Respiration is the process by which organisms obtain energy from food through biochemical oxidation. In plants and animals, respiration occurs through the exchange of gases between organisms and their environments. In humans and other animals, respiration occurs through inhalation of oxygen into the lungs and exhalation of carbon dioxide. The respiratory system involves the nose, pharynx, larynx, trachea, bronchi, bronchioles and alveoli where gas exchange occurs.

1. Respiration

2.  It is defined as the process of biochemical
oxidation of nutrients at cellular level.
 It occurs in the presence of specific enzymes
at optimum temperature in the cells to
release energy for various metabolic
activities.
 It is a process of catabolic process in which
exchange of gases takes place between the
organism and the outside environment.

3.  The leaves of plants have tiny pores on their
surface which are called stomata.
 The exchange of gases in the leaves during
respiration takes place through stomata.
 This happens as follows:
 Oxygen from the air enters into a leaf through
stomata and reaches all the cells by the process
of diffusion.
 This oxygen is used in respiration in cells of the
leaf.
 The carbon dioxide produced during diffuses out
from the leaf into the air through same stomata.

4.  Plants like other animals also respire. Plants also
need energy.
 The plants get energy through the process of
respiration in which glucose food breaks down in
the presence of oxygen to form carbon dioxide
and water with the release of energy.
 This energy is used by the plant for carrying out its
various life processes.
 Thus, Like other organisms, plants also respire for
their survival.
 The respiration in plants differs from that
of animals.
 In other words, in plants, each part can
independently take in oxygen from air, utilize it to
obtain energy, and give out carbon dioxide.

6.  The photosynthesis reaction makes glucose
and the respiration reaction break it down.
 In photosynthesis, the energy which goes
into the reaction is light energy.
 In respiration, the energy which comes out
is chemical energy.

8.  The roots of plants are under the ground but
root cells also need oxygen to carry out
respiration and release energy for their own
use.

9.  The roots of a plant take up air from the
spaces between the soil particles.
 Root hairs are in contact with the air in the
soil particles.
 Oxygen from the air in soil particles diffuse
into root hair and reach all the cells of the
root where it is utilized in respiration.
 Carbon dioxide produced in the cells of the
root during respiration goes out through the
same root hair by the process of diffusion.

10.  If a potted plant is over watered for a long time,
then the plant may ultimately die.
 This is because too much water expels all the air
from inbetween the soil particles.
 Due to this, oxygen is not available to the roots
for aerobic respiration.
 In this condition, the roots of plant respire
anaerobically producing alcohol.
 This may kill the plant.
 Germinating seeds during early stage respire
anaerobically because they have seed coat which
does not allow the oxygen to enter through it.

11.  Respiration in plants happens throughout the
day and night thereby carbon dioxide is
produced.
 However, during the daytime, the amount of
carbon dioxide released is negligible
compared to the amount of oxygen produced
as a result of photosynthesis.
 Hence, one should not sleep under a tree at
night.

12.  There are two types of respiration which we
classify on the basis of the presence or
absence of oxygen:
 Aerobic respiration
 C6H12O6 + 6O2⟶6CO2 + 6H2O + Energy
 Anaerobic Respiration
 Glucose ⟶ Alcohol + CO2 + Energy

13.  The respiration that takes place in the presence of oxygen is
called aerobic respiration because it uses ‘air’ which
contains oxygen.
 The aerobic respiration involves utilization of oxygen for the
breakdown of chemical bonds in glucose to release energy in
high amounts.
 It is the chief source of energy for plants and animals.
Animals and plants that use oxygen for respiration
are aerobes.
 Majority of animals have aerobic respiration.
 All the organisms that obtain energy by aerobic respiration
cannot live without the oxygen.
 This is because if there is no oxygen, they cannot get energy
from the food which they eat.
 Aerobic respiration produces more energy because
a complete breakdown of glucose occurs during respiration
by the use of oxygen.

14.  The respiration that takes place in the absence of
oxygen is anaerobic respiration.
 In this process, incomplete oxidation of food material is
being and produces carbon dioxide and alcohol.
 Beside this other organic matter like citric acid, oxalic
acid, lactic acid, etc are also produced.
 This process is also known as intramolecular
Respiration.
 The anaerobic respiration takes place in organisms like
yeast, some bacteria, and parasitic worms.
 The animals and plants that can survive and obtain
energy even in the absence of oxygen are called
Anaerobic.

