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Quizzes > Science > Biology

Take the Photosynthesis and Cellular Respiration Quiz Now!

Think you can ace these photosynthesis and cellular respiration questions?

Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art leaf sun cell icons cycle arrows on coral background for photosynthesis and cellular respiration quiz

Are you ready to challenge your understanding with our free photosynthesis and cellular respiration quiz? Designed for aspiring biologists, this interactive photosynthesis vs respiration quiz will test your grasp of plant energy cycles and delve into crucial cellular respiration questions. You'll learn how plants convert light into fuel, explore the steps of metabolism in cells, and compare energy pathways in this plant energy cycles quiz. Perfect for exam prep or as a biology metabolism quiz warm-up, you'll reinforce key concepts. Feeling curious? Start the challenge today and explore more fun quizzes that sharpen your science skills now!

Where does photosynthesis primarily occur in plant cells?
Mitochondrion
Nucleus
Chloroplast
Golgi apparatus
Photosynthesis occurs in chloroplasts, which contain the pigment chlorophyll and the necessary machinery for capturing light energy. The thylakoid membranes inside chloroplasts house the light-dependent reactions. The Calvin cycle also takes place in the stroma of chloroplasts .
Which pigment is primarily responsible for capturing light energy in photosynthesis?
Phycocyanin
Carotene
Chlorophyll a
Xanthophyll
Chlorophyll a is the main pigment that absorbs light in the blue-violet and red wavelengths, initiating the light-dependent reactions. Other pigments like carotene and xanthophyll assist in photoprotection but do not drive the primary reactions. The structure of chlorophyll a allows it to effectively transfer excited electrons to the photosystems .
What are the main stable end products of the photosynthesis process?
Glucose and oxygen
Carbon dioxide and water
ATP and NADPH
Amino acids and oxygen
The overall photosynthesis reaction converts carbon dioxide and water into glucose and oxygen using light energy. ATP and NADPH are intermediate products used during the Calvin cycle but are not the stable end products. Oxygen is released as a byproduct when water is split during the light-dependent reactions .
Where do the light-dependent reactions of photosynthesis occur?
Stroma
Thylakoid membrane
Cytosol
Mitochondrial matrix
Light-dependent reactions take place on the thylakoid membranes where chlorophyll is embedded and photon absorption occurs. The movement of electrons through the photosystems drives proton pumping into the thylakoid lumen. This buildup of protons powers ATP synthesis via ATP synthase .
Which stage of cellular respiration produces the most ATP?
Fermentation
Krebs cycle
Electron transport chain
Glycolysis
The electron transport chain generates the bulk of ATP by oxidative phosphorylation, using a proton gradient to drive ATP synthesis. Glycolysis and the Krebs cycle produce a small amount of ATP via substrate-level phosphorylation. Fermentation yields no additional ATP beyond glycolysis .
In which part of the cell does glycolysis occur?
Endoplasmic reticulum
Cytosol
Chloroplast stroma
Mitochondrial matrix
Glycolysis takes place in the cytosol and breaks down glucose into pyruvate, yielding ATP and NADH. It does not require mitochondria or oxygen to proceed. The pyruvate produced may then enter the mitochondria for further processing .
What is the net ATP yield from one molecule of glucose during glycolysis?
2 ATP
4 ATP
3 ATP
1 ATP
Glycolysis produces 4 ATP molecules but consumes 2 ATP in early steps, resulting in a net gain of 2 ATP per glucose. Additionally, glycolysis generates 2 NADH molecules that can be used in the electron transport chain. This process is independent of oxygen .
What molecule acts as the final electron acceptor in the mitochondrial electron transport chain?
NAD+
Oxygen
Carbon dioxide
Water
Oxygen serves as the final electron acceptor, combining with electrons and protons to form water. Without oxygen, the electron transport chain cannot function and ATP synthesis halts. This is why oxygen is essential for aerobic respiration .
Which gas is released as a byproduct during photosynthesis?
Oxygen
Nitrogen
Carbon dioxide
Methane
Oxygen is released when water molecules are split during the light-dependent reactions. This oxygen diffuses out of the chloroplast and the plant cell into the atmosphere. The process replenishes atmospheric O2 that supports aerobic life .
What is the primary function of the Calvin cycle in photosynthesis?
Fix carbon dioxide into sugars
Generate ATP from light energy
Split water molecules
Produce oxygen
The Calvin cycle uses ATP and NADPH produced in light-dependent reactions to fix CO2 into three-carbon sugars like G3P. This process occurs in the stroma of chloroplasts and does not directly require light. The fixed carbon can later form glucose and other carbohydrates .
What is photolysis in the context of photosynthesis?
Emission of photons
Reduction of NADP+
Formation of ATP
Splitting water molecules by light energy
