Climate Change and Photosynthesis Quiz

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Questions and Answers

What is the primary cause of the increased global warming effect?

Natural fluctuations in Earth's orbit

Human activities releasing CO2 (correct)

Increased solar radiation

Increased volcanic activity

What is the main goal of the Paris Agreement?

To enforce strict penalties on countries exceeding emission targets

To limit global warming to less than 2°C by 2100 (correct)

To completely eliminate greenhouse gas emissions by 2100

To create a global fund to compensate developing countries for climate change damage

Which of the following is NOT a consequence of climate change?

Increased prevalence of tropical diseases

Droughts and water shortages

Melting of polar ice caps

Increased volcanic activity (correct)

How much has the average global temperature increased since 1900 due to human activities?

1°C (1.8°F) Signup and view all the answers

What is the significance of forests in the context of climate change?

Forests help absorb CO2 from the atmosphere. Signup and view all the answers

What role does photosynthesis play in both causing and potentially solving climate change?

Fossil fuels, formed by ancient photosynthesis, contribute to climate change, while modern photosynthesis combats it. Signup and view all the answers

What is the difference between climate change and weather?

Climate change refers to long-term global changes, while weather is short-term atmospheric conditions. Signup and view all the answers

What is the Paris Agreement's approach to reducing greenhouse gas emissions?

Encouraging the use of renewable energy sources and energy efficiency measures. Signup and view all the answers

How does deforestation contribute to climate change?

Trees absorb CO2 from the atmosphere, and deforestation reduces this absorption. Signup and view all the answers

What is the connection between science, technology, and society in addressing climate change?

Scientists study climate change, engineers develop solutions, and governments and citizens implement them. Signup and view all the answers

What is the primary contribution of water to the process of photosynthesis?

Providing the hydrogen ions and electrons Signup and view all the answers

Which of the following accurately describes the relationship between photosynthesis and cellular respiration?

They are opposite reactions, where products of one are the reactants of the other. Signup and view all the answers

In photosynthesis, how does the potential energy of electrons change as they move from water to carbon dioxide?

The potential energy increases. Signup and view all the answers

What is the direct role of light energy in photosynthesis?

To split water molecules and boost the potential energy of electrons. Signup and view all the answers

What are the two main stages of photosynthesis?

The light reactions and the Calvin cycle. Signup and view all the answers

Where do the light reactions of photosynthesis occur?

On and inside the thylakoids of the chloroplast. Signup and view all the answers

Which of these is not a direct product or output of the light reactions?

Sugar Signup and view all the answers

What is the role of NADPH in photosynthesis?

It provides ‘reducing power’ for the Calvin cycle. Signup and view all the answers

Which process is described as ‘carbon fixation’ in photosynthesis?

The incorporation of carbon from carbon dioxide into organic molecules. Signup and view all the answers

Where does the Calvin cycle take place?

In the stroma of the chloroplast. Signup and view all the answers

Why is the Calvin cycle also known as the ‘dark reactions’?

Because its steps do not directly require light. Signup and view all the answers

What is the main purpose of the Calvin cycle?

To assemble sugar molecules using carbon dioxide and the products of the light reactions. Signup and view all the answers

What does the term ‘photo’ refer to it the of photosynthesis?

The light reactions. Signup and view all the answers

What is the most accurate description of electromagnetic energy?

Energy that travels as rhythmic waves. Signup and view all the answers

In the electromagnetic spectrum, where does visible light lie?

In a small fraction of the spectrum between about 380 nm and 750 nm. Signup and view all the answers

Which structural component of the chloroplast is responsible for housing the chlorophyll molecules?

Thylakoid membranes Signup and view all the answers

In the light reactions of photosynthesis, what is the direct source of electrons that reduce NADP+ to NADPH?

Water Signup and view all the answers

What is the primary function of the stomata in plant leaves?

To facilitate the exchange of carbon dioxide and oxygen Signup and view all the answers

In the overall process of photosynthesis, what is the source of the oxygen that is released?

