Worksheets2025SE112A
Total questions: 120
Worksheet time: 3600secs
Rina observed 500 cells undergoing mitosis in her biology lab and recorded the number in each stage. If 200 cells were in interphase, 150 in prophase, 75 in metaphase, 50 in anaphase, and 25 in telophase, what percentage of the total time in the cell cycle is spent in metaphase?
15%
25%
10%
20%
In a research lab, Nita is studying different types of human cells to understand their regenerative capabilities. She wonders which type of human cell would be expected to have the highest telomerase activity, as this could be crucial for her experiments on aging. Which type of cell should she focus on?
Embryonic stem cells
Skin epithelial cells
Mature red blood cells
Neurons
In a biology class, the teacher explains the relationship between genes and proteins. She asks the students, Wahyu, Dian, and Dewi, to identify which statement about genes and proteins is correct.
All genes code for proteins
All proteins are coded by single genes
Some genes code for functional RNA molecules that are not translated into proteins
Gene mutations always result in non-functional proteins
Dian is studying the composition of a DNA molecule in her biology class. She discovers that if 32% of the bases are guanine, what percentage would be thymine?
68%
18%
36%
32%
A plant physiologist named Maya measured solute concentrations in three different tissues from various plants in her research garden. Sample X had high sucrose and amino acids but low minerals; Sample Y had balanced mineral concentrations similar to soil solution; Sample Z had very high potassium and organic acid concentrations. Which samples most likely came from xylem vessels?
X only
Y only
X and Z
Z only
During a high-intensity workout, Sari notices that her muscles are not getting enough oxygen. She learns about the factors that contribute to the Bohr effect in hemoglobin, which helps her understand how her body responds to exercise.
Decreased temperature and increased O2 concentration
Increased temperature and decreased O2 concentration
Decreased pH and increased CO2 concentration
Increased pH and decreased CO2 concentration
Rizky has a mutation in his hemoglobin that causes it to have a higher affinity for oxygen. How would this affect the oxygen dissociation curve and oxygen delivery to his tissues?
Curve shifts left, reduced oxygen delivery
Curve shifts right, improved oxygen delivery
Curve shifts left, improved oxygen delivery
Curve shifts right, reduced oxygen delivery
During a visit to the doctor, Wawan learns about his asthma condition and the importance of managing it. The doctor explains that bronchodilators like salbutamol can help him breathe easier. Which mechanism explains how bronchodilators like salbutamol work to treat asthma?
They stimulate mucus production to trap allergens
They reduce inflammation of the airway lining
They promote relaxation of smooth muscles in the airways
They cause contraction of smooth muscles in the airways
During a biology class, Maya and Indah are discussing the respiratory system. Maya asks Indah, "Which tissues are found in both the trachea and the smallest bronchioles?"
Goblet cells and pseudostratified epithelium
Cartilage and ciliated epithelium
Alveoli and surfactant-producing cells
Smooth muscle and elastic fibers
During a biology class, Arif and Surya are discussing the human respiratory system. Surya asks Arif, "In the respiratory system, which structure is primarily responsible for gas exchange?"
Bronchi
Trachea
Alveoli
Bronchioles
During a biology field trip, Nita observes a photomicrograph of lung tissue that shows numerous small air sacs surrounded by capillaries. Which respiratory structure is being viewed?
Trachea
Bronchus
Bronchiole
Alveolus
If insecticide-treated bed nets reduce malaria deaths in children under 5 by 20%, and there are 500,000 such deaths annually worldwide, how many lives would be saved each year?
50,000
100,000
200,000
150,000
During a community health fair, a group of volunteers, including Nisa, Rahman, and Maya, is tasked with cleaning up the park and ensuring the safety of the environment. They notice that some harmful substances have been left behind, and they need to identify which group of volunteers is best suited to handle the cleanup and removal of these substances.
Which volunteers are primarily responsible for phagocytosis during the innate immune response?
B lymphocytes
Neutrophils
Plasma cells
T lymphocytes
In a lush garden, Faisal is curious about how plants transport essential nutrients. He observes a tall tree and wonders, which plant tissue primarily transports water and dissolved minerals from roots to leaves?
