11th Class Biology Chapter 13 Gaseous Exchange Short Question Answers

Respiratory activity which occurs in plants during daytimes is called photorespiration. It is a light dependent process during which oxygen is absorbed and carbon dioxide is released. Or the photorespiration is a process in which ribulose bisphosphate carboxylase/oxygenase (rubisco) fixes oxygen instead of carbon dioxide which results in lowering the overall rate of carbon dioxide fixation and plants growth.

Land plants get their oxygen directly from air which enters the leaves through stomata. Aquatic plants obtain their oxygen for respiration by diffusion from dissolved oxygen in water.

When oxygen is more then rubisco acts as oxygenase and photorespiration starts. On the other hand if carbon dioxide is more then Calvin-Benson cycle starts.

In the older parts of the plant i.e., both stems and roots, there is present cork tissue which is formed of dead cells and has special pores called lenticels which are involved in gaseous exchange.

The gill surface is all the time ventilated by constant flow of water.

The main tracheal trunk of cockroach communicates with exterior by paired apertures called spiracles present in the sides of the body.

The direction of the blood flow in the lungs of birds is opposite to the air flow through the parabronchi . This is called counter current exchange which increases the amount of oxygen which enters the blood.

In the lungs of bird instead of alveloli tiny thin walled ducts are present called parabronchi. These parabronchi are open at both ends and the air is constantly ventilated. The walls of the parabronchi are chief sites of gaseous exchange.

The lungs of birds has also developed several extensions known as air sacs, which reach into all parts of the body and even penetrate some of the bones. In most birds the air sacs are nine which become inflated by atmospheric pressure when the ribs are rotated forward and upward. The inflated air sacs act as bellows and send air into the parabronchi for gaseous exchange.

Organism respiration: It is also known as breathing or ventilation during which the moist surface absorbs oxygen from the surrounding and carbon dioxide is removed. Organismic respiration in fact provides the basis of cellular respiration is the process by which cell utilizes oxygen, produces carbon dioxide, extracts and converse the energy from food molecules in biologically useful form such as ATP.

It is the covering over the gills present in bony fishes.

Epiglottis is one of the cartilages of larynx which has a muscularly controlled, hinge like action and serves as a lid which automatically covers the opening of the larynx during the act of swallowing so as to prevent the entry of food or liquids into the larynx. Whereas the opening of larynx is called glottis and is also lined by mucous membrane.

The active site of rubisco is evolved to bind both carbon dioxide and oxygen together. Originally it was not a problem as there was little oxygen in the atmosphere and the carbon dioxide binding activity was the only was used. The photorespiration started when the quantity of oxygen become more.

This is become the stomata close to prevent the loss of water. The level of carbon dioxide falls because it is being consumed and the level of oxygen rises because closed stomata do not let it out.

At all level of organization, the living things such as trees, humans, frogs, worms and bacteria etc., carry on activities that require an uninterrupted supply of energy. The sun is also the ultimate source of energy for almost all of these biological systems. The production of energy is not possible without gaseous exchange or respiration.

Air has higher oxygen content. There is quick diffusion of oxygen in air. There is no active transport mechanism to move respiratory gases across biological membranes. For that matter air is better respiratory medium than water.

1. Higher oxygen content of air: The oxygen content of air is much higher than the oxygen content of equal volume of water. A liter of ideal water can not contain even 10 ml of oxygen whereas oxygen content of fresh air is about 200 ml per litre. 2. Quick diffusion of oxygen: Oxygen diffuses about 8000 times more quickly in air than in water.

More dense: Breathing or ventilation of water is for more difficult than the ventilation of air. Because water is 8000 times more denser than air. More viscous: In terms of viscosity the water is 50 times more viscous, which makes it more difficult for exchange of gases, as compared to air.

Tracheae are the branching system of air tubules present in cockroach for respiration.

The main tracheae divide and subdivided forming very fine tubules called tracheoles. These tracheoles form something like end cell partly filled with fluid, in which the oxygen dissolves. They continuously supply oxygen to the living cells directly.

In most fishes there are four to five pairs of gills which may open through openings called gill slits and are visible on the surface area for gaseous exchange.

The gaseous exchange through the skin is known as cutaneous respiration.

Gaseous exchange through the lungs is called pulmonary respiration.

The intake of air is known as inhalation or inspiration while the removal of consumed air out of the lungs is called exhalation or expiration.

