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North Rhine-Westphalia Zentralabitur Biology study materials
North Rhine-Westphalia Zentralabitur Biology study resources

North Rhine-Westphalia Zentralabitur Biology practice questions

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Question 1Biological inquiry and interpretation of evidence

A researcher predicts that tomato plants given a nitrogen-enriched fertilizer will produce more fruit than plants given a standard fertilizer. In this study, the amount of fruit produced is best described as which of the following?

  1. The hypothesis
  2. A controlled variable
  3. The dependent variable Correct answer.
  4. The independent variable

Explanation

The dependent variable is the measured outcome that responds to the manipulation, which here is fruit yield. The fertilizer type is the factor the researcher deliberately changes, so it is the independent variable rather than the measured result.

Question 2Biological inquiry and interpretation of evidence

A student measures the mass of the same sample five times and obtains nearly identical values, but the balance was never zeroed and reads 2.0 g too high. How should these measurements be described?

  1. Both accurate and precise
  2. Precise but not accurate Correct answer.
  3. Accurate but not precise
  4. Neither accurate nor precise

Explanation

Precision refers to how closely repeated measurements agree with one another, while accuracy refers to how close they are to the true value. Because the readings cluster tightly but are systematically offset by the unzeroed balance, they are precise but inaccurate.

Question 3Biological inquiry and interpretation of evidence

Which of the following best distinguishes a scientific hypothesis from a scientific theory?

  1. A hypothesis is a testable proposed explanation, while a theory is a well-supported explanatory framework built from extensive evidence Correct answer.
  2. A hypothesis is always correct once tested, while a theory remains an untested guess
  3. A hypothesis is a broad framework, while a theory is a single testable prediction
  4. A hypothesis applies only to biology, while a theory applies only to physics

Explanation

In science, a hypothesis is a testable proposed explanation for a specific observation, whereas a theory is a broad, well-substantiated explanation supported by many lines of evidence. The common usage of theory as a mere guess is incorrect in scientific contexts.

Question 4Biological inquiry and interpretation of evidence

A scientist repeats an experiment several times and obtains consistent results. Which conclusion is most justified?

  1. The findings are reliable and reproducible under the tested conditions Correct answer.
  2. The results now apply to all organisms everywhere
  3. The hypothesis has been proven true beyond any doubt
  4. The experiment has no remaining sources of error

Explanation

Reproducible results indicate reliability, meaning the procedure yields consistent outcomes under the tested conditions. Science does not establish absolute proof, and replication does not eliminate error or guarantee universal applicability.

Question 5Biological inquiry and interpretation of evidence

A graph plots plant height on the y-axis against days of growth on the x-axis. Which statement correctly identifies the placement of these variables?

  1. Days of growth is the independent variable on the x-axis, and height is the dependent variable on the y-axis Correct answer.
  2. Both variables are dependent and should share the x-axis
  3. Days of growth is the dependent variable because it is measured over time
  4. Height is the independent variable on the y-axis, and days of growth is the dependent variable on the x-axis

Explanation

By convention, the independent variable is placed on the x-axis and the dependent variable on the y-axis. Height responds to elapsed time, so time is independent and height is dependent.

Question 6Biological inquiry and interpretation of evidence

A student notices that mold grows on bread left in a warm, humid place but not on bread stored in a dry, cool place. Which of the following is the most appropriate next step in the scientific process?

  1. Formulate a testable hypothesis and design a controlled experiment to test it Correct answer.
  2. Conclude immediately that warmth and moisture cause mold growth
  3. Publish the observation as a confirmed scientific law
  4. Discard the observation because it was not made in a laboratory

Explanation

An observation generates questions that should be framed as a testable hypothesis and examined through a controlled experiment. Reaching a firm causal conclusion from a single uncontrolled observation is premature.

Question 7Biochemistry

Which property of water is most directly responsible for its ability to moderate temperature in living organisms and large bodies of water?

  1. Its low specific heat
  2. Its inability to form hydrogen bonds
  3. Its nonpolar covalent bonds
  4. Its high specific heat Correct answer.

Explanation

Water has a high specific heat because hydrogen bonds must absorb or release substantial energy before water molecules change temperature. This allows water and water-rich organisms to resist large temperature swings, helping maintain homeostasis.

