The Respiratory System

Need for energy

a. Synthesis of proteins from amino acids
b. Production of enzymes
c. Contraction of muscles for movement

 The need for energy production is greater in animals as compared to plants because animals have to
move from one place to another, either to obtain food or to escape from their enemies.

 Respiration is the catabolic process of releasing energy from simple sugar, glucose, for carrying out
various life processes.

C6H12O6 + 6O2 6CO2 + 6H2O + ATP

Glucose Oxygen Carbon dioxide Water Energy

Characteristics of Respiration
a. The breakdown of glucose to carbon dioxide and water does not occur in a single step. It involves
a series of chemical reactions—glycolysis, Krebs cycle and electron transport.
b. Each breakdown step is carried out by a specific enzyme.
c. A small amount of energy liberated in the breakdown of the glucose molecule is released as heat
energy. But a major part of it is converted into chemical energy in the form of Adenosine
Triphosphate (ATP).

Kinds of Respiration
 Aerobic Respiration: The breakdown of glucose in the presence of oxygen is called aerobic
respiration. Most of the animals such as human beings, several bacteria and fungi are aerobic in
nature.

 Anaerobic Respiration: The breakdown of glucose in the absence of oxygen is called anaerobic
respiration. The unicellular organisms such as yeast and some bacteria are examples of anaerobes.

 Fermentation: The breakdown of pyruvic acid to ethanol and carbon dioxide in the absence of
oxygen is called fermentation. Certain microorganisms or their enzymes carry out fermentation.
  Differences between Aerobic and Anaerobic Respiration in Plants

AEROBIC RESPIRATION ANAEROBIC RESPIRATION

1. Also called oxybiotic respiration. 1. Also called anoxybiotic respiration.
2. Proceeds in the presence of oxygen. 2. Proceeds in the absence of oxygen.
3. Occurs in mitochondria. 3. Occurs in cytoplasm.
4. Complete breakdown of glucose. 4. Incomplete breakdown of glucose.
5. End products are carbon dioxide and 5. End products are ethyl alcohol and
water. carbon dioxide.
6. Large quantity of energy is liberated (38 6. Small quantity of energy is liberated (2
ATP) from one mole of glucose. ATP) from one mole of glucose.
7. Normally occurs throughout life. 7. Occurs temporarily for short periods.

Parts of Respiration
a. Breathing: It is a physical process in which the atmospheric air is taken in and forced out of the
oxygen-absorbing organs, the lungs.
b. Gaseous transport: Oxygen absorbed by the blood in the lungs is transported by the red blood
cells (RBCs) as oxyhaemoglobin throughout the body by the means of arteries. Carbon dioxide
from the tissues is transported to the lungs by the blood via veins in two ways.
o As bicarbonates dissolved in plasma.
o In combination with haemoglobin of RBCs as carbamino-haemoglobin.
c. Tissue respiration: The terminal blood vessels or the capillaries transport the oxygen to the body
cells or tissues, where the oxygen diffuses through their thin walls. Likewise, the capillaries pick up
the carbon dioxide released by them.
d. Cellular respiration: The complex chemical changes which occurs inside the cells to release the
energy from glucose.

 Cellular respiration consists of three main stages: glycolysis, Krebs cycle and electron transport.

 The respiratory system in human beings consists of the nose, pharynx, larynx, trachea, bronchi and
lungs.
 COMPONENT OF DESCRIPTION
THE RESPIRATORY
SYSTEM
Nose Consists of nostrils which open into the nasal cavity.
Nasal hair prevents the entry of large particles inside the nose.
Pharynx Muscular chamber is connected to the larynx through glottis.
Air from the pharynx enters the larynx when the food enters the
oesophagus.
Larynx Hollow, cartilaginous structure that connects the pharynx to the
trachea.
Contains vocal cords. Air is expelled forcibly through the vocal
cords vibrates them to produce sound.
Trachea Begins from the larynx, situated below the neck, and enters the
thoracic cavity.
Walls of the trachea are strengthened by several C-shaped rings of
cartilage that provide flexibility.
Moves the air into the lungs through the bronchi.
Bronchi Branches of trachea.
Bronchi→Secondary bronchi→Tertiary
bronchi→Bronchioles→Alveoli
Helps in gaseous exchange.
Lungs Pair of spongy and elastic respiratory organs.
Enable rapid exchange of gases between air and blood.
Separate the CO2 from the blood and also excrete water vapour.
Diaphragm Curved, musculo-fibrous sheath.
Plays a major role during respiration.

Blood supply to the Lungs

 The deoxygenated blood is brought from the heart into the lungs through the pulmonary artery. The
pulmonary artery divides into fine capillaries, which surround the alveoli.

 The concentration of oxygen in the alveolar air is more than the concentration of oxygen in the blood
capillaries surrounding the alveoli. Hence, oxygen from the alveolar air moves into the blood capillaries
by the process of diffusion.

