Biology Test Questions and Answers

Green plants absorb light energy through the process of photosynthesis. Chlorophyll molecules, which are present in the chloroplasts of plant cells, are responsible for absorbing light energy. These molecules are able to capture the energy from sunlight and convert it into chemical energy, which is then used to fuel the process of photosynthesis. The other options, such as grana, stroma, and starch granules, are not directly involved in the absorption of light energy.

During photosynthesis, light reactions occur in the thylakoid membrane of the chloroplasts. These reactions capture energy from sunlight and convert it into chemical energy in the form of ATP and NADPH. ATP is a molecule that provides energy for cellular processes, while NADPH is a molecule that carries high-energy electrons. The Calvin cycle, on the other hand, takes place in the stroma of the chloroplasts and uses ATP and NADPH to convert carbon dioxide into sugar molecules. Therefore, the correct answer is that light reactions produce NADPH and ATP, while the Calvin cycle produces sugar.

The dark reaction in photosynthesis is called so because it does not require light energy. It is also known as the Calvin cycle or the light-independent reaction. This process takes place in the stroma of the chloroplasts and uses the products of the light reaction (ATP and NADPH) to convert carbon dioxide into glucose. Unlike the light reaction, the dark reaction can occur during both day and night, as it does not rely on light energy for its functioning.

Chlorophyll (a) reflects green light the most. This is because chlorophyll absorbs light most efficiently in the red and blue regions of the electromagnetic spectrum, while reflecting or transmitting light in the green region. As a result, plants appear green to our eyes because the chlorophyll in their cells reflects green light back to us.

In the experiment, the color of light that will cause the plant to produce the smallest number of gas bubbles is green. This is because plants primarily absorb red and blue light for photosynthesis, while green light is reflected and not absorbed as efficiently. Therefore, the green light will have the least impact on the plant's photosynthetic process, resulting in the smallest number of gas bubbles being produced.

In photosynthesis, oxygen is produced during the light reactions. During this process, light energy is absorbed by chlorophyll in the chloroplasts of plant cells. This energy is then used to split water molecules into oxygen, hydrogen ions, and electrons. The oxygen is released as a byproduct, while the hydrogen ions and electrons are used in the production of ATP and NADPH, which are energy-rich molecules needed for the dark reactions. Therefore, the correct answer is light reactions.

During the light reaction in photosynthesis, ATP, a hydrogen donor, and O2 are formed. ATP is produced through the process of photophosphorylation, where light energy is used to convert ADP and inorganic phosphate into ATP. The hydrogen donor in this reaction is water, which is split into hydrogen ions (H+) and oxygen (O2) through a process called photolysis. The oxygen is released as a byproduct. Therefore, the correct answer is ATP, hydrogen donor, and O2.

The diagram shows a plant cell with a large central vacuole, chloroplasts, and a cell wall. These features are characteristic of mesophyll cells, which are found in the middle layer of a leaf. Mesophyll cells are responsible for photosynthesis and have a high concentration of chloroplasts to capture sunlight. The presence of a large central vacuole helps maintain turgor pressure and supports the leaf structure.

Chlorophyll is a pigment found in the chloroplasts of plant cells and is responsible for capturing sunlight during photosynthesis. It absorbs light energy from the sun and converts it into chemical energy, which is then used to power the conversion of carbon dioxide and water into glucose and oxygen. Therefore, the chlorophyll in photosynthesis is primarily used for capturing sunlight.

Light is necessary in the process of photosynthesis to produce ATP and a reducing substance. ATP is the energy currency of cells, and it is produced during the light-dependent reactions of photosynthesis. The reducing substance, usually NADPH, is also produced during these reactions and is used in the Calvin cycle to convert carbon dioxide into glucose. Without light, the light-dependent reactions cannot occur, and ATP and the reducing substance cannot be produced, hindering the process of photosynthesis.

Thylakoids are membrane-bound structures within the chloroplast that contain chlorophyll and other pigments. These pigments are responsible for absorbing light energy during photosynthesis. The primary role of thylakoids is to provide the site for the light-dependent stage of photosynthesis, where light energy is converted into chemical energy in the form of ATP and NADPH. This energy is then used in the light-independent stage of photosynthesis to convert carbon dioxide into glucose. Therefore, the correct answer is that thylakoids provide the site for the light-dependent stage of photosynthesis.

