241. Which process is responsible for the production of haploid gametes in sexually reproducing organisms?
A) Mitosis
B) Meiosis
C) Binary fission
D) Budding
Correct Answer: B) Meiosis
Explanation:
Meiosis is a specialized type of cell division that occurs in the reproductive organs, producing gametes (sperm and eggs) with half the number of chromosomes as the parent cell. This reduction is crucial for maintaining chromosome number across generations, as the fusion of two gametes during fertilization restores the diploid number. Without meiosis, chromosome numbers would double each generation, leading to genetic instability.
242. Where does most nutrient absorption occur in the human digestive system?
A) Stomach
B) Small intestine
C) Large intestine
D) Esophagus
Correct Answer: B) Small intestine
Explanation:
The small intestine is highly adapted for nutrient absorption, featuring finger-like projections called villi and microvilli that greatly increase its surface area. Digestive enzymes from the pancreas and bile from the liver break food into absorbable molecules, which are then transported into the bloodstream. The stomach mainly digests proteins, while the large intestine absorbs water and electrolytes.
243. What is the main function of hemoglobin in red blood cells?
A) Clotting
B) Immunity
C) Oxygen transport
D) Nutrient transport
Correct Answer: C) Oxygen transport
Explanation:
Hemoglobin is an iron-containing protein that binds oxygen in the lungs and releases it to tissues throughout the body. Each hemoglobin molecule can carry four oxygen molecules. This efficient transport system ensures that oxygen is delivered to cells for aerobic respiration, which is vital for energy production.
244. Which structure in the human ear is responsible for amplifying sound vibrations?
A) Cochlea
B) Ossicles
C) Eardrum
D) Auditory nerve
Correct Answer: B) Ossicles
Explanation:
The ossicles—malleus, incus, and stapes—are three tiny bones in the middle ear that transmit and amplify sound vibrations from the eardrum to the inner ear. This amplification is necessary because sound loses energy as it moves from air (low density) to fluid (high density) in the cochlea.
245. What is the primary function of the pancreas in the human body?
A) Production of bile
B) Production of insulin and digestive enzymes
C) Filtration of blood
D) Storage of glycogen
Correct Answer: B) Production of insulin and digestive enzymes
Explanation:
The pancreas has both endocrine and exocrine functions. It produces insulin and glucagon, which regulate blood sugar levels. It also secretes digestive enzymes (such as amylase, lipase, and protease) into the small intestine, where they break down carbohydrates, fats, and proteins.
246. Which of the following best describes the process of osmosis?
A) Movement of water across a semipermeable membrane from low to high solute concentration
B) Movement of ions across a membrane
C) Active transport of molecules
D) Movement of large particles into a cell
Correct Answer: A) Movement of water across a semipermeable membrane from low to high solute concentration
Explanation:
Osmosis is the passive movement of water molecules through a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. This process is essential for maintaining cell turgor in plants and for the movement of water between body compartments in animals.
247. What is the main function of the spleen in the human body?
A) Production of insulin
B) Storage of blood
C) Digestion of fats
D) Production of bile
Correct Answer: B) Storage of blood
Explanation:
The spleen acts as a blood reservoir and filters blood, removing old or damaged red blood cells. It also plays a role in the immune system by producing white blood cells and antibodies. While it does not digest fats or produce bile, it is crucial for maintaining healthy blood and immune function.
248. Which vitamin is synthesized in the skin upon exposure to sunlight?
A) Vitamin A
B) Vitamin D
C) Vitamin E
D) Vitamin K
Correct Answer: B) Vitamin D
Explanation:
Vitamin D is synthesized in the skin when ultraviolet B (UVB) rays from sunlight convert a precursor molecule (7-dehydrocholesterol) into cholecalciferol (vitamin D₃). This vitamin is essential for calcium absorption in the gut, promoting bone health and preventing diseases like rickets.
249. What is the primary function of the alveoli in the lungs?
A) Production of mucus
B) Exchange of gases
C) Filtration of blood
D) Production of sound
Correct Answer: B) Exchange of gases
Explanation:
Alveoli are tiny, balloon-like structures at the ends of the bronchioles in the lungs. Their thin walls and large surface area facilitate the exchange of oxygen and carbon dioxide between the air and the blood. Oxygen diffuses into the blood, while carbon dioxide diffuses out to be exhaled.
