151. Which of the following best explains why red blood cells lack a nucleus in mammals?
a) To increase the surface area for oxygen transport
b) To allow more space for hemoglobin and enhance oxygen-carrying capacity
c) To prevent the cell from dividing
d) To reduce energy consumption
Correct Answer: b) To allow more space for hemoglobin and enhance oxygen-carrying capacity
Explanation: The absence of a nucleus and other organelles in red blood cells maximizes the space for hemoglobin, improving their ability to transport oxygen.
152. In a population of bacteria exposed to an antibiotic, which process is most likely responsible for the development of resistance?
a) Mitosis
b) Meiosis
c) Mutation
d) Conjugation
Correct Answer: c) Mutation
Explanation: Random mutations can give rise to antibiotic resistance, which is then selected for in the presence of the antibiotic.
153. If a plant is placed in a dark room for several days, which of the following outcomes is most likely?
a) Increased rate of photosynthesis
b) Yellowing of leaves due to lack of chlorophyll synthesis
c) Enhanced root growth
d) Increased transpiration
Correct Answer: b) Yellowing of leaves due to lack of chlorophyll synthesis
Explanation: Chlorophyll synthesis requires light. In darkness, chlorophyll degrades and new chlorophyll cannot be made, resulting in yellowing leaves.
154. Which scenario would most likely result in a decrease in genetic diversity within a population?
a) Migration of new individuals into the population
b) Natural selection favoring a specific trait
c) Random mating within the population
d) Mutations occurring at a high rate
Correct Answer: b) Natural selection favoring a specific trait
Explanation: Natural selection favoring a specific trait can reduce genetic diversity by increasing the frequency of that trait and decreasing others.
155. What would happen if the myelin sheath around a neuron is damaged?
a) The neuron would produce more neurotransmitters
b) Nerve impulse transmission would slow down
c) The neuron would divide more rapidly
d) The neuron would become less sensitive to stimuli
Correct Answer: b) Nerve impulse transmission would slow down
Explanation: The myelin sheath insulates axons and speeds up nerve impulse transmission. Damage to the myelin sheath slows down signal conduction.
156. Which of the following would be a direct result of a mutation in the gene encoding RNA polymerase?
a) Increased protein synthesis
b) Impaired transcription
c) Enhanced DNA replication
d) Accelerated cell division
Correct Answer: b) Impaired transcription
Explanation: RNA polymerase is essential for transcription. A mutation in its gene would impair the synthesis of RNA from DNA.
157. If a cell is placed in a hypertonic solution, what is the most likely outcome?
a) The cell will swell and burst
b) The cell will shrink
c) The cell will remain unchanged
d) The cell will divide
Correct Answer: b) The cell will shrink
Explanation: In a hypertonic solution, water moves out of the cell, causing it to shrink (plasmolysis in plant cells, crenation in animal cells).
158. Which of the following best describes the role of tRNA in protein synthesis?
a) It carries amino acids to the ribosome
b) It forms the structure of the ribosome
c) It carries the genetic code from DNA
d) It catalyzes peptide bond formation
Correct Answer: a) It carries amino acids to the ribosome
Explanation: tRNA brings specific amino acids to the ribosome, where they are added to the growing polypeptide chain.
159. What is the most likely consequence of a non-functional lysosome in a cell?
a) Increased ATP production
b) Accumulation of cellular waste
c) Enhanced protein synthesis
d) Increased lipid synthesis
Correct Answer: b) Accumulation of cellular waste
Explanation: Lysosomes digest cellular waste and foreign materials. If they are non-functional, waste will accumulate.
160. Which of the following is an example of a negative feedback mechanism in the human body?
a) Release of oxytocin during childbirth
b) Release of insulin in response to high blood glucose
c) Release of adrenaline during stress
d) Release of growth hormone during sleep
Correct Answer: b) Release of insulin in response to high blood glucose
Explanation: Insulin lowers blood glucose levels, counteracting the initial stimulus (high glucose), which is characteristic of negative feedback.