15. Yeast
 Yeast is a single-celled fungus. In yeast, a
single cell represents the whole organism.
 Very low amount of energy is released in this
process.
 Yeast respires anaerobically and during this
process, yeast converts glucose into alcohol.
 Therefore it is used to make alcohol bread,
etc.

16.  Anaerobic respiration produces much less energy
because the only partial breakdown of glucose
occurs in anaerobic respiration in the absence
of oxygen.
 All the organisms which obtain energy by
anaerobic respiration can live without the
oxygen.
 For example, yeast is an organism which can live
without the oxygen of air because it obtains
energy by the process of anaerobic respiration.
 Yeast can survive in the absence of oxygen.

17.  Human beings normally obtain energy by aerobic
respiration.
 But when we need extra energy, anaerobic respiration
takes place in our muscles for a short time.
 When we do a heavy physical exercise, our muscles need
more oxygen.
 But the supply of oxygen through blood is limited and
hence insufficient.
 During heavy exercise, Some of our muscles respire
anaerobically.
 The anaerobic respiration by muscles brings about the
partial breakdown of glucose to form lactic acid.
 This lactic acid accumulates in the muscles. The
accumulation of lactic acid in the muscles causes muscles
cramps.

18. Aerobic respiration Anaerobic respiration
 It occurs in the presence of air
rich in oxygen.
 Food materials are completely
oxidized to release
carbon dioxide water and
energy.
 Sufficient amount of energy is
released.
 It takes places in all organisms.
 Enzymes responsible for this
process are found in
mitochondria.
 It occurs in the air absence of
oxygen.
 Food materials are
incompletely oxidized to
release alcohol, carbon
dioxide and energy.
 A small amount of energy is
released.
 It takes place in very few
organisms like yeast and in
muscles of the human beings.
 Enzymes responsible for this
process are found in
protoplasm.

19. Aerobic respiration Anaerobic respiration
 In aerobic respiration,
energy is produced by
the breakdown of
food(like glucose).
 Aerobic respiration
takes place in the
cells of the organism.
 In anaerobic
respiration, energy is
also produced by the
breakdown of food
(like glucose).
 Anaerobic respiration
also takes place in
the cells of the
organism

20.  In all higher living organisms, the respiratory
organ is lungs and gaseous exchange takes
place from these lungs. The lungs are the
most important organs that help human
beings in respiration. Air is sucked into the
lungs through a series of cavities and tubes
which together make up the
whole respiratory system.

22.  Air enters the body through the nose. Externally,
the nose consists of two nostrils. Nostrils are
lined with membranes that are coated with a
moist, sticky mucus. Some of the membranes
have moving cilia.
 As air passes over the membranes, it is warmed
and moistened. Dust particles falling on the
sticky surface are swept out by cilia, towards the
throat, where they are either swallowed or
coughed up. This removes most of the large
foreign particles from the air.

24.  The throat, also referred to as the pharynx (FAYR-inx), is a
muscular, hollow tube about 5 inches long.
 As part of both the respiratory and the digestive systems,
it functions as a passageway for air, food and liquid.
 It begins at the back of the nasal cavity and curves down
to meet the esophagus and trachea (windpipe).
 It is divided into three parts: the nasopharynx, the
oropharynx and the hypopharynx.

26.  The nasal cavity leads into the Pharynx.
 Posterior part of the nasal passage is called pharynx
which is connected to the mouth.
 The air passes through the pharynx and enters the
trachea, or windpipe, which is in the middle of the
neck.
 The trachea is about 12 cm long and 2.5cm in
diameter.

27.  The larynx is a sound producing organ which is the
enlarged upper end of the trachea.
 Its occur four type of cartilages-
 (a) One thyroid
 (b) One Cricoid
 (c) paired arytenoids cartilages, which have one pair of the
vocal cord, it is a sound producing organs.

28.  The trachea divides into two tubes, The right and left
bronchi.
 After air has passed through the trachea, it enters the
bronchi.
 Each bronchus enters a lung.
 Air is further pulled into branches of the bronchi.
 The bronchi then divide into smaller tubes
called bronchioles.

29.  The bronchioles connect to tiny ducts that lead into air
sacs called alveoli.
 Alveoli are usually surrounded by tiny blood vessels.
 It is in the alveoli of the lungs where gaseous exchange
occurs.
 Oxygen from the alveoli passes into the blood cells and is
carried to different parts of the body.
 At the same time, carbon dioxide from the blood vessels
passes into the alveoli.

