Biology

181. Which one of the following statements regarding digestion is correct?

Which one of the following statements regarding digestion is correct?

[amp_mcq option1=”Fat present in the food is digested by trypsin and chymotrypsin.” option2=”Starch of food is digested by lipases.” option3=”Fat of food is digested by lipases.” option4=”Nucleic acid is digested by amylases.” correct=”option3″]

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Digestion involves enzymatic breakdown of macromolecules in food. Different types of enzymes are specific for different types of molecules. Fats (lipids, primarily triglycerides) are digested by enzymes called lipases. For example, pancreatic lipase is the main enzyme responsible for fat digestion in the small intestine, breaking triglycerides down into fatty acids and glycerol.
Let’s examine the other options:
A) Trypsin and chymotrypsin are proteases, enzymes that digest proteins into smaller peptides and amino acids. They do not digest fats.
B) Starch is a complex carbohydrate. Carbohydrates like starch are digested by amylases (e.g., salivary amylase, pancreatic amylase) into smaller sugars. Lipases digest fats.
D) Nucleic acids (DNA and RNA) are digested by nucleases into nucleotides. Amylases digest carbohydrates.
Thus, the correct statement is that fat of food is digested by lipases.
Specific enzymes are required to digest different classes of macromolecules: Lipases for fats, Amylases for carbohydrates (like starch), Proteases for proteins, and Nucleases for nucleic acids.
Bile salts, produced by the liver and stored in the gallbladder, are also important for fat digestion. They emulsify large fat globules into smaller droplets, increasing the surface area available for lipases to act upon.

182. Which one of the following statements regarding muscle contraction and

Which one of the following statements regarding muscle contraction and relaxation is correct?

[amp_mcq option1=”It involves movement of Zn++ ion.” option2=”It involves Ca++ ion of blood.” option3=”It involves release of Ca++ from sarcoplasmic reticulum (SR) and pumping Ca++ back in SR.” option4=”It involves exchange of Na and K.” correct=”option3″]

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Muscle contraction is initiated by a signal (usually from a motor neuron) that leads to a sequence of events culminating in the sliding of actin and myosin filaments. A critical step in this process is the increase in the concentration of calcium ions (Ca++) in the sarcoplasm (the cytoplasm of a muscle cell). This Ca++ is primarily stored in the sarcoplasmic reticulum (SR), a specialized endoplasmic reticulum in muscle cells. Upon receiving the signal, Ca++ is released from the SR into the sarcoplasm. These released Ca++ ions bind to regulatory proteins on the actin filaments, allowing myosin heads to bind and cause contraction. Muscle relaxation occurs when the signal stops. Ca++ ions are then actively transported back into the SR by Ca++ pumps (SERCA pumps) located on the SR membrane. The reduction in sarcoplasmic Ca++ concentration causes the regulatory proteins to block myosin binding sites again, leading to muscle relaxation. Therefore, the release of Ca++ from the SR and its subsequent pumping back into the SR are central events in muscle contraction and relaxation.
Muscle contraction and relaxation are directly regulated by the concentration of Ca++ ions in the sarcoplasm, which is controlled by the release and re-uptake of Ca++ by the sarcoplasmic reticulum.
While other ions like Na+ and K+ are crucial for the electrical signaling (action potential) that triggers muscle contraction, and Zn++ is involved in various metabolic processes, the direct mechanism governing the binding and unbinding of myosin to actin, which constitutes the contraction/relaxation cycle, is primarily regulated by the availability of intracellular Ca++.

183. Which one of the following statements about blood elements is correct?

Which one of the following statements about blood elements is correct?

[amp_mcq option1=”Red blood cells’ number is same as that of white blood cells and platelets.” option2=”The number of white blood cells is more than red blood cells.” option3=”The number of red blood cells is the highest.” option4=”The number of red blood cells is lower than platelets.” correct=”option3″]

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Blood is composed of plasma and blood cells (also called formed elements). The main types of blood cells are Red Blood Cells (RBCs or erythrocytes), White Blood Cells (WBCs or leukocytes), and Platelets (thrombocytes). Their relative numbers per unit volume of blood are vastly different. RBCs are by far the most numerous, with typical counts in millions per microliter (around 4-6 million/µL). Platelets are the second most numerous, with counts in the hundreds of thousands per microliter (around 150,000-450,000/µL). WBCs are the least numerous, with counts in the thousands per microliter (around 4,000-11,000/µL). Therefore, the number of red blood cells is the highest among the blood elements.
The relative abundance of formed elements in blood follows the order: Red Blood Cells > Platelets > White Blood Cells.
Each type of blood cell has distinct functions: RBCs transport oxygen, WBCs are involved in the immune system, and Platelets are crucial for blood clotting. Abnormal counts of any of these can indicate various health conditions.