Xylem vessels and tracheids
Phloem sieve elements
Cambium meristem cells
Cortex parenchyma cells
During a high-intensity workout, Adi notices that he is breathing harder and feels more fatigued. He learns that this is due to the Bohr effect, which influences how his hemoglobin carries oxygen in his blood. What is the Bohr effect in hemoglobin physiology?
Reduced oxygen affinity at lower pH
Increased oxygen affinity at lower pH
Unchanged oxygen affinity with pH
Complete denaturation at low pH
During a yoga class, Dian is practicing deep breathing exercises. As she inhales deeply, which change occurs in her thoracic cavity?
Diaphragm relaxes and domes
Diaphragm contracts and flattens
Lung volume decreases markedly
Ribs move downward and inward
During a biology class, Faisal learns about the respiratory system and its components. His teacher asks the class, "Which component of the respiratory system is the primary site of gas exchange?"
Nasal conchae
Tracheal cartilage
Bronchial smooth muscle
Alveolar air sacs
Yuni is feeling unwell and goes to the doctor, who informs her that she has influenza. Yuni asks the doctor why antibiotics won't help her recover from the flu.
Viruses use bacterial ribosomes
Viruses lack antibiotic targets
Viruses divide by mitosis
Viruses have thick cell walls
In a small town, a new virus has emerged, and the local health department is preparing the community's immune response. Which sequence correctly represents a typical primary immune response in the town's health strategy?
Antibody production then antigen presentation then T-cell activation then B-cell activation
B-cell activation then antigen presentation then T-cell activation then antibody production
Antigen presentation then T-cell activation then B-cell activation then antibody production
T-cell activation then antigen presentation then B-cell activation then antibody production
In a vibrant garden, Rina notices that some plants are thriving under the sunlight, particularly those that seem to absorb light at 500 nm, even though the chlorophyll a and b in those plants show low absorption at that wavelength. What could explain the activity of these plants at 500 nm?
Measurements of plant health were inaccurate
Chlorophyll a peak occurs at 500 nm
Chlorophyll b absorbs strongly at 500 nm
Accessory pigments absorb and transfer energy
In a controlled experiment, Dimas placed a group of seeds in a sealed container where they respired, consuming 25 cm³ of O2 and producing 20 cm³ of CO2. What is the respiratory quotient and substrate indicated?
RQ 1.25 suggesting lipid metabolism
RQ 0.8 suggesting carbohydrate metabolism
RQ 0.8 suggesting lipid metabolism
RQ 1.25 suggesting protein metabolism
Ina and Dimas are studying two forests, each with 12 species of trees. Forest X has a Simpson's index of 0.9, indicating a high level of diversity, while Forest Y has a Simpson's index of 0.3, suggesting lower diversity. What does this difference indicate?
Forest X has fewer individuals than Forest Y
Forest X has lower richness but higher evenness
Forest Y is dominated by few species while X is more even
Forest Y is in an earlier successional stage than Forest X
In a study conducted by Rina on butterflies in a local park, bright red marks were used to identify individuals. However, these bright red marks made the butterflies more visible to predators. How will estimates of the butterfly population be biased?
Population underestimated due to higher mortality
Population overestimated due to higher mortality
Recapture easier giving better accuracy
No effect because color vision is absent
In a coastal research project, Lina is tasked with studying how vegetation changes from the shore to inland across the dunes. Which sampling method should she use to best track these changes?
Line transect sampling along a gradient
Stratified random sampling only
Random quadrat sampling across area
Mark–release–recapture of plants
Surya is studying different forms of life and comes across a peculiar entity that doesn't fit into the three-domain classification system. He wonders why this entity, which he learns is a virus, is excluded from this classification. What could be the reason for its exclusion?