Question 8Cell structure, membranes and division

Which structure is found in a typical plant cell but NOT in a typical animal cell?

  1. Mitochondrion
  2. Nucleus
  3. Ribosome
  4. Cell wall made of cellulose Correct answer.

Explanation

Plant cells have a rigid cell wall composed primarily of cellulose that surrounds the plasma membrane, providing structural support. Animal cells lack a cell wall, relying on the cytoskeleton and extracellular matrix instead.

Question 9Genetics, inheritance and molecular information

Meiosis differs from mitosis in that meiosis produces

  1. Two genetically identical diploid cells
  2. One diploid cell with double the chromosomes
  3. Two haploid cells identical to the parent
  4. Four genetically varied haploid cells Correct answer.

Explanation

Meiosis consists of two divisions that produce four haploid gametes, each with half the chromosome number of the parent. Crossing over and independent assortment generate genetic variation, distinguishing meiosis from the identical-diploid products of mitosis.

Question 10Metabolism

An enzyme lowers the activation energy of a reaction. Which statement best describes how this affects the reaction?

  1. It increases the reaction rate without being consumed in the reaction Correct answer.
  2. It changes the overall free-energy difference between reactants and products
  3. It supplies the energy needed to make an endergonic reaction exergonic
  4. It permanently binds to the product to stop the reaction

Explanation

Enzymes are biological catalysts that lower activation energy, speeding up reactions without being consumed. They do not change the net free-energy difference (delta G) between reactants and products; they only make the reaction reach equilibrium faster.

Question 11Neurobiology

What ionic mechanism is directly responsible for the rapid depolarizing phase of a neuronal action potential once the threshold potential (~ -55 mV) is reached?

  1. Opening of voltage-gated Na+ channels, causing rapid inward influx of Na+ down its electrochemical gradient Correct answer.
  2. Opening of voltage-gated K+ channels, causing rapid outward efflux of K+
  3. Active extrusion of 3 Na+ ions in exchange for 2 K+ ions by the Na+/K+ pump
  4. Opening of ligand-gated Cl- channels, causing hyperpolarizing influx of Cl-

Explanation

When depolarization reaches the threshold potential (~ -55 mV), voltage-gated sodium channels rapidly open. Sodium ions (Na+) rush into the axon down their steep electrical and chemical gradients, depolarizing the membrane potential to approximately +35 to +40 mV.

Question 12Physiology

Which feature allows a steroid hormone to pass directly through the plasma membrane?

  1. Its lipid (hydrophobic) nature lets it dissolve through the phospholipid bilayer Correct answer.
  2. Its large size lets it push proteins aside
  3. Its negative charge attracts it to the membrane interior
  4. Its attachment to a carbohydrate tag opens a channel

Explanation

Steroid hormones are lipid-soluble (hydrophobic), so they can dissolve through the hydrophobic interior of the phospholipid bilayer without a transport protein. Once inside, they typically bind intracellular receptors that act on the DNA to regulate gene expression.

Question 13Ecology

In an energy pyramid, only about 10 percent of the energy at one trophic level is transferred to the next. Most of the remaining energy is

  1. Converted directly into new biomass at the next level
  2. Lost as heat, largely through cellular respiration and metabolic processes Correct answer.
  3. Stored permanently in the soil
  4. Recycled back to producers as light energy

Explanation

At each trophic level, organisms use most of the energy they consume for metabolism and lose much of it as heat through cellular respiration. Only about 10 percent is stored as biomass available to the next level, which limits food chain length.

Question 14Evolution

Which of the following is a necessary condition for natural selection to occur in a population?

  1. All individuals are genetically identical
  2. Heritable variation exists and affects survival or reproduction Correct answer.
  3. The environment never changes
  4. Every individual produces the same number of offspring

Explanation

Natural selection requires heritable variation among individuals and differences in reproductive success linked to that variation. Individuals with advantageous heritable traits leave more offspring, shifting the population's traits over generations.

Question 15Neurobiology

What is the typical resting membrane potential of a neuron?

  1. Approximately -70 mV Correct answer.
  2. Approximately +70 mV
  3. Approximately 0 mV
  4. Approximately -200 mV

Explanation

A neuron's resting membrane potential is typically around -70 mV, maintained by unequal ion distribution and the sodium-potassium pump.