Water ($H_2O$) Signup and view all the answers

In what order do Photosystem II and Photosystem I function during the light reactions?

Photosystem II functions first, then Photosystem I Signup and view all the answers

What is the primary function of the electron transport chain in the light reactions?

To create a proton gradient for ATP synthesis Signup and view all the answers

Which of the following best describes the role of veins in plant leaves?

To deliver water to the leaves and export sugar Signup and view all the answers

What is the name of the fluid-filled space inside the chloroplast where thylakoids are suspended?

Stroma Signup and view all the answers

What molecule is the final electron acceptor in the light reactions?

NADP+ Signup and view all the answers

What is the main function of photosynthetic pigments such as chlorophyll?

To absorb light energy for photosynthesis Signup and view all the answers

What is the process called when the potential energy of a proton gradient is used to power the synthesis of ATP?

Photophosphorylation Signup and view all the answers

Where does the splitting of water occur during the light reactions?

In the thylakoid space Signup and view all the answers

Which of the following is the primary location of chloroplasts in plant leaves?

Mesophyll cells Signup and view all the answers

What is the function of the reaction-center complex within a photosystem?

To absorb light energy and boost electrons to a higher energy level Signup and view all the answers

What is the term for the interconnected membranous sacs found within the chloroplast that contain chlorophyll?

Thylakoids Signup and view all the answers

What is the immediate source of carbon for the synthesis of sugar during photosynthesis?

Carbon dioxide Signup and view all the answers

What are the direct products of the light reactions that are then used in the Calvin cycle?

ATP and NADPH Signup and view all the answers

What is released when water is split during the light reactions?

Oxygen, electrons and protons Signup and view all the answers

Why was van Niel's work with photosynthesizing bacteria important to understanding oxygen release in plants?

It suggested that water, not carbon dioxide, is the source of released oxygen. Signup and view all the answers

What is the role of ATP synthase in the light reactions?

To use the proton gradient to synthesize ATP Signup and view all the answers

Which of the following best describes a granum?

A stack of thylakoids Signup and view all the answers

How does a prism separate white light into different colors?

By bending different wavelengths at different angles. Signup and view all the answers

What did the use of the oxygen isotope O-18 help determine about photosynthesis?

The source of released oxygen in photosynthesis Signup and view all the answers

In the light reactions, what happens to the electron when it reaches the primary electron acceptor of photosystem II?

It is transported to the electron transport chain Signup and view all the answers

What is the final destination of the oxygen produced during the splitting of water in the light reactions?

It diffuses out of the leaf through stomata Signup and view all the answers

What characteristic of a photon determines the amount of energy it carries?

Its wavelength. Signup and view all the answers

How do chloroplasts interact with plant cells to perform photosynthesis?

They use light to create chemical energy which is then used to produce sugars inside the cell. Signup and view all the answers

What is the relationship between the thylakoid membranes and the thylakoid space?

The thylakoid membranes enclose the thylakoid space. Signup and view all the answers

What is the process by which light energy is converted to chemical energy in the form of ATP and NADPH?

Photophosphorylation Signup and view all the answers

Why can ultraviolet (UV) radiation be harmful to living organisms?

Because the photons of UV light carry high amounts of energy. Signup and view all the answers

What energy transformation occurs when electrons move down the electron transport chain?

Kinetic energy to potential energy Signup and view all the answers

What is the role of the mesophyll in relation to photosynthesis?

It is a layer of cells in the leaf where photosynthesis primarily occurs. Signup and view all the answers

What happens to the wavelengths of light that are absorbed by pigment molecules?

Their energy is captured by the pigment molecules. Signup and view all the answers

Where are the photosystems and other components of the light reactions located in the chloroplast?

Embedded in the thylakoid membrane Signup and view all the answers

Why do leaves appear green?

Because chlorophyll reflects and transmits green wavelengths. Signup and view all the answers

What role does chlorophyll b have in photosynthesis?