Air passage ways consist of nostril, nasal cavities, pharynx, larynx, trachea, bronchi, bronchioles and alveolar ducts which ultimately lead into the alveolar sac.

The nasal cavity is subdivided into three passage ways by the projection of bones from the walls of the internal nose.

Nasal cavities perform the following functions: i) Air enters the nasal cavity through nostril. ii) The large dust particles are trapped by the hair present in the nasal cavities. iii) Air while passing through the nasal cavity., becomes moist, warm and filtered or smaller foreign particles by mucous membrane.

The larynx or voice box is a complex cartilaginous structure surrounding the upper end of the trachea.

In the glottis the mucous membrane is stretched across into two thin edged fibrous bands called vocal cords, which help in voice production, when vibrated by air.

The trachea or wind pipe is a tubular structure lying ventral to the oesophagus and ektends to the chest cavity or thorax where it is divided into right and left bronchi.

Bronchi are the main branches of trachea. Each bronchus on entering the lung divides and subdivides progressively into smaller bronchi. When the smaller bronchi attain a diameter of one mm or less then they are called bronchioles.

Each air-sac is like a cluster of grapes and constant of several microscopic signal layered structure called alveoli. The alveoli are surrounded by the rich network a blood capillaries to produce an excellent site for the exchange of gases.

The air-sac is the functional unit of the lungs.

The lungs are connected to the outside by the way of the trachea and the nostrils or mouth.

Lungs are spongy because of the presence of millions of alveoli.

The floor of the chest is called diaphragm which is sheet of skeletal muscles.

lungs are covered with double layered thin membranous sacs called pleura.

Breathing is a process in which fresh air containing more oxygen is pumped into the lungs and air with more carbon dioxide is pumped out of the lungs.

During rest breathing occurs rhythmically at the frequency of 15 to 20 times per minute in human beings.

In human beings the respiratory pigment is haemoglobin.

Hemoglobin readily combines with oxygen to form bright red oxyhaemoglobin.

The maximum amount of oxygen which normal human blood absorbs and carries at the sea-level is about 20ml/100ml of blood.

When carbon dioxide pressure increases, the oxygen tension decreases, the capacity of hemoglobin to hold oxygen becomes less. In this way increased carbon dioxide tension favours the greater liberation of oxygen from the blood to the tissue.

Rise in temperature causes a decreases in the oxygen-carrying capacity of blood, e.g., in the increased muscular activity.

As the pH of the blood declines, the amount of oxygen bound to haemoglobin also declines. This occur because decreases pH result from an increase in hydrogen ions, and the hydrogen ions combine with the protein part of the haemoglobin molecules, causing a decrease in the ability of haemoglobin to bind oxygen. Conversely an increase in blood pH results in an increased ability of haemoglobin to bind oxygen.

Carboxhaemoglobin is formed when carbon dioxide combines wits amino groups of haemoglobin .

Most of the carbon dioxide (about 70%) is carried as bicarbonate ion combined with sodium is the plasma.

It has been found that arterial blood contains about 50 ml of carbon dioxide per 100 ml of blood whereas venous blood has 54 ml of carbon dioxide per 100 ml blood.

Cancer or carcinoma is basically malignant (spreading or recurring or cancerous) tumour (mass of cancer cells) of potentially unlimited growth that expends locally by invasion and systemically by metastasis (spread of cancer called beyond original site to other organs or systems.).

It is caused by Mycobacterium tuberculosis.

Arterial blood contains 50 ml of carbon dioxide per 100 ml of blood whereas venous blood has 54 ml of carbon dioxide per 100 ml of blood.

Water is 8000 times more dense than air.

Aquatic plants obtain their oxygen by diffusion from dissolved oxygen is water.

Respiratory activity which occurs in plants during daytime is called photorespiration.Photorespiration is a light dependent process during which oxygen is absorbed and carbon dioxide is released. This oxygen is derived from the early reaction of photosynthesis. The pathway in which RuBP (Ribulose Biphosphala) is converted into serine is called photorespiration.

Gaseous Exchange in plants: Gaseous exchange is plants takes place through three methods

Through Stomata: In most cells of mesophyll which are specialized for photosynthesis, there are present large spaces. Theses air spaces are directly involved in gaseous exchange. Stomata are the main sites of exchange of gases in plants. Stomata are largely present in the leaves and in young stem. These stomata lead to intercellular spaces of mesophyll tissue.