250. Which process results in the conversion of atmospheric nitrogen into a form usable by plants?
A) Nitrification
B) Denitrification
C) Nitrogen fixation
D) Ammonification
Correct Answer: C) Nitrogen fixation
Explanation:
Nitrogen fixation is the process by which atmospheric nitrogen (N₂) is converted into ammonia (NH₃) by nitrogen-fixing bacteria, such as Rhizobium in legume root nodules. This ammonia can then be converted into nitrates and nitrites, which are absorbed by plants for protein synthesis.
251. What is the main function of the ribosome in a cell?
A) Energy production
B) Protein synthesis
C) Lipid synthesis
D) DNA replication
Correct Answer: B) Protein synthesis
Explanation:
Ribosomes are cellular structures that read messenger RNA (mRNA) and assemble amino acids into proteins according to the genetic code. They can be found free in the cytoplasm or attached to the rough endoplasmic reticulum, and are essential for all cellular activities.
252. Which hormone is responsible for regulating blood sugar levels by lowering glucose concentration?
A) Glucagon
B) Insulin
C) Adrenaline
D) Thyroxine
Correct Answer: B) Insulin
Explanation:
Insulin is produced by the beta cells of the pancreas in response to high blood glucose levels. It promotes the uptake of glucose by cells, especially in the liver, muscle, and fat tissue, and stimulates the conversion of glucose into glycogen for storage. This helps maintain stable blood sugar levels.
253. Which part of the human brain is responsible for maintaining balance and coordination?
A) Cerebrum
B) Cerebellum
C) Medulla oblongata
D) Hypothalamus
Correct Answer: B) Cerebellum
Explanation:
The cerebellum, located at the back of the brain, coordinates voluntary movements such as posture, balance, and speech. It receives information from the sensory systems, the spinal cord, and other parts of the brain to fine-tune motor activity and ensure smooth, coordinated movements.
254. What is the primary function of the thyroid gland?
A) Regulation of calcium levels
B) Regulation of metabolism
C) Production of insulin
D) Production of adrenaline
Correct Answer: B) Regulation of metabolism
Explanation:
The thyroid gland produces hormones (thyroxine and triiodothyronine) that regulate the body’s metabolic rate, growth, and development. These hormones influence almost every organ and are essential for normal brain development, heart function, and energy production.
255. Which process describes the breakdown of complex molecules into simpler ones to release energy?
A) Anabolism
B) Catabolism
C) Metabolism
D) Homeostasis
Correct Answer: B) Catabolism
Explanation:
Catabolism is the set of metabolic pathways that break down complex molecules, such as carbohydrates, fats, and proteins, into simpler ones, releasing energy in the process. This energy is stored in the form of ATP and is used to power cellular activities.
256. What is the main function of the nucleus in a cell?
A) Energy production
B) Genetic control and cell regulation
C) Protein synthesis
D) Waste removal
Correct Answer: B) Genetic control and cell regulation
Explanation:
The nucleus is the control center of the cell, housing the genetic material (DNA) that contains the instructions for protein synthesis and cellular activities. It regulates gene expression, ensuring that the right proteins are made at the right time, which is essential for cell function and reproduction.
257. Which of the following is a function of the lysosome?
A) Energy production
B) Digestion of cellular waste
C) Protein synthesis
D) Lipid synthesis
Correct Answer: B) Digestion of cellular waste
Explanation:
Lysosomes are membrane-bound organelles containing digestive enzymes that break down cellular waste, damaged organelles, and foreign materials such as bacteria. This process, called autophagy, is crucial for recycling cellular components and maintaining cellular health.
258. Which of the following is a function of the chloroplast in plant cells?
A) Cellular respiration
B) Photosynthesis
C) Protein synthesis
D) Lipid synthesis
Correct Answer: B) Photosynthesis
Explanation:
Chloroplasts are organelles found in plant cells that contain chlorophyll, a green pigment that captures light energy. They use this energy to convert carbon dioxide and water into glucose and oxygen during photosynthesis, providing energy for the plant and releasing oxygen into the atmosphere.
259. What is the main function of the vacuole in plant cells?
A) Protein synthesis
B) Storage and maintaining turgidity
C) Energy production
D) Waste removal
Correct Answer: B) Storage and maintaining turgidity
Explanation:
Vacuoles in plant cells store nutrients, waste products, and pigments. They also help maintain cell turgidity by regulating water content, which is essential for plant structure and support. A full vacuole keeps the cell rigid, enabling the plant to stand upright.
