Respiration Questions in English

(B) Multicellular organisms,such as humans,possess complex body designs.
They have specialized cells and tissues for performing various necessary functions of the body,such as the intake of food and oxygen.
Unlike unicellular organisms,most cells in multicellular organisms are not in direct contact with the outside environment.
Therefore,diffusion is a slow process and cannot meet the oxygen requirements of all cells in a complex body.

(C) Terrestrial organisms take up oxygen from the atmosphere,whereas aquatic animals must utilize oxygen dissolved in water.
Air contains a significantly higher concentration of $O_2$ compared to water.
Because the availability of $O_2$ in the atmosphere is high,terrestrial animals do not need to breathe as rapidly as aquatic animals to obtain sufficient oxygen.
Consequently,terrestrial organisms do not require the same complex adaptations for gaseous exchange that aquatic organisms often possess.

(N/A) Glucose is first broken down in the cell cytoplasm into a three-carbon molecule called pyruvate. This process is known as glycolysis.
Pyruvate is further broken down by different pathways to provide energy depending on the availability of oxygen:
$1$. In yeast (anaerobic respiration): Pyruvate is converted into ethanol,$CO_2$,and energy.
$2$. In human muscle cells (lack of oxygen): During vigorous exercise,pyruvate is converted into lactic acid and energy.
$3$. In mitochondria (aerobic respiration): Pyruvate is broken down in the presence of oxygen to produce $CO_2$,water,and a large amount of energy.

(N/A) The exchange of gases takes place between the blood of the capillaries that surround the alveoli and the gases present in the alveoli.
Thus,alveoli are the site for the exchange of gases.
The lungs get filled with air during the process of inhalation as the ribs are lifted up and the diaphragm is flattened.
The air that rushes inside the lungs fills the numerous alveoli present in the lungs.
Each lung contains $300-350$ million alveoli.
These numerous alveoli significantly increase the surface area for gaseous exchange,making the process of respiration more efficient.

(A) The breakdown of pyruvate into carbon dioxide $(CO_2)$,water $(H_2O)$,and energy $(ATP)$ occurs during aerobic respiration. This process takes place in the mitochondria of the cell,where the pyruvate produced in the cytoplasm enters the Krebs cycle and the electron transport chain to release energy.

(N/A)

Aerobic Respiration	Anaerobic Respiration
$1.$ Occurs in the presence of $O_2$.	$1.$ Occurs in the absence of $O_2$.
$2.$ Complete breakdown of glucose occurs.	$2.$ Incomplete breakdown of glucose occurs.
$3.$ Occurs in the cytoplasm and mitochondria.	$3.$ Occurs only in the cytoplasm.
$4.$ End products are $CO_2$ and $H_2O$.	$4.$ End products are ethanol,lactic acid,or $CO_2$.
$5.$ Yields a large amount of energy ($36-38$ $ATP$).	$5.$ Yields a small amount of energy ($2$ $ATP$).

Organisms that use anaerobic respiration include yeasts,certain bacteria,parasitic worms (like Ascaris),and human muscle cells during intense physical activity.

(N/A) The alveoli are small,balloon-like structures present in the lungs.
The walls of the alveoli consist of an extensive network of blood vessels (capillaries).
Each lung contains $300-350$ million alveoli,making a total of approximately $700$ million in both lungs.
When spread out,the total alveolar surface area covers about $80\, m^2$.
This large surface area and the thin,moist walls facilitate efficient gaseous exchange.

(D) In yeast,the process of respiration is anaerobic (occurs in the absence of oxygen).
$1$. First,glucose $(C_6H_{12}O_6)$ is broken down into pyruvate in the cytoplasm of the cell,which is a common step for both aerobic and anaerobic respiration.
$2$. In the absence of oxygen,the pyruvate is further converted into ethanol $(C_2H_5OH)$ and carbon dioxide $(CO_2)$ within the cytoplasm of the yeast cell.
$3$. Therefore,the correct sequence is: Glucose $\xrightarrow{\text{cytoplasm}}$ Pyruvate $\xrightarrow{\text{cytoplasm}}$ Ethanol + Carbon dioxide.

