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Quizzes > Science

Photosynthesis and Cellular Respiration Quiz

Quick, free biology check with instant results. Try the photosynthesis and respiration quiz.

Editorial: Review CompletedCreated By: Brian FlynnUpdated Aug 23, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration of leaves sun mitochondria on teal background for photosynthesis and cellular respiration quiz

This quiz helps you check your understanding of photosynthesis and cellular respiration, from key inputs and outputs to where each step happens. For extra practice, see cellular respiration basics, try the cell structure and function quiz, or explore the plant biology quiz. Get instant feedback and pinpoint topics to review.

What is the primary site of photosynthesis in plant cells?
Ribosome
Vacuole
Chloroplast
Mitochondrion
Photosynthesis takes place in chloroplasts where light energy is converted into chemical energy. These organelles contain chlorophyll and the membranes needed for the light reactions. Chloroplasts are unique to plants and algae. .
Which gas is produced as a byproduct of photosynthesis?
Nitrogen
Methane
Oxygen
Carbon dioxide
During the light-dependent reactions, water molecules are split to release oxygen. This O? is expelled into the atmosphere as a byproduct. Oxygen evolution is a hallmark of photosynthesis in plants, algae, and cyanobacteria. .
Which molecule is the main product of the Calvin cycle?
NADPH
Oxygen
ATP
Glucose (G3P)
The Calvin cycle fixes CO? into a three-carbon sugar, glyceraldehyde-3-phosphate (G3P). Two G3P molecules combine to form one glucose. ATP and NADPH from light reactions provide the energy and reducing power for this process. .
What is the balanced overall equation for photosynthesis?
6 CO? + 6 H?O ? C?H??O? + 6 O?
6 CO? + 6 O? ? C?H??O? + 6 H?O
C?H??O? + 6 O? ? 6 CO? + 6 H?O
C?H??O? ? 2 C?H?O?
Photosynthesis uses six molecules of carbon dioxide and six of water to produce one glucose and six oxygen molecules. This equation represents the net inputs and outputs of both light and dark reactions. It is the reverse of cellular respiration. .
Where does glycolysis occur in eukaryotic cells?
Endoplasmic reticulum
Chloroplast stroma
Cytosol
Mitochondrial matrix
Glycolysis takes place in the cytosol of cells, where glucose is broken down into pyruvate. This process does not require oxygen. The products move into mitochondria if aerobic respiration follows. .
Which molecule is the main energy carrier produced by cellular respiration?
Chlorophyll
Glucose
ATP
CO?
Adenosine triphosphate (ATP) is the universal energy currency of the cell. Cellular respiration generates ATP through substrate-level and oxidative phosphorylation. Glucose fuels this process and oxygen is the final electron acceptor. .
Which stage of cellular respiration produces the most ATP?
Oxidative phosphorylation
Fermentation
Glycolysis
Citric acid cycle
Oxidative phosphorylation via the electron transport chain and ATP synthase produces the majority of ATP. It generates about 26 - 28 ATP molecules per glucose in eukaryotes. Other stages produce far fewer molecules. .
What structure on the leaf allows gas exchange for photosynthesis?
Stomata
Cuticle
Xylem
Palisade layer
Stomata are pores on the leaf surface that regulate gas exchange and water loss. They open to allow CO? in and O? out during photosynthesis. Guard cells control these openings. .
In which part of the chloroplast does the Calvin cycle occur?
Stroma
Inner membrane
Thylakoid lumen
Outer membrane
The Calvin cycle enzymes are located in the stroma of chloroplasts. It is here that CO? is fixed into organic molecules. Light reactions supply ATP and NADPH to the stroma for this cycle. .
Which pigment-protein complex is responsible for capturing light energy in photosystem II?
P700 reaction center
Chlorophyll b complex
P680 reaction center
Carotenoid antenna
Photosystem II has a reaction center chlorophyll known as P680. It absorbs light at 680 nm and initiates electron transport by splitting water. P700 is found in Photosystem I at a different wavelength. .
What is the primary role of ATP synthase in chloroplasts?
Absorb light energy
Fix CO? into sugars
Synthesize ATP using a proton gradient
Split water molecules
ATP synthase uses the proton gradient across the thylakoid membrane to convert ADP and inorganic phosphate into ATP. This process is called photophosphorylation. It is essential for providing energy to the Calvin cycle. .
How many net ATP molecules are produced per glucose molecule during glycolysis?
32
2
36
4
Glycolysis yields a net gain of 2 ATP molecules per glucose by substrate-level phosphorylation. Although four ATP are produced, two are consumed in early steps. It also produces NADH and pyruvate. .
Where does the electron transport chain occur in mitochondria?
