Life Processes (b) Respiration

Respiration is the process in which complex food particles breaks down into simpler ones through the process of oxidation to release enormous energy.

Substances which undergo respiration to release energy are known as respiratory substrates.

Example : Some respiratory substrates are glucose, proteins etc

Respiration on the basis of presence or absence of oxygen can be of two types: aerobic respiration and anaerobic respiration. Aerobic respiration occurs in the presence of oxygen while anaerobic occurs in the absence of oxygen.

Site of aerobic respiration is mitochondria.

During aerobic respiration 38 ATPs get released in complete oxidation of one glucose molecule.

During aerobic respiration, the product is CO₂ & H₂O. While during anaerobic respiration, the product can be either lactic acid or ethanol+CO₂ on the basis of enzyme involved.

If the product is ethanol &CO₂, the process is termed as Fermentation.

Initially glucose gets converted into pyruvic acid (by the process of glycolysis-common in both aerobic & anaerobic respiration). In fermentation, this pyruvic acid produces ethanol & carbon-dioxide in the presence of enzyme alcohol dehydrogenase. This fermentation process is also used for industrial production of alcohol.

ATP is an acronym of Adenosine Tri Phosphate. It is formed by the addition of 3 phosphate groups to adenosine (adenine+ pentose sugar). It is a highly energetic compound and thus is used to save energy in the chemical form. Thus it is called the energy currency of the cell.

Usually human body performs only aerobic respiration. But in certain conditions (like heavy exercises), when body needs enormous amount of energy but oxygen supply is not enough, our body gets bounded to perform anaerobic respiration. It occurs in our muscle cells where due to anaerobic respiration, lactic acid gets produced.

You might have experienced pain in arms or legs after doing some heavy physical exercise or work. It is because of accumulation of lactic acid in muscle cells.

External respiration is an alternate term used for breathing. It includes inhalation of O₂ & exhalation of CO₂. While internal respiration occurs inside the body between blood and tissues where there is transfer of oxygen from blood to each and every tissue of body to fulfil its demand.

Diffusion is a phenomenon explaining movement of substances from its higher concentration to its lower concentration. In plants, diffusion of gases occurs. Factors affecting diffusion are:-

(i) Concentration gradient:- More steeper the concentration gradient, greater will be the diffusion.

(ii) Temperature:- Diffusion rate increase with increase in the temperature because speed of ions increases.

(iii) Size of molecules:- Molecules with smaller size can diffuse easily as compared to molecules with larger size.

During day time, both respiration and photosynthesis occurs in plant. Both respiration & photosynthesis are opposite processes. In respiration, there is an intake of O₂ and release of CO₂, while in photosynthesis CO₂ is taken inside and O₂ is released. But the rate of photosynthesis is much higher than the rate of respiration. Due to this reason, release of O₂ is also much higher than release of CO₂.

Lenticels are pores present on the woody bark of a tree stem. Usually a stem is covered with a tough layer of suberin. The places where suberin is absent, some pores are develop. These pores are called as Lenticels. They help in the exchange of gases.

The respiratory surface of animals must always be moist for better diffusion of gases. Both oxygen and carbon-dioxide gets dissolved in water quickly and their diffusion becomes easier & quicker. This is the reason for moist respiratory surfaces.

In aquatic animals, the respiration process involves the usage of oxygen dissolved in water. As the amount of oxygen dissolved in water is much less than the amount of O₂ available on land, aquatic animals have higher breathing rate.

The essential feature of respiratory organs of terrestrial animals is that they must be protected under layers of tissue so as to avoid any shock or damage. They must also be supplied with a large number of blood vessels for easy and fast exchange of gases.

In almost all the organisms the breathing surface is very fine and delicate for easy and fast exchange of gases. Since they are very delicate they must be protected from external environmental conditions. So for protection these structures are covered well in a layer of tissues. Like in human beings the exchange of gases take place through alveoli which are present in the lungs which are further protected from environment by ribs and diaphragm.

The organism in which the cell membrane acts as a respiratory surface is Amoeba. In amoeba, the unicellular animal, the exchange of gases takes place through the cell membrane or the plasma membrane. The cell membrane of amoeba absorbs oxygen from the surrounding area and release carbon dioxide by the process of diffusion.

In humans, lungs are the major respiratory organ. Internally, lungs are divided into numerous sac like structures called as alveoli. These alveoli (sing. alveolus) are thin walled and are the major site for exchange of gases. They take up carbon dioxide from the deoxygenated blood and fill it with oxygen.

(i) Oxygen enters the body in the mouth and nose, passes through the larynx and the trachea.

As shown in the diagram given below:

(ii) Nose - The nose is the primary organ of smell and also functions as part of the body's respiratory system.

Mouth – Mostly the breathing is done through nose i.e. nasal cavity. But, it can be done through oral cavity as well.

