Excretory waste products Questions in English

(B) The correct answer is $B$.
Urine is a transparent,light yellow liquid with a slightly acidic $pH$ (average $pH \ 6.0$).
The yellow colour of urine is caused by the pigment urochrome.
Urochrome is a breakdown product of haemoglobin derived from worn-out red blood corpuscles $(RBCs)$.

(B) The Ornithine cycle,also known as the Urea cycle,is a series of biochemical reactions that occur primarily in the liver cells (hepatocytes).
In this cycle,toxic ammonia $(NH_3)$ produced during protein metabolism is converted into urea,which is less toxic and can be safely excreted from the body via the kidneys.

(B) Creatinine is a breakdown product of creatine phosphate in muscle,and it is produced at a relatively constant rate depending on the muscle mass of the individual.
Unlike urea,uric acid,or ammonium salts,which are directly influenced by the intake of dietary proteins and nitrogenous metabolism,the excretion of creatinine remains largely independent of the protein content in the diet.
Therefore,a protein-rich diet does not significantly alter the levels of creatinine in the urine.

(D) The correct answer is $D$. The process of urea synthesis occurs through a repetitive cyclic sequence of biochemical reactions in the liver cells,known as the urea cycle.
This cycle involves the formation and transformation of three specific amino acids: ornithine,citrulline,and arginine.
Due to the involvement of these intermediates,this cycle is also commonly referred to as the ornithine cycle or the arginine cycle.

(D) Nitrogenous waste substances such as $Ammonia$, $urea$, or $uric \text{ } acid$ are produced during protein metabolism depending on the species.
$A$ small amount of nitrogenous waste substances is also produced during the metabolism of nucleic acids.
$Ammonia$ is the most toxic, followed by $urea$, and $uric \text{ } acid$ is the least toxic among these.

(C) The urea cycle,also known as the ornithine cycle,is a series of biochemical reactions that occur in the liver to convert toxic ammonia into urea for excretion. This cycle was discovered by Hans Krebs and Kurt Henseleit in $1932$. Therefore,the correct option is $C$.

(C) The ornithine cycle,also known as the urea cycle,occurs in the liver.
It is a metabolic pathway that converts toxic ammonia $(NH_3)$ and carbon dioxide $(CO_2)$ into urea.
Therefore,these two waste substances are removed from the blood during this process.

(D) Deamination is a biochemical process that occurs primarily in the liver.
In this process,the amino group $(-NH_2)$ is removed from an amino acid molecule.
The remaining carbon skeleton is then used for energy production or converted into glucose or fat.
The removed amino group is converted into ammonia $(NH_3)$,which is highly toxic and is subsequently converted into urea in the urea cycle to be excreted from the body.
Therefore,the breakdown of amino acids to release ammonia is the core of this process.

(A) Deamination is the process of removing an amino group $(-NH_2)$ from an amino acid or other compound.
In the liver,excess amino acids are broken down through deamination,where the amino group is removed to form ammonia $(NH_3)$ and a keto acid.
The ammonia is subsequently converted into urea for excretion.

(A) The primary function of the kidney is the excretion of metabolic wastes.
In addition to this,the kidney performs the vital function of osmoregulation,which is the regulation of the osmotic pressure of blood and body fluids.
It maintains the homeostasis of the body by controlling the water and electrolyte balance,ensuring that the concentration of body fluids remains within a narrow range.

(A) Ornithine is a non-protein amino acid that plays a crucial role in the urea cycle (also known as the Ornithine cycle).
In this cycle,ornithine acts as a carrier molecule that combines with ammonia and carbon dioxide to eventually produce urea,which is the primary nitrogenous waste excreted by mammals.
Therefore,it is found as an intermediate during the process of urea synthesis in the liver.

(C) The $Ornithine$ cycle,also known as the $Urea$ cycle,is a series of biochemical reactions that occur in the liver.
It converts toxic ammonia $(NH_3)$ into urea $(CO(NH_2)_2)$,which is less toxic and can be safely excreted from the body through urine.
Therefore,this cycle is a fundamental process of the excretory system.

(A) Transamination refers to the transfer of an amino group $(-NH_2)$ from an amino acid to a keto acid to form a new amino acid.
This process is crucial for the synthesis of non-essential amino acids and for the metabolism of proteins.
In vertebrates,the primary site for transamination is the liver,where enzymes called transaminases (or aminotransferases) facilitate this reaction.

(C) The correct answer is $C$. When urine is left to stand for some time,it develops a strong,pungent smell of ammonia. This occurs because bacteria present in the environment act upon the urea $(NH_2CONH_2)$ present in the urine,breaking it down into ammonia $(NH_3)$ and carbon dioxide $(CO_2)$ through the process of bacterial degradation.

