Buffer system

Contents…...
 INTRODUCTION
 ACIDS & BASES
 TYPES OF ACIDS & BASES
 pH
 BUFFERS
 TYPES OF BUFFER (MECHANISM)
 DISORDERS
 ROLE OF NUTRITION

Introduction

 Acid-base regulation

– Regulation of hydrogen ion
• Buffer system

• Respiratory regulation

• Renal regulation

Why To Regulate
 To maintain homeostasis

 Regulates enzymatic functions

Acids And Bases

 Acids

– Release protons (H) ;Eg-H2CO3 , HCL

 Bases

– Accept protons (H) ; Eg-HCO3

Types of acids and bases
 Strong acids
– Release large amount of Hydrogen ions
 Weak acids
– Release small amount of Hydrogen ions
 Strong bases
– Accept large amount of Hydrogen ions
 Weak bases
– Accept small amount of Hydrogen ions

pH
 Hydrogen ion conc. Determines pH

What Is Buffer ???
 A buffer is a solution (or a substance) that has

the ability to maintain pH and bring it back to
its optimal value by addition or removal of
hydrogen ions

Buffer + H H buffer

Contd….
 When Hydrogen ion conc. Increases
– Reaction shifts towards right
 When Hydrogen ion conc. Decreases
– Reaction shifts towards left
In this way hydrogen ion concentration is
maintained

Types of chemical buffer
– Carbonic acid-bicarbonate –

– Buffering changes caused by organic and fixed
acids

– Protein buffer system-Amino acids

– Minor buffering system-

– Phosphate –Buffer pH in the ICF

Buffer Systems in Body Fluids

Figure 27.7

Carbonic Acid-Bicarbonate
Buffering System
 Carbonic acid-bicarbonate buffer system

 Weak acid – H2CO3

 Bicarbonate salt (NaHCO3)

Strong acid is added

– When HCL is added Hydrogen conc.
increases

– CO2 + H2O H2CO3 H + HCO3

Contd…
 Strong base is added
H+ conc. Reduces
NaOH + H2CO3 NaHCO3+H2O

In this way CO2 conc. decreases

This inhibits respiration.

Carbonic Acid-Bicarbonate Buffer
System

Bicarbonate buffer-
 Has the following limitations:
– Cannot protect the ECF from pH changes due
to increased or depressed CO2 levels

– Only functions when respiratory system and
control centers are working normally

– It is limited by availability of bicarbonate
ions (bicarbonate reserve).

Phosphate buffer system-
 Main elements of phosphate buffer system-
- H2PO4, and HPO4

 Phosphoric acid changes pretty quickly into
dihydrogen phosphate, or H2PO4-.

 This dihydrogen phosphate is an efficient
buffer.

Contd….
 Phosphate buffer system in the ECF is low
compared to the bicarbonate buffer.

 Its buffering power is less compared to the
bicarbonate buffer.

 It has its importance in the renal
tubules of kidneys for two reasons.
.

Contd
 1.Conc. of phosphate is more in tubules.

 2. Tubular fluid has lower pH.

 Conc. of phosphate is more in ICF compared
to ECF.

Protein buffer system

 Proteins are made up of amino acids
 Amino acids have a central carbon with four
groups off of it:
1.a carboxyl group (COOH)
2.an amino group (NH2)
3.a hydrogen atom
4.an R group
.

Contd…
 The carboxyl and amino groups are what enable
proteins to act as buffers.

 Carboxyl group is attached to the amino acid central
carbon: C - COOH

 Carboxyl group consists of a double bond
to one of the oxygens and a single bond to the
hydroxyl group.

Contd...
 At neutral pH the carboxyl ion is present as
COO instead of COOH.

 Acidic medium – becomes COOH

 Basic medium – becomes COO.

Contd…
 Amino group is attached to the amino acid
central carbon: C - NH2.

 Neutral pH, the amino group is actually-
NH3+ rather than just NH2.

 Acidic medium – becomes NH3+

 Basic medium- becomes NH2

Respiratory regulation

When alveolar ventilation increases

CO2 conc. In ECF decreases

H+ conc. decreases

Or vice versa.......

Respiratory regulation Contd…
 Pulmonary expiration of CO2 balances metabolic
formation of CO2
– 1.2 mol/L of dissolved CO2 is present in the ECF
corresponding to pCO2 of 40 mm/hg

– Rate of pulmonary ventilation is inversely
proportional to CO2 & pCO2

– So either pulmonary ventilation rate of CO2
– or its formation by tissues can change pCO2

in ECF.