Through Lenticels: In older stems, cork tissue is present which is formed of dead cells. The cork tissue has special pores called lenticels which are involved in gaseous exchange.

Through Roots: The roots of the land plants get their oxygen from the air existing in the spaces between the soil particles.

Respiration: Respiration is one of the most important metabolic activities of all organisms. Cellular respiration is the process whereby cell utilizes oxygen, produce carbon dioxide, extract and conserves the energy from food molecules in biologically useful form, such as ATP.

Breathing: Organismic respiration is also known as breathing ventilation. During which oxygen is taken from atmosphere and carbon dioxide is released. Breathing provides the basis of cellular respiration.

The photorespiration is a process in which ribose biphosphala carboxylase/oxygenase fixes oxygen instead of carbon dioxide which results in lowering the overall rate of carbon dioxide fixation and plant growth.

Rubisco, the most abundant protein in chloroplasts and probably the most abundant protein in the world. The rubisco is carboxylase as well as oxygenase.

When RuBP react with oxygen, a two carbon compound glycolate is produced:

RuBP + O₂ ———–>Glycolate

That glycolate thus produced diffuses into membrane bounded by organelles known as peroxisomes.

In the peroxisomes the glycolate is converted into glycine, through a series of reactions.

Glycolate —————> Glycine

The glycine us the simplest amino acid which soon after its formation diffuses into the mitochondria where two glycine molecules are converted into serine and a molecule of carbon dioxide is formed.

2 Glycine ——————> Serine CO₂

Air always remain in the lungs of human beings due to difference in the concentration gradient of carbon dioxide and oxygen in the lungs.

Photosynthesis:

1. Photosynthesis is the process by which energy is acquired by inorganic oxidized compounds of carbon and hydrogen are reduced to energy rich carbohydrates using light energy that is absorbed by chlorophyll.
2. During photosynthesis carbon dioxide is absorbed and oxygen is released.
3. In this process Rubisco acts as carboxylase.

Photorespiration:

1. Respiratory activity that occurs during daytime is called photorespiration.
2. It is a light dependent process during which oxygen is absorbed and carbon dioxide is released.
3. During this process Rubisco acts as oxygenase and in this way rate of oxygen in atmosphere is lowered.

The respiratory surfaces in most animals exhibit the following features:

Large Surface and Moisture: The surface area should be large and kept moist as is in lungs and gills.

Thin Epithelium: The distance for diffusion must be short. In animals, the epithelium is only two cells thick which separates blood and air.

Ventilation: There should be the difference is the gases at two points which bring about diffusion.

Capillary Network: The respiratory site should possess steps diffusion gradient and extensive network of capillaries through which blood should flow all the time at and adequate speed.

Inspiration:

1. Inspiration is the intake of air inside the lungs.
2. During inspiration the space inside the chest cavity is raised.
3. Muscles of ribs contract and elevate the rib upwards and forwards.
4. The muscles of diaphragm contract and become less dome-like.
5. Pressure from the lungs is removed and they expand and vacuum is created due to which air rushes inside the lungs.

Expiration:

1. Expiration is the expulsion of air from the lungs.
2. During expiration from the sides of chest cavity the space becomes less.
3. The muscles of ribs and relaxed and ribs move downward and inward.
4. The muscles of diaphragm relax becoming more dome-like.
5. The lungs are pressed and the air moves outside the lungs.

The active site of rubisco is evolved to bind both carbon dioxide and oxygen together. Originally it was not a problem as there was little oxygen in the atmosphere and the carbon dioxide binding activity was the only one used. The photorespiration started when the quantity of oxygen became more.

Respiratory surfaces in animals are the sites where gaseous exchange takes place.

Hydra has no specialized organs for respiration. Exchange of gases i.e., intake of oxygen and removal of carbon dioxide, occurs through entire general surface in contact with water.

Skin is richly supplied with blood capillaries and is always kept moist by the secretion of epidermal mucous gland cells and also by coelomic fluid exuding out through the dorsal pores. Oxygen dissolved on the wet surfaces passes through the cuticle and epidermal cells into the blood.

The main tracheal trunk communicates with exterior by 10 pairs of apertures called spiracles.

The main tracheae divide and subdivide forming very fine thin walled tubules called tracheoles.