(C) The production of urea occurs in the liver through the urea cycle (ornithine cycle). In the final step of this cycle,the enzyme $Arginase$ catalyzes the hydrolysis of arginine into urea and ornithine. Therefore,$Arginase$ is the enzyme responsible for the production of urea.

(A) Ammonia is a highly toxic nitrogenous waste product formed in the body cells during the catabolism of amino acids. Specifically,the oxidative deamination of amino acids like glutamic acid in tissue cells results in the production of ammonia. While putrefying bacteria in the large intestine also produce ammonia,this occurs in the lumen of the gut,not within the tissue cells themselves. The Ornithine cycle is the process by which ammonia is converted into urea in the liver,not the process that produces ammonia. Therefore,only option $(a)$ is correct regarding production within tissue cells.

(A) In ureotelic animals,such as mammals and many terrestrial amphibians,ammonia produced by metabolism is converted into urea in the liver.
This process is known as the Ornithine cycle,also called the Urea cycle or Krebs-Henseleit cycle.
In this cycle,ammonia and carbon dioxide are combined to form urea,which is less toxic and requires less water for excretion compared to ammonia.

(A) The ornithine cycle,also known as the urea cycle,is a metabolic pathway that converts toxic ammonia into urea in the liver.
This process is essential for ureotelic animals to safely excrete nitrogenous waste.
Therefore,the end product of the ornithine cycle is urea.

(B) In humans,the primary nitrogenous waste product formed as a result of protein metabolism is urea.
This urea is transported by the blood to the kidneys,where it is filtered and processed to form urine.
Therefore,urea is the main substance excreted in the urine of humans.

(C) The biosynthesis of urea,also known as the Ornithine cycle or Urea cycle,occurs primarily in the liver.
Some enzymes of the urea cycle are located in the mitochondria (such as Carbamoyl phosphate synthetase $I$ and Ornithine transcarbamylase),while others are located in the cytosol.
Therefore,the statement that urea cycle enzymes are located inside mitochondria is correct in the context of the provided options,as it is a site of key initial reactions.
Urea is not synthesized in the kidney,nor is uric acid the starting material; ammonia and carbon dioxide are the primary substrates.

(D) Terrestrial animals face the constant challenge of water loss due to evaporation and metabolic processes.
To survive in environments with limited water access,these animals have evolved mechanisms to conserve water.
Uric acid is the least soluble nitrogenous waste,and $1 \,g$ of uric acid requires only $10 \,ml$ of water for excretion.
Therefore,uricotelism is a significant evolutionary adaptation for terrestrial life,allowing animals to minimize water loss during the excretion of nitrogenous waste.

(B) The liver is the primary site for the detoxification of ammonia into urea via the urea cycle (ornithine cycle).
Ammonia,which is a toxic byproduct of amino acid metabolism,is converted into urea in the liver cells (hepatocytes).
Consequently,the blood exiting the liver through the hepatic vein and moving towards the heart contains a significantly higher concentration of urea compared to the blood entering the liver.

(B) The ornithine cycle (also known as the urea cycle) is a series of biochemical reactions that convert toxic ammonia into urea in the liver.
The key amino acids involved in this cycle are ornithine,citrulline,and arginine.
Ornithine acts as a carrier molecule that combines with carbamoyl phosphate to form citrulline.
Citrulline then reacts with aspartate to form argininosuccinate,which is eventually converted into arginine.
Finally,arginine is hydrolyzed by the enzyme arginase to produce urea and regenerate ornithine,allowing the cycle to continue.

(B) Excretory products are substances formed as a result of metabolic activities that need to be eliminated from the body.
$1$. $Allantoin$ is a nitrogenous waste product formed from the oxidation of uric acid in many mammals.
$2$. $Hippuric$ $acid$ is formed in the liver by the conjugation of benzoic acid with glycine and is excreted in urine.
$3$. $Uric$ $acid$ is the primary nitrogenous waste product in uricotelic animals (like birds and reptiles).
Therefore,the group containing final excretory products is $Allantoin, hippuric acid, uric acid$.

(A) The primary function of the mammalian kidney is osmoregulation and the excretion of metabolic wastes.
It filters the blood to remove nitrogenous wastes,primarily $Urea$,which is the main excretory product in mammals (ureotelic organisms).
Additionally,the kidney regulates the body's water balance and electrolyte concentration by excreting excess water and excess salts (such as $NaCl$) to maintain homeostasis.
Amino acids are typically reabsorbed by the renal tubules and are not excreted in significant amounts in healthy individuals.

(A) The animals that excrete nitrogenous waste mainly in the form of uric acid are called uricotelic animals.
Since uric acid is the least toxic and relatively insoluble in water,it can be stored or excreted in the form of a pellet or paste (almost solid form) with very little loss of water.
This is a significant evolutionary adaptation for animals living in arid or water-scarce environments to conserve water.

