Class 7 Respiration In Organism Quick Revision Notes

Types of Respiration by Web Tutors Point
Types of Respiration by Web Tutors Point

What is respiration?

Respiration (breathing) is the way our body gets oxygen into the lungs from the air outside.

This energy is derived by the breakdown of the food consumed by us into carbon-dioxide, water and energy.

What are cells?

Cells are the basic building blocks of all living things. The human body is composed of trillions of cells. They provide structure for the body, take in nutrients from food, convert those nutrients into energy, and carry out specialized functions.

What do you mean by Cellular Respiration?

Respiration at smallest level of our body (cell level). Cellular respiration refers to the process of breakdown of food in the cell with the release of energy. This cellular respiration can take place in either aerobic respiration or anaerobic respiration.

What is the difference between cellular respiration and breathing (respiration)?

The cell is the structural and functional unit of life and each cell requires energy to perform its functions. Therefore, respiration that takes place at the smallest level of our body i.e cellular level is called cellular respiration. The process ensures that each cell performs its function perfectly. It describes how our cells make ATP  (energy-carrying molecule) – a molecule used to provide energy for chemical reactions.

Respiration (breathing) is the way our body gets oxygen into the lungs from the air outside. It is a biochemical process involving breakdown of glucose in the presence of oxygen resulting in the release of carbon dioxide, water. While breathing we breathe in Oxygen breathe out carbon-dioxide.

The breathed in oxygen is transported to the entire body parts and to each cell. This oxygen is required by the cells for breakdown of food in order to derive energy to perform necessary functions for survival.

Types of Respiration

Two general categories of respiration exist:

Aerobic Respiration

When food is broken down into carbon dioxide and water in the presence of oxygen, this process is called aerobic respiration.

In this form of respiration, the oxygen that is breathed in is distributed throughout the body and to the cells, where it is used to break down food into carbon dioxide, water, and energy. For instance, aerobic respiration occurs in humans.

Respiration in organism Web Tutors Point

Anaerobic Respiration

When there is no oxygen present, food is broken down into carbon dioxide and water, a process known as anaerobic respiration.

In this type of respiration, food is converted into energy and carbon dioxide in the absence of oxygen. Anaerobes that are obligatory and facultative, for example.

Anaerobes that can breathe both with and without oxygen are referred to as facultative anaerobes. Escherichia coli, as an illustration.

Those creatures that can only breathe without oxygen are known as obligatory anaerobes. Take Clostridium tetani as an example.

Respiration in organism WTP

Anaerobic respiration can further be classified into two types:

Lactic acid fermentation and alcohol fermentation.

Lactic acid fermentation refers to the metabolic process in which glucose are converted into cellular energy and the metabolite lactate.

Alcoholic fermentation refers to the biological process in which glucose and other sugars such as fructose, and sucrose are converted into cellular energy, producing ethanol and carbon dioxide.

Respiration in yeast

Yeast is a single-celled creature. During anaerobic respiration, which is also known as fermentation, yeast creates ethanol or alcohol as a byproduct, which is used to make wine and beer. In the bread-making process, yeast produces carbon dioxide. The bread dough rises as a result of the release of carbon dioxide gas during this process.

Glucose —-(In the Absence of Oxygen)——-> Carbon-dioxide + alcohol + Energy

Respiration in muscule cells

The ability of muscle cells to survive without air allows them to breathe anaerobically, just like yeast.

The muscle cells respire anaerobically to meet the transient requirement for oxygen and provide energy.

The protein carrier transports this lactic acid to the body’s cells, where it is used as fuel by the energy fibres in muscle cells.

The muscle cells in the body store it as glycogen.

Glucose (In Muscle) ——–(In the absence of oxygen)—-> Lactic Acid + Energy

What is the reason for muscle cramps?

The muscles’ cells breathe anaerobically when there is a momentary lack of oxygen. Anaerobic energy production is quicker. Lactic acid and energy are produced when glucose is broken down by muscle cells. This causes a partial breakdown of glucose into lactic acid, which builds up in the body (particularly in our muscles) and causes cramps.

Blood circulation is improved by taking a hot bath or receiving a massage, which increases the amount of oxygen delivered to the muscles. Because the cells receive a enough amount of oxygen, the lactic acid completely breaks down into carbon dioxide and water, providing you with comfort.


In order to digest food and turn it into energy, as well as to release carbon dioxide gas, respiration requires oxygen. We require a medium that can absorb oxygen and release carbon dioxide in order to accomplish this. Breathing is the method used to achieve this goal.

Breathing is the process of taking in oxygen-rich air and exhaling air that is carbon dioxide-rich. It is an unending process that lasts the entirety of an organism’s life.

The respiratory organs efficiently carry out the act of breathing.

What is breathing in or Inhalation?

Inhalation is the process of taking oxygen-rich air in through the respiratory system.

What is exhalation?

Exhalation is the process of breathing out air that is rich in carbon dioxide through the respiratory system.

How faster breathing energizes a person?

The average breathing rate of an adult is 15-18 breaths per minute.

Why person performing heavy exercise breathes faster?

However, the body uses far more energy during vigorous exercise. Therefore, more food must be broken down to create the same amount of energy. More oxygen is needed for this process, and normal breathing cannot supply it.