The equation A + C → B + D represents the photosynthesis process in the figure. This equation shows that A and C are reactants that combine to form products B and D.

NADPH2 is used to fix carbon dioxide in the dark reactions of photosynthesis. These reactions, also known as the Calvin cycle, occur in the stroma of the chloroplasts and involve the conversion of carbon dioxide into glucose. NADPH2 is a reduced form of NADP+ and acts as a source of high-energy electrons for the reduction of carbon dioxide. It is produced during the light-dependent reactions of photosynthesis and is used in the Calvin cycle to power the synthesis of glucose.

The primary function of a photosystem in a chloroplast is to absorb light energy for photosynthesis. Photosystems are protein complexes that contain chlorophyll and other pigments. These pigments are responsible for capturing light energy and converting it into chemical energy, which is used to drive the process of photosynthesis. The absorbed light energy is used to power the synthesis of ATP and NADPH, which are essential for the production of glucose and other organic molecules.

Graph D shows the effect of temperature on the rate of photosynthesis because it shows an increase in the rate of photosynthesis with an increase in temperature up to a certain point, after which the rate starts to decrease. This is consistent with the concept of temperature affecting enzyme activity, where an increase in temperature initially increases the rate of enzyme-catalyzed reactions, but beyond a certain temperature, the enzymes denature and the reaction rate decreases.

The graph shows the amount of oxygen produced by a green plant during a 24-hour period. The x-axis represents time, with each letter representing a specific hour. The y-axis represents the amount of oxygen produced. The graph shows a gradual increase in oxygen production from A to D, with the highest point at D. Since midnight is the start of a new day, it would make sense for the highest point of oxygen production to represent midnight. Therefore, letter D represents midnight.

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Xerophytic plants are adapted to survive in arid or dry environments, where water is scarce. To minimize water loss through transpiration, xerophytic leaves have adaptations such as reduced leaf size, thick cuticle, and sunken stomata. Stomata are small openings on the leaf surface that allow for gas exchange, but also lead to water loss. By having stomata on the lower surface, xerophytic leaves can reduce exposure to direct sunlight and wind, which helps to conserve water and prevent excessive transpiration. Therefore, the correct answer is "On lower surface".

The diagram illustrates processes that occur in living organisms. Chlorella alga is the correct answer because it is a type of algae that undergoes photosynthesis, which is one of the vital processes shown in the diagram. Bilharzia worms are parasites that infect humans and animals, and their processes are not depicted in the diagram. Yeast fungus is a single-celled organism that undergoes fermentation, which is not shown in the diagram. Orobanche plant is a parasitic plant that obtains nutrients from other plants, and its processes are not represented in the diagram. Therefore, Chlorella alga is the only organism in the given options that matches the processes depicted in the diagram.

If NADP compound is absent during light reactions, it means that there will be no NADPH formed. NADPH is essential for the fixation of CO2 during the Calvin cycle, which is the dark reaction of photosynthesis. Without NADPH, the CO2 molecules cannot be converted into glucose or other organic compounds. Therefore, the absence of NADP compound during light reactions will result in no fixation of CO2.

In the given figure, the products of photosynthesis reactions are represented. The reactions that occur in this stage are the reduction of CO2. This means that carbon dioxide is being converted into a different form during photosynthesis. The other options, photophosphorylation, reduction of NADP, and splitting of water molecule, are not represented in the figure and therefore do not occur in this stage.

During the dark reaction of photosynthesis, CO2 is reduced to organic compounds. This process, also known as the Calvin cycle, occurs in the stroma of the chloroplasts. In this reaction, ATP and NADPH produced during the light reaction are used to convert CO2 into glucose and other organic molecules. This reduction of CO2 allows plants to store energy in the form of carbohydrates, which can be used for growth and other metabolic processes.

The rate of photosynthesis refers to the speed at which plants convert light energy into chemical energy. While the quality and intensity of light, as well as temperature, can affect the rate of photosynthesis, the duration of light does not have a direct impact. As long as plants receive enough light during the day, the duration of light does not significantly affect the rate of photosynthesis. Therefore, the correct answer is that the rate of photosynthesis does not depend on the duration of light.

14C is the correct answer because it is a radioactive isotope of carbon that can be easily traced and detected. It is commonly used in scientific research to study the dark reactions of photosynthesis, which occur in the stroma of chloroplasts and involve the fixation of carbon dioxide into organic molecules. By labeling carbon dioxide with 14C, scientists can track its movement and incorporation into different compounds during photosynthesis, providing valuable insights into the overall process.