161. If a plant with red flowers is crossed with a plant with white flowers and all offspring have pink flowers, what type of inheritance is this?
a) Complete dominance
b) Incomplete dominance
c) Codominance
d) Multiple alleles
Correct Answer: b) Incomplete dominance
Explanation: In incomplete dominance, the heterozygote expresses an intermediate phenotype (pink), different from both parents.
162. Which of the following would most likely increase the rate of transpiration in a plant?
a) Closing the stomata
b) Increasing humidity
c) Increasing temperature
d) Decreasing light intensity
Correct Answer: c) Increasing temperature
Explanation: Higher temperatures increase the rate of water evaporation from leaves, thereby increasing transpiration.
163. What is the primary role of the Calvin cycle in photosynthesis?
a) To split water molecules
b) To capture light energy
c) To fix carbon dioxide into organic molecules
d) To produce oxygen
Correct Answer: c) To fix carbon dioxide into organic molecules
Explanation: The Calvin cycle uses ATP and NADPH from the light-dependent reactions to fix CO₂ into sugars.
164. Which of the following is a direct effect of a mutation in a tumor suppressor gene?
a) Increased cell division
b) Decreased cell division
c) Enhanced DNA repair
d) Increased apoptosis
Correct Answer: a) Increased cell division
Explanation: Tumor suppressor genes normally inhibit cell division. Mutations can lead to uncontrolled cell growth.
165. If a person’s blood pH drops below 7.35, what is the most likely physiological response?
a) Increased breathing rate
b) Decreased heart rate
c) Increased insulin secretion
d) Decreased urine output
Correct Answer: a) Increased breathing rate
Explanation: The body increases breathing to expel more CO₂, which helps raise blood pH back to normal.
166. 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 across a semipermeable membrane toward higher solute concentration.
167. What is the most likely outcome if a plant’s xylem is blocked?
a) Reduced water transport
b) Increased sugar transport
c) Enhanced photosynthesis
d) Increased transpiration
Correct Answer: a) Reduced water transport
Explanation: Xylem transports water and minerals from roots to shoots. Blockage would reduce water transport.
168. Which of the following is a function of the lymphatic system?
a) Transport of oxygen
b) Immune defense
c) Digestion
d) Excretion
Correct Answer: b) Immune defense
Explanation: The lymphatic system is part of the immune system, helping to defend against infections.
169. What is the primary function of the alveoli in the lungs?
a) To produce mucus
b) To exchange gases
c) To filter blood
d) To produce sound
Correct Answer: b) To exchange gases
Explanation: Alveoli are the sites of gas exchange between the lungs and blood.
170. Which of the following best describes the role of the hypothalamus?
a) Regulates body temperature
b) Produces insulin
c) Filters blood
d) Stores bile
Correct Answer: a) Regulates body temperature
Explanation: The hypothalamus regulates body temperature, among other homeostatic functions.
171. If a person has a vitamin C deficiency, what is the most likely symptom?
a) Night blindness
b) Scurvy
c) Rickets
d) Beriberi
Correct Answer: b) Scurvy
Explanation: Vitamin C deficiency leads to scurvy, characterized by bleeding gums and poor wound healing.
172. Which of the following is a function of the spleen?
a) Production of bile
b) Storage of blood
c) Digestion of proteins
d) Production of insulin
Correct Answer: b) Storage of blood
Explanation: The spleen stores blood and plays a role in immune function.
173. What is the primary function of the pancreas?
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 produces insulin (hormone) and digestive enzymes (exocrine function).
174. Which of the following is a direct effect of adrenaline release?
a) Decreased heart rate
b) Increased blood sugar levels
c) Decreased breathing rate
d) Increased digestion
Correct Answer: b) Increased blood sugar levels
Explanation: Adrenaline increases blood sugar by stimulating glycogen breakdown in the liver.
175. What is the most likely outcome if the glomerulus in the kidney is damaged?
a) Increased urine output
b) Decreased filtration of blood
c) Increased reabsorption of water
d) Decreased secretion of hormones
Correct Answer: b) Decreased filtration of blood
Explanation: The glomerulus filters blood. Damage would reduce filtration efficiency.