(A) The correct statement is that when water is not available,camels do not produce urine but store urea in their tissues to maintain osmotic balance.
Camels are adapted to desert environments where they produce nearly dry feces and highly concentrated urine to conserve water.
In conditions of extreme water scarcity,they rely on metabolic water and accumulate urea in their tissues to prevent water loss.

(C) Protein catabolism involves the breakdown of amino acids. The amino group $(-NH_2)$ is removed through deamination,resulting in the formation of ammonia $(NH_3)$. Ammonia is highly toxic and is converted into urea in the liver via the urea cycle. Additionally,other nitrogenous waste products like uric acid and creatine are also formed during the metabolic breakdown of proteins and nucleic acids. Therefore,the primary nitrogenous waste products of protein catabolism include urea,$NH_3$,and uric acid.

(D) Coprosterol is a sterol derivative formed by the reduction of cholesterol by bacteria in the intestine. It is a major component of the lipid fraction found in human feces (excretory products). Therefore,it is considered a lipid derivative found in excretory products.

(B) The liver is the primary site for the metabolism of amino acids.
Excess amino acids cannot be stored in the body.
Through the process of deamination,the amino group $(-NH_2)$ is removed from the amino acids in the liver.
This process produces ammonia,which is highly toxic.
The liver then converts this ammonia into urea via the urea cycle (ornithine cycle).
Urea is less toxic and is subsequently transported to the kidneys for excretion.

(B) The liver is the primary site for the detoxification of ammonia into urea through the $Ornithine$ cycle (or urea cycle).
Since the liver synthesizes urea from ammonia,the blood that exits the liver via the hepatic vein and travels towards the heart contains a significantly higher concentration of urea compared to the blood entering the liver.
Therefore,the correct option is $B$.

(C) The ornithine cycle,also known as the urea cycle,is a series of biochemical reactions that occur in the liver.
In this cycle,ammonia $(NH_3)$,which is a toxic byproduct of protein metabolism,is converted into urea $(CO(NH_2)_2)$.
Urea is less toxic than ammonia and is subsequently transported to the kidneys for excretion.
Therefore,the ornithine cycle is essential for the detoxification of ammonia in the liver.

(D) Ammonia is highly toxic and requires a large amount of water for its elimination from the body.
Therefore,animals that excrete ammonia as their primary nitrogenous waste are called ammonotelic.
Since ammonia is highly soluble in water,this process is common in aquatic animals such as bony fishes,many amphibians,and aquatic insects.
Terrestrial animals typically excrete urea or uric acid to conserve water.

(B) Ammonia is highly toxic and requires a large amount of water for its elimination. Tadpoles live in an aquatic environment,which allows them to excrete nitrogenous waste as ammonia. Adult frogs,however,are semi-terrestrial and have evolved to convert ammonia into urea,which is less toxic and requires less water for excretion,thus conserving water in their environment.

(B) Excretion is the biological process by which an organism eliminates metabolic waste products and other toxic or unnecessary substances from its body.
These substances include metabolic wastes (like urea,uric acid,ammonia) and excess substances (like excess water,salts,or ions) that are present in the body beyond the required levels.
Therefore,excretion involves the removal of both unnecessary metabolic waste and excess substances to maintain homeostasis.

(D) Excretory products are the metabolic waste substances produced as a result of various biochemical reactions occurring within all living cells of the body. While organs like the kidneys and liver are specialized for the processing and elimination of these wastes,the actual formation of metabolic byproducts (such as $CO_2$,urea,ammonia,etc.) occurs in all somatic cells during cellular metabolism. Therefore,the correct answer is $D$.

(B) Animals that excrete nitrogenous waste in the form of uric acid are called uricotelic animals.
Uric acid is excreted in the form of a pellet or paste with a minimum loss of water.
This is an adaptation for water conservation.
Birds,reptiles (like lizards and snakes),and land snails are examples of uricotelic organisms.
Therefore,birds and lizards excrete uric acid as their primary nitrogenous waste product.

(A) Metabolic wastes are substances produced during metabolic processes that cannot be used by the body and must be excreted.
Nitrogenous wastes are the primary metabolic wastes produced from the breakdown of proteins and nucleic acids.
These include ammonia $(NH_3)$,urea,uric acid,and creatinine.
Option $A$ correctly lists urea,ammonia,and creatinine as nitrogenous metabolic wastes.
Oxygen and $N_2$ (Option $B$) are gases,not metabolic wastes.
Alanine (Option $C$) is an amino acid used for protein synthesis.
$CO_2$ (Option $D$) is a metabolic waste but is not nitrogenous.

(D) The process of excreting ammonia is known as ammonotelism. Ammonia is highly toxic and requires a large amount of water for its elimination. Therefore,it is primarily excreted by aquatic organisms such as bony fishes,many amphibians,and aquatic insects. Among the given options,freshwater fishes are ammonotelic. Cartilaginous fishes (like sharks) are ureotelic,and mammals (like camels and whales) are also ureotelic.