They lack cells and independent metabolism
They contain only RNA and never DNA
They are too small for light microscopes
They reproduce only inside host cells
In a botanical study, researchers observed that a new invasive plant species, brought in from a distant land, began to thrive in a local ecosystem. They proposed the Novel Weapons Hypothesis to explain this phenomenon. According to this hypothesis, the invasive plants succeed primarily because they:
Develop deeper root systems always
Attract more pollinators consistently
Have much higher photosynthetic rates
Release unfamiliar allelochemicals to natives
In a study conducted by Yuni, the Spearman rank correlation between soil pH and plant diversity was found to be rs = 0.75 with a critical value of 0.60 at α = 0.05. What conclusion is valid?
Result invalid due to high value
Significant negative correlation exists
No significant correlation exists
Significant positive correlation exists
At a wildlife reserve, Rina is overseeing a captive breeding program for endangered species. Despite her careful management, the health of the animals declines over generations. What is the most likely cause?
Inbreeding depression masked by apparent diversity
Environment lacks natural selection pressures
Genetic diversity is too high overall
Adaptation to captivity is excessive
In a village of 20,000 residents, the frequency of the homozygous recessive genotype (aa) among the local plant species is 0.36. Assuming Hardy-Weinberg equilibrium, how many individuals of this plant species would be expected to be heterozygous (Aa)?
4,800
9,600
12,800
7,200
In a small agricultural town, farmers noticed that a certain population of insects on their crops showed variation in pesticide resistance. After applying a new pesticide, the frequency of resistant individuals increased from 10% to 85% over three generations. Which evolutionary mechanism best explains this observation?
All non-resistant insects died immediately after pesticide application
The pesticide caused mutations that produced resistance
Non-resistant insects developed resistance in response to the pesticide
Resistant insects had higher survival and reproductive success in the presence of pesticide
In a garden maintained by Ina, the allele for white flowers (w) is recessive to purple flowers (W). If the frequency of the recessive allele (q) is 0.6, what percentage of the flowering plants in her garden would be expected to have white flowers under Hardy-Weinberg equilibrium?
16%
36%
64%
48%
Rudi, a biologist, wants to compare the mean beak sizes of finches from two different islands. Which statistical test would be most appropriate?
Simpson's diversity index
Chi-squared test
Spearman's rank correlation
Student's t-test
In a population of birds, individuals with very small beaks can efficiently eat small seeds, and individuals with very large beaks can crack large seeds. Birds with medium-sized beaks are inefficient at eating both types of seeds and have lower survival rates. What type of selection is occurring?
Directional selection
Stabilizing selection
Disruptive selection
Sexual selection
On a remote island chain, Maya and her friends observe a group of birds that have become separated from their mainland relatives due to rising sea levels. Over time, these birds adapt to their new environment, leading to changes in their physical traits and behaviors. Eventually, they can no longer interbreed with their mainland counterparts. Which sequence correctly describes the process of allopatric speciation?
Geographic isolation → Genetic divergence → Reproductive isolation
Reproductive isolation → Geographic isolation → Genetic divergence
Genetic drift → Mutation → Geographic isolation
Natural selection → Reproductive isolation → Geographic isolation
After a long day of hiking, Wahyu found his friend Nisa unresponsive at their campsite. Several hours later, he noticed that her body had become stiff. What causes rigor mortis to develop several hours after death?
Calcium accumulation causes continuous muscle contraction
Bacterial decomposition produces toxins that stiffen muscles
ATP depletion prevents myosin heads from detaching from actin filaments
Lysosomal enzymes digest muscle proteins
Heri, a farmer, uses organophosphate pesticides to protect his crops. However, he notices that after applying the pesticide, the muscles of his farm animals seem to be continuously contracting. What effect would this have at neuromuscular junctions?
Nerve impulses would fail to reach the muscles
Muscles would experience continuous contraction due to acetylcholine accumulation
Muscles would become paralyzed due to lack of acetylcholine
Calcium release from the sarcoplasmic reticulum would be inhibited
In a busy city, a delivery truck driven by Rudi is responsible for transporting goods across various neighborhoods. However, due to road construction, Rudi's route is altered, leading to delays in deliveries. Why does this slow down the delivery process?