Photolysis refers to the light-driven splitting of water into oxygen, protons, and electrons during the light-dependent reactions. This process replenishes electrons lost by photosystem II and generates O2 as a byproduct. The protons contribute to the proton gradient used for ATP synthesis .
Which process utilizes chemiosmosis to synthesize ATP?
Calvin cycle
Photorespiration
Glycolysis
Both photosynthetic light reactions and oxidative phosphorylation
Chemiosmosis involves the movement of protons down their gradient through ATP synthase to generate ATP. It occurs in chloroplasts during the light reactions and in mitochondria during oxidative phosphorylation. Glycolysis and the Calvin cycle do not use a proton gradient for ATP production .
What role does NADP+ play in photosynthesis?
Enzyme cofactor in the Krebs cycle
Substrate for the Calvin cycle
Electron carrier in light-dependent reactions
Photosynthetic pigment
NADP+ accepts electrons and a proton at the end of the electron transport chain in the light-dependent reactions, forming NADPH. NADPH then provides reducing power to convert CO2 to sugars in the Calvin cycle. Its cycling between oxidized and reduced forms is key for energy transfer .
Where does the citric acid cycle (Krebs cycle) occur in eukaryotic cells?
Mitochondrial matrix
Nuclear membrane
Cytosol
Chloroplast stroma
The citric acid cycle takes place in the mitochondrial matrix where acetyl-CoA is oxidized to CO2. Enzymes of the cycle are located in the matrix along with NAD+ and FAD. This location facilitates direct transfer of NADH and FADH2 to the electron transport chain .
What is substrate-level phosphorylation?
ATP synthesis driven by a proton gradient
Light absorption by pigments
Direct transfer of a phosphate group to ADP from a phosphorylated intermediate
Splitting of water to yield ATP
Substrate-level phosphorylation involves an enzyme transferring a phosphate group from a metabolic intermediate directly to ADP to form ATP. This occurs in glycolysis and the Krebs cycle. It differs from oxidative phosphorylation, which relies on a proton gradient .
Which enzyme catalyzes the fixation of carbon dioxide in the Calvin cycle?
RuBisCO
NADP+ reductase
ATP synthase
Phosphofructokinase
Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) catalyzes the attachment of CO2 to RuBP in the first step of the Calvin cycle. It is considered the most abundant enzyme on Earth. Despite its slow catalytic rate, it is essential for carbon fixation in plants .
Which high-energy molecules are produced by the citric acid cycle for use in the electron transport chain?
ATP and CO2
Glucose and pyruvate
NADH and FADH2
O2 and water
The citric acid cycle generates NADH and FADH2 as electron carriers, which deliver electrons to the electron transport chain. These reduced coenzymes drive ATP production by oxidative phosphorylation. CO2 is also released as a byproduct .
Approximately how many ATP molecules are generated from one glucose molecule during aerobic respiration?
36 to 38 ATP
2 to 4 ATP
100 ATP
10 ATP
Aerobic respiration yields about 36 to 38 ATP per glucose, including ATP from glycolysis, the Krebs cycle, and oxidative phosphorylation. The exact number can vary slightly depending on shuttle systems and conditions. This efficiency underscores the advantage of aerobic metabolism .
Which statement correctly distinguishes cyclic photophosphorylation from noncyclic photophosphorylation?
Noncyclic photophosphorylation does not involve water splitting
Noncyclic photophosphorylation occurs only in bacteria
Cyclic photophosphorylation produces only ATP and recycles electrons to photosystem I
Cyclic photophosphorylation generates NADPH but no ATP
In cyclic photophosphorylation, electrons from photosystem I are cycled back to the electron transport chain, generating ATP without producing NADPH or oxygen. Noncyclic photophosphorylation involves both photosystem I and II, produces NADPH, ATP, and evolves O2 by splitting water. This distinction is key to balancing cellular ATP and NADPH needs .
In the mitochondrial electron transport chain, how is NADH utilized?
It donates electrons to complex I
It forms a proton gradient directly
It binds to ATP synthase to produce ATP
It accepts protons from the intermembrane space
NADH donates electrons to complex I (NADH dehydrogenase) of the electron transport chain, initiating proton pumping across the inner mitochondrial membrane. This electron transfer drives the generation of a proton gradient used by ATP synthase. NADH thus serves as a key electron donor in oxidative phosphorylation .
What is photorespiration and why is it considered inefficient?
Light-induced damage to chlorophyll molecules
Oxygenation of RuBP by RuBisCO leading to CO2 release and ATP loss
Excessive oxygen production during photosynthesis
Mitochondrial respiration occurring in chloroplasts
Photorespiration occurs when RuBisCO fixes O2 instead of CO2, producing a two-carbon compound that cannot enter the Calvin cycle, leading to CO2 release and ATP consumption. This process wastes energy and reduces photosynthetic efficiency. It is more prevalent under high oxygen concentrations and warm temperatures .
What is the compensation point in photosynthesis?
The light intensity at which CO2 uptake equals CO2 release
The temperature at which enzyme activity is halved
The CO2 concentration where photosynthesis stops
