Photosynthesis and Air Quality Experiments

Questions and Answers

Which part of the chloroplast is primarily responsible for trapping light energy?

Grana (correct)

Matrix stroma

Stroma lamellae

Mesophyll cells

What are the light reactions of photosynthesis primarily responsible for producing?

Sugars

ATP and NADPH (correct)

Starch

Oxygen

In which part of the chloroplast does the synthesis of sugars occur?

Stroma (correct)

Thylakoid space

Cell membrane

Grana

Which statement describes dark reactions in photosynthesis?

They rely on products from light reactions. Signup and view all the answers

Where are chloroplasts primarily aligned for optimal light absorption?

Parallel to the walls of the mesophyll cells Signup and view all the answers

What did Priestley hypothesize about plants and their interaction with the air?

Plants restore to the air whatever breathing animals and burning candles remove. Signup and view all the answers

What did Jan Ingenhousz demonstrate about sunlight in relation to plants?

Sunlight is essential for the process that purifies the air. Signup and view all the answers

What relationship did Julius von Sachs establish in his research about glucose production in plants?

Glucose is made in the green parts of plants and stored as starch. Signup and view all the answers

What did T.W. Engelmann use to study the sites of oxygen evolution in plants?

A prism to split light. Signup and view all the answers

In Engelmann's experiment, where did the bacteria accumulate the most?

In regions of blue and red light. Signup and view all the answers

What is the role of chlorophyll as established later in studies?

Chlorophyll is found in chloroplasts and is vital for glucose production. Signup and view all the answers

How did Priestley demonstrate the effect of plants on air quality in his experiments?

By placing a mint plant with a burning candle and observing its flame. Signup and view all the answers

What important finding did Ingenhousz have regarding the green part of plants?

The green parts release oxygen when exposed to sunlight. Signup and view all the answers

What is the primary purpose of phosphorylation in chloroplasts?

To synthesize ATP from ADP and inorganic phosphate Signup and view all the answers

Which process occurs when both Photosystem II and Photosystem I are active?

Non-cyclic photo-phosphorylation Signup and view all the answers

What is a key characteristic of cyclic photo-phosphorylation?

It involves only Photosystem I Signup and view all the answers

What is the electron transport chain's role in the photosystems?

Connecting the two photosystems during electron flow Signup and view all the answers

In which location does cyclic photo-phosphorylation primarily occur?

In the stroma lamellae membranes Signup and view all the answers

What does the cyclic flow of electrons ultimately lead to?

Only the synthesis of ATP Signup and view all the answers

What is missing from the stroma lamellae membranes compared to the grana membranes?

Photosystem II and NADP reductase enzyme Signup and view all the answers

When only Photosystem I is functioning, what process occurs?

Electrons are cycled back within Photosystem I Signup and view all the answers

What is the primary function of stomata in leaves during photosynthesis?

To allow the entry of carbon dioxide Signup and view all the answers

Which chlorophyll molecule absorbs light at 700 nm?

P700 Signup and view all the answers

What is a byproduct of the photosynthesis process linked to photosystem II?

Oxygen Signup and view all the answers

What compound is initially formed when CO2 is fixed in the Calvin cycle?

3-PGA Signup and view all the answers

What role does RuBisCO play in photosynthesis?

It catalyses CO2 fixation Signup and view all the answers

Which of these statements about C3 plants is true?

They engage in a wasteful process called photorespiration Signup and view all the answers

What type of light wavelengths initiate cyclic photophosphorylation?

Wavelengths above 680 nm Signup and view all the answers

During the light reaction of photosynthesis, what is produced as a result of the proton gradient?

ATP Signup and view all the answers

In the process of photosynthesis, where do the light reactions occur?

On the thylakoid membranes Signup and view all the answers

In the chemiosmotic hypothesis, where do protons accumulate during photosynthesis?

Inside the thylakoid lumen Signup and view all the answers

What role does the primary electron acceptor play in the development of the proton gradient?

Removes a proton from the stroma while transporting an electron Signup and view all the answers

Which enzyme is located on the stroma side of the membrane during photosynthesis?

NADP reductase Signup and view all the answers

What is the difference between proton accumulation in photosynthesis compared to respiration?

In respiration, protons accumulate in the intermembrane space of mitochondria Signup and view all the answers

Which process contributes to the formation of a proton gradient in thylakoids?

Movement of electrons through the ETS Signup and view all the answers

What initiates the splitting of water molecules in the thylakoids?

Absorption of light energy Signup and view all the answers

What happens to protons during the transport of electrons across the thylakoid membrane?

They accumulate inside the thylakoid lumen Signup and view all the answers

Study Notes

Priestley's Experiment

Priestley discovered that a burning candle or an animal breathing air depletes the air quality.
Introduction of a mint plant in a closed setup allowed the candle to stay lit and a mouse to survive, indicating that plants can restore air quality.
This led to the hypothesis that plants replenish the air by counteracting what animals and burning candles remove.

Ingenhousz's Findings

Jan Ingenhousz demonstrated that sunlight is crucial for plants to purify the air.
His experiment used an aquatic plant to show that bubbles, later identified as oxygen, formed in sunlight but not in darkness.
He concluded that only the green parts of plants can release oxygen.

Contributions of Julius von Sachs

In 1854, Sachs provided evidence that plants produce glucose, which is stored as starch.
He identified chlorophyll in plant cells, particularly concentrated in chloroplasts.
This confirmed that the green parts of plants are key sites for glucose production.

Engelmann's Experiment

T.W. Engelmann illuminated a green alga with a prism to split light, using aerobic bacteria to locate oxygen production sites.
Bacteria thrived in blue and red light, indicating these wavelengths enhance photosynthesis.
Photosynthesis occurs in green leaves and also in other green plant parts.

Chloroplast Structure and Function

Chloroplasts contain a membranous system with grana, stroma lamellae, and matrix stroma.
Grana membranes conduct light energy trapping and ATP/NADPH synthesis.
Stroma is responsible for enzymatic reactions synthesizing sugars, typically from products of light reactions.

Photosynthetic Reactions

Photosynthesis includes light reactions (light-driven) and dark reactions (dependent on light product availability, not directly driven).
Photophosphorylation generates ATP through light energy, while the electron transport chain connects PS I and PS II.

Chemiosmotic Hypothesis

ATP synthesis is linked to proton gradient development across thylakoid membranes during photosynthesis.
Protons accumulate in the thylakoid lumen due to water splitting and electron transport processes.
Movement of protons through ATP synthase releases energy for ATP formation.

Summary of Photosynthesis

Green plants utilize photosynthesis to produce glucose and starch from carbon dioxide and sunlight.
This process occurs mainly in leaves, specifically the mesophyll cells containing chloroplasts.
The two main stages of photosynthesis are light reactions and carbon-fixing reactions, involving specific pigments and enzymes, including RuBisCO.
C3 plants may experience photorespiration, while some tropical plants utilize a C4 pathway to enhance carbon fixation efficiency.

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Description

Explore the groundbreaking experiments by Priestley, Ingenhousz, and Sachs that revealed how plants purify air and produce glucose. This quiz covers their findings and implications for understanding photosynthesis and the role of sunlight. Test your knowledge of these key scientific contributions!