The delivery schedule becomes more complicated
Fuel efficiency becomes less optimal
The loss of direct routes increases travel time, requiring Rudi to navigate through more streets instead of taking shortcuts
The weight of the truck increases due to additional cargo
Dewi is conducting an experiment with barley seeds in her biology lab. She knows that gibberellin stimulates the production of amylase by binding to receptors on aleurone cells. However, she accidentally introduces a mutation that prevents gibberellin from binding to its receptor. What would be the effect on seed germination?
Germination would be inhibited due to lack of amylase production
Germination would be enhanced
Germination would proceed normally
Germination would be delayed but eventually occur
In a vibrant garden, a population of butterflies has a variety of wing colors. Over time, the butterflies with colors that blend in with the flowers and leaves are more likely to survive and reproduce. Which process most directly changes allele frequencies within this butterfly population from one generation to the next?
Learning and behavior modifying genetic sequences
Environmental changes altering acquired traits
Individual development during the organism’s life
Natural selection acting on heritable variation
In a small village, Titi is a farmer who wants to improve the quality of her corn crop. She decides to use selective breeding to enhance the traits of her plants. Selective breeding in crops primarily relies on which genetic principle?
Mutation rates rising due to cultivation
Gene flow introducing wild alleles unpredictably
Random mating increasing heterozygosity
Artificial selection favoring desired phenotypes
Wawan, a farmer, is aware that conserving genetic diversity in wild crop relatives is important mainly because it can
Replace the need for soil nutrients
Prevent all pest outbreaks globally
Guarantee higher yields every season
Provide novel alleles for future breeding
In a natural forest, Eko observes a population of butterflies over several generations. He notes that certain traits, such as wing color and size, change in frequency due to various factors. Which combination best describes three processes that can change allele frequencies in this butterfly population?
Natural selection, genetic drift, gene flow
Transcription, translation, replication
Photosynthesis, respiration, fermentation
Growth, differentiation, morphogenesis
In a bustling city, Rani, Mega, and Eko are studying the human gas exchange system in their biology class. They learn that one structure in the lungs provides the largest surface area for diffusion. Which structure are they referring to?
Larynx with vocal fold structures
Trachea with C-shaped cartilage rings
Alveoli with extensive capillary networks
Bronchi with smooth muscle layers
Imagine a small, bustling café in the heart of the city where customers are constantly coming and going. The café has a unique design that allows for quick service and a pleasant atmosphere. Which feature of the café's layout most enhances efficient customer service?
Open seating and a friendly staff
Cramped tables and long wait times
High noise levels and distractions
Limited menu and slow preparation
During a high-altitude trek, Rudi notices that as he climbs higher, he feels more fatigued and breathes harder. He learns that this phenomenon is related to how
Increased O2 raises blood buffering power
Increased CO2 lowers hemoglobin affinity
Decreased pH increases alveolar ventilation
Decreased CO2 increases plasma viscosity
During a marathon, Agus notices that his muscles are feeling fatigued. He remembers learning about the Bohr effect and how it benefits tissues during vigorous exercise.
Promoting oxygen unloading where needed
Preventing CO2 from entering red cells
Reducing blood flow to active tissues
Raising hemoglobin affinity in muscles
Imagine a bustling factory where workers are responsible for assembling products. When a signal is sent to the factory, which event occurs immediately after the signal reaches the control room?
Voltage-gated Ca2+ channels open
Acetylcholine binds postsynaptic sites
Acetylcholinesterase degrades transmitter
Myosin heads undergo power stroke
During a critical experiment in a laboratory, a researcher named Yuni is studying the effects of blocking presynaptic voltage-gated calcium channels at the neuromuscular junction. She hypothesizes that this action would most directly
Enhance acetylcholinesterase activity
Trigger continuous muscle contraction
Increase acetylcholine receptor density
Prevent acetylcholine vesicle release
In a small town, a local athlete named Tiara is experiencing sudden muscle weakness during her training sessions. After consulting with a doctor, she learns that her body is producing antibodies that block nicotinic receptors. Which immediate effect explains her muscle weakness?