It conveys absorbed energy to chlorophyll a. Signup and view all the answers

Besides broadening the spectrum of light that can drive photosynthesis, what is another important function of carotenoids?

To protect chlorophyll from damage by excessive light energy. Signup and view all the answers

When a pigment molecule absorbs a photon, what happens to one of its electrons?

It jumps to an excited state further from the nucleus. Signup and view all the answers

What form of energy does an excited electron release when it drops back to its ground state if no other process is acting on it?

It releases light and heat. Signup and view all the answers

What is fluorescence?

The emission of light and heat by an excited pigment molecule upon returning to ground state. Signup and view all the answers

How is the light energy captured before an excited electron falls back to its ground state in an intact chloroplast?

The excited electron is captured by the primary electron acceptor. Signup and view all the answers

What are photosystems and what is their purpose?

They are collections of light-harvesting complexes and reaction centers to capture light energy. Signup and view all the answers

How do light-harvesting complexes function?

They transfer light energy from pigment to pigment until reaching the reaction center. Signup and view all the answers

Within a photosystem, what is the role of the reaction-center complex?

To capture excited electrons using the primary electron acceptor. Signup and view all the answers

What is the immediate outcome of the primary electron acceptor capturing an electron from the reaction center?

The initiation of the process to convert light into chemical energy. Signup and view all the answers

What is the primary role of NADPH in the Calvin cycle?

To supply high-energy electrons for reducing CO2. Signup and view all the answers

What is the output of the Calvin cycle?

Glyceraldehyde 3-phosphate (G3P). Signup and view all the answers

Why is the Calvin cycle considered a 'cycle'?

Because the starting material is regenerated as molecules enter and leave the cycle. Signup and view all the answers

What is the enzyme responsible for the initial carbon fixation step in the Calvin cycle of most plants?

Rubisco. Signup and view all the answers

Why does photorespiration occur?

When rubisco adds O2 instead of CO2 to RuBP. Signup and view all the answers

Which of the following is NOT a characteristic of photorespiration?

It produces sugar. Signup and view all the answers

What is the primary advantage of C4 plants in hot, dry climates?

They minimize photorespiration by concentrating CO2 in bundle-sheath cells. Signup and view all the answers

How do C4 plants initially fix carbon?

Using an enzyme in the mesophyll cells that has a high affinity for CO2. Signup and view all the answers

In C4 plants, where does the Calvin cycle primarily occur?

In the bundle-sheath cells. Signup and view all the answers

How do CAM plants adapt to dry climates?

By fixing carbon into a four-carbon compound at night and releasing it during the day. Signup and view all the answers

In CAM plants, when does carbon fixation occur?

Only at night when the stomata are open. Signup and view all the answers

How do CAM plants manage to conduct the Calvin cycle during the day, even with their stomata closed?

By storing carbon fixed at night, and releasing it during the day. Signup and view all the answers

What feature do C4 and CAM pathways have in common that helps minimize photorespiration?

They both initially fix CO2 into a four-carbon compound. Signup and view all the answers

What is the primary role of the light reactions in photosynthesis?

To produce ATP and NADPH. Signup and view all the answers

What is the role of rubisco in the Calvin cycle?

It combines CO2 with RuBP. Signup and view all the answers

What is one of the primary products of photosynthesis that plants use as food?

Glucose Signup and view all the answers

How do plants primarily store excess carbohydrates made from photosynthesis?

As starch Signup and view all the answers

What effect has been noted regarding plant growth rates with increasing CO2 levels?

Weeds grow more than useful crop plants. Signup and view all the answers

What is the main purpose of the Free-Air CO2 Enrichment (FACE) experiment?

To observe effects of elevated CO2 on forest ecosystems. Signup and view all the answers

What unexpected finding was observed in poison ivy under elevated CO2 levels?

It became more toxic to humans. Signup and view all the answers

What is the primary source of energy for nearly all organisms on Earth?