Respiratory pigments play a very important role in the body of an organism. It helps in the transportation of respiratory gases to the various body organs.

Respiratory pigment present in humans is haemoglobin. It is a red color pigment present in our blood. It helps in transporting oxygen from lungs to various body tissues and also helps in the removal of carbon-dioxide from cells.

Haemoglobin is the respiratory pigment present in the human beings. It helps in the transportation of respiratory gases; mainly O₂ & some amount of CO₂ also.

Carbon monoxide (CO) has a great affinity with haemoglobin. Increase in amount of CO in body can even cause the death of organism due to suffocation (insufficient blood supply).

(i) The substances which gets oxidised during respiration are known as respiratory substrates. Examples of some respiratory substrates are glucose, proteins, fatty acids etc.

(ii) Lungs are divided into small sac like structures called alveoli. These alveoli increase the surface area of lungs for better gaseous exchange.

Both in respiration and transpiration stomata are active. The only difference is that in respiration stomata helps in exchange of gases, while in transpiration, it helps in evaporation of water.

Breathing in humans is divided into 2 steps

(i) Inhalation:- diaphragm contracts and move downwards, rib cage moves outward with the help of intercostal muscles. Thus the size of thoracic cavity increases, its pressure gets reduced and air rushes in.

(ii) Exhalation:- diaphragm gets relaxed and move outwards, rib cage moves inward with the help of intercostal muscles. Thus the size of thoracic cavity decreases, its pressure gets increased and air rushes out.

When we inspire, the air moves through our nasal passage where the presence of nasal hairs and mucus prevents the entry of harmful substances into the body with this air. Moreover, they also reduce the temperature of air.

If we start taking air from the mouth instead of nose, all these harmful substances will enter into our body and may cause disease.

The difference between the different ways of oxidation of glucose in organism are as follows :

Fermentation is a name given to anaerobic respiration in which the product is ethanol and CO₂.

Fermentation in yeast is very helpful for food industry as it helps in the formation of alcohol & bread. A fungi named Saccharomyces cerevisiae also called as bakers' yeast & brewers' yeast is extensively used commercially for the production of alcohol and bread.

Respiration occurs at the same rate in both day & night. But the difference is because of photosynthesis. During day time both respiration & photosynthesis occurs in plant. Both respiration & photosynthesis are opposite processes. In respiration, there is an intake of O₂ and release of CO₂, while in photosynthesis CO₂ is taken inside and O₂ is released. But the rate of photosynthesis is much higher than the rate of respiration. Due to this reason, release of O₂ is also much higher than release of CO₂. Since there is no net release of CO₂, it seems that no respiration occurs in plant.

ATP - Adenosine Tri Phosphate. It is called the energy currency of cell because it helps in the storage of energy in chemical form.

ATP is released by a process called as Oxidative Phosphorylation which occurs in mitochondria during respiration. When oxidation of food occurs, it releases energy in the form of ATP.

Aerobic respiration is that type of respiration in which respiration occurs in the presence of oxygen while anaerobic respiration occurs in the absence of oxygen. Aerobic respiration is more fruitful then anaerobic respiration. It is so because in aerobic respiration much more ATPs are released than anaerobic respiration

Number of ATPs released in aerobic respiration = 38 molecules of ATP

Number of ATPs released in anaerobic respiration= 2 molecules of ATP

So a huge difference in ATP release in aerobic & anaerobic respiration can be observed.

Different respiratory adaptations of human beings are as follows :

• The respiratory surface, which helps in exchange of gases must be very thin for easy and fast exchange of gases.

• The respiratory surface must be richly supplied with blood vessels for exchange of gases.

• The thin and delicate respiratory structures must be well protected under layers of tissues so as to protect them from the external environment.

Each and every respiration organ is designed by the nature in a specialised way. This all is done in order to maximise its functional capability.

For e.g. - Nostrils have mucous lining and hair so that it can prevent entry of harmful bacteria in the body.

Trachea gets divided into bronchi & bronchioles to supply air to each & every part of lungs.

Lungs have numerous sac like structure called as alveoli which increases the surface area of lungs so that better exchange of gases can take place.

Alveoli are very thin walled in order to promote better and easier diffusion of gases.

Oxygen enters the body through nostrils, then it passes through the nasal passage and come in the pharynx. Now the oxygen travels into trachea via larynx. Trachea gets divided into left and right bronchi which further gets divided into bronchioles. Bronchioles get terminated into alveolar sacs.

Nostrils → nasal passage → pharynx → larynx → trachea → bronchi → bronchioles → alveoli

Diffusion is a process of movement of substances from its higher concentration to its lower concentration. The pressure which is responsible for creating the diffusion ability of a molecule is called as diffusion pressure.