Outer mitochondrial membrane
Matrix
Intermembrane space
Inner mitochondrial membrane
The electron transport chain complexes are embedded in the inner mitochondrial membrane. They transfer electrons from NADH and FADH? to oxygen, creating a proton gradient. ATP synthase then uses this gradient to make ATP. .
Which enzyme catalyzes the first step of carbon fixation in the Calvin cycle?
RuBisCO
NADP? reductase
Phosphofructokinase
ATP synthase
Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) fixes CO? to ribulose-1,5-bisphosphate. It is the most abundant enzyme on Earth. RuBisCO's activity is crucial for sugar production in plants. .
Which molecule acts as the final electron acceptor in aerobic respiration?
Carbon dioxide
Water
Oxygen
NAD?
In aerobic respiration, oxygen accepts electrons at the end of the electron transport chain. This forms water when combined with protons. Without oxygen, the chain would back up and ATP production would halt. .
What is the role of NADP? in photosynthesis?
Generator of proton gradient
Fixer of CO? molecules
Substrate for ATP synthase
Electron carrier to form NADPH
NADP? accepts electrons at the end of the light reactions, becoming NADPH. NADPH provides reducing power for the Calvin cycle. It is essential for biosynthetic reactions in the stroma. .
Under what conditions does photorespiration increase in plants?
High CO? and low O? concentrations
High O? and low CO? concentrations
Low light intensity
High water availability
Photorespiration occurs when RuBisCO fixes O? instead of CO?, producing a two-carbon compound. This happens more under high oxygen and low carbon dioxide levels. It reduces photosynthetic efficiency by consuming ATP and releasing CO?. .
What differentiates cyclic from noncyclic photophosphorylation?
Cyclic produces only ATP and no NADPH
Noncyclic occurs in mitochondria
Cyclic produces both ATP and NADPH
Noncyclic produces only NADPH
In cyclic photophosphorylation, electrons cycle back to photosystem I, creating only ATP. Noncyclic flow moves electrons from water to NADP?, generating both ATP and NADPH. The cyclic route adjusts the ATP/NADPH ratio for the Calvin cycle. .
How many NADH molecules are produced per acetyl-CoA in the citric acid cycle?
1
3
2
4
Each turn of the citric acid cycle yields three NADH molecules per acetyl-CoA. NADH carries electrons to the electron transport chain for ATP production. Additionally, one FADH? and one ATP (or GTP) are produced. .
Which step in cellular respiration releases the first CO? molecule?
Oxidative phosphorylation
Glycolysis
Electron transport chain
Pyruvate oxidation
Pyruvate oxidation converts pyruvate to acetyl-CoA in the mitochondrial matrix, releasing CO?. This step links glycolysis and the citric acid cycle. It also produces NADH for further ATP generation. .
Which of the following is a product of cyclic photophosphorylation?
ATP and NADPH
NADPH only
ATP only
Oxygen only
Cyclic photophosphorylation recycles electrons from photosystem I back into its electron transport chain, generating ATP only. No NADPH or oxygen is produced because water is not split. This helps balance the ATP/NADPH ratio. .
What drives the synthesis of ATP in both chloroplasts and mitochondria?
Direct use of light energy
Proton motive force across a membrane
High NADPH concentration
High ADP concentration alone
Both organelles use a proton motive force - protons flowing down their gradient through ATP synthase - to produce ATP. In chloroplasts, this gradient is across the thylakoid membrane; in mitochondria, across the inner membrane. It is a shared chemiosmotic mechanism. .
Which fermentation pathway yields ethanol and CO??
Alcoholic fermentation
Mixed acid fermentation
Butyric acid fermentation
Lactic acid fermentation
Alcoholic fermentation by yeast converts pyruvate into ethanol and carbon dioxide. NADH is oxidized back to NAD? during this process. Lactic acid fermentation produces lactate instead of ethanol. .
Which molecule replenishes the Calvin cycle when RuBP levels drop?
3-Phosphoglycerate (3-PGA)
Fructose-6-phosphate
Glyceraldehyde-3-phosphate (G3P)
Ribulose-1,5-bisphosphate (RuBP)
RuBP is regenerated in the Calvin cycle's final steps using ATP. This replenishment allows the cycle to continue fixing CO?. Without RuBP regeneration, the cycle would halt. .
How does the herbicide DCMU (Diuron) inhibit the photosynthetic electron transport chain?
Prevents ATP synthase activity
Inhibits rubisco carboxylation
Blocks electron transfer from photosystem II to plastoquinone
Blocks electron flow in photosystem I
DCMU binds to the Q_B site of photosystem II, preventing plastoquinone from receiving electrons. This stops the flow of electrons, halting ATP and NADPH production. It effectively shuts down the light reactions. .
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Study Outcomes