Photosynthesis Signup and view all the answers

What greenhouse gas is significant for trapping heat in the Earth's atmosphere?

Carbon Dioxide Signup and view all the answers

How much has atmospheric CO2 risen since the start of the Industrial Revolution?

About 45% Signup and view all the answers

What do plants and other photosynthesizers depend on to produce their own food?

Sunlight Signup and view all the answers

What effect has rising CO2 had specifically on woody plants in the FACE experiment?

Minimal increases in biomass. Signup and view all the answers

What is the role of ATP in the Calvin cycle?

It provides energy for chemical reactions. Signup and view all the answers

What is the main component of plant cell walls?

Cellulose Signup and view all the answers

What overall impact could rising atmospheric CO2 levels have on ecosystem dynamics?

Increased plant biomass. Signup and view all the answers

Why do humans depend on photosynthesis despite being unable to make their own food?

Humans directly consume plants and animals that rely on photosynthesis. Signup and view all the answers

What is the primary energy source that powers life on Earth?

Solar energy Signup and view all the answers

Which of the following best describes the role of chloroplasts in plant cells?

They capture light energy for photosynthesis. Signup and view all the answers

What are the primary inputs for the process of photosynthesis?

Carbon dioxide and water Signup and view all the answers

Which of the following by-products is released during photosynthesis?

Oxygen Signup and view all the answers

How are autotrophs distinct from heterotrophs, based on the content provided?

Autotrophs create their own food, while heterotrophs must consume other organisms. Signup and view all the answers

What is the significance of photoautotrophs in the biosphere?

They are the producers, forming the base of the food chain. Signup and view all the answers

The energy stored within fossil fuels originally comes from what source, according to the text?

The sun's energy captured by past photoautotrophs Signup and view all the answers

Which of the following is NOT mentioned as an example of photoautotrophs in the text?

Fungi Signup and view all the answers

Study Notes

Photosynthesis: The Process of Life on Earth

Life on Earth is solar-powered, with chloroplasts in plants capturing light energy from the sun (150 million kilometers away).
Plants are photoautotrophs, meaning they make their own food through photosynthesis.
Photosynthesis converts carbon dioxide (CO2) and water (H2O) into sugars and other organic molecules, releasing oxygen (O2) as a byproduct.
Plants are the ultimate source of organic molecules for nearly all other organisms.

Location and Structure of Chloroplasts

Chloroplasts are found in all green parts of plants, but leaves are the primary sites of photosynthesis.
A leaf section measuring 1 mm² typically contains about half a million chloroplasts, concentrated in the mesophyll cells.
Chlorophyll, a light-absorbing pigment in chloroplasts, gives leaves their green color.
CO2 enters and O2 exits the leaf through tiny pores called stomata.
Water, absorbed by roots, is delivered to leaves through veins. Sugar, produced in leaves, is transported out through the veins.
Chloroplasts have an envelope of two membranes.
The inner compartment is filled with stroma, a thick fluid containing thylakoids.
Thylakoids are interconnected membranous sacs that enclose the thylakoid space.
Grana are stacks of thylakoids.
Chlorophyll molecules are embedded in the thylakoid membranes.
Membranes form a framework for photosynthetic reactions.
Reactant molecules (CO2 and water) reach chloroplasts through stomata and, in the case of water, through vascular systems.

The Discovery of Photosynthesis: Oxygen's Source

Early scientists hypothesized that CO2 was split during photosynthesis.
C. B. van Niel proposed in the 1930s that water was the source of oxygen.
Experiments using O-18 isotopes confirmed van Niel's hypothesis. Plants released O2 containing O-18 only when provided with labeled H2O, not labeled CO2.
Melvin Calvin and colleagues, using radioactive C-14 tracing, elucidated the Calvin cycle in the 1940s.
The majority of the mass in organic matter comes from the CO2 in the air, with hydrogen from water contributing to the structure.