The first stable product of the Calvin cycle is a three-carbon molecule called 3-phosphoglycerate. This molecule is formed through a series of reactions in the cycle, starting with the fixation of carbon dioxide by the enzyme Rubisco. The three-carbon molecule is then further modified and converted into other compounds to eventually regenerate the starting molecule, RuBP, for the continuation of the cycle.

Red light is the most effective in photosynthesis because it is absorbed most efficiently by chlorophyll, the pigment responsible for capturing light energy. Red light has the right energy level to excite the electrons in chlorophyll, allowing them to participate in the light-dependent reactions of photosynthesis. This leads to the production of ATP and NADPH, which are essential for the synthesis of glucose and other organic molecules. Therefore, red light is crucial for driving the photosynthetic process.

In Melvin Calvin's experiment, hot alcohol is important for killing the algae and stopping biochemical reactions. This is necessary to prevent any interference or contamination from the algae, which could affect the accuracy and reliability of the experiment. By stopping biochemical reactions, the hot alcohol allows for the isolation and measurement of specific processes or compounds in the experiment.

Photosynthesis is a complex metabolic process in which plants, algae, and some bacteria convert sunlight, carbon dioxide, and water into glucose and oxygen. It is a reductive process because it involves the reduction of carbon dioxide to glucose, requiring the absorption of energy from sunlight. Additionally, it is an anabolic process because it involves the synthesis of complex molecules (glucose) from simpler ones (carbon dioxide).

Chlorophyll is a pigment found in chloroplasts that is responsible for capturing light energy during photosynthesis. It has Mg+2 as the central metal ion, which allows it to absorb and transfer energy. It also has 55 atoms of carbon, which contribute to its complex structure. Additionally, its molecules are activated by light, allowing them to participate in the energy conversion process. However, chlorophyll is not found in the stroma of chloroplasts. The stroma is the fluid-filled space inside the chloroplast, while chlorophyll is primarily located in the thylakoid membranes.

Phosphoglyceraldhyde is a product of the dark reaction of photosynthesis. The dark reaction, also known as the Calvin cycle, occurs in the stroma of the chloroplast and involves the conversion of carbon dioxide (CO2) into glucose. Phosphoglyceraldhyde is an intermediate molecule formed during this process and is later used to produce glucose and other organic compounds. ATP and NADPH are products of the light reaction, which provide the energy and reducing power needed for the dark reaction, but they are not direct products of the dark reaction itself.

The dark reactions of photosynthesis, also known as the Calvin cycle, are not completely independent of light because they utilize the products of the light reactions. The light reactions of photosynthesis, which occur in the thylakoid membranes of chloroplasts, convert light energy into chemical energy in the form of ATP and NADPH. These products are then used in the dark reactions, which take place in the stroma of the chloroplasts, to convert carbon dioxide into glucose through a series of enzymatic reactions. Therefore, the dark reactions depend on the products generated by the light reactions to fuel the synthesis of carbohydrates.

The production of enzymes inside the chloroplast will be affected by decreasing nitrogen element. Nitrogen is an essential component of amino acids, which are the building blocks of proteins. Enzymes are proteins that catalyze biochemical reactions, so a decrease in nitrogen availability would result in a decrease in enzyme production.

Green plants require sunlight for photosynthesis, which is the process by which they convert light energy into chemical energy. In the deep oceans, sunlight can only penetrate to a certain depth, beyond which the light intensity is very low. As a result, green plants are unable to receive enough light to carry out photosynthesis and therefore cannot survive in these conditions.

In the dark reactions of photosynthesis, NADPH2 is used to fix CO2. This means that NADPH2 provides the necessary reducing power to convert carbon dioxide into organic molecules such as glucose. This process is essential for the production of carbohydrates and other organic compounds needed for plant growth and metabolism.

The dark reactions, also known as the Calvin cycle, occur in the stroma of the chloroplasts in the presence of carbon dioxide, NADPH2, and ATP. These reactions use the energy from ATP and the reducing power of NADPH2 to convert carbon dioxide into glucose through a series of enzyme-catalyzed reactions. The carbon dioxide is fixed and reduced using the energy and reducing power provided by NADPH2 and ATP, respectively. Therefore, the correct answer is carbon dioxide, NADPH2, and ATP.