In order to obtain more oxygen, a person engaging in vigorous exercise breathes more quickly than a person who is at rest. A person who is exercising vigorously breaths about 25 times each minute.

Fast breathing gives the cells more oxygen, which in turn has the effect of accelerating the breakdown of food and releasing more energy.


The air we breathe contains a variety of outer substances, such as smoking, dust, pollen, etc. Numerous outer objects enter the nostrils during inhalation and become lodged in the nasal cavity’s hair. Some of the particles may become caught in the hair, while some may even pass through and irritate the lining of the nasal canal. This discomfort causes a sneeze, which expels the alien, filthy particles that have entered the cavity.

Sneezing is the reflex reaction brought on by the common cold, the flu, or by breathing in outer particles that irritate the nose.

Respiration in earthworm

An invertebrate (it does not have a backbone) that is brownish-red in colour is an earthworm.

They are present in the top soil layer and increase the soil’s fertility.

It consumes the decomposing and dead soil matter.

They lack specialist respiratory equipment. However, due to the combination of the mucus in their bodies and the moisture in the soil, they breathe through their slimy, damp skin.

Hemoglobin found in the blood of earthworms is used to draw oxygen from the water in the soil.

The earth is excessively damp during the rainy season. The earthworm’s breathing is hampered as a result. Thus, they emerge to the surface where they can safely breathe.

Respiration in cockroach

A terrestrial or earthly organism called a cockroach is found in damp places.

It is an omnivore insect that eats both plants and animals, including grains and cereals. Any organic material can be eaten by them. The cockroach’s tracheal system, or network of trachea, serves as its respiratory system.

Through the tiny apertures known as spiracles, they breathe. The skeletal spinchters control these apertures.

Respiration in frog

Frogs are amphibians with tiny bodies and little legs.

They consume meat (flesh eating).

They have a dual breathing system that aids them to breathe.

Like humans, they too have a set of lungs.

However, they may also breathe through their slimy, damp skin.

They breathe through their thin, membrane skin, which is permeable to both water and gases, when their skin is damp or when they are submerged in water.

When they are on land, they force air into their lungs by closing their nostrils and doing so while pushing air out of their lips.

Respiration in fish

Vertebrate (organisms which have an internal backbone surrounded by bone) aquatic animals include fish.

As a result of the oxygen content of water being lower than that of the atmosphere, aquatic creatures breathe more quickly than terrestrial (species that dwell on land) animals do. Therefore, they can breathe more quickly and so take in more oxygen.

Fish have distinctive bodily projections called gills. To facilitate the simple exchange of gases, these gills are joined to blood arteries. These gills aid aquatic life, such as fish, in using the dissolved oxygen in the water.

It can take in water because its gills are constantly moving. It draws water into its mouth and pushes it through its gills.

Dissolved oxygen enters into blood vessels and then travels to the various cells and tissues of the fish’s body when water flows through the gills’ thin walls.

Respiration in plants

6CO2 + 6H2O + Light Energy —> C6H12O6 + 6O2

For survival, plants too need the process of breathing.

Through the microscopic pores called as stomata that are located in the bottom surface of the leaves, they breathe in oxygen-rich air from the atmosphere and exhale air rich in carbon dioxide. To exchange gases, plants have stomata, lenticels, and root hairs among other features.

Plant roots also breathe to produce energy, but they do so in a different way. They absorb oxygen-rich air from the gaps between soil particles.

Plants create glucose through photosynthesis, but they also need energy to produce food. The energy molecules, ATP, is created from the glucose. The cells receive the oxygen that is breathed in (during respiration) and use it to break down glucose into carbon dioxide and water.

What is difference between respiration and photosynthesis?

The conversion of light energy into chemical energy in the form of glucose or sugar occurs during the process of photosynthesis, which takes place in green plants and some other organisms when carbon dioxide and water are present.

In plants, respiration is the mechanism through which energy for plant development is produced by combining oxygen and the sugars created during photosynthesis. The opposite of photosynthesis in many respects is respiration.

6CO2 + 6H2O -> C6H12O6 + 6O2

Do plant respire at night only?

Photosynthesis can only take place in the presence of sunlight during the day, respiration happens all day long like human beings. As a result, plants’ respiration is visible at night.

Plants breathe at a slower rate than animals do. Because plants release oxygen during photosynthesis, whereas mammals must absorb it from their environment. Thus, less oxygen needs to be obtained from the environment.

Do plants take CO2 during respiration?

Similar to animals, plants breathe by taking in oxygen and exhaling carbon dioxide. Plants only absorb carbon dioxide and produce oxygen as a byproduct during photosynthesis.

Why does an athlete breathe more deeply and quickly than usual after a race?

Energy is needed heavily during a run, yet there is a finite amount of oxygen available to create that energy. In order to meet the need for energy, anaerobic respiration occurs in the muscle cells. Athletes breathe deeper and faster than usual after a race to ensure that more oxygen reaches their cells.

List the similarities between aerobic and anaerobic respiration.

(i) In both aerobic and anaerobic respiration, food is broken down to release energy.

(ii) Both takes place inside cells.

(iii) Both produces byproducts.

Why do we frequently sneeze after breathing in a lot of dust-filled air?

We frequently sneeze to eject these alien particles when we breathe in a lot of dust-filled air. These particles enter the nasal canal through the hair and irritate the lining, causing irritation and sneezing.

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