30.  The thoracic cavity is hollow cavity divided into two
pleural cavities each enclosing a lung. The floor of the
thoracic cavity is completely closed by a thin muscular
septum called diaphragm. The thorax is separated from
the abdomen below by the diaphragm.

31.  Breathing is a mechanical Process. In
breathing, an organism takes in oxygen from
its environment and released carbon-
dioxide.Breathing involves the transport of
oxygen and carbon dioxide between the
external environment and the body cells.
This process is also called pulmonary
respiration.

32.  Organisms carry out external respiration in
various ways depending on their size and
environment. For example, exchange of
oxygen and carbon dioxide happens directly
with the environment through any cell
membrane. In human beings and some
animals, lungs are the chief organs of
breathing.

34.  We take in the air present in the environment through our
nostrils which travels through the nasal cavity.
 Then it moves through the windpipe and reaches the lungs.
 The lungs are located in the chest cavity which is surrounded by
the ribs.
 On the floor of the chest cavity lays a muscle sheet called
diaphragm.
 During the breathing process, the movement of the ribs and
diaphragm takes place. This is so because the lungs expand and
contract during breathing.
 As we take in the air it fills up the lungs. This moves the
diaphragm downwards and the ribs outwards.
 The lungs when releasing out air from the body which brings back
the diaphragm and the ribs to their original positions.

35.  Blood rich in carbon dioxide i.e.
deoxygenated blood enters the capillary
network of the alveolus.
 CO2 diffuses into the alveolar cavity because of its
higher concentration in the blood.
 Alveolus has a higher concentration of oxygen as compared
to the blood capillaries.
 Therefore, O2 diffuses into the capillaries and combines
with haemoglobin of the RBC to form oxyhaemoglobin to
be transported throughout the body.

36.  In the cells, continuous metabolism of
glucose and other substances results in the
production of co2 and utilization of O2
 The concentration of oxygen in the cells and
the tissue fluid decreases while the
concentration of CO2 is higher than in the
capillaries.
 Therefore, oxyhaemoglobin breaks down
releasing O2 diffuses out from the capillaries
into the tissue fluid and then into each and
every cell.

38.  Many insects like Cockroaches have small openings called spiracles present on the
sides of the bodies.
 Also, they have an air tube-like structure called the trachea that allows the
exchange of gases in these insects.
 The air enters the body through the spiracles and diffuses in the cells via the
trachea.
 Similarly, the air from the cells enters the trachea and moves out of the body
through spiracles.

39.  Earthworms have a soft, slimming and moist skin.
 Hence the gases can easily pass in and out of the earthworm
through its skin.
 Similarly, frogs also have a slippery and moist skin that can help
in breathing. However, frogs contain lungs too.

40.  Animals that live underwater have special respiratory organs called
gills.
 They are a comb-like structure present on the skin of these animals.
 Gills allow the exchange of gases between animals and the water
easily.
 Some animals called the amphibians can breathe on land by lungs and
through moist skin under water. For example frogs and toads.

42.  As we inhale the air present in the
surroundings sometimes various unwanted
elements such as smoke and dust are also
included in it.
 However, they get stuck in the hair in our
nostrils but some of them can get through
the nasal cavity.
 They thus cause irritation in the nasal cavity
which makes us sneeze.
 This helps in getting rid of the unwanted
particles out of the nasal cavity.

43.  The right lung is larger as it does not need to
make space for the heart .the left lung,needs
to make space for the heart as the heart is
located slightly to the left.

44.  Mouth has no hair and mucous lining like
nose . Therefore it is not advised to breathe
through mouth. As air coming from mouth is
not filtered as it is from nose

45.  Asthma is what is known as an acute obstructive
disease. In other words a condition that can
come on suddenly and make it difficult to exhale
air. The changes you would see if you could see
inside the airways during an attack which
contribute to this difficulty breathing out include
constriction of the smooth muscle in the airway,
making it narrower, increase mucus production
and swelling in the lining (odema) which all
reduce the diameter of the airways. The lungs
themselves can become hyper inflated (think of
the alveoli as overinflated balloons) as the
patient is still breathing in air (often rapidly) but
is unable to expel the trapped air passed narrow
airways.