Question 16Neurobiology

Which ion movement primarily causes the depolarization phase of an action potential?

  1. Na+ influx through voltage-gated sodium channels Correct answer.
  2. K+ influx through voltage-gated potassium channels
  3. Cl- efflux
  4. Ca2+ efflux from the cell

Explanation

Depolarization is driven by a rapid influx of Na+ ions as voltage-gated sodium channels open, making the inside of the membrane more positive.

Question 17Neurobiology

What restores the membrane potential toward resting levels after depolarization (repolarization)?

  1. K+ efflux through voltage-gated potassium channels Correct answer.
  2. Na+ influx continuing unabated
  3. Cl- influx only
  4. Simultaneous Na+ and K+ influx

Explanation

Repolarization occurs as voltage-gated sodium channels inactivate and voltage-gated potassium channels open, allowing K+ to flow out and restore negative internal charge.

Question 18Neurobiology

What is the refractory period in neuron signaling?

  1. A brief period after an action potential during which a new one cannot (or is harder to) be triggered Correct answer.
  2. The time it takes for a neurotransmitter to be synthesized
  3. The resting state before any stimulus arrives
  4. The period during which myelin is formed

Explanation

The refractory period follows an action potential and ensures signal directionality and limits firing frequency, due to inactivated sodium channels and ongoing potassium efflux.

Question 19Neurobiology

At a chemical synapse, what triggers neurotransmitter release into the synaptic cleft?

  1. Ca2+ influx into the presynaptic terminal triggering vesicle fusion Correct answer.
  2. Direct electrical current jumping the gap
  3. K+ efflux from the postsynaptic cell
  4. Glucose diffusion into the presynaptic terminal

Explanation

Arrival of an action potential opens voltage-gated Ca2+ channels in the presynaptic terminal; the resulting Ca2+ influx triggers synaptic vesicles to fuse with the membrane and release neurotransmitter.

Question 20Neurobiology

What is the function of acetylcholinesterase at a cholinergic synapse?

  1. It breaks down acetylcholine to terminate the signal Correct answer.
  2. It synthesizes new acetylcholine
  3. It transports acetylcholine into the presynaptic cell unchanged
  4. It opens postsynaptic sodium channels directly

Explanation

Acetylcholinesterase degrades acetylcholine in the synaptic cleft, ending the neurotransmitter's action and allowing the synapse to reset.

Question 21Neurobiology

What does an EPSP (excitatory postsynaptic potential) do to the postsynaptic membrane?

  1. Depolarizes it, making an action potential more likely Correct answer.
  2. Hyperpolarizes it, making an action potential less likely
  3. Has no effect on membrane potential
  4. Destroys the postsynaptic membrane

Explanation

An EPSP depolarizes the postsynaptic membrane, bringing it closer to the threshold needed to trigger an action potential.

Question 22Neurobiology

What is spatial summation at a neuron's postsynaptic membrane?

  1. Combining postsynaptic potentials from multiple synapses at different locations at roughly the same time Correct answer.
  2. Combining signals from one synapse fired repeatedly over time
  3. The physical growth of a longer axon
  4. The myelination of multiple axons

Explanation

Spatial summation combines the effects of postsynaptic potentials from different synaptic inputs at approximately the same time, which can push the membrane over threshold.

Question 23Neurobiology

What is the role of myelin sheaths on axons?

  1. They increase conduction velocity through saltatory conduction Correct answer.
  2. They slow down signal conduction intentionally
  3. They generate the action potential itself
  4. They synthesize neurotransmitters

Explanation

Myelin insulates the axon, forcing action potentials to jump between Ranvier nodes (saltatory conduction), which greatly increases conduction speed.

Question 24Neurobiology

What are the Ranvier nodes (Schnürringe) on a myelinated axon?

  1. Small gaps in the myelin sheath where the axon membrane is exposed and action potentials regenerate Correct answer.
  2. The synaptic terminals at the axon's end
  3. The cell body of the neuron
  4. The dendritic branching points

Explanation

Ranvier nodes are periodic unmyelinated gaps where voltage-gated channels cluster, allowing the action potential to regenerate as it 'jumps' along the axon.