260. Which of the following is a function of the plasma membrane?
A) Energy production
B) Regulates entry and exit of substances
C) Protein synthesis
D) Waste removal
Correct Answer: B) Regulates entry and exit of substances
Explanation:
The plasma membrane is a selectively permeable barrier that surrounds the cell, controlling the movement of substances in and out. It maintains homeostasis by allowing nutrients to enter and waste products to exit while blocking harmful substances, ensuring the cell’s internal environment remains stable.
261. Which of the following is a function of the nucleolus?
A) DNA replication
B) Ribosome synthesis
C) ATP production
D) Lipid synthesis
Correct Answer: B) Ribosome synthesis
Explanation:
The nucleolus is a region within the nucleus where ribosomal RNA (rRNA) is synthesized and assembled with proteins to form ribosomes. These ribosomes are then exported to the cytoplasm, where they participate in protein synthesis.
262. What is the most likely outcome if a cell is placed in a hypotonic solution?
A) The cell will shrink
B) The cell will swell
C) The cell will remain unchanged
D) The cell will divide
Correct Answer: B) The cell will swell
Explanation:
In a hypotonic solution, the concentration of solutes outside the cell is lower than inside, causing water to move into the cell by osmosis. This influx of water can cause the cell to swell and, in some cases, burst (lyse), especially in animal cells lacking a rigid cell wall.
263. Which of the following is a function of the centriole in animal cells?
A) Protein synthesis
B) Cell division (forms spindle fibers)
C) Energy production
D) Waste removal
Correct Answer: B) Cell division (forms spindle fibers)
Explanation:
Centrioles are cylindrical structures found in animal cells that play a key role in organizing microtubules during cell division. They help form the spindle fibers that separate chromosomes, ensuring accurate distribution of genetic material to daughter cells.
264. What is the primary function of the peroxisome?
A) Energy production
B) Digestion of cellular waste
C) Breakdown of hydrogen peroxide
D) Protein synthesis
Correct Answer: C) Breakdown of hydrogen peroxide
Explanation:
Peroxisomes are organelles that contain enzymes such as catalase, which break down hydrogen peroxide—a harmful byproduct of metabolism—into water and oxygen. This detoxification process protects the cell from oxidative damage.
265. Which of the following best describes the role of the Golgi apparatus?
A) Synthesizes proteins
B) Modifies, sorts, and packages proteins
C) Produces ATP
D) Breaks down cellular waste
Correct Answer: B) Modifies, sorts, and packages proteins
Explanation:
The Golgi apparatus receives proteins and lipids from the endoplasmic reticulum, modifies them (e.g., by adding carbohydrates), sorts them, and packages them into vesicles for transport to their final destinations inside or outside the cell. This process is essential for secretion and cellular organization.
266. What is the process by which DNA is copied to RNA called?
A) Replication
B) Transcription
C) Translation
D) Transduction
Correct Answer: B) Transcription
Explanation:
Transcription is the process by which the genetic information in DNA is copied into messenger RNA (mRNA) by the enzyme RNA polymerase. This mRNA then carries the genetic code from the nucleus to the ribosome, where it is translated into protein.
267. What is the process by which RNA is used to make proteins called?
A) Replication
B) Transcription
C) Translation
D) Transduction
Correct Answer: C) Translation
Explanation:
Translation is the process by which ribosomes read the genetic code in mRNA and assemble amino acids into proteins. Transfer RNA (tRNA) brings the appropriate amino acids to the ribosome, where they are joined together to form a polypeptide chain.
268. Which of the following is a function of the rough endoplasmic reticulum?
A) Lipid synthesis
B) Protein synthesis and modification
C) Detoxification
D) Energy production
Correct Answer: B) Protein synthesis and modification
Explanation:
The rough endoplasmic reticulum is studded with ribosomes, which synthesize proteins. These proteins are then modified (e.g., folded, glycosylated) and transported to the Golgi apparatus for further processing and distribution.