(B) Animals are classified based on their primary nitrogenous waste product:
$1$. Ammonotelic: Excrete ammonia (e.g.,most aquatic invertebrates and bony fishes).
$2$. Ureotelic: Excrete urea (e.g.,mammals,many terrestrial amphibians,and marine fishes).
$3$. Uricotelic: Excrete uric acid (e.g.,reptiles,birds,land snails,and insects).
Since the question asks for 'Ureotelic' animals,the primary nitrogenous waste product is urea.

(C) The Ornithine cycle,also known as the Urea cycle,occurs in the liver cells (hepatocytes).
In this cycle,two molecules of ammonia $(NH_3)$ and one molecule of carbon dioxide $(CO_2)$ are utilized to synthesize one molecule of urea $(NH_2CONH_2)$.
Therefore,$CO_2$ and ammonia are the primary substances consumed/removed from the blood circulation to produce urea as an excretory product.
Thus,the correct pair is $CO_2$ and ammonia.

(D) Organisms are classified based on their nitrogenous waste products as follows:
$1$. Ammonotelic: Excrete ammonia (e.g.,most bony fishes,aquatic amphibians).
$2$. Ureotelic: Excrete urea (e.g.,mammals,terrestrial amphibians,and marine fishes).
$3$. Uricotelic: Excrete uric acid (e.g.,reptiles,birds,land snails,and insects).
Snakes,birds,and insects are uricotelic,meaning they excrete uric acid to conserve water. Therefore,none of the given options are ureotelic.

(C) When a person undergoes fasting (not taking food or drink),the body begins to break down its own stored energy reserves to maintain metabolic functions.
Since the person is not consuming dietary proteins,the body catabolizes its own tissue proteins (muscle proteins) to provide amino acids for essential processes.
The deamination of these amino acids leads to the production of nitrogenous waste,specifically urea.
Consequently,the concentration of urea in the urine increases compared to a normal state,as the body is actively breaking down internal proteins for energy and maintenance.

(C) In the liver,the urea cycle (also known as the Ornithine cycle) converts toxic ammonia into urea for excretion.
During this process,one molecule of ammonia $(NH_3)$ and one molecule of carbon dioxide $(CO_2)$ are used to form carbamoyl phosphate.
Subsequently,another nitrogen atom is donated by the amino acid aspartic acid to complete the formation of urea $(NH_2CONH_2)$.
Therefore,the synthesis of urea requires ammonia,carbon dioxide,and aspartic acid.

(A) When a person is on a long hunger strike,the body does not receive any dietary proteins.
Since urea is the end product of protein metabolism,the breakdown of body proteins (catabolism) continues to provide energy.
However,the overall intake of nitrogenous compounds is zero.
As the body breaks down its own tissues for survival,the urea production decreases significantly compared to a normal diet.
Therefore,the amount of urea excreted in the urine will be less.

(B) The Ornithine cycle,also known as the Urea cycle,is a series of biochemical reactions in which ammonia $(NH_3)$ is converted into urea $(CO(NH_2)_2)$ in the liver.
This process is essential for the removal of toxic nitrogenous waste from the body.
Therefore,the Ornithine cycle is directly related to the process of excretion.

(C) Urea is synthesized in the $Liver$ through a metabolic cycle known as the $Ornithine$ cycle or $Urea$ cycle.
In this process, ammonia $(NH_3)$, which is a toxic byproduct of protein metabolism, is converted into less toxic urea $(NH_2CONH_2)$ using carbon dioxide $(CO_2)$.
After production in the liver, urea is released into the blood and subsequently filtered by the kidneys to be excreted in the urine.

(A) Proteins are composed of amino acids. When amino acids are metabolized,the amino group $(-NH_2)$ is removed through a process called deamination. This process releases ammonia $(NH_3)$,which is toxic. In the liver,the ornithine cycle (urea cycle) converts this ammonia into urea $(CO(NH_2)_2)$. Therefore,a high-protein diet leads to an increased production and subsequent excretion of urea by the kidneys.

(C) In the urea cycle (ornithine cycle) occurring in the liver,the enzyme $Arginase$ catalyzes the hydrolysis of $L-arginine$ into $L-ornithine$ and $Urea$. This is the final step of the urea cycle where urea is released as a metabolic waste product.

(A) Organisms that live in environments where water conservation is critical,such as birds,reptiles,and insects,excrete nitrogenous waste as uric acid.
Uric acid is relatively non-toxic and is poorly soluble in water.
Because it is insoluble,it can be excreted in the form of a paste or a solid pellet with very little loss of water.
This adaptation is highly beneficial for survival in arid or water-scarce environments.