Test: Photosynthesis: Introduction & Historical Background - ACT MCQ

During this process, the electrons in water are removed and passed to the reaction center chlorophyll. The associated hydrogen ions are released from the water molecule, and after two water molecules are thus split, the oxygen atoms join to form molecular oxygen (O2), a waste product of photosynthesis.

About 80 to 90 % of photosynthesis is carried out by the algae or phytoplankton due to the abundance of their habitat all over the Earth while land plants can carry out only 10% of it due to the limitation of their conditions and habitat.

The process of taking in CO₂ by plants and releasing O₂ is occurs in photosynthesis. Photosynthesis is the process by which green plants prepare their own food from CO2 and water using the energy from the sunlight. Glucose is formed in this process which acts as food for the plants. Reaction of photosynthesis is:

6 CO₂ + 6 H₂O → C₆H₁₂O₆ + 6 O₂

Photosynthesis is the process by which plants use carbon dioxide and water in presence of sunlight and chlorophyll to produce glucose and oxygen. Carbon dioxide is taken from the atmosphere and water is absorbed from the soil. Oxygen is released in the air as a by-product of the process.

Photosynthesis is the process by which organisms that contain the pigment chlorophyll convert light energy into chemical energy which can be stored in the molecular bonds of organic molecules (e.g., sugars). During the process of photosynthesis, light penetrates the cell and passes into the chloroplast. The light energy is intercepted by chlorophyll molecules on the granal stacks. Some of the light energy is converted to chemical energy. During this process, a phosphate is added to a molecule to cause the formation of ATP. The third phosphate chemical bond contains the new chemical energy. The ATP then provides energy to some of the other photosynthetic reactions that are causing the conversion of CO₂ into sugars.

In photosynthesis:
- Plants use light energy to convert carbon dioxide and water into glucose.
- Chlorophyll in plant cells captures light energy for this process.
- Glucose is a form of chemical energy that plants use for growth and metabolism.
- Oxygen is released as a byproduct.
- This process is fundamental for life on Earth as it produces food and oxygen.

Frederick Frost Blackman proposed the law of limiting factors. Blackman proposed this law in 1905 according to which, a chemical process depends on multiple factors the rate of the process will be limited by the pace of the slowest factor or limiting factor.

Glucose is not a product of the light reactions of photosynthesis. It is produced in the Calvin cycle, which uses ATP and NADPH generated during the light reactions to fix carbon dioxide into glucose.

The maximum photosynthesis takes place in blue and red regions of the visible light as indicated by the absorption spectra of chlorophyll a and chlorophyll b. Absorption spectrum of a particular pigment is the curve plotted on a graph paper representing the amount of light absorbed at each wavelength by that pigment. The absorption spectra of these pigments show that they absorb maximum at 480 nm (blue light) and 680 nm (red light) regions of spectrum.

Thus, the correct answer is option C.

CO₂ is reduced in carbohydrates or sugars. Hence it is more essential as a raw material for food formation.

The correct answer is B: 0.03%.

- The concentration of CO2 in the atmosphere is crucial for understanding climate change.
- CO2 levels are typically measured in parts per million (ppm) or percentage (%).
- 0.03% represents 300 parts per million, which is close to the current atmospheric CO2 concentration.
- This level is significant because even small percentage changes can have substantial effects on the Earth's climate.
- Monitoring and controlling CO2 levels are essential for environmental sustainability.

Rubisco (Ribulose-1,5-bisphosphate carboxylase/oxygenase) is the enzyme responsible for fixing carbon dioxide in the Calvin cycle. It catalyzes the first step of the cycle, the carboxylation of ribulose-1,5-bisphosphate, which is a critical step in the synthesis of organic molecules from carbon dioxide.

Chlorophyll a is indeed essential for photosynthesis as it plays a central role in capturing light energy and converting it into chemical energy, which is the basis of the assertion. The reason correctly explains this role

The isotope of carbon extensively used in photosynthesis studies is:

- Correct Answer: B: C¹⁴

Explanation:
- C¹⁴ is the isotope utilized in carbon dating and tracing the pathways of carbon in biological systems.
- Its presence allows researchers to track the movement of carbon through various biological processes.
- The radioactive nature of C¹⁴ makes it a valuable tool for understanding carbon cycling in living organisms.