Contd…
 Increasing alveolar ventilation decreases ECF
hydrogen ion conc. And raises pH

– If alveolar ventilation increases the pCO2 decreases.

– If alveolar ventilation decreases the

pCO2 increases.

– Twice rise of AV--rises pH of ECF by about 0.23

– Decrease of AV to ¼ -- decreases pH by 0.45

Contd…
 Increased Hydrogen ion conc. Stimulates
alveolar ventilation

 Change in alveolar ventilation rate is much
greater in reduced levels of pH than in
increased levels of pH

Reason
Alveolar ventilation rate decreases

Increases pH

O2 added in blood reduces

Demand of O2 in blood increases

pO2 also decreases

Stimulates ventilation

Feedback control of Hydrogen
ion conc. By RS
H conc. Falls below normal

Respiration is depressed

Alveolar ventilation decreases

H increases back to normal

Bufffering power of RS
 The kidneys work in elimination of hydrogen
ion conc. and control imbalance.

 Its capacity is 1-2 times as much as other
chemical buffers.

Impairment of lungs function:

 Impairment of lung function leads to

emphysema and respiratory disorders.

 Kidneys play a major physiologic mechanism

for returning pH to normal

Renal mechanism of acid-base
regulation
 Kidneys regulate the blood pH by

 1. maintaining alkali reserves

 2. excreting / reabsorbing acid/base.

 Urine pH is lower than blood pH

 Kidneys- Acidification of urine.

Contd…
 Excretion of hydrogen ions

 Reabsorption of bicarbonate ion

 Excretion of ammonium ions

Disorders of acid-base regulation

 MAY LEAD TO---------

 ALKALOSIS--

OR

 ACIDOSIS--

Disorders of acid-base regulation
cont…
 Respiratory acidosis

 Respiratory alkalosis

 Metabolic acidosis

 Metabolic alkalosis

Contd…
 Respiratory acid-base disorders are initiated by
an increase or decrease in partial pressure of
carbondioxide whereas metabolic disorders are
initiated by an increase or decrease in
bicarbonate ion.

Contd…
 Alkalosis - Partial pressure of oxygen
increases.

 Acidosis – Partial pressure of carbondioxide
increases.

Contd…
Respiratory acidosis-
 Decrease in rate of pulmonary ventilation-
 Increased pCO2 of ECF.

Respiratory alkalosis-
 Increased rate of ventilation-
 Decrease the pCO2

Respiratory acidosis

Figure 27.12a

Respiratory alkalosis

Figure 27.12b

Contd…
 Metabolic acidosis-
 Decreased ECF bicarbonate ion conc.

 Metabolic alkalosis-
 Increased ECF bicarbonate ion conc.

Contd…
DISTURBANCE pH PRIMARY RATIO SECONDARY
CHANGE CHANGE

Metabolic Acidosis Decreased Deficit of bi- <20 Decrease in PaCO2
carbonate

Metabolic Increased Excess of >20 Increase in PaCO2
Alkalosis bicarbonate

Respiratory Decreased Excess of <20 Increase in bicarbonate
acidosis carbonic acid

Respiratory Increased Deficit of >20 Decrease in bicarbonate
alkalosis carbonic acid

Contd…
 Causes - Metabolic acidosis
 1. Renal tubular acidosis
 2. Diarrhea
 3. Vomiting of intestinal contents
 4. Diabetes Mellitus
 5. Ingestion of acids
 6. Chronic renal failure

Contd…
 Causes- Metabolic alkalosis
 1. Vomiting of gastric contents
 2. Ingestion of alkaline drugs etc.

Correction by renal for…
 Acidosis-
 Increased excretion of hydrogen ions and
addition of bicarbonate ions to the ECF.