Greater summation producing stronger twitch
Increased Ca2+ entry strengthening signal
Excess acetylcholine causing tetanus
Reduced end plate potentials below threshold
During a medical conference, Dr. Agung discusses a suitable symptomatic treatment for myasthenia gravis. He explains that this treatment targets which mechanism?
Inhibiting acetylcholinesterase to prolong action
Blocking voltage-gated sodium channels
Stimulating muscarinic receptors in glands
Enhancing breakdown of acetylcholine faster
Organophosphate inhibition of acetylcholinesterase at neuromuscular junctions would most likely cause
Sustained depolarization and spasm
Complete loss of presynaptic action potentials
Immediate depletion of calcium stores
Permanent receptor downregulation only
Loss of myelin slows nerve conduction primarily because it
Increases membrane capacitance along axon
Greatly boosts Na+/K+ pump turnover
Makes threshold potential highly negative
Eliminates all voltage-gated channels
The absolute refractory period ensures one-way propagation by
Inactivating Na+ channels just opened
Hyperpolarizing the soma permanently
Blocking K+ channels from closing
Depleting neurotransmitter stores fully
Which mechanism best explains why conserving wild relatives aids future food security?
Conversion of annuals to perennials
Removal of all agricultural pests
Guaranteed identical climate patterns
Reservoirs of stress-tolerance alleles
Which change would most increase the rate of diffusion of oxygen across the alveolar membrane?
Increasing surface area and gradient
Thickening the membrane barrier
Decreasing temperature substantially
Reducing capillary blood perfusion
Gene flow between neighboring populations typically
Causes speciation in a single generation
Eliminates all recessive alleles quickly
Reduces genetic differences between them
Always increases local adaptation strongly
A bottleneck event most strongly affects allele frequencies through
Directional selection favoring extremes
Stabilizing selection around the mean
Genetic drift due to small population
Balanced polymorphism by heterosis
Which statement best describes xylem vessels in flowering plants?
They transport water under negative pressure
They have perforated end walls forming sieve plates
They transport sucrose under positive pressure
They are living cells with nuclei and cytoplasm
What is the primary role of phloem sieve tubes?
Support of stems with lignified thick walls
Storage of starch granules in parenchyma
Translocation of assimilates between sources and sinks
Uptake of minerals by active transport
Which adaptation enables efficient water transport in xylem?
Thin cellulose walls with plasmodesmata
Presence of many chloroplasts in cells
Lignified walls and absence of end walls
Large vacuoles maintaining high turgor
In the pressure-flow hypothesis, what generates the pressure in source phloem?
Transpiration pull from stomata opening
Capillary action within narrow vessels
Root pressure pushing solution upward
Osmotic water influx following sucrose loading
Which immune component provides immediate, non-specific defense?
Plasma cells secreting specific antibodies
Memory B cells producing rapid antibodies
Cytotoxic T lymphocytes recognizing antigens
Phagocytic neutrophils and macrophages
Which statement distinguishes primary from secondary immune responses?
Primary response is faster and stronger
Secondary response lacks memory cells
Secondary response is faster and stronger
Both responses have identical kinetics
Why are antibiotics generally ineffective against viruses?
Viruses lack metabolic targets like cell walls
Viruses have thicker peptidoglycan walls
Viruses synthesize their own ribosomes
Viruses replicate only by binary fission
Cancer cells often evade immune detection primarily by
Downregulating MHC class I presentation
Producing highly immunogenic neoantigens
Increasing antigen presentation on APCs
Activating helper T cells directly
Which immunotherapy pairs correctly with its mechanism?
Antibiotics target viral polymerase directly
Antihistamines activate cytotoxic lymphocytes
Checkpoint inhibitors release T cell inhibition
Live attenuated vaccines block mitosis in tumors
Which structure is first to receive filtrate in a nephron?
Bowman's capsule surrounding glomerulus
Loop of Henle descending limb
Distal tubule near vasa recta
Proximal convoluted collecting duct
What is the main site of selective reabsorption of glucose in the nephron?
Proximal convoluted tubule with microvilli
Bowman's capsule filtration space
Descending limb of the loop of Henle
Collecting duct under ADH influence
How does the loop of Henle enable production of concentrated urine?