269. Which of the following is a function of the smooth endoplasmic reticulum?
A) Protein synthesis
B) Lipid synthesis and detoxification
C) Energy production
D) Waste removal
Correct Answer: B) Lipid synthesis and detoxification
Explanation:
The smooth endoplasmic reticulum lacks ribosomes and is involved in lipid synthesis, including steroids and phospholipids. It also plays a role in detoxifying drugs and harmful substances, especially in liver cells.
270. What is the main function of the cytoskeleton?
A) Cell movement
B) Structural support
C) Intracellular transport
D) All of the above
Correct Answer: D) All of the above
Explanation:
The cytoskeleton is a network of protein filaments (microtubules, microfilaments, and intermediate filaments) that provides structural support, enables cell movement (e.g., contraction, crawling), and facilitates the transport of organelles and vesicles within the cell.
271. Which of the following is a function of the adrenal gland?
A) Production of insulin
B) Production of adrenaline
C) Production of bile
D) Production of growth hormone
Correct Answer: B) Production of adrenaline
Explanation:
The adrenal glands, located on top of the kidneys, produce adrenaline (epinephrine) and other hormones that help the body respond to stress. Adrenaline increases heart rate, dilates airways, and mobilizes energy stores, preparing the body for “fight or flight.”
272. What is the main function of the fallopian tube in females?
A) Production of eggs
B) Transport of eggs from the ovary to the uterus
C) Production of hormones
D) Storage of sperm
Correct Answer: B) Transport of eggs from the ovary to the uterus
Explanation:
The fallopian tube (oviduct) is the site where fertilization typically occurs. It transports eggs released from the ovary to the uterus. Cilia and muscular contractions help move the egg and, if fertilization occurs, the early embryo toward the uterus for implantation.
273. What is the main function of the placenta during pregnancy?
A) Production of sperm
B) Exchange of nutrients and gases between mother and fetus
C) Production of bile
D) Storage of urine
Correct Answer: B) Exchange of nutrients and gases between mother and fetus
Explanation:
The placenta is a temporary organ that develops during pregnancy, connecting the fetus to the uterine wall. It allows the exchange of oxygen, nutrients, and waste products between the mother’s and fetus’s blood, while preventing their blood from mixing. The placenta also produces hormones that support pregnancy.
274. Which of the following is a function of the thymus?
A) Production of T-cells
B) Production of red blood cells
C) Digestion
D) Storage of calcium
Correct Answer: A) Production of T-cells
Explanation:
The thymus is a lymphoid organ located in the chest, where T-lymphocytes (T-cells) mature and become capable of recognizing foreign antigens. It is most active during childhood and plays a crucial role in the development of the immune system.
275. What is the main function of the prostate gland in males?
A) Production of sperm
B) Production of seminal fluid
C) Production of testosterone
D) None of the above
Correct Answer: B) Production of seminal fluid
Explanation:
The prostate gland secretes a milky, alkaline fluid that forms part of semen. This fluid nourishes and protects sperm, increasing their motility and viability as they travel through the female reproductive tract.
276. Which of the following is a function of the seminal vesicles?
A) Production of sperm
B) Production of seminal fluid
C) Production of testosterone
D) None of the above
Correct Answer: B) Production of seminal fluid
Explanation:
The seminal vesicles are glands that produce a significant portion of the seminal fluid, which contains fructose (energy source for sperm), prostaglandins, and other substances that enhance sperm viability and motility.
277. What is the main function of the epididymis?
A) Production of sperm
B) Storage and maturation of sperm
C) Production of testosterone
D) None of the above
Correct Answer: B) Storage and maturation of sperm
Explanation:
The epididymis is a coiled tube located on the back of each testis, where sperm are stored and undergo maturation. During this process, sperm gain the ability to swim and fertilize an egg.
278. Which of the following is a function of the urinary bladder?
A) Filtration of blood
B) Storage of urine
C) Production of urine
D) Absorption of nutrients
Correct Answer: B) Storage of urine
Explanation:
The urinary bladder is a muscular sac that stores urine produced by the kidneys until it is excreted from the body. Its walls can expand to accommodate increasing volumes of urine, and contraction of its muscles expels urine during urination.
279. What is the main function of the urethra?
A) Transport of urine from the kidney to the bladder
B) Transport of urine from the bladder to the outside
C) Filtration of blood
D) Storage of urine
Correct Answer: B) Transport of urine from the bladder to the outside
Explanation:
The urethra is a tube that carries urine from the bladder to the exterior of the body. In males, it also serves as a passage for semen during ejaculation.
