Human Respiratory system - part 1

ENERGY - All living organisms need energy for carrying on their functions.They obtain this energy from food.The complex insoluble substances present in food are converted into simple , soluble substances with the help of enzymes.Their bond energy is released by oxidation in the cells.In oxidation, usually oxygen is used, carbon dioxide and water are produced as by-products and energy is released.During this process , energy released is trapped by forming bonds between adenosine diphosphate and inorganic phosphate to synthesize adenosine triphosphate molecules.The energy obtained from ATP molecules is called biologically useful energy.

C6H12O6  +  6O2  →  6CO2  +  6H2O  +  Energy

                                      (stored in ATP)

   ATP  →  ADP  +  Pi  +  Energy used in life activities

 (on hydrolysis)

RESPIRATION - This process generally involves :

• intake of molecular oxygen from the environment
• step-wise oxidation of food with the incoming oxygen
• elimination of carbon dioxide produced in oxidation
• release of energy in small doses during oxidation 
• conservation of energy so released in biologically useful forms, such as ATP

              Difference between breathing and respiration :

BREATHING (Ventilation)	RESPIRATION
1. It is a physical process.	1. It is a biochemical process.
2. It does not release any energy.	2. It releases energy that is stored in ATP.
3. It is an extracellular process.	3. It is an intracellular process.
4. It does not involve enzyme action.	4. It involves a number of enzymes in oxidation.
5. Breathing mechanism varies in different animals.	5. Respiratory mechanism is similar in all animals.
6. It is confined to certain organs only.	6. It occurs in all cells of the body.

TYPES AND PHASES OF RESPIRATION -

1. Aerobic respiration : Respiration which involves use of molecular oxygen and release of carbon dioxide simultaneously is known as aerobic respiration.

Aerobic respiration is of two main types:direct and indirect

• Direct respiration - It is the exchange of environmental oxygen with the carbon dioxide of body cells  without special respiratory organs or blood.E.g.aerobic bacteria , protista,plants , sponges, flatworms etc.
• Indirect respiration - It involves special respiratory organs , such as skin, gills, lungs and blood. Types of indirect respiration includes:
• Cutaneous respiration
• Buccopharyngeal respiration
• Branchial respiration
• Pulmonary respiration

2.Anaerobic respiration : In some organisms, respiration may or may not produce carbon dioxide but does not use molecular oxygen.E.g. yeast

C6H12O6  →  2C2H5OH  +  2CO2  +  Energy

Glucose            Ethanol

In certain bacteria and parasitic worms , glucose is metabolised to lactic acid without the use of oxygen and without the formation of carbon dioxide.

C6H12O6   →  2CH3CHOHCOOH  +  Energy

Glucose               Lactic acid

           Difference between aerobic and anaerobic metabolism:      

ANAEROBIC METABOLISM	AEROBIC METABOLISM
1. It does not use molecular oxygen.	1. It uses molecular oxygen.
2. It may or may not release carbon-dioxide.	2. It always releases carbon-dioxide.
3. It does not produce water.	3. It produces water.
4. It. Provides less energy.	4. It provides more energy.
5. It occurs in cytoplasm only.	5. It occurs partly in cytoplasm and mitochondria.
6. It occurs in yeast, some bacteria and parasitic worms.	6. It occurs in majority of animals and plants.

 DIFFERENCE BETWEEN COMBUSTION AND RESPIRATION :

COMBUSTION (Burning)	RESPIRATION
1. Many chemical bonds break simultaneously, releasing a large amount of energy at a time.	1. Chemical bonds break one after another, releasing energy gradually.
2. No enzymes are involved.	2. Each step is controlled by enzyme.
3. No intermediate products are formed.	3. Many intermediate products are formed.
4. Most of the energy dissipates away as heat.	4. Most of the energy is trapped in chemical bonds(ATP).
5. It is an uncontrolled process.	5. It is a controlled process.
7. Light is often emitted.	6. No light is emiited.

 DIFFERENCE BETWEEN PHOTOSYNTHESIS AND RESPIRATION:

PHOTOSYNTHESIS	RESPIRATION
1. It is an anabolic process.	1. It is a catabolic process.
2. It uses carbon-dioxide and water.	2. It releases carbon-dioxide and water.
3. It takes place in sunlight only.	3. It takes place all the time.
4. It is confined to green parts of the plant.	4. It occurs in the cells of all parts.
5. It occurs in the chloroplast.	5. It occurs in cytoplasm and mitochondria.
6. It is an endergonic process.	6. It is an exergonic process.

Adaptations for Gas exchange : For efficient gas exchange  

1. The respiratory surfaces have large area and are thin , moist and permeable to respiratory gases.

2. Respiratory surface is highly vascular.

3. Many animals have developed special respiratory pigments which greatly increase the capacity of blood to carry oxygen and carbon dioxide..