The wavelength where pigment absorption is maximal
The photosynthetic compensation point is the light intensity where the rate of photosynthetic CO2 fixation matches the rate of CO2 release by respiration. Below this point, the plant consumes more CO2 than it produces. It is an important metric for understanding plant productivity under varying light conditions .
How does temperature generally affect the rate of photosynthesis in C3 plants?
Rate increases exponentially without limit
Rate increases to an optimum then declines due to enzyme denaturation
Rate is unaffected by temperature
Rate decreases linearly with temperature rise
As temperature rises, enzyme activity in photosynthesis increases up to an optimum, enhancing reaction rates. Above the optimum, enzymes like RuBisCO begin to denature, and membrane integrity is compromised, reducing photosynthetic efficiency. This response is characteristic of most C3 plants .
What does the P/O ratio represent in mitochondrial oxidative phosphorylation?
Number of ATP molecules synthesized per oxygen atom reduced
Ratio of pyruvate to oxygen consumption
Number of protons pumped per ADP phosphorylated
Phosphate to oxygen binding affinity
The P/O ratio indicates how many ATP molecules are synthesized for each oxygen atom (or half O2 molecule) reduced in the electron transport chain. It is a measure of the efficiency of oxidative phosphorylation. Typical values are 2.5 for NADH and 1.5 for FADH2 .
What is the overall balanced chemical equation for aerobic cellular respiration?
C6H12O6 ? 2 C3H6O3 + ATP
6 CO2 + 6 H2O ? C6H12O6 + 6 O2
C6H12O6 + 6 O2 ? 6 CO2 + 6 H2O + energy
Glucose + ATP ? ADP + Pi
The balanced equation for aerobic respiration shows glucose reacting with oxygen to produce carbon dioxide, water, and release energy in the form of ATP. This process is essentially the reverse of photosynthesis. It summarizes glycolysis, the Krebs cycle, and oxidative phosphorylation .
What role does the antenna complex play in photosynthesis?
It transports electrons between complexes
It synthesizes ATP from ADP and phosphate
It captures and transfers light energy to the reaction center
It fixes carbon dioxide into sugars
The antenna complex consists of multiple pigment molecules that absorb photons and funnel the excitation energy to the reaction center chlorophyll. This maximizes light-harvesting efficiency across different wavelengths. Without it, the reaction center would capture far fewer photons .
How is RuBisCO activity regulated in C3 plants?
Stimulated by low temperatures
Repressed during the day
Inhibited by high NADPH levels
Activated by light-induced changes in stroma pH and Mg2+ concentration
RuBisCO is activated in the light as protons are pumped into the thylakoid lumen, raising stroma pH and releasing Mg2+, which binds RuBisCO and enhances its activity. This ensures carbon fixation coincides with light availability. Dark conditions reverse these changes, deactivating the enzyme .
Which statement correctly describes how the proton motive force differs between chloroplasts and mitochondria?
Both organelles pump protons into their outer membranes
Chloroplasts generate a proton gradient across the plasma membrane; mitochondria across the inner membrane
In chloroplasts, protons accumulate in the thylakoid lumen; in mitochondria, they accumulate in the intermembrane space
In chloroplasts, protons are pumped into the stroma; in mitochondria, into the matrix
In chloroplasts, the light reactions pump protons into the thylakoid lumen creating a gradient across the thylakoid membrane. In mitochondria, the electron transport chain pumps protons into the intermembrane space across the inner mitochondrial membrane. ATP synthase uses these gradients to produce ATP in both organelles .
What adaptation in C4 plants reduces photorespiration under high temperature conditions?
Use of alternative electron acceptors instead of oxygen
Direct fixation of O2 instead of CO2
Spatial separation of initial CO2 fixation in mesophyll and the Calvin cycle in bundle sheath cells
Stomatal closure during daytime
C4 plants initially fix CO2 into a four-carbon compound in mesophyll cells by PEP carboxylase, which has no oxygenase activity. This compound is transported to bundle sheath cells where CO2 is released for the Calvin cycle, minimizing RuBisCO's exposure to O2. This spatial separation reduces photorespiration especially under high temperatures .
What is the function of the alternative oxidase pathway in plant mitochondria?
Facilitates ATP synthesis at higher efficiency than complex IV
Binds CO2 to form organic acids in mitochondria
Transports electrons directly to oxygen to form water without pumping protons
Allows electron flow when the main chain is over-reduced, minimizing reactive oxygen species and generating heat
The alternative oxidase pathway allows electrons from ubiquinol to reduce oxygen directly, bypassing complexes III and IV. This pathway does not contribute to the proton gradient and thus does not produce ATP, but it prevents over-reduction of the electron transport chain and limits reactive oxygen species formation. It can also produce heat in certain plant tissues .
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Study Outcomes