Question 25Neurobiology

In the vertebrate eye, which photoreceptor cells are primarily responsible for color vision?

  1. Cones Correct answer.
  2. Rods
  3. Bipolar cells
  4. Horizontal cells

Explanation

Cones are responsible for color vision and function best in bright light, while rods handle low-light, achromatic vision.

Question 26Neurobiology

What happens during signal transduction in a rod cell when light strikes rhodopsin?

  1. Rhodopsin's retinal component changes shape, triggering a signaling cascade that closes ion channels and hyperpolarizes the cell Correct answer.
  2. The cell depolarizes immediately upon light exposure with no intermediate steps
  3. Rhodopsin directly generates an action potential
  4. The rod cell releases acetylcholine directly

Explanation

Light isomerizes retinal within rhodopsin, triggering a G-protein cascade (transducin) that ultimately closes cGMP-gated channels, hyperpolarizing the photoreceptor.

Question 27Neurobiology

Which part of the human ear converts mechanical vibrations into electrical nerve signals?

  1. The cochlea, via hair cells in the organ of Corti Correct answer.
  2. The outer ear pinna
  3. The Eustachian tube
  4. The pharynx

Explanation

The cochlea's hair cells (in the organ of Corti) transduce fluid vibrations into electrical signals sent via the auditory nerve.

Question 28Neurobiology

What is a reflex arc (Reflexbogen)?

  1. A rapid, largely involuntary neural pathway from a sensory receptor to an effector, often bypassing conscious brain processing Correct answer.
  2. A voluntary decision-making circuit in the cerebral cortex
  3. The pathway used only for long-term memory formation
  4. A pathway exclusive to the digestive system

Explanation

A reflex arc is a rapid, often involuntary response pathway (e.g. knee-jerk reflex) that can be mediated at the spinal cord level, without requiring conscious cortical processing.

Question 29Neurobiology

Which division of the nervous system controls involuntary functions like heart rate and digestion?

  1. The autonomic nervous system Correct answer.
  2. The somatic nervous system
  3. The central nervous system exclusively
  4. The peripheral sensory-only system

Explanation

The autonomic nervous system (sympathetic and parasympathetic divisions) regulates involuntary functions such as heart rate, digestion, and glandular secretion.

Question 30Neurobiology

How do the sympathetic and parasympathetic nervous systems typically relate to each other?

  1. They often act antagonistically, e.g. sympathetic increases heart rate while parasympathetic decreases it Correct answer.
  2. They always produce identical effects on organs
  3. Only the sympathetic system exists in humans
  4. Parasympathetic activation always increases blood pressure

Explanation

The sympathetic and parasympathetic divisions frequently have antagonistic effects, such as the sympathetic system raising heart rate ('fight or flight') and the parasympathetic system lowering it ('rest and digest').

Question 31Neurobiology

What is habituation, as a simple form of learning studied in neurobiology?

  1. A decrease in response to a repeated, harmless stimulus over time Correct answer.
  2. An increase in response to a novel stimulus
  3. A permanent structural change to DNA
  4. A reflex present only in plants

Explanation

Habituation is a basic non-associative learning process in which the response to a repeated, harmless stimulus decreases over time as the nervous system 'learns' to ignore it.

Question 32Neurobiology

Which neurotransmitter is most associated with the neuromuscular junction between motor neuron and skeletal muscle?

  1. Acetylcholine Correct answer.
  2. Serotonin
  3. Dopamine
  4. GABA

Explanation

Acetylcholine is the neurotransmitter released at the neuromuscular junction, binding nicotinic receptors on the muscle fiber to trigger contraction.

Question 33Neurobiology

What effect do many recreational and medicinal drugs have at the synaptic level?

  1. They can mimic, block, or alter the release/reuptake of specific neurotransmitters Correct answer.
  2. They physically rebuild damaged neurons
  3. They always increase the number of neurons in the brain
  4. They have no measurable effect on synapses

Explanation

Many drugs act at synapses by mimicking neurotransmitters, blocking receptors, or altering neurotransmitter release and reuptake, which is why drug action is closely tied to synaptic physiology in the Kernlehrplan.

Question 34Neurobiology

What does the all-or-nothing principle of the action potential mean?

