Respiration notes Class X (respiratory system)

Respiration -

The process of releasing energy from food is called respiration. The process of respiration involves taking in oxygen (of air) into the cells, using it for releasing energy by burning food, and then eliminating the waste products (carbon dioxide and water) from the body.

Food + Oxygen----gives--------- Carbon dioxide + Water + Energy

The process of respiration which releases energy takes place inside the cells of the body. So, it is also known as cellular respiration.

Respiration is essential for life because it provide energy for carrying out all the life processes which are necessary to keep the organism alive.

Types of Respiration -

In most of the cases, the organisms carry out respiration by using oxygen. However there are some organisms which carry out respiration without using oxygen. Based on this, we have two types of respiration:

1. Aerobic respiration 2. Anaerobic respiration

1. Aerobic Respiration: The respiration which uses oxygen is called aerobic respiration.

In aerobic respiration, the glucose food is completely broken down into carbon dioxide and water by oxidation. Aerobic respiration produces a considerable amount of energy for use by the organism.

Aerobic respiration -----Glycolysis   +  Crebs cycle

                                  Glucose--------      Pyruvate ----------  6CO₂ + 6H₂O + energy

Mitochondria are the sites of aerobic respiration in the cells. Thus, the breakdown of pyruvate to give carbon dioxide, water and energy takes place in mitochondria

2.Anaerobic Respiration: The respiration which takes place without oxygen is called anaerobic respiration.

The microscopic organisms like yeast and some bacteria obtain energy by anaerobic respiration (which is called fermentation). In anaerobic respiration, the microorganisms like yeast break down glucose (food) into ethanol and carbon dioxide, and release energy.

Anaerobic respiration produces much less energy.

Glycolysis   In absence of oxygen

Glucose---------Pyruvate--------- 2C₂H₅OH + 2CO₂ + energy

In cytoplasm Yeast (Fermentation) (Ethanol)

Sometimes, when there is lack of oxygen in our muscle cells, another pathway for the breakdown of pyruvate is taken. Here the pyruvate is converted into lactic acid (which is also a three-carbon molecule) with the release of small amount of energy.

Glycolysis      In absence of oxygen

Glucose -------Pyruvate------- 2 Latic acid + energy

In cytoplasm Muscle tissue

ATP (Energy Currency)

The energy produced during respiration is stored in the form of ATP molecules in the cells of the body and used by the organism as when required.

ADP (Adenosine Di-Phosphate, low energy content), Inorganic Phosphate (Pi) and ATP (Adenosine Tri-Phosphate, high energy content) are the substances present inside a cell.

The energy released during respiration is used to make ATP molecules form ADP and inorganic phosphate.

ADP + Phosphate + Energy

Thus, energy is stored in the form of ATP.

When the cell needs energy, then ATP can be broken down using water to release energy.

Thus:

ATP -------ADP + Phosphate + Energy

(For use in cells)

The energy equivalent to 30.5KJ/mole is released in this process.

ATP is known as energy currency of cells.

Aerobic Respiration	Anaerobic Respiration
In this respiration, oxygen is required.	In this respiration, oxygen is not required.
Large energy is produced.	Less energy is produced.
In aerobic respiration, CO2 and H2O are produced.	In anaerobic respiration, ethanol, Lactic acid are produced.

Exchange of Gases during Respiration -

Different organisms use different methods for exchange of gases. Diffusion is the method which is utilized by unicellular and some simple organisms for this purpose. In plants also, diffusion is utilized for exchange of gases. In complex animals like human, respiratory system does the job of exchange of gases.

Animals	Respiratory Organ
Unicellular animals like Amoeba, Planaria	Cell membrane
Earthworm	Skin
Aquatic animals like Fish, Prawns	Gills
Insects like Grasshopper, Cockroach	Spiracles and tracheae
Land animals like human, birds	Lungs

Respiratory System in Humans

Draw It In The Notebook

In human beings, many organs take part in the process of respiration. These organs are called organs of respiratory system.