Uniform osmolarity equalizes tubular and blood fluids
Countercurrent multiplier establishes medullary gradient
Water secretion into ascending limb lumen
Active urea secretion in proximal segments
ADH increases water reabsorption by
Inhibiting aldosterone release from cortex
Blocking Na+ channels in proximal tubule
Decreasing medullary interstitial osmolarity
Inserting aquaporins in collecting duct cells
Which trend best describes temperature effects on enzyme-catalyzed respiration rate in yeast?
Rate decreases steadily as temperature increases
Rate is highest at the lowest temperature tested
Rate rises with temperature to optimum then decreases
Rate is constant across all temperatures tested
Why does respiration rate fall above the optimum temperature?
Glycolysis stops due to high oxygen levels
Enzymes denature disrupting active sites
Substrate concentration becomes infinite
Mitochondria increase membrane surface area
Why do the light-independent reactions stop in prolonged darkness?
CO2 becomes unavailable without light energy
Rubisco requires direct photon absorption
Thylakoid membranes disintegrate in the dark
ATP and NADPH supply from light reactions ceases
In photosynthesis, which sequence correctly matches location and process?
Thylakoid membranes: photophosphorylation; stroma: Calvin cycle
Stroma: photolysis of water; grana: Calvin cycle
Cytosol: Calvin cycle; thylakoid: glycolysis reactions
Matrix: Krebs cycle; stroma: oxidative phosphorylation
A heterozygous parent for Huntington's disease (Hh) mates with a homozygous recessive partner (hh). What is the probability their child has the disease?
Fifty percent of offspring affected
Twenty-five percent of offspring affected
Seventy-five percent of offspring affected
Zero percent of offspring affected
Why are X-linked recessive disorders more common in males?
Males express the single X allele unmasked
Males carry two X alleles with dominance
Females inherit Y-linked protective alleles
Females lack any X-linked gene expression
Which statement about gene expression is correct?
All genes encode polypeptides for ribosomes
Some genes code for functional RNAs not proteins
Every allele produces identical phenotypic effects
Only exons are transcribed into mRNA always
Which oxygen-carrying metric is closest to normal arterial oxygen saturation in healthy adults at sea level?
12% saturation in arterial blood
18% saturation under resting conditions
15% saturation in venous plasma
21% saturation during light exercise
Which cell type can differentiate into any cell type of the body but not extraembryonic tissues?
Induced pluripotent fibroblast lines
Embryonic stem cells derived from blastocyst
Adult stem cells from bone marrow
Totipotent cells from zygote stage
Why do some genes not produce polypeptides yet remain functional?
They are pseudogenes with silent mutations
They code for functional RNA molecules only
They are transcribed but never translated
They regulate chromatin without transcription
Which approximate proportion by volume describes oxygen in dry atmospheric air at sea level?
18% of total gas mixture
12% of total gas mixture
24% of total gas mixture
30% of total gas mixture
Which chromosome is present in a human gamete carrying only the sex chromosome Y?
Neither X nor Y present
Both X and Y together
Y only without an X chromosome
X only without any autosomes
In plants, which process moves products of photosynthesis from leaves toward non-photosynthetic tissues?
Diffusion through intercellular spaces
Photosynthate transport from leaves to roots
Translocation through phloem loading
Transpiration via xylem tension
Which change favors oxygen unloading from hemoglobin in active tissues?
Decreased CO2 and lower 2,3-BPG
Higher pH and lower partial pressure O2
Increased pH and decreased temperature
Decreased pH and increased CO2 concentration
A leftward shift of the oxygen dissociation curve most likely leads to which outcome?
Greater CO2 transport in plasma
Unaffected oxygen binding capacity
Reduced oxygen delivery to tissues
Enhanced oxygen delivery to tissues
Why are beta-2 agonists used in asthma management?
They increase alveolar macrophage activity
They constrict bronchial smooth muscle strongly
They stimulate mucus secretion to trap allergens
They promote relaxation of smooth muscles in the airways
Which lung components primarily allow airway recoil and compliance during breathing?