 Alkalosis-
 Decreased tubular secretion of hydrogen ions
and increased excretion of HCO3_

EAT MORE -- Alkaline (80%)
AcidAlkaline food chart
EAT LESS -- Acidic (20%)
Highly Alkaline Moderately Alkaline Mildly Alkaline Neutral/ Mildly Acidic Moderately Highly Acidic
Acidic
pH 9.5 alkaline water Avocado Artichokes Black Beans Fresh, Natural Juice Alcohol
Himalayan salt Beetroot Asparagus Chickpeas/Garbanzos Ketchup Coffee & Black Tea
Grasses Capsicum/Pepper Brussels Sprouts Kidney Beans Mayonnaise Fruit Juice
Cucumber Cabbage Cauliflower Seitan Butter (Sweetened)
Kale Celery Carrot Cantaloupe Apple Cocoa
Kelp Collard/Spring Greens Chives Currants Apricot Honey
Spinach Endive Courgette/Zucchini Fresh Dates Banana Jam
Parsley Garlic Leeks Nectarine Blackberry Jelly
Broccoli Ginger New Baby Potatoes Plum Blueberry Mustard Miso
Sprouts(soy, alfalfa etc) Green Beans Peas Sweet Cherry Cranberry Rice Syrup
Sea Vegetables (Kelp) Lettuce Rhubarb Watermelon Grapes Soy Sauce
Green drinks Mustard Greens Swede Amaranth Mango Vinegar
All Sprouted Beans/ Sprouts Okra Watercress Millet Mangosteen Yeast
Onion Grapefruit Oats/Oatmeal Orange Dried Fruit
Radish Coconut Spelt Peach Beef
Red Onion Buckwheat Soybeans Papaya Chicken
Rocket/Arugula Spelt Rice/Soy/Hemp Protein Pineapple Eggs
Tomato Lentils Freshwater Wild Fish Strawberry Farmed Fish
Lemon Tofu Rice & Soy Milk Brown Rice Pork
Lime Other Beans & Legumes Brazil Nuts Oats Shellfish
Butter Beans Goat & Almond Milk Pecan Nuts Rye Bread Cheese
Soy Beans Most Herbs & Spices Hazel Nuts Wheat Dairy
White Haricot Beans Avocado Oil Sunflower Oil Wholemeal Bread Artificial Sweeteners
Chia/Salba Olive Oil Grapeseed Oil Wild Rice Syrup
Quinoa Coconut Oil ` Wholemeal Pasta Mushroom
Flax Oil/ Udo’s Oil Ocean Fish

SO WHY NOT CONTROL THE
ACID BASE BALANCE WITH
FOOD…???

References

 Guyton's medical physiology,(Buffer System)

 Ionic changes By Rudolf Jensen

The Central Role of the Carbonic
Acid-Bicarbonate Buffer System in
the Regulation of Plasma pH

Figure 27.11a

The Central Role of the Carbonic
Acid-Bicarbonate Buffer System in
the Regulation of Plasma pH

Figure 27.11b

Acid-Base Disorders

 Respiratory acid base disorders
– Result when abnormal respiratory function causes
rise or fall in CO2 in ECF
 Metabolic acid-base disorders
– Generation of organic or fixed acids
– Anything affecting concentration of bicarbonate ions
in ECF

Respiratory acidosis
 Results from excessive levels of CO2 in body
fluids

Respiratory alkalosis
 Relatively rare condition
 Associated with hyperventilation

Metabolic acidosis
 Major causes are:
– Depletion of bicarbonate reserve
– Inability to excrete hydrogen ions at kidneys
– Production of large numbers of fixed / organic acids
– Bicarbonate loss due to chronic diarrhea

Figure 27.13 The Response to
Metabolic Acidosis

Figure 27.13

Figure 27.14 Metabolic Alkalosis

Figure 27.14

Detection of acidosis and
alkalosis

 Diagnostic blood tests
– Blood pH
– PCO2
– Bicarbonate levels
 Distinguish between respiratory and
metabolic
Animation: Acid-Base Homeostasis

Changes with age include
 Reduced total body water content
 Impaired ability to perform renal compensation
 Increased water demands
– Reduced ability to concentrate urine
– Reduced sensitivity to ADH/ aldosterone
 Net loss of minerals
 Inability to perform respiratory compensation
 Secondary conditions that affect fluid, electrolyte, acid-
base balance

You should now be familiar with:
 What is meant by “fluid balance,” “electrolyte
balance,” and “acid-base balance”
 The compositions of intracellular and
extracellular fluids
 The hormones that play important roles in
regulating fluid and electrolyte balance
 The movement of fluid that takes place within
the ECF, between the ECF and the ICF, and
between the ECF and the environment

You should now be familiar with:
 How sodium, potassium, calcium and chloride
ions are regulated to maintain electrolyte
balance
 The buffering systems that balance the pH of
the intracellular and extracellular fluids
 The compensatory mechanisms involved in
acid-base balance

Buffer system

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