176. Which of the following best describes the role 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 where T-cells mature, playing a key role in immunity.
177. If a person’s thyroid gland is overactive, what is the most likely symptom?
a) Weight gain
b) Weight loss
c) Low heart rate
d) Cold intolerance
Correct Answer: b) Weight loss
Explanation: An overactive thyroid (hyperthyroidism) increases metabolism, often leading to weight loss.
178. 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 gland produces adrenaline, which prepares the body for stress.
179. What is the primary function of the fallopian tube?
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 transports eggs from the ovary to the uterus.
180. Which of the following is a function of the placenta?
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 facilitates the exchange of nutrients, gases, and wastes between mother and fetus.
181. What is the most likely outcome if a plant’s stomata are closed during the day?
a) Increased photosynthesis
b) Decreased transpiration
c) Increased water uptake
d) Enhanced root growth
Correct Answer: b) Decreased transpiration
Explanation: Closed stomata reduce water loss through transpiration.
182. Which of the following best describes the role 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, forming solid feces.
183. What is the primary function of the ribosome?
a) Energy production
b) Protein synthesis
c) Lipid synthesis
d) DNA replication
Correct Answer: b) Protein synthesis
Explanation: Ribosomes are the sites of protein synthesis.
184. Which of the following is a 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 provides structural support, enables cell movement, and facilitates intracellular transport.
185. What is the most likely outcome if a cell’s mitochondria are non-functional?
a) Increased protein synthesis
b) Decreased ATP production
c) Increased lipid synthesis
d) Enhanced DNA replication
Correct Answer: b) Decreased ATP production
Explanation: Mitochondria are the primary sites of ATP production. Non-functional mitochondria would reduce ATP synthesis.
186. Which of the following best describes the role of the Golgi apparatus?
a) Energy production
b) Protein modification and packaging
c) DNA replication
d) Lipid synthesis
Correct Answer: b) Protein modification and packaging
Explanation: The Golgi apparatus modifies, sorts, and packages proteins for secretion or use within the cell.
187. What is the primary function of the nucleus?
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 contains DNA and controls all cellular activities by regulating gene expression.
188. 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 synthesizes lipids and detoxifies drugs and poisons.
189. What is the most likely outcome if a plant is deficient in magnesium?
a) Increased chlorophyll production
b) Yellowing of leaves
c) Enhanced root growth
d) Increased flower production
Correct Answer: b) Yellowing of leaves
Explanation: Magnesium is a component of chlorophyll. Deficiency leads to chlorosis (yellowing of leaves).
190. Which of the following best describes the role 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 and is involved in protein synthesis and modification.
191. What is the primary 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 contain digestive enzymes that break down cellular waste and foreign materials.
192. Which of the following is a function of the chloroplast?
a) Cellular respiration
b) Photosynthesis
c) Protein synthesis
d) Lipid synthesis
Correct Answer: b) Photosynthesis
Explanation: Chloroplasts contain chlorophyll and are the sites of photosynthesis in plant cells.
193. What is the most likely outcome if a plant’s root system is damaged?
a) Increased photosynthesis
b) Reduced water and nutrient uptake
c) Enhanced flower production
d) Increased transpiration
Correct Answer: b) Reduced water and nutrient uptake
Explanation: Roots absorb water and nutrients. Damage would reduce uptake.
194. Which of the following best describes the role 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 store nutrients and waste, and help maintain cell turgidity in plant cells.
195. What is the primary 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 regulates the movement of substances in and out of the cell.
196. 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 involved in ribosome synthesis.
197. 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, water moves into the cell, causing it to swell.
198. Which of the following best describes the role 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 help organize spindle fibers during cell division in animal cells.
199. 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 contain enzymes like catalase that break down hydrogen peroxide.
200. Which of the following best describes the role of the nuclear envelope?
a) Protects the nucleus
b) Regulates movement of substances in and out of the nucleus
c) Both a and b
d) None of the above
Correct Answer: c) Both a and b
Explanation: The nuclear envelope protects the nucleus and regulates the movement of molecules between the nucleus and cytoplasm.