Cartilaginous rings of bronchi
Ciliated epithelium with goblet cells
Alveolar surfactant phospholipids
Smooth muscle and elastic fibers
Gas exchange with blood occurs mainly across which structures in the lungs?
Bronchioles with thick smooth muscle
Trachea lined with ciliated cells
Alveoli with thin epithelial walls
Pleural membranes of thorax
Which structure is the singular, functional gas-exchange unit in the lung?
Terminal bronchiole without cartilage
Alveolus with surrounding capillaries
Pleural cavity surrounding lungs
Bronchus supplying lobular segments
Approximately how many human genes code for proteins?
10,000 coding loci total
100,000 coding loci total
9,600 coding loci total
20,000 coding loci total
Which innate immune cells most directly engulf and digest extracellular bacteria?
Natural killer lymphocytes
T cells and dendritic cells
Basophils and eosinophils
Macrophages and neutrophils
Why are antibiotics generally ineffective against viruses?
Viruses rapidly evolve thicker cell walls
Viruses lack the cellular structures that antibiotics target
Viruses neutralize drugs using plasmids
Viruses divide by mitosis like host cells
Which sequence best represents activation leading to antibody production in adaptive immunity?
Antibody production → T-cell activation → B-cell activation → Antigen presentation
Antigen binding → Complement cascade → Antibody production → T-cell activation
Antigen presentation → T-cell activation → B-cell activation → Antibody production
B-cell activation → Antigen presentation → T-cell activation → Antibody production
A fall in antidiuretic hormone (ADH) secretion will cause what renal effect?
Greater urea reabsorption in tubules
Less water reabsorption in collecting ducts
No change in urine osmolality overall
More water reabsorption in collecting ducts
An action potential from a stretch receptor produced 80 microamperes on a recording device. Which current magnitude matches this measurement?
120 μA during refractory period
40 μA during peak depolarization
8 μA during baseline noise
80 μA during stimulus response
Which statement describes the primary role of accessory pigments in photosynthesis?
They reflect all wavelengths except far-red
They absorb at 500 nm and transfer energy to chlorophyll
They block light energy from reaching photosystems
They reduce photon capture near 700 nm
A respiratory quotient (RQ) of 0.8 in a fasting individual most strongly indicates metabolism of which substrate?
Carbohydrates as the main fuel
Alcohols metabolized for ATP
Proteins exclusively supplying ATP
Lipids predominating during energy production
Which process directly changes allele frequencies due to random sampling in small populations?
Natural selection acting on phenotypes
Mutation producing new alleles
Genetic drift causing random changes
Gene flow via migrant interbreeding
Non-random mating by assortative choice
A conservation program crosses domesticated crops with wild relatives. What is the main genetic benefit?
Lowered mutation rate in seedlings
Restored MHC expression in leaves
Reduced recombination across loci
Increased genetic diversity for breeding
Enhanced lignification of phloem walls
Artificial selection differs from natural selection primarily because
It reduces allele heritability drastically
It prevents genetic variation entirely
It operates only in small populations
It uses human choice of breeding traits
It eliminates mutation over time
Identify structures in the airway pathway: trachea → bronchus → alveolus. Which option lists them in order from largest to smallest?
Bronchus, trachea, alveolus
Alveolus, bronchus, trachea
Bronchus, alveolus, trachea
Alveolus, trachea, bronchus
Trachea, bronchus, alveolus
Which adaptation most increases gas exchange efficiency in alveoli?
Large surface area with thin walls
Thick walls with rigid collagen
Dry surface with poor perfusion
Ciliated lining with mucus traps
Small area with elastic cartilage
During intense exercise, the oxygen dissociation curve shifts right mainly because
Reduced blood flow to muscles
Higher hemoglobin concentration
Lower temperature in tissues
Increased CO2 and decreased pH
Decreased CO2 and increased pH
Which list correctly identifies the basic parts of a chemical synapse?