The Z-scheme represents the linear flow of electrons from water to NADP⁺ during the light reactions of photosynthesis. This model illustrates how the energy from sunlight is used to drive the electrons' movement across the photosystems, ultimately leading to the production of ATP and NADPH. Interesting fact: The Z-scheme is named for its characteristic shape when the energy levels of the electron transport components are plotted, resembling the letter "Z."

Enzyme RUBISCO has an affinity for both CO₂ and O₂ and its name changes depending on who it is binding to. When it binds to oxygen, it is called ribulose bisphosphate oxygenase. Though the affinity of RUBISCO to oxygen is said to be more than that for CO₂, it depends upon the concentration of O₂ and CO₂ and temperature conditions which ultimately decide what RUBISCO binds to.

The mitochondrion is not a component of a chloroplast. Chloroplasts, the site of photosynthesis in plant cells, contain thylakoids, stroma, and grana as their main components. Mitochondria are separate organelles responsible for cellular respiration.

• The raw materials of photosynthesis are water and CO₂.
• During photosynthesis in plants, water, and carbon dioxide react in the presence of light and chlorophyll, to give carbohydrates (glucose) and oxygen.

6CO₂ + 6H₂O + Sunlight = C₆H₁₂O₆ + 6O₂ 

The correct answer is:

- Carbohydrates and oxygen

Explanation:
- During photosynthesis, plants take in carbon dioxide and water, and using sunlight, they convert these raw materials into carbohydrates (such as glucose) and oxygen.
- Carbohydrates are essential for providing energy to the plant and serving as building blocks for growth.
- Oxygen is released into the atmosphere as a byproduct of photosynthesis, which is crucial for the survival of most living organisms on Earth.

The Calvin cycle primarily produces glucose, utilizing ATP and NADPH generated during the light reactions of photosynthesis. This cycle is a series of enzyme-assisted chemical reactions that convert carbon dioxide and other compounds into glucose.

J. Priestley (1772) carried out very interesting experiment on Bell jar, rat, pudina or mint and candle. He came to conclude that plants purify air (burning of candles), and gaseous exchange occurs during photosynthesis.

Priestley observed that a candle burning in a closed space – a bell jar, soon gets extinguished. Similarly, a mouse would soon suffocate in a closed space. He concluded that a burning candle or an animal that breathe the air, both somehow, damage the air. But when he placed a mint plant in the same bell jar, he found that the mouse stayed alive and the candle continued to burn. Priestley hypothesized as follows: Plants restore the air which breathing animals and burning candles remove.

Blackmann had proposed several limiting factors for photosynthesis. Water is an essential component of photosynthesis. It is a limiting factor as well. 1% of absorbed water is used during photosynthesis.

The correct answer is C: Photosynthesis.
- Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy, usually from the sun, into chemical energy stored in glucose.
- Chlorophyll, the green pigment in plants, is responsible for capturing light energy needed for photosynthesis.
- Only the green parts of plants, like leaves, contain chlorophyll and are capable of carrying out photosynthesis.
- During photosynthesis, plants use carbon dioxide and water to produce glucose and oxygen.
- This process is vital for the survival of plants and many other organisms on Earth.

• Light energy is mainly used in photosynthesis for activation of chlorophyll.
• Chlorophyll is in an inactive state. It becomes active only in the presence of sunlight.
• These rays fall on chloroplast which in turn activates the chlorophyll.

Von Sachs did not provide evidence for the production of carbon dioxide during photosynthesis. Instead, he showed that plants release oxygen when exposed to light. 

Photosynthesis is a crucial process on Earth, but not all its outcomes are universally positive. Here's why the "Increase in greenhouse effect" is not a significant of photosynthesis:

- Photosynthesis reduces the greenhouse effect by absorbing CO2.
- It does not contribute to an increase in the greenhouse effect.
- The process actually helps to mitigate climate change by converting CO2 into oxygen and glucose.
- The other options listed (Glucose synthesis, O2 for ozone, O2 for respiration) highlight the vital roles of photosynthesis.

A milestone contribution to the understanding of photosynthesis was that made by a microbiologist, Cornelius van Niel (1897-1985), who, based on his studies of purple and green bacteria, demonstrated that photosynthesis is essentially a light-dependent reaction  

• Greenlight is the least effective among the following.
• Greenlight is reflected by green leaves, so cannot be absorbed.
• But blue light gives maximum absorption peak of chlorophyll and is most effective.

Jan Ingenhousz (1730-1799) showed that sunlight is essential to the plant process