 The exchange of gases between the air and the blood is called external respiration.

 The blood contains RBCs which contain the pigment haemoglobin. Haemoglobin has an affinity for
oxygen and hence acts as an oxygen carrier. The oxygen combines with the haemoglobin to form
oxyhaemoglobin.

 Whenever oxyhaemoglobin is exposed to an environment deficient of oxygen, it dissociates and

releases oxygen. In tissues, the concentration of oxygen is low. Hence, oxyhaemoglobin dissociates
and releases oxygen. The oxygen diffuses inside the tissues. The haemoglobin is re-formed in the
process. In this way, the oxygen is supplied to all the tissues of the body which are deficient in oxygen.

 Exchange of gases between the cells and blood is called internal respiration.
 A large fraction of carbon dioxide produced inside the tissue is converted into bicarbonate, which gets
dissolved in the blood plasma. A small fraction of carbon dioxide diffuses into the RBCs and combines
with the haemoglobin, forming carbamino-haemoglobin.

 The blood rich in carbon dioxide is then transported back to the heart through the veins. From the
heart, the blood is supplied to the lungs through fine branches of the pulmonary artery.

 The concentration of carbon dioxide is more in the blood capillaries surrounding the alveoli as
compared to the alveolar air. Hence, the carbon dioxide from the blood moves into the alveolar air by
the process of diffusion. The carbon dioxide is released from the body by the process of expiration.

 Differences between Breathing and Respiration

BREATHING RESPIRATION
 Physical process.  Chemical process.
 Process of taking oxygen into the lungs.  Process of taking oxygen from the
lungs into the bloodstream or inside
the cells.
 Occurs outside the cells.  Occurs inside the cells.
 No energy is released.  Energy is released.

 The respiratory cycle consists of inspiration and expiration, with a short respiratory pause.

 The inspiration or inhalation is the movement of air from the outside environment to the inside of the
body. The oxygen from the air enters inside the body.

 The expiration or exhalation is the movement of air from the inside of the body to the outside
environment. The carbon dioxide from the body is released into the outside environment.

 A breath consists of one inhalation and one exhalation.

 The number of times a person breathes in a minute is called the breathing rate or respiratory rate.
 Differences between Inspiration and Expiration

PART OF THE INSPIRATION EXPIRATION

RESPIRATORY
SYSTEM
 Diaphragm  Contracts and flattens  Relaxes and moves upwards
downwards. to form a dome shape.
 External intercostal  Muscles contract.  Muscles relax.
muscles
 Internal intercostal  Relaxed/stretched.  Contracted for forced
muscles expiration.
 Rib cage and  Moves upwards and  Moves downwards and
sternum outwards. inwards.
 Thoracic cavity  Increases.  Decreases.
 Air pressure  Decreases inside the  Increases inside the thorax
thorax and lungs. and lungs.
 Air movement  External air pressure drives  Air is forced out of the lungs
air into the lungs at low by thoracic compression and
pressure. elastic recoil of the lungs.

 Breathing movements are largely controlled by a respiratory centre located in the medulla oblongata of
the brain.

 They are normally not under the control of our will. They are involuntary. However, one can consciously
increase or decrease the rate of breathing.

 Air at higher altitudes contains a lesser amount of oxygen. Therefore, one may suffer from air sickness
due to a lack of oxygen. Air sickness results in dizziness, unsteady vision, loss of hearing, lack of
muscular coordination and even complete blackouts at times.

 Hypoxia is a condition in which the tissue is deprived of adequate supply of oxygen. It may occur due to
sitting for long hours in a crowded room with poor ventilation. It may also occur at higher altitudes,
where the oxygen concentration is low.

 Asphyxiation is a condition of severely deficient supply of oxygen to the body. It may occur due to
several causes such as strangulation, drowning, choking or any other obstruction in the respiratory
tract.
 Comparison of Respiration in Plants and Animals

SIMILARITIES
 The process of cellular respiration releases energy. This energy released in the form
of ATP is stored in the mitochondria.
 The end products of aerobic respiration are carbon dioxide and water.
DIFFERENCES
RESPIRATION IN PLANTS RESPIRATION IN ANIMALS
 Do not exhibit external ventilation or  Higher animals such as human show
breathing movements. external ventilation or breathing
movements.
 No gaseous transport involved during  The tissue fluid—blood—is
respiration. The respiratory gases simply responsible for the transport of gases.
diffuse in and out of the cell.
 Oxygen released during the process of  Air is the only source of oxygen.
photosynthesis acts as an additional
source of oxygen.
 End product of anaerobic respiration is  End product of anaerobic respiration
ethanol. is lactic acid.
 Produces a small amount of heat.  Produces a large amount of heat.
 Rate of respiration is comparatively  Rate of respiration is comparatively
lower. higher.