Photosynthesis vs. Cellular Respiration

Photosynthesis and cellular respiration are opposing reactions.
In photosynthesis, electrons gain potential energy as water is oxidized and CO2 is reduced to sugar.
In cellular respiration, electrons lose potential energy as glucose is oxidized to CO2 and O2 is reduced to H2O.
Both involve redox reactions and energy transformation.

The Two Stages of Photosynthesis

Photosynthesis involves two linked processes: the light reactions and the Calvin cycle.
Light reactions occur in thylakoid membranes.
The light reactions convert light energy into chemical energy and release O2.
Water is split, and electrons are transferred to the electron acceptor NADP+ forming NADPH, which provides reducing power to the Calvin cycle.
ATP is generated from ADP and a phosphate group.
The Calvin cycle occurs in the stroma.
The Calvin cycle uses CO2, ATP, and NADPH from the light reactions to assemble sugar molecules. This process is also known as carbon fixation.
The Calvin cycle does not require light directly.

Light and Photosynthetic Pigments

Sunlight is electromagnetic energy traveling in waves.
Visible light is a small part of the electromagnetic spectrum (380-750 nm).
Light also behaves as discrete packets of energy called photons.
Shorter wavelengths of light have higher energy photons.
Pigments absorb some wavelengths of light and reflect or transmit others.
Chlorophyll a absorbs blue-violet and red light.
Chlorophyll b absorbs blue and orange light.
Carotenoids absorb other wavelengths, absorb excessive light, and protect chlorophyll.
Absorbed light excites electrons in pigment molecules to higher energy levels.

Photosystems and the Light Reactions

Photosystems are clusters of chlorophyll molecules and proteins in thylakoid membranes.
Light-harvesting complexes capture light energy and transfer it to the reaction-center complex.
A reaction-center complex contains chlorophyll a molecules and a primary electron acceptor. The primary electron acceptor accepts high-energy electrons.
Two types of photosystems cooperate in light reactions: photosystem II and photosystem I (Photosystem II functions first).
Electrons moved from water to NADP+, forming NADPH, during this process.
Light energy powers the transport of H+ into the thylakoid space.
The H+ concentration gradient powers ATP synthesis via chemiosmosis (photophosphorylation).

The Calvin Cycle

The Calvin cycle is a cyclic series of reactions that use CO2 and products of light reactions to assemble sugar molecules (starting with the five-carbon sugar RuBP).
It turns three times to make one G3P molecule, incorporating three molecules of CO2.
Plants use CO2 directly from the air through carbon fixation.
C3 plants use the enzyme rubisco to fix carbon.

C3, C4, and CAM Plants: Adaptations in Varying Environments

C3 plants are widely distributed but can suffer from photorespiration due to CO2 depletion in hot, dry conditions.
C4 plants have a separate carbon fixation step that minimizes photorespiration in hot, dry conditions and concentrates needed CO2 levels..
CAM plants conserve water by opening stomata at night, fixing CO2 into a four-carbon compound and releasing it during the day for the Calvin cycle.
These variations minimise photorespiration.

The Importance of Photosynthesis

Photosynthesis is a cause and potential solution to climate change.
Burning fossil fuels and deforestation increase atmospheric CO2. Conservation of forests and responsible energy usage can mitigate climate change.
Photosynthesis supplies food for plants and virtually all other organisms, along with much-needed oxygen for cellular respiration.

Effects of Rising CO2 Levels

Increasing atmospheric CO2 levels increase plant productivity (growth rates).
Weeds often experience greater growth than crop plants and trees under high CO2 environments.
Plants in high CO2 environments may produce more potent toxins.
Research methods range from small chambers to large-scale field experiments (e.g., FACE experiments).

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Test your understanding of climate change, its causes, and the role of photosynthesis in addressing this global issue. The quiz covers important concepts such as the Paris Agreement, greenhouse gas emissions, and the impact of human activities on climate. Explore the connections between science, technology, and society in relation to climate-related challenges.