  1. An action potential either fires at full amplitude or does not fire at all, once threshold is reached Correct answer.
  2. The amplitude of an action potential varies continuously with stimulus strength
  3. Only the first action potential in a series is full strength
  4. Action potentials only occur in sensory neurons

Explanation

Once the membrane potential crosses threshold, an action potential fires at a fixed amplitude regardless of how much the stimulus exceeded threshold - it is all-or-nothing, not graded.

Question 35Neurobiology

What role does the sodium-potassium pump (Na+/K+-ATPase) play in neuron physiology?

  1. It actively transports Na+ out and K+ into the cell, using ATP, to maintain the resting ion gradients Correct answer.
  2. It passively allows Na+ and K+ to equalize across the membrane
  3. It only functions during an action potential itself
  4. It transports neurotransmitters across the synaptic cleft

Explanation

The Na+/K+-ATPase actively pumps 3 Na+ out and 2 K+ into the cell per cycle, using ATP, which is essential for restoring and maintaining the resting ion gradients after signaling.

Question 36Neurobiology

In a typical data-based Abitur task on neurobiology, what should students do with a graph of membrane potential over time?

  1. Identify phases (resting, depolarization, repolarization, hyperpolarization/refractory) and relate them to underlying ion movements Correct answer.
  2. Ignore the graph and answer from memory alone
  3. Assume the graph shows enzyme kinetics instead
  4. Treat every graph as identical regardless of labeled axes

Explanation

Data-analysis tasks require reading the graph's phases and correctly linking them to the ion channel behavior that produces each phase - a core Materialauswertung skill in NRW Biologie.

Question 37Neurobiology

Why can damage to myelin (as in demyelinating diseases) impair nerve signal conduction?

  1. Loss of insulation slows or blocks saltatory conduction between nodes Correct answer.
  2. It causes neurons to produce excess neurotransmitter
  3. It converts action potentials into graded potentials permanently
  4. It has no effect on conduction velocity

Explanation

Without intact myelin, saltatory conduction is disrupted, current leaks across the membrane, and conduction velocity slows or fails - the physiological basis of diseases like multiple sclerosis.

Question 38Neurobiology

What is the main advantage of temporal summation at a synapse?

  1. Repeated subthreshold inputs in quick succession can add up to reach threshold and trigger a response Correct answer.
  2. It always prevents any signal from being transmitted
  3. It only functions in cardiac muscle
  4. It eliminates the need for neurotransmitters

Explanation

Temporal summation allows successive subthreshold postsynaptic potentials, arriving close together in time from the same synapse, to combine and potentially reach the threshold for firing.

Question 39Biochemistry

What is the primary function of an enzyme in a metabolic reaction?

  1. To lower the activation energy required, speeding up the reaction without being consumed Correct answer.
  2. To supply the energy needed to drive the reaction forward
  3. To permanently change the products of the reaction
  4. To act as a structural building block of the cell membrane only

Explanation

Enzymes are biological catalysts that lower activation energy, accelerating reactions without being permanently altered or consumed themselves.

Question 40Biochemistry

According to the lock-and-key/induced-fit models, what determines an enzyme's specificity for its substrate?

  1. The complementary shape (and often induced conformational fit) of the active site to the substrate Correct answer.
  2. The enzyme's color
  3. The total mass of the enzyme molecule
  4. The temperature of the surrounding solution alone

Explanation

Enzyme specificity arises from the active site's shape and chemical complementarity to the substrate, with induced fit allowing some flexibility during binding.

Question 41Biochemistry

What is competitive enzyme inhibition?

  1. An inhibitor resembling the substrate binds the active site, and can be outcompeted by higher substrate concentration Correct answer.
  2. An inhibitor binds a site other than the active site and cannot be overcome by more substrate
  3. An inhibitor permanently destroys the enzyme
  4. An inhibitor increases the enzyme's affinity for its substrate

Explanation

Competitive inhibitors resemble the substrate and compete for the active site; their effect can typically be overcome by increasing substrate concentration.

Question 42Biochemistry

In an enzyme kinetics graph plotting reaction rate against substrate concentration, what does the plateau at high substrate concentration typically indicate?