The main organs of human respiratory system are: Nose, Nasal passage, Trachea (wind pipe), Bronchi, Lungs and Diaphragm.

The human respiratory system begins from the nose. The air then goes into nasal passage.

The nasal passage is lined with fine hair and mucus.

When air passes through the nasal passage, the dust particles and other impurities present in it are trapped by nasal hair and mucus so that clean air goes into lungs.

The part of throat between the mouth and wind pipe is called pharynx.

From the nasal passage, air enters into pharynx and then goes into the wind pipe. Trachea does not collapse even when there is no air in it because it is supported by rings of soft bones called cartilage.

The trachea runs down the neck and divides into two smaller tubes called bronchi at its lower end.

The bronchi are connected to the two lungs. The lungs lie in the chest cavity or thoracic cavity which is separated from abdominal cavity by a muscular partition called diaphragm.

Each bronchus divides in the lungs to form a large number of still smaller tubes called `bronchioles'.

The pouch-like air sacs at the ends of the smallest bronchioles are called alveoli.

The walls of alveoli are very thin and they are surrounded by very thin blood capillaries. It is in the alveoli that gaseous exchange takes place.

Mechanism of Respiration:

When we breathe in, we lift our ribs and flatten our diaphragm and the chest cavity becomes larger as a result. Because of this, air is sucked into the lungs and fills the expanded alveoli.

The alveoli are surrounded by thin blood vessels called capillaries carrying blood in them. So, the oxygen of air diffuses out from the alveoli walls into the blood.

The oxygen is carried by blood to all the parts of the body. As the blood passes through the tissues of the body, the oxygen present in it diffuses into the cells.

The oxygen combines with the digested food present in the cells to release energy.

Carbon dioxide gas is produced as a waste product during respiration in the cells of the body tissues. This carbon dioxide diffuses into the blood.

Blood carries the CO₂ back to the lungs where it diffuses into the alveoli.

When we breathe out air, the diaphragm and muscles attached to the ribs relax due to which our chest cavity contracts and becomes smaller. This contraction movement of the chest pushes out CO₂ from the alveoli of lungs into the trachea, nostrils and then out of the body into air.

Note: During the breathing cycle, when air is taken in and let out, the lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released.

Carbon dioxide is more soluble in water than oxygen is and hence is mostly transported in the dissolved form in our blood.

Rate of breathing:

The process of breathing pumps in oxygen into our body (and removes CO2).

Breathing occurs involuntarily but the rate of breathing is controlled by the respiratory system of brain.

The average breathing rate in an adult man at rest is about 15 to 18 times per minute. This breathing rate increases with increased physical activity.

Oxygen required for breathing and respiration is carried by hemoglobin pigment present in our blood. The normal range of hemoglobin in the blood of a healthy adult person is from 12 to 18 grams per deciliter of blood.

The deficiency of hemoglobin in the blood of a person reduces the oxygen carrying capacity of blood resulting in breathing problems, tiredness and lack of energy.

Activity to show production of carbon dioxide during respiration:

Take some freshly prepared lime water in a test tube.

Blow air from our lungs into this lime water.

You will see that lime water becomes highly milky.

Use a syringe or pichkari to pass air through some fresh lime water taken in another test tube.

Now you will see that lime water in second test tube becomes slightly milky.

Thus, we can conclude that CO₂ when passes through limewater, limewater turns milky.

when we blow air through lime water, the lime water becomes more milky as compare to atmospheric air, It means that atmospheric air have less CO₂ and air released from our lungs have more CO₂.

Exchange of gases in other organisms:

Respiration in Amoeba:

Amoeba is single-celled animal. Amoeba depends on simple diffusion of gases for breathing.

The exchange of gases in Amoeba takes place through its cell membrane.

Amoeba lives in water. This water has oxygen dissolved in it. The oxygen from water diffuses into the body of Amoeba through its cell membrane.

Since the amoeba is very small in size, so the oxygen spreads quickly into the whole body of Amoeba.