(A) Aerobic respiration occurs in two main stages:
$1$. Glycolysis: This process takes place in the cytoplasm,where glucose ($6$-carbon molecule) is broken down into pyruvate ($3$-carbon molecule) and releases a small amount of energy.
$2$. Krebs Cycle and Electron Transport Chain: Pyruvate enters the mitochondria,where it is completely oxidized in the presence of oxygen to produce $CO_2$,$H_2O$,and a large amount of energy $(ATP)$.
Therefore,the correct sequence is: Glucose $\xrightarrow{\text{cytoplasm}}$ Pyruvate + Energy $\xrightarrow{\text{mitochondria}}$ $CO_2 + H_2O$ + Energy.

(B) Statement $(i)$ is false because during inhalation,the ribs move outward and the diaphragm moves downward (flattens) to increase the thoracic cavity volume.
Statement $(ii)$ is true because alveoli are the sites of gaseous exchange where oxygen diffuses into the blood and carbon dioxide diffuses out.
Statement $(iii)$ is false because haemoglobin has a much higher affinity for oxygen than for carbon dioxide.
Statement $(iv)$ is true because the millions of alveoli in the lungs significantly increase the surface area available for the exchange of gases.
Therefore,statements $(ii)$ and $(iv)$ are correct.

(C) During inhalation,the air enters the body through the nostrils.
From the nostrils,it passes into the pharynx,which is the common passage for air and food.
Then,the air moves into the larynx (voice box) and enters the trachea (windpipe).
The trachea branches into bronchi,which further divide into bronchioles and finally reach the alveoli,where gas exchange occurs.
Therefore,the correct sequence is: Nostrils $\to$ pharynx $\to$ larynx $\to$ trachea $\to$ alveoli.

(D) During the process of respiration,the exchange of gases ($O_2$ and $CO_2$) occurs in the alveoli of the lungs.
Alveoli are tiny,balloon-like structures present at the terminal ends of the bronchioles.
They provide a large surface area for the diffusion of gases between the air in the lungs and the blood in the surrounding capillaries.

(D) During cellular respiration,cells consume oxygen to produce energy and release $CO_2$ as a metabolic waste product.
As blood passes through the tissues,oxygen diffuses from the blood into the cells,while $CO_2$ produced by the cells diffuses into the blood.
Therefore,the blood leaving the tissues has a higher concentration of carbon dioxide compared to the blood entering the tissues.

(D) Statement $(i)$ is correct: In yeast,during fermentation,pyruvate is converted into ethanol and $CO_2$ in the absence of oxygen.
Statement $(ii)$ is incorrect: Fermentation is an anaerobic process,not aerobic.
Statement $(iii)$ is incorrect: Fermentation occurs in the cytoplasm,not in the mitochondria.
Statement $(iv)$ is correct: Fermentation is a type of anaerobic respiration where glucose is incompletely oxidized without oxygen.
Therefore,statements $(i)$ and $(iv)$ are correct.

(A) During intense physical activity,such as cricket,the demand for energy in muscle cells increases significantly.
When the oxygen supply becomes insufficient to meet this demand,muscle cells switch to anaerobic respiration.
In this process,the pyruvate produced from glucose breakdown is converted into lactic acid instead of entering the aerobic pathway.
The accumulation of lactic acid in the muscle tissues causes muscle fatigue and painful cramps.

(C) In human muscle cells,when there is a temporary deficiency of oxygen (anaerobic conditions),the pyruvic acid produced during glycolysis is reduced to lactic acid.
This process occurs in the cytoplasm of the cell.
Glycolysis itself takes place in the cytoplasm,and the subsequent reduction of pyruvate to lactate under anaerobic conditions also occurs in the cytoplasm,not in the mitochondria.

(N/A) No,this statement is not entirely correct.
During the day,plants perform both photosynthesis and respiration. Since the rate of photosynthesis is significantly higher than the rate of respiration,the net result is the release of oxygen.
At night,photosynthesis stops because there is no sunlight,but respiration continues. Therefore,plants only release carbon dioxide at night.
Thus,while the statement is partially true regarding the net gas exchange,it is inaccurate to say plants 'only' give out oxygen during the day,as they are also respiring.