184. Which one of the following statements about transport mechanism in pla

Which one of the following statements about transport mechanism in plants is correct?

[amp_mcq option1=”Diffusion of ions and small molecules across cell membrane requires energy.” option2=”Active transport of ions and small molecules across cell membrane against concentration gradient requires energy.” option3=”Cells conserve energy and no energy is required for transport of ions and small molecules against concentration gradient.” option4=”Cells do not transport ions across their membrane as these are charged molecules.” correct=”option2″]

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The correct answer is B) Active transport of ions and small molecules across cell membrane against concentration gradient requires energy.
Statement A is incorrect: Diffusion (simple or facilitated) is a passive process driven by the concentration gradient; it does not require metabolic energy (ATP).
Statement B is correct: Active transport involves moving substances across a cell membrane against their concentration gradient (from a region of lower concentration to a region of higher concentration). This process requires the cell to expend metabolic energy, usually in the form of ATP, to power transport proteins (pumps).
Statement C is incorrect: Moving substances against a concentration gradient requires energy input. Cells use active transport precisely for this purpose, even though it consumes energy.
Statement D is incorrect: Cells regularly transport ions across their membranes using both passive mechanisms (ion channels) and active mechanisms (ion pumps) to maintain electrochemical gradients, osmotic balance, and for signalling. Ions are charged molecules, but their transport is essential for cell function.
Transport across cell membranes can be broadly classified into passive transport (diffusion, facilitated diffusion) and active transport. Passive transport does not require energy input and follows concentration gradients. Active transport requires energy and can move substances against gradients. Plants, like other organisms, use both types of transport for uptake of nutrients from the soil and for movement of substances within the plant.

185. Which one of the following statements about proteins in mammalian cell

Which one of the following statements about proteins in mammalian cells is correct?

[amp_mcq option1=”Proteins in mammalian cells are synthesized in cell membrane.” option2=”Proteins in mammalian cells are not synthesized in cell membrane but directly absorbed from food.” option3=”Proteins in mammalian cells are synthesized in rough endoplasmic reticulum.” option4=”Proteins in mammalian cells are synthesized in Golgi apparatus.” correct=”option3″]

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The correct answer is C) Proteins in mammalian cells are synthesized in rough endoplasmic reticulum.
Protein synthesis, or translation, occurs on ribosomes. Ribosomes can be found freely in the cytoplasm or attached to the surface of the endoplasmic reticulum, forming the rough endoplasmic reticulum (RER). Proteins destined for secretion out of the cell, insertion into cell membranes (including the plasma membrane and membranes of organelles like RER, Golgi, lysosomes), or delivery to organelles within the secretory pathway (like lysosomes) are synthesized on ribosomes attached to the RER. Proteins destined for the cytoplasm, nucleus, mitochondria, or peroxisomes are typically synthesized on free ribosomes in the cytoplasm. Therefore, the rough endoplasmic reticulum is a major site of protein synthesis in mammalian cells, particularly for proteins entering the secretory pathway.
Statement A is incorrect; the cell membrane is where some proteins reside, but not where they are synthesized. Statement B is incorrect; cells synthesize their own proteins from amino acids. Statement D is incorrect; the Golgi apparatus modifies, sorts, and packages proteins synthesized elsewhere, but does not synthesize them.

186. Which one of the following is NOT decomposed by bacterial action ?

Which one of the following is NOT decomposed by bacterial action ?

[amp_mcq option1=”Vegetable remains” option2=”Plastic materials” option3=”Animal carcasses” option4=”Wastes of flowers” correct=”option2″]

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The correct option is B.
Bacterial action, along with fungi and other microorganisms, is responsible for the decomposition of organic matter. Vegetable remains (A), animal carcasses (C), and wastes of flowers (D) are all composed of organic materials that are readily biodegradable by bacteria and other decomposers in the environment. Plastic materials (B), on the other hand, are typically synthetic polymers derived from petroleum. Their complex chemical structure makes them resistant to breakdown by most common bacteria and natural decomposition processes, leading to their persistence in the environment.
While some specialized microorganisms or specific conditions can lead to the degradation of certain types of plastics over very long periods, common plastics are largely considered non-biodegradable by typical bacterial action in the environment compared to organic waste.