This oxygen is used for respiration inside the Amoeba cell. The process of respiration produces carbon dioxide gas continuously. This carbon dioxide gas diffuses out through the membrane of amoeba into the surrounding water.

Respiration in Earthworm:

The earthworm exchanges the gases through its skin. The earthworm absorbs the oxygen needed for respiration through is moist skin.

The oxygen is then transported to all the cells of the earthworm by its blood where it is used in respiration.

The carbon dioxide produced during respiration is carried back by the blood. This CO2 is expelled from the body of the earthworm through its skin.

Why simple respiratory systems can  not be used in humans?

Surface moist: If humans would have used simple respiratory system then our skin would be more moist.

If gases diffuse through skin in human, they will not receive sufficient oxygen.

If gases were to travel in human body through diffusion, it will take years to reach from one end to another.

Respiration in Fish:

The fish has special organs for breathing called 'gills'. The fish has gills on both the sides of its head.

The fish lives in water and water contains dissolves oxygen in it. The fish breathes by taking in water through its mouth and sending it over the gills.

When water passes over gills, the gills extract dissolved oxygen from this water. The water then goes out through the gill slits.

The extracted oxygen is absorbed by the blood and carried to all the parts of the fish.

The carbon dioxide produced by the respiration is brought back by the blood into the gills for expelling into the surrounding water.

Note:

Human die under water, because their lungs are made to work in air not in water.

Terrestrial animals can breathe in the atmosphere, but animals that live in water (aquatic animals) need to use the oxygen dissolved in water. Since the amount of dissolved oxygen in water is fairly low compared to the amount of oxygen in the air, the rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms.

Exchange of gases in plants -

Like animals, plants also need energy. The plants get this energy by the process of respiration. Plants also use oxygen of air for respiration and release carbon dioxide.

The respiration in plants differs from the animals in three respects:

Respiration in plants	Respiration in animals
All the parts of a plant (like root, stem and leaves) perform respiration individually.	Animal performs respiration as a single unit.
During respiration in plants, there is a little transport of respiratory gases from one part of the plant to the other.	Respiratory gases are usually transported over long distance inside an animal during respiration.
The respiration in plants occurs at a slow rate.	The respiration in animals occurs at a much faster rate.

Plants get Oxygen by Diffusion:

Plants have a branching shape, so they have quite a large surface area in comparison to their volume. Therefore, diffusion alone can supply all the cells of the plants with as much oxygen as they need for respiration.

Diffusion occurs in the roots, stems and leaves of plants.

Respiration in Roots:

Air occurs in soil interspaces. Root hairs of the roots are in direct contact with them.

Oxygen of the soil air diffuses through root hair and reaches all internal cells of the root for respiration.

Carbon dioxide produced by root cells diffuses in the opposite direction.

In water-logged conditions, soil air becomes deficient. In the absence of oxygen, metabolic activity of the root declines and the plant may wither.

Respiration in Stems:

The stems of herbaceous plants have stomata. The oxygen from air diffuses into the stem of a herbaceous plant through stomata and reaches all the cells for respiration.

The carbon dioxide gas produced during respiration diffuses out into the air through the same stomata.

In woody stems, the bark has lenticels for gaseous exchange.

Respiration in Leaves:

The leaves of a plant have tiny pores called stomata. The exchange of respiratory gases in the leaves takes place by the process of diffusion through stomata.

Net gaseous exchange in the leaves of the plant:

I. During day time when photosynthesis occurs oxygen is produced. The leaves use some of this oxygen for respiration and rest of the oxygen diffuses out into air. Again, during the day time, carbon dioxide produced by respiration is all used up in photosynthesis by leaves. Even more carbon dioxide is taken in from air. Thus, net gas exchange in leaves during day time is: O₂ diffuses out; CO₂ diffuses in.

II. At night time, when no photosynthesis occurs and hence no oxygen is produced, oxygen from air diffuses into leaves to carry out respiration. And carbon dioxide produced by respiration diffuses out into air. Thus, net gas exchange in leaves at night is: O₂ diffuses in; CO₂ diffuses out.