
ct=8&ved=0ahUKEwjOqtT9xPnSAhXLVRQKHbgVAjAQFggaMAA&url=https%3A%2F%
2Fwww.hach.com%2Fasset-get.download.jsa%3Fid%3D7639984488&usg=AFQjCNEH
wWGS08MlrmsKrzi_pjv2WPY2_A&sig2=0lDmdzy7uHNDc89UhYsF0w
● Introduction-to-organic-and-biochemistry-7th-edition (pg 151)
● Mark's Basic Medical Biochemistry 4th edition 2013 ( pg 45-46)

33. HAVE A NICE DAY.