Dendrite spine, soma, axon initial segment
Nucleus, ribosome, endoplasmic reticulum
Axon hillock, node of Ranvier, myelin
Presynaptic terminal, synaptic cleft, postsynaptic membrane
Sarcomere, T-tubule, myofibril
What is the correct sequence at a cholinergic synapse after an action potential arrives?
Depolarization → receptor binding → action potential
Vesicle fusion → calcium influx → depolarization
Calcium influx → vesicle fusion → neurotransmitter release
Receptor binding → action potential → calcium influx
Neurotransmitter release → vesicle fusion → binding
Myasthenia gravis causes fewer functional acetylcholine receptors. The immediate effect at the neuromuscular junction is
Higher calcium influx at axon
Increased synaptic vesicle release
Weaker end-plate potentials
Longer action potential duration
Stronger depolarization of muscle
Which treatment best increases acetylcholine availability at synapses in myasthenia gravis?
Voltage-gated sodium blockers
Nicotinic receptor antagonists
Acetylcholinesterase inhibitors
Calcium channel antagonists
Adrenergic beta blockers
Which statement correctly contrasts xylem and phloem structure and function?
Phloem forms continuous hollow dead tubes
Xylem has lignified walls for upward water transport
Xylem transports organics bidirectionally
Phloem uses dead cells for mineral flow
Xylem uses living cells for sugar flow
A plant stem section labeled X shows thick lignified walls and empty lumens. X most likely represents
Guard cells in epidermis
Phloem sieve tubes
Meristematic tissues
Companion cells
Xylem vessel elements
Which structural adaptation helps xylem resist collapse under tension during transpiration?
Cellulose-rich thin walls
Lignified thickened walls
Pits sealed by suberin
Active proton pumping
Starch-packed lumens
Why are antibiotics ineffective against viruses such as influenza?
Viruses replicate by binary fission
Viruses produce peptidoglycan enzymes
Viruses lack ribosomes and cell walls
Viruses hide in xylem conduits
Viruses have thicker cell walls
Which description best distinguishes primary from secondary immune response to the same antigen?
Primary shows rightward Bohr shift always
Primary is rapid with high IgG; secondary is slow with IgM
Primary uses cytotoxic T cells; secondary does not
Primary is slow with low IgM; secondary is rapid with high IgG
Primary uses memory cells; secondary lacks memory cells
A tumor downregulates MHC molecules. Which immune evasion outcome is most likely?
Reduced recognition by cytotoxic T cells
Increased antibody neutralization efficiency
Greater activation of complement proteins
Improved vaccine memory generation
Enhanced antigen presentation to T cells
Checkpoint inhibitors as cancer therapy primarily act by
Blocking antibody production permanently
Inhibiting angiogenesis in tumors
Releasing brakes on T‑cell activation
Replacing mutated MHC genes
Destroying tumor ribosomes directly
ADH primarily acts on which nephron segment to reduce urine volume?
Collecting duct epithelium
Glomerular capillary tuft
Proximal convoluted tubule
Descending limb of Henle
Bowman’s capsule lumen
Which mechanism best explains how the kidney produces highly concentrated urine?
Countercurrent multiplier with ADH-regulated permeability
Uniform medullary solute with constant water reabsorption
Active sodium pumping in Bowman’s capsule
Filtration barrier secreting urea to cortex
High flow rate through proximal tubule
A temperature–rate graph for an enzyme shows a peak near 40°C. What is the best explanation for the decline above this temperature?
Substrate concentration becomes zero
Active site denaturation reduces activity
Activation energy increases with heat
More collisions raise catalytic efficiency
pH rises and increases binding strength
During the Calvin cycle, which molecules from the light reactions are directly required?
Rubisco and glucose
ATP and NADPH
CO2 and O2
FADH2 and NADH
Water and oxygen
In a cross Hh × hh for an autosomal dominant disorder, the probability the child is affected equals
0% or 0
100% or 1.0
25% or 0.25
50% or 0.5
75% or 0.75
Why are X‑linked recessive disorders more common in males than females?
Males have two X chromosomes
Females lack Y-linked modifiers
Males express a single recessive allele
Females express heterozygous advantage
Males undergo higher crossing over