(N/A) The release of $CO_2$ and the intake of $O_2$ indicates that either photosynthesis is not occurring or its rate is significantly lower than the rate of cellular respiration. Under normal daylight conditions,the rate of photosynthesis is much higher than the rate of respiration. Consequently,the $CO_2$ produced during respiration is consumed in the process of photosynthesis,meaning no $CO_2$ is released into the atmosphere.

(N/A) Fishes respire with the help of gills. Gills are richly supplied with blood capillaries and can readily absorb oxygen dissolved in water. Since fishes cannot absorb gaseous oxygen from the atmosphere,they die soon after they are taken out of water.

(N/A)

Aerobic respiration	Anaerobic respiration
$1.$ Oxygen is utilised for the breakdown of respiratory substrate.	$1.$ Oxygen is not required.
$2.$ It takes place in cytoplasm (glycolysis) and inside mitochondria (Krebs cycle).	$2.$ It takes place in cytoplasm only.
$3.$ End products are carbon dioxide and water.	$3.$ End products are lactic acid or ethanol and carbon dioxide.
$4.$ More energy is released.	$4.$ Less energy is released.

(B) Aquatic organisms,such as fishes,obtain oxygen from water in a dissolved state through their gills.
Since the concentration of dissolved oxygen in water is significantly lower compared to the concentration of oxygen in the atmosphere,aquatic organisms must breathe much faster to extract sufficient oxygen for their metabolic needs.
In contrast,terrestrial organisms have easy access to the high concentration of oxygen present in the air,allowing for a slower rate of breathing.

(N/A) The energy currency in living organisms is Adenosine Triphosphate $(ATP)$.
It is produced during the process of cellular respiration in the mitochondria of cells.
In plants,it is also produced during the light-dependent reactions of photosynthesis within the chloroplasts.

(N/A) The process of breathing in humans involves two main phases: inhalation and exhalation.
$1.$ Inhalation: The diaphragm contracts and moves downward,and the rib muscles contract,lifting the ribs upward and outward. This increases the volume of the thoracic cavity,decreasing the air pressure inside the lungs. Consequently,air from the atmosphere rushes into the lungs through the respiratory tract.
$2.$ Exhalation: The diaphragm relaxes and moves upward,and the rib muscles relax,causing the ribs to move downward and inward. This decreases the volume of the thoracic cavity,increasing the air pressure inside the lungs. Consequently,air is pushed out of the lungs into the atmosphere.
$3.$ Gaseous Exchange: This occurs in the alveoli. Oxygen from the inhaled air diffuses into the blood,while carbon dioxide from the blood diffuses into the alveoli to be exhaled.

(D) The breakdown of glucose in living organisms occurs through three main pathways:
$1$. In the absence of oxygen (anaerobic respiration) in yeast: Glucose is converted into ethanol $(C_2H_5OH)$,carbon dioxide $(CO_2)$,and energy.
$2$. In the lack of oxygen (anaerobic respiration) in muscle cells: Glucose is converted into lactic acid $(C_3H_6O_3)$ and energy. This usually happens during vigorous exercise.
$3$. In the presence of oxygen (aerobic respiration) in mitochondria: Glucose is converted into carbon dioxide $(CO_2)$,water $(H_2O)$,and a large amount of energy.

(B) The cell organelle in which the breakdown of pyruvate occurs to produce carbon dioxide,water,and energy is the $Mitochondria$. This process is known as aerobic respiration,which takes place in the presence of oxygen.

(N/A) The air passage,specifically the trachea and bronchi,is supported by $C$-shaped cartilaginous rings. These rings provide structural rigidity and prevent the airway from collapsing when the air pressure inside decreases during exhalation.

(B) The rate of breathing in aquatic organisms is much faster because the amount of dissolved oxygen in water is significantly lower compared to the amount of oxygen available in the atmosphere. To obtain the same amount of oxygen required for metabolic processes,aquatic organisms must process a larger volume of water through their respiratory organs.

(N/A) The common features of respiratory organs in both aquatic and terrestrial animals are as follows:
$1$. Large surface area: Respiratory organs have a large surface area to facilitate the maximum exchange of gases.
$2$. Thin-walled: The surface of the respiratory organs is very thin to allow for easy diffusion of gases.
$3$. Richly supplied with blood: They are well-supplied with blood vessels to ensure efficient transport of oxygen and carbon dioxide.
$4$. Well protected: These organs are usually located inside the body or protected by structures to prevent damage and maintain a moist environment.

