Respiration (Life processes)

Respiration :- 

Respiration is a metabolic process that occurs in all organisms. It is a biochemical process that occurs within the cells of organisms. In this process, the energy (ATP-Adenosine triphosphate) is produced by the breakdown of glucose which is further used by cells to perform various functions. Every living species, from a single-celled organism to dominant  Multicellular  Organisms form respiration.

Types of Respiration:- 

Respiration is of two types: Aerobic and Anaerobic Respiration. The food material consumed during the process of nutrition is used in cells to

provide energy for various lifeprocesses. Different organisms follow different ways – some use oxygen to break-down glucose into carbon dioxide and water, some employ other pathways that do not involve oxygen.

*  In every case, the break-down of glucose, asix-carbon molecule, into a

three-carbon molecule called pyruvate is the first step which occurs in the

cytoplasm.

*In Yeast, the pyruvate may be converted into ethanol and carbondioxide, a process called fermentation. This process takes place in the absence of air

(oxygen), hence called anaerobic respiration.

* The break-down of pyruvate into carbon dioxide occurs in mitochondriain the presence of oxygen. The other product is water. This process occurs in the presence of air (oxygen), hence called aerobic respiration.

* The energy released in aerobic respiration is much higher than anaerobic respiration.

* During strenuous exercise, pyruvate is converted into lactic acid due to

unavailability of oxygen in skeletal muscles. Lactic acid is also athree-

carbon compound. The build-up of this lactic acid causes muscular cramp.

* The energy released by cellular respiration isbimmediately used in the

formation of amolecule named ATP, which fuels all other activities in the

cell.

* When ATP is brokendown, afixed amount of energy is given out which

can drive the endothermic reactions occurring inside the cell.

* Quoting  NCERT, "ATP is the energy currency for most processes

occurring within a cell.The energy released during the process of

respiration is used to make an ATP molecule from ADP and inorganic

phosphate".

* Endothermic processes in the cell

then use this ATP to drive the

reactions. When the terminal

phosphate link agein ATP is broken

using water, the energy equivalent

to 30.5kJ/mol is released.

Respiration in plants :- 

* Plants predominantly exchange gases through stomata, and the large

inter cellular spaces ensure that all cells are in contact with air. Exchange

of oxygen and carbon dioxide occurs by diffusion here.

* Lenticels found on the epidermis of plant stem made up of

parenchymatous cells are pores that always remain open helping in

gaseous exchange.

* Atnight, when there is no photosynthesis occurring, there is the

elimination of carbon dioxide. Carbon dioxide generated during

respiration in the day time is used up for photosynthesis; hence oxygen

release is the major event at this time.

Respiration in Animals :- 

* Terrestrial animals use atmospheric oxygen, but aquatic ones use

dissolved oxygen.

* Lower aquatic animals like sponges, cnidarians exchange gases through

their body surface.

* Earthworm of phylum Annelid are spire through its moist skin.

* Terrestrial organisms have organs with an increased surface area which is in contact with the oxygen-rich atmosphere. The surface of this should also be delicate to allow

efficient diffusion of gases.

* Dissolved oxygen in water is less compared to that of atmospheric oxygen hence rate of breathing among aquatic organisms is higher than that of terrestrial animals.

* Fish take in water through their mouths and force it past the gills where the dissolved oxygen is taken up by the blood.

* Gills are usually placed with in the body for protection. Also, there is a

mechanism for the movement of air in this area where the oxygen is absorbed. 

Human Respiratory system :- 

* In human beings, air enters the body through two openings called the

nostrils. There are fine hair-like structures that filters the air.

* nasal cavity which filters the air and mucus glands which helps in trapping

dust particles.

* The part between the mouth and wind pipe is called the pharynx. From the nasal passage, air enters into the pharynx and then enters the windpipe (or trachea).

* The trachea is a tube which is also known as the windpipe.

* The trachea is supported by incomplete (c-shaped) cartilaginous rings which can prevent its collapse when there is no air.

* The upper end of the trachea has a voice box called the  larynx.  The trachea runs down and divides into two smaller tubes called 'bronchi' at its lower end.(The singular of bronchi is bronchus). The two bronchi lead to the two lungs. 

* The lungs rest on a muscular partition called diaphragm which divides the body into the upper thoracic cavity and lower abdominal cavity. There are two thin membranes called pleura.

* Pleural membranes cover the lungs. The rib bonesvform a cage-like structure which protects the internal organs like lungs and heart.

* Each bronchus is divided in

the lungs to form a large number of still smaller tubes called 'bronchioles'. The bronchioles branch

further and end in small sac-likes tructures which are very thin-walled

called  'Alveoli' (singular- alveolus). The alveolar membrane is very thin,

and blood capillaries surround them. It is across this thin membrane,

exchange of oxygen and carbon dioxide occurs. If the alveolar surface

were spread out, it would cover about 80m2. 

* During inhalation, when we breathe in, the ribs move upward and outward,

and our diaphragm flattens, which increases the volume of the chest

cavity. Because of this, the air is sucked into the lungs and fills the

expanded alveoli.

* Oxygen diffuses from a region of its higher concentration (alveoli) to its

lower concentration (blood capillaries) which is then transported to the rest of the body parts. Carbon dioxide released by the cells after cellular respiration is transported to the lungs by blood, and it diffuses from its higher concentration (blood capillaries) to its lower concentration (alveoli). Residual air remains in the lungs to ensure there is sufficient time for oxygen to be reabsorbed and carbon dioxide to be released.

*  When the size of the animal is large, diffusion pressure alone cannot deliver oxygen to all parts of the body. Respiratory pigments take up

oxygen from the lungs and carry it to tissues which are deficient in oxygen.

* In human beings, the respiratory pigment - haemoglobin, which is present in red blood corpuscles has a very high affinity for oxygen.

* The solubility of carbon dioxide is more than oxygen in the water and hence is mostly transported in the dissolved form in our blood.