Biology Archives

131. Lactic acid is formed in the muscles during exercise or running. It is

Lactic acid is formed in the muscles during exercise or running. It is formed :

[amp_mcq option1=”to give extra energy from fat.” option2=”to give extra oxygen from lungs.” option3=”to give extra energy from glucose.” option4=”to give extra energy from vitamins.” correct=”option3″]

This question was previously asked in

UPSC CAPF – 2023

Download PDF Attempt Online

During intense exercise, when oxygen supply to muscles may not meet the demand for aerobic respiration, muscle cells can generate ATP (energy) through anaerobic glycolysis. Glucose is broken down to pyruvate, which is then converted to lactate (lactic acid) in the absence of sufficient oxygen. This process regenerates NAD+, allowing glycolysis to continue and produce a small amount of ATP from glucose, providing extra energy when aerobic pathways are limited.

Lactic acid is produced during anaerobic respiration in muscles, which occurs when oxygen is insufficient for aerobic metabolism. This process allows glycolysis to continue, yielding ATP from glucose for energy.

Anaerobic respiration primarily uses glucose, not fat, as the substrate. Lactic acid formation happens due to a lack of sufficient oxygen supply, not to provide extra oxygen. Vitamins are not used as a direct energy source.

132. For the digestion of carbohydrate, protein and fat, enzymes such as am

For the digestion of carbohydrate, protein and fat, enzymes such as amylase, trypsin and lipase are required. It is secreted into the duodenum through :

[amp_mcq option1=”Bile” option2=”Plasma” option3=”Lymph” option4=”Pancreatic juice” correct=”option4″]

This question was previously asked in

UPSC CAPF – 2023

Download PDF Attempt Online

Amylase (for carbohydrates), trypsin (for proteins), and lipase (for fats) are major digestive enzymes secreted by the pancreas. The pancreas releases these enzymes, along with other components, as pancreatic juice. Pancreatic juice is secreted into the duodenum, the first part of the small intestine, through the pancreatic duct to facilitate the digestion of food entering from the stomach.

The pancreas produces and secretes a suite of digestive enzymes (amylase, lipase, proteases like trypsin and chymotrypsin) via the pancreatic duct into the duodenum.

Bile is produced by the liver and stored in the gallbladder, then secreted into the duodenum. Bile aids in fat digestion by emulsification, but it does not contain the enzymes amylase, trypsin, or lipase. Plasma and lymph are components of the circulatory and lymphatic systems, not involved in secreting digestive enzymes into the digestive tract.

133. The lymph is mainly formed from the plasma of blood and it surrounds t

The lymph is mainly formed from the plasma of blood and it surrounds the cells. The main difference between blood and lymph is :

[amp_mcq option1=”Lymph does not contain red blood cells.” option2=”Lymph does not contain white blood cells.” option3=”Lymph contains both red blood cells and white blood cells.” option4=”Lymph does not contain any cells.” correct=”option1″]

This question was previously asked in

UPSC CAPF – 2023

Download PDF Attempt Online

Lymph is essentially interstitial fluid that has entered the lymphatic vessels. Interstitial fluid is formed from blood plasma that filters out of capillaries. While plasma contains red blood cells, white blood cells, platelets, proteins, water, and dissolved substances, red blood cells are generally too large to pass through capillary walls into the interstitial space. Therefore, lymph, derived from interstitial fluid, does not contain red blood cells.

Blood contains red blood cells, white blood cells, platelets, and plasma. Lymph consists of plasma components and white blood cells (mainly lymphocytes), but significantly lacks red blood cells and platelets.

Lymph does contain white blood cells, particularly lymphocytes, which are crucial for the immune system and are found in large numbers in lymph nodes. The absence of red blood cells is a key distinguishing feature compared to blood.

134. In humans, urea is mainly formed from the metabolism of which one of t

In humans, urea is mainly formed from the metabolism of which one of the following components of food ?

[amp_mcq option1=”Fatty acids” option2=”Vitamins” option3=”Amino acids” option4=”Glucose” correct=”option3″]

This question was previously asked in

UPSC CAPF – 2023

Download PDF Attempt Online

Urea is the main nitrogenous waste product excreted by mammals. It is formed in the liver through the urea cycle, which processes excess amino groups from the breakdown of amino acids. Amino acids are the building blocks of proteins, and their metabolism yields nitrogen that must be eliminated from the body, primarily as urea.

Amino acids, derived from protein digestion, contain nitrogen. The liver converts this excess nitrogen into urea for excretion.