(A) During intense physical activity like running,the demand for energy in muscle cells increases rapidly.
When the oxygen supply is insufficient to meet this demand,muscle cells perform anaerobic respiration.
In this process,pyruvate is converted into lactic acid instead of entering the aerobic pathway.
The accumulation of lactic acid in the muscle fibers leads to muscle fatigue and cramps.

(A) Organism $B$ is undergoing aerobic respiration because it produces a high yield of $38$ $ATP$ molecules per glucose molecule.
$(b)$ Organism $A$ is undergoing anaerobic respiration because it produces a low yield of only $2$ $ATP$ molecules per glucose molecule.
$(c)$ Organism $A$ can convert glucose into alcohol through the process of fermentation.
$(d)$ Yeast is an organism that behaves like $A$ (undergoes anaerobic respiration).
$(e)$ Human beings and aerobic bacteria are two examples of organisms that behave like $B$ (undergo aerobic respiration).

(N/A) $(i)$ Nasal passage
$(ii)$ Bronchioles
$(iii)$ Alveoli
$(iv)$ Diaphragm
$(b)$ Since the amount of dissolved oxygen in water is fairly low compared to the amount of oxygen in the air,aquatic organisms must breathe much faster to obtain sufficient oxygen for their metabolic needs compared to terrestrial organisms.

(N/A) In tissues,oxygen is consumed for metabolic activities,leading to a low concentration of oxygen and a high concentration of carbon dioxide. Conversely,blood arriving from the lungs has a high concentration of oxygen and a low concentration of carbon dioxide. Due to this partial pressure gradient,gases move between the blood and tissues via the process of simple diffusion.
$(b)$ The respiratory pigment in humans is Haemoglobin. It is found inside the Red Blood Corpuscles $(RBCs)$.

(B) This happens due to the build-up of lactic acid in our muscles.
During vigorous exercise,the demand for energy increases,leading to a shortage of oxygen in our muscle cells.
Under these anaerobic conditions,the muscle cells switch to an alternative pathway where pyruvate is converted into lactic acid instead of entering the aerobic respiration cycle.
The accumulation of this lactic acid causes muscle fatigue and cramps.

(B) During inhalation,air enters through the nostrils.
From the nostrils,it passes into the nasal cavity and then into the pharynx.
The pharynx leads to the larynx (voice box).
From the larynx,air moves into the trachea (windpipe).
The trachea branches into bronchi,which further divide into bronchioles and finally reach the alveoli in the lungs for gas exchange.
Therefore,the correct sequence is: Nostrils $\rightarrow$ pharynx $\rightarrow$ larynx $\rightarrow$ trachea $\rightarrow$ alveoli.

(C) During the process of respiration,the exchange of gases ($O_2$ and $CO_2$) occurs in the $alveoli$ of the lungs.
$Alveoli$ are tiny,balloon-like structures present at the terminal ends of the bronchioles.
These structures provide a large surface area for the diffusion of gases between the air in the lungs and the blood in the surrounding capillaries.
The trachea and larynx are parts of the conducting zone and do not participate in gas exchange.

(D) Statement $(i)$ is correct: In yeast,during fermentation,pyruvate is converted into ethanol and carbon dioxide.
Statement $(ii)$ is incorrect: Fermentation is an anaerobic process,not an aerobic one.
Statement $(iii)$ is incorrect: Fermentation occurs in the cytoplasm,not in the mitochondria.
Statement $(iv)$ is correct: Fermentation is a type of anaerobic respiration that occurs in the absence of oxygen.
Therefore,statements $(i)$ and $(iv)$ are correct.

(A) During intense physical activity,such as playing cricket,the demand for energy in muscle cells increases significantly.
When the supply of oxygen is insufficient to meet this demand,muscle cells switch to anaerobic respiration.
In this process,the pyruvate produced from glucose breakdown is converted into lactic acid instead of entering the aerobic pathway (Krebs cycle).
The accumulation of lactic acid in the muscle tissues causes fatigue and painful muscle cramps.