187. Which one of the following is a major effect of long term consumption

Which one of the following is a major effect of long term consumption of drinking water containing little (less than 0.5 ppm) or no fluoride ?

[amp_mcq option1=”Cavity of tooth” option2=”Erosion of nail” option3=”Deformation of bone” option4=”Mottling of tooth” correct=”option1″]

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The correct option is A.
Fluoride in drinking water is crucial for maintaining dental health, particularly for strengthening tooth enamel and preventing cavities (dental caries). Long-term consumption of water with insufficient fluoride (less than 0.5 ppm, or no fluoride) leads to weaker enamel, making teeth more susceptible to acid attacks from bacteria and increasing the risk of cavities.
Options B, C, and D describe effects related to other factors or excessive fluoride intake. Erosion of nails (B) is not a known effect of fluoride levels in water. Deformation of bone (skeletal fluorosis) (C) and mottling of teeth (dental fluorosis) (D) are caused by *excessive* long-term consumption of fluoride, not insufficient amounts.

188. Free swimming macroscopic animals in an aquatic environment are referr

Free swimming macroscopic animals in an aquatic environment are referred to as

[amp_mcq option1=”Plankton” option2=”Periphyton” option3=”Benthos” option4=”Nekton” correct=”option4″]

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Aquatic organisms are broadly classified based on their mode of life. Plankton are typically microscopic or small organisms that drift passively in the water column. Periphyton are organisms that are attached to submerged surfaces. Benthos are organisms that live on or in the bottom sediments of a body of water. Nekton are actively swimming aquatic animals that can move independently of water currents, such as fish, marine mammals, and large invertebrates. The description “free swimming macroscopic animals” directly matches the definition of nekton.
Nekton are actively swimming aquatic animals, distinguishing them from passively drifting plankton, attached periphyton, or bottom-dwelling benthos.
Examples of nekton include most fish species, whales, dolphins, seals, squids, and diving beetles. They occupy various trophic levels within the aquatic ecosystem. The ability to swim actively allows them to seek food, avoid predators, and navigate within their environment.

189. Which one of the following elements is present in the green pigment of

Which one of the following elements is present in the green pigment of leaves ?

[amp_mcq option1=”Magnesium” option2=”Iron” option3=”Calcium” option4=”Copper” correct=”option1″]

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Magnesium is present in the green pigment of leaves (chlorophyll).
– The green pigment in leaves is called chlorophyll.
– Chlorophyll molecules are crucial for photosynthesis, the process by which plants convert light energy into chemical energy.
– The core structure of the chlorophyll molecule is a porphyrin ring, similar to the heme group in hemoglobin, but with a central magnesium atom coordinating the nitrogen atoms, whereas hemoglobin has iron at its center.
While iron is essential for the synthesis of chlorophyll, it is not a structural component of the chlorophyll molecule itself. Magnesium is the central metal ion within the chlorophyll structure. Calcium is important for cell wall structure and signaling, and copper is a cofactor in various enzymes.

190. Which of the following diseases are caused by the consumption of water

Which of the following diseases are caused by the consumption of water contaminated by mercury and nitrate ?

[amp_mcq option1=”Minamata disease and Osteoporosis” option2=”Osteoporosis and Blue Baby Syndrome” option3=”Minamata disease and Blue Baby Syndrome” option4=”Osteoporosis and Minamata disease” correct=”option3″]

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Consumption of water contaminated by mercury can cause Minamata disease, and contamination by nitrate can cause Blue Baby Syndrome.
Minamata disease is a neurological syndrome caused by severe mercury poisoning. It was first discovered in Minamata, Japan, caused by the release of methylmercury into industrial wastewater. Blue Baby Syndrome (Methemoglobinemia) is caused by the consumption of nitrates, especially in infants. Nitrates are converted to nitrites, which interfere with the oxygen-carrying capacity of hemoglobin, causing a bluish discoloration of the skin.
Osteoporosis is a disease where bones become weak and brittle, typically linked to calcium and Vitamin D deficiency, hormonal changes, and aging, not directly caused by mercury or nitrate water contamination.
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