Fatty acids are primarily metabolized for energy storage and production. Vitamins are organic compounds required in small amounts for various metabolic processes. Glucose is the primary source of energy through cellular respiration. While the metabolism of fats, carbohydrates, and proteins are interconnected, urea formation specifically relates to the detoxification of nitrogen from amino acid breakdown.

135. In some viral infections, number of platelets are reduced quickly. Pla

In some viral infections, number of platelets are reduced quickly. Platelets are essential because :

[amp_mcq option1=”they along with red blood cells carry oxygen.” option2=”platelets are important to carry food to cells through blood.” option3=”platelets remove carbon dioxide from blood.” option4=”platelets have a role in blood clotting.” correct=”option4″]

This question was previously asked in

UPSC CAPF – 2023

Download PDF Attempt Online

Platelets, or thrombocytes, are small, irregular-shaped cell fragments found in blood. Their main function is to stop bleeding (hemostasis) by clumping together to form a plug at the site of injury and by releasing factors that promote blood clotting. In viral infections like dengue fever, a decrease in platelet count (thrombocytopenia) is common and can lead to increased risk of bleeding, highlighting their essential role in blood clotting.

– Platelets are involved in hemostasis (stopping bleeding).
– Platelets facilitate blood clotting.
– Low platelet count (thrombocytopenia) increases bleeding risk.

Red blood cells are responsible for oxygen transport. White blood cells are part of the immune system. Plasma carries dissolved substances like nutrients, hormones, and waste products throughout the body. Carbon dioxide is transported in blood primarily as bicarbonate ions, bound to hemoglobin, or dissolved in plasma. Platelets are specifically critical for initiating and supporting the coagulation cascade, forming a blood clot.

136. Both starch and glycogen are made up of glucose, however:

Both starch and glycogen are made up of glucose, however:

[amp_mcq option1=”starch is present in liver and glycogen is present in red blood cells.” option2=”glycogen is made in animal cells, but starch is made in plant cells.” option3=”both starch and glycogen are present in animal and plant cells.” option4=”both starch and glycogen are present in plant cells only.” correct=”option2″]

This question was previously asked in

UPSC CAPF – 2023

Download PDF Attempt Online

Starch and glycogen are both polysaccharides composed of glucose units, serving as energy storage molecules. Starch is the primary storage carbohydrate in plants, found in plastids like chloroplasts and amyloplasts. Glycogen is the primary storage carbohydrate in animals and fungi, mainly stored in the liver and muscles in animals. Therefore, glycogen is made and stored in animal cells, while starch is made and stored in plant cells.

– Both starch and glycogen are glucose polymers used for energy storage.
– Starch is found in plants.
– Glycogen is found in animals and fungi.

Starch exists in two forms: amylose (linear chain) and amylopectin (branched chain). Glycogen is highly branched, more so than amylopectin. The different structures affect their physical properties and rate of breakdown. Neither starch nor glycogen are typically found in both animal and plant cells in significant quantities; their roles are specific to different domains of life. Red blood cells in animals do not store glycogen as they lack the necessary organelles.

137. The rate of an enzyme catalyzed reaction depends :

The rate of an enzyme catalyzed reaction depends :

[amp_mcq option1=”upon substrate concentration and pH, but not on temperature.” option2=”only on substrate concentration and pH, but not on temperature.” option3=”only on pH and temperature, but not on substrate concentration.” option4=”only on temperature, but not on pH and substrate concentration.” correct=”option1″]

This question was previously asked in

UPSC CAPF – 2023

Download PDF Attempt Online

The rate of an enzyme-catalyzed reaction is influenced by multiple factors. Substrate concentration is a key factor, as the rate typically increases with substrate concentration until enzyme saturation is reached (Michaelis-Menten kinetics). pH affects the ionization state of amino acid residues in the enzyme’s active site and the substrate, influencing enzyme-substrate binding and catalysis; enzymes have optimal pH values. Temperature affects the kinetic energy of molecules, increasing reaction rates with increasing temperature up to an optimum, after which the rate decreases sharply due to enzyme denaturation. Therefore, the rate depends on substrate concentration, pH, and temperature. Option A states the rate depends “upon substrate concentration and pH, but not on temperature”. While the premise that the rate does *not* depend on temperature is scientifically incorrect, among the given options, Option A acknowledges dependence on two crucial factors (Substrate concentration and pH). However, it must be stated that the rate *also* depends significantly on temperature. The phrasing of the options appears flawed as dependence on temperature is a fundamental aspect of enzyme kinetics. Assuming there is an intended correct answer among the choices, Option A includes dependencies on two critical factors, even though its exclusion of temperature is incorrect.