  1. Understand Key Processes -

    Grasp the fundamental stages, reactants, and products of photosynthesis and cellular respiration, building a solid foundation for energy conversion in living organisms.

  2. Compare Energy Pathways -

    Analyze how energy flows through photosynthesis and cellular respiration, identifying similarities and differences in their overall functions and efficiency.

  3. Analyze Respiration Steps -

    Break down the specific phases of cell respiration, including glycolysis, the Krebs cycle, and the electron transport chain, to answer targeted cell respiration questions accurately.

  4. Differentiate Reaction Types -

    Distinguish between light-dependent vs. light-independent reactions in photosynthesis and aerobic vs. anaerobic respiration in cells to master key concepts.

  5. Apply Knowledge to Practice Questions -

    Use your understanding to tackle practice photosynthesis and cellular respiration comparison quizzes, reinforcing your learning through hands-on test questions.

  6. Evaluate Common Misconceptions -

    Identify and correct frequent misunderstandings about energy processes in plants and cells, enhancing clarity and confidence in your test performance.

Cheat Sheet

  1. Light-Dependent vs Light-Independent Reactions -

    Make sure you can distinguish the light reactions (producing ATP and NADPH in the thylakoid membranes) from the Calvin cycle (fixing CO2 into glucose in the stroma). A helpful mnemonic is "Light Delivers bright Energy, Calvin Crafts Carbs." Using practice photosynthesis and cellular respiration comparison charts from reputable sources like Khan Academy will solidify how energy carriers shuttle between these stages.

  2. Stages of Cellular Respiration -

    Recall that cellular respiration occurs in three main stages: glycolysis in the cytosol, the Krebs cycle in the mitochondrial matrix, and the electron transport chain along the inner membrane. A handy mnemonic is "Good Kids Eat" (Glycolysis, Krebs, Electron transport) to recall the sequence quickly. Reviewing cell respiration questions on platforms like HHMI BioInteractive will strengthen your command of reaction inputs and outputs.

  3. Balancing the Equations -

    Master the balanced equations: photosynthesis 6CO2 + 6H2O → C6H12O6 + 6O2 and cellular respiration as its reverse equation. Practice writing these in your free photosynthesis and cellular respiration test to build recall under time pressure. Checking your work against textbook standards (e.g., Campbell Biology) ensures you capture every molecule and coefficient correctly.

  4. ATP Yield Breakdown -

    Understand that glycolysis yields 2 ATP, the Krebs cycle nets 2 ATP, and the electron transport chain can produce up to ~34 ATP per glucose, totaling about 38 ATP under ideal conditions. Knowing where most ATP is generated helps you tackle cell respiration questions on ATP accounting. A quick tip is to memorize "2-2-34" as your go-to summary for ATP yield breakdown.

  5. Electron Carriers & Pathway Integration -

    Learn how NADP+/NADPH shuttle electrons in photosynthesis and how NAD+/FAD do the same in respiration to drive ATP production. Drawing electron flow diagrams for both processes in your photosynthesis practice will illuminate the elegant interplay between these pathways. University of Illinois resources emphasize that mastering these carriers unlocks deeper insights into the energy transformation in cells.

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