  1. Understand the stages of photosynthesis -

    Explore how light-dependent and light-independent reactions capture and convert solar energy into glucose.

  2. Identify the steps of cellular respiration -

    Trace glycolysis, the Krebs cycle, and oxidative phosphorylation to see how cells extract energy from glucose.

  3. Differentiate between photosynthesis and cellular respiration -

    Contrast the inputs, outputs, and energy flow of plant energy cycles to clarify their complementary roles.

  4. Analyze ATP production and usage -

    Examine how adenosine triphosphate functions as the energy currency in both photosynthetic and respiratory pathways.

  5. Apply concepts to quiz questions -

    Use your understanding of plant energy cycles to confidently answer photosynthesis and cellular respiration quiz items.

  6. Evaluate common misconceptions -

    Identify and correct typical misunderstandings about light reactions, dark reactions, and cellular metabolism.

Cheat Sheet

  1. Light-Dependent Reactions -

    These reactions take place in the thylakoid membranes and use light energy to split water into O₂ while generating ATP and NADPH (2 H₂O + 2 NADP❺ + 3 ADP + 3 Pi + light → O₂ + 2 NADPH + 3 ATP). A handy mnemonic is "Water Splits, Energy Flips" to remember H₂O cleavage and energy transfer. According to UC Berkeley's plant biology resources, mastering this step is key for any photosynthesis quiz.

  2. Calvin Cycle (Light-Independent Reactions) -

    Happening in the chloroplast stroma, the Calvin cycle fixes CO₂ into G3P using 9 ATP and 6 NADPH per 3 CO₂ molecules (3 CO₂ + 9 ATP + 6 NADPH → G3P + 9 ADP + 8 Pi + 6 NADP❺). Use the memory phrase "Fix, Reduce, Regenerate" to track the three phases: carbon fixation, reduction, and ribulose regeneration. This cycle is detailed in the American Society of Plant Biologists' curriculum for a strong foundation.

  3. Glycolysis & Krebs Cycle Yields -

    In glycolysis (cytosol), one glucose nets 2 ATP and 2 NADH, while the Krebs cycle (mitochondrial matrix) produces 2 ATP, 6 NADH, and 2 FADH₂ per glucose. A popular trick is "Goodness Gracious, Great Mammals Ferment" to remember Glycolysis, Glucose, G3P, Mitochondria, and FADH₂. Peer-reviewed biochemistry texts like Lehninger confirm these energy totals for cellular respiration questions.

  4. Electron Transport Chain & Chemiosmosis -

    Protons pumped across the inner mitochondrial membrane create a gradient that drives ATP synthase to produce roughly 28 - 34 ATP per glucose via chemiosmosis. You can visualize the "proton waterfall" powering the turbine-like ATP synthase to cement the concept. This mechanism is described in depth by the National Center for Biotechnology Information.

  5. Photosynthesis vs Cellular Respiration Balance -

    These processes are biochemical mirror images: photosynthesis builds glucose (6 CO₂ + 6 H₂O → C₆H₝₂O₆ + 6 O₂) while respiration breaks it down (C₆H₝₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O). A simple rhyme - "Light In, Sugar Out; Sugar In, Energy Out" - helps you nail any photosynthesis and cellular respiration quiz. This equation pairing is fundamental in high school and university biology curricula worldwide.

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