This diffusion pressure plays a major role in exchange of gases in plants and in smaller animals but fails in bigger animals. It is so because in bigger animals not every body part faces the external environment. That is why they cannot take part in the diffusion process. Due to this reason, diffusion pressure is unable to deliver O₂ to all over the body of bigger animals.

The difference between aquatic and terrestrial respiration is as follows:

Respiration is a cellular process which occurs in each and every cell of body. It starts with glycolysis- a reaction in which breakdown of glucose occurs. Glucose gets converted into pyruvic acid. The process of glycolysis takes place in cytoplasm. Now this pyruvic acid enters into mitochondria via link reaction in which it gets converted into acetyl-CoA. Now this acetyl-CoA enters in the mitochondria where it performs kreb's cycle in mitochindrial matrix. All the ATP and NADH2 and FADH2 produced till now performs ETS cycle (Electron transport chain) which is located in the mitochondrial membranes. Finally it undergoes oxidative phosphorylation and ATPs are released.

GLYCOLYSIS(in cytoplasm) → LINK REACTION(in cytoplasm) → KREB CYCLE(mitochondrial matrix) → ELECTRON TRANSPORT SYSTEM(mitochondrial membrane) → OXIDATIVE PHOSPHORYLATION(mitochondrial membrane)

Breathing involves intake of oxygen and release out of CO₂ from the body. If this process does not occur in the body, there will be no exchange of gases. Imagine a situation when we stop breathing, that is there will be no intake of oxygen and no release out of CO₂. In that situation, oxygen supply will be stopped in our body and there will be continuous accumulation of CO₂ inside the body. This can be fatal and the person may die because of suffocation. That is why it is said that breathing cycle is an essential process for the exchange of gases.

If a person holds his breath for 25 seconds after expiration, even then exchange of respiratory gases would occur in lungs. It is so because, even after we exhale, some amount of air remains in the lungs. This volume of air is called as residual volume which has a quantity of about 1200ml. So even if a person hasn't inhale the air for 25 seconds, then also this residual volume will continue gaseous exchange in lungs for some time. But if this period last some more longer, then this can be lethal.

(i) The plant died because of excessive watering. Excessive watering causes water logging in the plant which blocks the proper supply of gases into it. That is the reason for plant's death.

(ii) Plants respire through the gaseous exchange occurring in stomata via diffusion process.

(a) In herbivorous plants, gaseous exchange occurs via stomata.

(b) In woody plants, gaseous exchange occurs via stomata and lenticels.

(iii) Raman has a good heart as he tried to grow a plant in his room and decided to take its care. But he is little careless and his carelessness has killed the plant. So he should little be more careful.

(i) Earthworms do not have any specialised organ for respiration. Instead they respire through their moist skin.

(ii) Respiratory pigments play a very important role in the body of an organism. It helps in the transportation of respiratory gases to the various body organs.

(iii) Aditi is a keen observer. She applied her academic knowledge which she has gained from her books into practical life which is very good.

Contraction of heart, digestion and homeostasis (maintaining a constant body temperature) requires a lot amount of energy while diffusion is a passive process which occurs according to the concentration gradient. Thus it do not require energy expenditure.

In respiration, O₂ is taken in and CO₂ is released while in photosynthesis, CO₂ is used up and O₂ is released. Both photosynthesis and respiration occurs in plant during daytime. But the rate of photosynthesis is much more than rate of respiration. Thus there is no net release of CO₂.

In anaerobic respiration, the product can be either lactic acid or ethanol + CO₂ on the basis of enzyme involved. Yeast contains the enzyme alcohol dehydrogenase which helps in the formation of alcohol. Due to this reason, fermentation will occur in yeast which will result in the formation of alcohol and CO₂.

Running is a heavy energy requiring process. Thus while running a 100m race, there will be a great need of energy to muscles. Thus they will start performing respiration at much higher rate. Due to this reason, there will be increased release of CO₂ by muscles.

Larynx (voice box) is present at the opening of trachea. Then the air goes into trachea-passage for air to lungs. Near the entry of trachea into lungs, it gets divided into bronchi (sing. bronchus) which further gets divided into bronchioles.

Lime water turns milky in the presence of CO₂.

In flask-1, the air containing CO₂ enters into the flask, but due to the presence of KOH all the CO₂ gets absorbed by it. So, there will be no change in the lime water.

While flask 2 is connected with a flask containing live animals which means that these animals will respire and will release CO₂. This CO₂will turn the lime water present in flask-2 milky.

While moving from position-x to position-y, the lungs are exhaling out the air. When lungs exhale out the air, both diaphragm & external intercostal muscles relax.

Air enters in our body through nostrils (external most portion of nose). From there it goes into pharynx (passage of air) and then into larynx (voice box). Then air comes into trachea and from here it reaches alveoli of lungs via bronchi and bronchioles.