Photosynthesis in Higher Plants Quiz
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Questions and Answers

What is the primary purpose of photosynthesis in higher plants?

  • To eliminate excess water from the plant
  • To convert sunlight into heat energy
  • To reduce CO<sub>2</sub> to carbohydrates and release O<sub>2</sub> (correct)
  • To oxidize glucose for energy

Which of the following is a necessary condition for photosynthesis to occur?

  • Absence of light
  • High temperatures
  • Presence of starch in the plant
  • Presence of chlorophyll (correct)

During photosynthesis, what is CO2 primarily undergoing?

  • Oxidation to form O<sub>2</sub>
  • Reduction to form glucose (correct)
  • Decomposition into water
  • Transformation into carbon monoxide

In the iodine test for starch, what does a blue color indicate?

<p>Presence of starch (A)</p> Signup and view all the answers

What will occur in a variegated leaf during the iodine test?

<p>Only the green parts will turn blue (D)</p> Signup and view all the answers

What is the role of KOH in Moll’s Half Leaf Experiment?

<p>To absorb CO<sub>2</sub> (D)</p> Signup and view all the answers

Which of the following components is NOT required for photosynthesis?

<p>Oxygen (B)</p> Signup and view all the answers

What does the Bell Jar Experiment demonstrate regarding plant respiration?

<p>Plants produce their own oxygen (C)</p> Signup and view all the answers

What is released as a by-product during photosynthesis?

<p>Oxygen (A)</p> Signup and view all the answers

Which part of the leaf will test positive for starch if it contains chlorophyll?

<p>Green parts of the leaf (D)</p> Signup and view all the answers

What must be done to a leaf before conducting the iodine test for starch?

<p>Destasch it (A)</p> Signup and view all the answers

In the Moll’s Half Leaf Experiment, what role does the KOH-soaked cotton play?

<p>It absorbs carbon dioxide (B)</p> Signup and view all the answers

What is the primary chemical change occurring in photosynthesis?

<p>Carbon dioxide is reduced to glucose (C)</p> Signup and view all the answers

Which statement correctly describes photosynthesis?

<p>It involves a redox reaction. (C)</p> Signup and view all the answers

What happens to the starch when a leaf is boiled in alcohol before the iodine test?

<p>It will be destroyed (A)</p> Signup and view all the answers

In the Bell Jar Experiment by Joseph Priestly, what was observed?

<p>Plants provide oxygen for animals (D)</p> Signup and view all the answers

What do chlorophyll and sunlight collectively enable during photosynthesis?

<p>Reduction of carbon dioxide to carbohydrates (D)</p> Signup and view all the answers

What is an indicator of a positive iodine test for starch?

<p>Blue-black color (C)</p> Signup and view all the answers

Flashcards

Photosynthesis

A process where plants convert carbon dioxide and water into sugar using sunlight and chlorophyll.

Photosynthesis Reaction

CO2 (carbon dioxide) + H2O (water) → C6H12O6 (sugar) + O2 (oxygen).

Chlorophyll

A green pigment in plants that absorbs sunlight for photosynthesis.

Light Dependence (Photosynthesis)

Proof that light is necessary for photosynthesis.

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Chlorophyll Necessity

Demonstrates that chlorophyll is crucial for photosynthesis.

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CO2 Necessity (Photosynthesis)

Shows how carbon dioxide is essential for photosynthesis.

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Destarched Leaf

A leaf that has been kept in the dark for 24 hours to remove any stored starch, used in experiments.

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Iodine Test

A test used to detect the presence of starch in a leaf.

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Photosynthesis: Redox Reaction?

Photosynthesis is a chemical reaction where carbon dioxide (CO2) is reduced to glucose (sugar) and water (H2O) is oxidized to oxygen (O2).

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Photosynthesis: What's the Equation?

The overall chemical equation is CO2 + H2O -> C6H12O6 + O2. Sunlight and chlorophyll are needed for this reaction to happen.

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Photosynthesis: By-product?

The removal of hydrogen ions (H+) from water, leading to the release of oxygen as a byproduct.

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Photosynthesis: Physical or Chemical Change?

Photosynthesis is a physico-chemical change. Inorganic compounds like CO2 and H2O are converted into organic compounds like glucose.

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Light is Necessary: How do we prove it?

A plant is destarched (kept in the dark to remove stored starch) and then placed in a light-blocking setup. Only the part exposed to light will show starch presence.

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Chlorophyll is Necessary: How do we know?

A variegated leaf plant (with green and yellow sections) is desfarched. After exposure to light, only the green areas containing chlorophyll will show starch presence.

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CO2 is Necessary: What's the experiment?

The Moll's Half Leaf Experiment uses KOH soaked cotton to absorb CO2. Only the part exposed to CO2 will show starch presence, proving it's needed for photosynthesis.

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Bell Jar Experiment: What did it show?

Joseph Priestly's Bell Jar experiment in the 1770s demonstrated that a mouse placed in a bell jar with a lit candle would eventually die, but a plant placed in the same environment could revive the air.

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Destarched Plants: Why are they used?

Removing stored starch from a plant before an experiment ensures that any detected starch is a result of photosynthesis during the experiment and not from previous storage.

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Iodine test: What does it tell us?

The iodine test is used to detect the presence of starch in a leaf. It turns bluish-black if starch is present, indicating that photosynthesis has occurred.

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Study Notes

Photosynthesis in Higher Plants

  • Photosynthesis is a redox reaction converting light energy into chemical energy.
  • Carbon dioxide (CO₂) is reduced to carbohydrate, and water (H₂O) is oxidized, releasing oxygen (O₂).
  • This process requires sunlight and chlorophyll.
  • The overall reaction is: CO₂ + H₂O → C₆H₁₂O₆ + O₂ (in the presence of sunlight and chlorophyll)

Demonstrating Photosynthesis

  • Light's Necessity: A plant should be kept in darkness for 24 hours to remove stored starch. Then exposing it to light will show starch production.

  • Chlorophyll's Role: A variegated leaf (with yellow and green sections) demonstrates that only the green parts (containing chlorophyll) produce starch when exposed to light.

Early Experiments in Photosynthesis

  • Bell Jar Experiment (Priestley): Mice placed in a sealed jar consumed oxygen, extinguishing a candle. Plants restored the air, allowing the candle to relight. This suggested plants produce oxygen.

  • Moll's Half-Leaf Experiment: Preventing part of a leaf from reaching light during starch production showed that light exposure is essential for photosynthesis. Exposing part of the leaf to light confirmed this role of light.

  • Other Discoveries: Jan Ingenhousz confirmed only daytime photosynthesis occurred, and others like Priestly identified oxygen's role and Julius von Sachs discovered that starch is produced in plant chloroplasts and then stored.

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Test your knowledge on the process of photosynthesis in higher plants, including its chemical reactions, the role of chlorophyll, and historic experiments that demonstrated this vital process. Explore how light energy is converted into chemical energy and understand the significance of carbon dioxide and water in forming glucose and oxygen.

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