A molecule of water, transported from the stem, passes through the xylem vessel, then the spongy mesophyll cell, and finally the air space before reaching the air surrounding the leaf. Therefore, the correct order is C.

The spongy tissue in plants consists of elongated parenchymatous cells with wide intercellular spaces in between them. These spaces allow for the exchange of gases, such as carbon dioxide and oxygen, during photosynthesis.

If NADP molecules are not reduced to NADPH2 in the light reactions of photosynthesis, phosphoglyceraldehyde will not be formed. NADPH2 is necessary for the conversion of carbon dioxide into phosphoglyceraldehyde, which is a crucial step in the Calvin cycle. Without phosphoglyceraldehyde, the production of glucose and other organic molecules cannot occur. This would ultimately disrupt the overall process of photosynthesis and hinder the plant's ability to produce energy and sustain itself.

The graph shows that at point X, the rate of photosynthesis is not increasing with increasing light intensity. This suggests that light intensity is not the limiting factor at this point. However, the graph does not provide any information about the other factors, such as carbon dioxide concentration, chlorophyll availability, and water availability. Therefore, we cannot determine if any of these factors are limiting the rate of photosynthesis at point X.

Van Niel was the first scientist to demonstrate that photosynthesis is a light dependent reaction in which hydrogen from an oxidisable compound reduces carbon dioxide to cellular material. This means that he discovered that photosynthesis requires light as an energy source and that the process involves the reduction of carbon dioxide to produce organic compounds. Blackman, Melvin Calvin, and the scientists at California University may have made important contributions to the understanding of photosynthesis, but they were not the first to demonstrate the light-dependent nature of the process.

The level of PGAL falls after CO2 is removed because carbon dioxide is the source of carbon that is reduced by hydrogen to form PGAL. Without CO2, there is no source of carbon for the formation of PGAL, leading to a decrease in its level.

The level of PGAL rises after the light is switched off because the formation of PGAL occurs in the dark reactions of photosynthesis where the light is not the limiting factor. This means that the production of PGAL can continue even in the absence of light.

The graph shows the amount of ATP produced inside plant cells. The only condition that leads to ATP production is light. This is supported by the fact that ATP is primarily generated through photosynthesis, which requires light as an energy source. Therefore, the graph indicates that ATP production is dependent on the presence of light.

In the given transverse section of a dicotyledonous plant leaf, structure (A) is the upper epidermis, structure (B) is the palisade tissue, structure (C) is the spongy tissue, structure (D) is the lower epidermis, and structure (E) is the stomata. The palisade tissue is located just below the upper epidermis and contains tightly packed, vertically oriented cells that are responsible for photosynthesis. The spongy tissue is located below the palisade tissue and contains loosely arranged cells with air spaces, allowing for gas exchange. The stomata are small openings on the lower epidermis that regulate the exchange of gases and water vapor between the leaf and the environment.

Photophosphorylation is the process in which energy from sunlight is used to convert ADP (adenosine diphosphate) into ATP (adenosine triphosphate), which is the main energy currency in cells. In the figure, it is shown that Energy 1 is used in photophosphorylation. Therefore, the correct answer is Photophosphorylation.

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The correct answer is that the midrib contains the main vascular bundle of the leaf. This can be inferred from the information given in the question, which states that by examining a T.S of the vascular bundle of a dicot plant leaf, we can see that the midrib contains the main vascular bundle. Therefore, the midrib is the location where the xylem and phloem tissues are found in the leaf.

In an experiment similar to that of Calvin, CO2 gas with O18 isotope was used. This isotope of oxygen would be incorporated into the compounds produced in the experiment. Since PGAL is an intermediate compound in the Calvin cycle, it would be one of the first compounds produced. Therefore, the correct answer is "PGAL contains O18".

In the dark reactions of photosynthesis, also known as the Calvin cycle, carbon dioxide (CO2) molecules are fixed and converted into glucose or other sugars. Hexose refers to a sugar molecule with six carbon atoms. Each molecule of hexose requires fixing six molecules of CO2. Therefore, to build up four molecules of hexose, a total of 24 molecules of CO2 are needed.

The diagram shows that the plant has leaves that are green in the middle and white around the edges. This suggests that the green middle part of the leaves is receiving the necessary factors for photosynthesis, while the white edges are not. Therefore, the leaf areas Q and S, which are white, have only one missing factor needed for photosynthesis.