– Enzyme reaction rate depends on substrate concentration, pH, and temperature.
– Substrate concentration affects the frequency of enzyme-substrate collisions and active site saturation.
– pH affects the ionization states of enzyme and substrate, influencing activity.
– Temperature affects molecular kinetic energy and enzyme stability (denaturation).

The relationship between reaction rate and substrate concentration is described by models like the Michaelis-Menten equation. Temperature dependence follows the Arrhenius equation up to the optimal temperature. pH dependence is often represented by a bell-shaped curve. All three factors are interdependent and influence the overall enzyme activity and reaction rate. The provided options contain a significant scientific inaccuracy by claiming the rate does not depend on one of the listed factors. Assuming this is a question from a specific exam where A was marked correct despite the flaw, the justification focuses on the factors mentioned in A.

138. In vertebrates, smooth endoplasmic reticulum in cells of which organ p

In vertebrates, smooth endoplasmic reticulum in cells of which organ plays a crucial role in detoxification of toxic compounds ?

[amp_mcq option1=”Spleen” option2=”Intestine” option3=”Kidney” option4=”Liver” correct=”option4″]

This question was previously asked in

UPSC CAPF – 2023

Download PDF Attempt Online

The smooth endoplasmic reticulum (SER) is involved in various metabolic processes, including lipid synthesis, steroid hormone production, and importantly, detoxification of drugs, poisons, and metabolic waste products. In vertebrates, the liver is the primary organ for detoxification, and its cells (hepatocytes) are particularly rich in SER, which contains enzymes like cytochrome P450 that metabolize these toxic compounds, often making them more soluble for excretion.

– Smooth endoplasmic reticulum is involved in detoxification.
– The liver is the main detoxification organ in vertebrates.
– Liver cells (hepatocytes) contain abundant smooth endoplasmic reticulum.

While other organs might have some detoxification capabilities or be involved in elimination (like kidneys), the liver’s role in metabolic detoxification via enzymes located in the SER is crucial and most prominent. The spleen is mainly involved in filtering blood, immune responses, and red blood cell turnover. The intestine is involved in digestion and absorption, and while it has some metabolic activity, its primary role is not systemic detoxification. The kidneys are primarily involved in filtering blood and excreting waste in urine.

139. For protein synthesis, the amino acids are recognized and carried by :

For protein synthesis, the amino acids are recognized and carried by :

[amp_mcq option1=”mRNA” option2=”snRNA” option3=”miRNA” option4=”tRNA” correct=”option4″]

This question was previously asked in

UPSC CAPF – 2023

Download PDF Attempt Online

Transfer RNA (tRNA) molecules are essential components of protein synthesis (translation). Each tRNA molecule has an anticodon loop that recognizes and binds to a specific codon on the messenger RNA (mRNA). At the other end, the tRNA is attached to a specific amino acid corresponding to that codon. Thus, tRNAs act as adapters, bringing the correct amino acid to the ribosome for incorporation into the growing polypeptide chain based on the mRNA sequence.

– Protein synthesis involves mRNA, ribosomes, and tRNA.
– mRNA carries the genetic code (codons).
– tRNA carries the specific amino acid corresponding to an mRNA codon and recognizes the codon via its anticodon.

Ribosomal RNA (rRNA) is a structural and catalytic component of ribosomes, where protein synthesis takes place. snRNA (small nuclear RNA) is involved in splicing, while miRNA (microRNA) and siRNA (small interfering RNA) are involved in post-transcriptional gene regulation. None of these directly recognize codons and carry amino acids for translation.

140. Which organelle other than nucleus in eukaryotic cells has its own DNA

Which organelle other than nucleus in eukaryotic cells has its own DNA, ribosomes and proteins ?

[amp_mcq option1=”Golgi” option2=”Mitochondria” option3=”Lysosomes” option4=”Nucleosomes” correct=”option2″]

This question was previously asked in

UPSC CAPF – 2023

Download PDF Attempt Online

In eukaryotic cells, besides the nucleus, mitochondria (and chloroplasts in plant cells) contain their own DNA (typically circular), ribosomes (different from cytoplasmic ribosomes), and the machinery for synthesizing some of their own proteins. This makes them semi-autonomous organelles.

Mitochondria are organelles responsible for cellular respiration and ATP production. The presence of their own genetic material and protein synthesis machinery is strong evidence supporting the endosymbiotic theory, which posits that mitochondria evolved from free-living prokaryotic organisms that were engulfed by early eukaryotic cells.

The Golgi apparatus, lysosomes, and nucleosomes (which are part of the chromatin structure within the nucleus and mitochondria/chloroplasts) do not possess their own independent DNA or ribosomes and are not capable of synthesizing proteins independently of the cytoplasmic protein synthesis machinery directed by nuclear DNA.