  1. The enzyme's active sites are saturated (Vmax is reached) Correct answer.
  2. The enzyme has stopped working entirely
  3. Substrate is being destroyed by the plateau effect
  4. The reaction has reversed direction

Explanation

The plateau represents Vmax, where essentially all enzyme active sites are occupied and the reaction rate cannot increase further despite more substrate being added.

Question 43Biochemistry

Why do most human enzymes lose activity at very high temperatures (e.g. above ~45-50°C)?

  1. Heat disrupts the enzyme's tertiary structure (denaturation), distorting the active site Correct answer.
  2. Heat always speeds up enzyme activity without limit
  3. Enzymes are unaffected by temperature
  4. Cold, not heat, denatures enzymes

Explanation

Excess heat breaks the weak bonds maintaining an enzyme's three-dimensional shape, denaturing it and distorting the active site so it can no longer bind substrate effectively.

Question 44Biochemistry

What effect does pH have on enzyme activity?

  1. Each enzyme has an optimal pH range; deviations can alter charge distribution and reduce activity or denature it Correct answer.
  2. pH never affects enzyme structure or function
  3. All enzymes share exactly the same optimal pH
  4. Only alkaline conditions can denature enzymes, never acidic ones

Explanation

Enzymes have characteristic optimal pH ranges (e.g. pepsin near pH 2, most cytosolic enzymes near neutral); deviations disrupt ionic bonds and charge distribution, reducing activity or denaturing the enzyme.

Question 45Biochemistry

Why are enzymes described as proteins that are not consumed during a reaction?

  1. They are released unchanged after catalyzing the conversion of substrate to product and can be reused Correct answer.
  2. They become part of the final product permanently
  3. They are destroyed after a single use
  4. They act only once and never catalyze again

Explanation

A defining feature of enzyme catalysis is that the enzyme itself emerges from the reaction unchanged, allowing it to be reused repeatedly to catalyze many reaction cycles.

Question 46Metabolism

Where does glycolysis occur in a eukaryotic cell?

  1. The cytoplasm (cytosol) Correct answer.
  2. The mitochondrial matrix
  3. The inner mitochondrial membrane
  4. The nucleus

Explanation

Glycolysis, the breakdown of glucose into pyruvate, takes place in the cytosol and does not require oxygen.

Question 47Metabolism

What are the net ATP and NADH products of glycolysis per glucose molecule (substrate-level only, ignoring later oxidative steps)?

  1. Net 2 ATP and 2 NADH Correct answer.
  2. Net 36 ATP and 0 NADH
  3. Net 0 ATP and 10 NADH
  4. Net 2 ATP and 0 NADH

Explanation

Glycolysis produces a net yield of 2 ATP (from substrate-level phosphorylation) and 2 NADH per glucose molecule, along with 2 pyruvate.

Question 48Metabolism

What is the primary role of the citric acid cycle (Citratzyklus) in cellular respiration?

  1. Oxidizing acetyl-CoA to release CO2 while generating NADH, FADH2, and a small amount of ATP/GTP Correct answer.
  2. Directly producing the majority of a cell's ATP without electron carriers
  3. Synthesizing glucose from CO2
  4. Breaking down proteins into amino acids exclusively

Explanation

The citric acid cycle oxidizes acetyl-CoA, releasing CO2 and generating electron carriers (NADH, FADH2) plus a small amount of ATP/GTP via substrate-level phosphorylation, feeding electrons to the electron transport chain.

Question 49Metabolism

Where does oxidative phosphorylation (electron transport chain and ATP synthase) occur?

  1. The inner mitochondrial membrane Correct answer.
  2. The cytosol
  3. The Golgi apparatus
  4. The mitochondrial matrix exclusively, without any membrane involvement

Explanation

The electron transport chain complexes and ATP synthase are embedded in the inner mitochondrial membrane, where the proton gradient drives ATP synthesis.

Question 50Metabolism

What is chemiosmosis in the context of cellular respiration?

  1. ATP synthesis driven by a proton gradient flowing through ATP synthase Correct answer.
  2. The active transport of glucose into the cell
  3. The diffusion of oxygen into the mitochondria only
  4. The breakdown of fatty acids into glycerol

Explanation

Chemiosmosis describes how the proton gradient built by the electron transport chain drives protons back through ATP synthase, powering ATP production.