280. Which of the following is a function of the liver?
A) Production of bile
B) Detoxification
C) Storage of glycogen
D) All of the above
Correct Answer: D) All of the above
Explanation:
The liver is a multifunctional organ that produces bile (for fat digestion), detoxifies harmful substances, stores glycogen (as an energy reserve), metabolizes drugs, and synthesizes proteins such as clotting factors.
281. What is the main function of the gallbladder?
A) Production of bile
B) Storage and concentration of bile
C) Digestion of fats
D) None of the above
Correct Answer: B) Storage and concentration of bile
Explanation:
The gallbladder stores and concentrates bile produced by the liver. When food, especially fatty food, enters the small intestine, the gallbladder contracts and releases bile to aid in fat digestion.
282. Which of the following is a function of the stomach?
A) Absorption of nutrients
B) Digestion of proteins
C) Production of bile
D) Storage of glycogen
Correct Answer: B) Digestion of proteins
Explanation:
The stomach secretes gastric juice containing hydrochloric acid and pepsin, which break down proteins into smaller peptides. It also churns food into a semi-liquid mass called chyme, which is gradually released into the small intestine.
283. Which of the following is a function of the large intestine?
A) Absorption of nutrients
B) Absorption of water
C) Digestion of proteins
D) Production of bile
Correct Answer: B) Absorption of water
Explanation:
The large intestine absorbs water and electrolytes from indigestible food matter, forming solid feces. It also houses beneficial bacteria that aid in digestion and produce certain vitamins.
284. What is the main function of the esophagus?
A) Digestion of food
B) Absorption of nutrients
C) Transport of food from the mouth to the stomach
D) Storage of food
Correct Answer: C) Transport of food from the mouth to the stomach
Explanation:
The esophagus is a muscular tube that connects the pharynx (throat) to the stomach. It propels food downward using rhythmic contractions called peristalsis, ensuring that food reaches the stomach for further digestion.
285. Which of the following is a function of the pharynx?
A) Digestion of food
B) Absorption of nutrients
C) Passageway for air and food
D) Production of sound
Correct Answer: C) Passageway for air and food
Explanation:
The pharynx serves as a common passageway for both air (to the trachea) and food (to the esophagus). During swallowing, the epiglottis closes over the trachea to prevent food from entering the respiratory tract.
286. What is the main function of the trachea?
A) Digestion of food
B) Absorption of nutrients
C) Transport of air to the lungs
D) Production of sound
Correct Answer: C) Transport of air to the lungs
Explanation:
The trachea, or windpipe, is a tube reinforced with cartilage rings that carries air from the larynx to the bronchi and lungs. It is lined with cilia and mucus to trap and remove dust and pathogens.
287. Which of the following is a function of the bronchi?
A) Digestion of food
B) Absorption of nutrients
C) Transport of air to the lungs
D) Production of sound
Correct Answer: C) Transport of air to the lungs
Explanation:
The bronchi are the main branches of the trachea that lead to each lung. They further divide into smaller bronchioles, delivering air to the alveoli for gas exchange.
288. What is the main function of the larynx?
A) Digestion of food
B) Absorption of nutrients
C) Production of sound
D) Transport of air to the lungs
Correct Answer: C) Production of sound
Explanation:
The larynx, or voice box, contains the vocal cords. When air passes through, the vocal cords vibrate, producing sound. The larynx also prevents food from entering the trachea during swallowing.
289. Which of the following is a function of the diaphragm?
A) Digestion of food
B) Absorption of nutrients
C) Breathing
D) Production of sound
Correct Answer: C) Breathing
Explanation:
The diaphragm is a dome-shaped muscle located below the lungs. When it contracts, it flattens and increases the volume of the thoracic cavity, drawing air into the lungs (inhalation). When it relaxes, air is expelled (exhalation).
290. What is the main function of the alveoli in the lungs?
A) Production of mucus
B) Exchange of gases
C) Filtration of blood
D) Production of sound
Correct Answer: B) Exchange of gases
Explanation:
Alveoli are tiny, balloon-like structures at the ends of the bronchioles where oxygen from inhaled air diffuses into the blood and carbon dioxide from the blood diffuses into the air to be exhaled. This gas exchange is essential for respiration and maintaining oxygen levels in the body.