Cell Bio - Chapter 7 (Photosynthesis)

Photosynthesis is the process by which organisms convert sunlight into energy. Plants are well-known for their ability to perform photosynthesis, but algae and some bacteria are also capable of this process. Algae are simple, plant-like organisms that can be found in various aquatic environments, while certain bacteria, such as cyanobacteria, possess pigments that enable them to carry out photosynthesis. Therefore, the correct answer is that plants, algae, and some bacteria are capable of photosynthesis.

Plants appear green because they reflect green wavelengths of light and absorb blue and red light. This is due to the presence of chlorophyll, the pigment responsible for photosynthesis. Chlorophyll absorbs light energy in the blue and red parts of the spectrum, while reflecting green light. This allows plants to utilize the absorbed light for energy production, while the reflected green light gives them their characteristic color.

Grana refers to a stack of thylakoid membrane structures in the chloroplast. Thylakoid membranes are where the light-dependent reactions of photosynthesis occur, and they contain chlorophyll and other pigments that capture sunlight. The grana are important for increasing the surface area available for photosynthesis and for organizing the thylakoid membranes in an efficient manner. They play a crucial role in the process of converting light energy into chemical energy in plants.

The stroma refers to the central fluid-filled space of the chloroplast. This space is where various metabolic reactions occur, including the synthesis of organic molecules through photosynthesis. The stroma also contains enzymes, DNA, and ribosomes, which are necessary for the chloroplast to carry out its functions.

Ribulose biphosphate carboxylase, also known as rubisco, is the major enzyme responsible for carbon dioxide fixation in photosynthesis. It catalyzes the first step of the Calvin cycle, where carbon dioxide is converted into an organic molecule. Rubisco combines carbon dioxide with a five-carbon sugar, ribulose biphosphate, to produce two molecules of a three-carbon compound called 3-phosphoglycerate. This reaction is crucial for plants and other photosynthetic organisms to convert atmospheric carbon dioxide into usable organic compounds for growth and energy production.

The Calvin cycle is a series of chemical reactions that occur in the chloroplasts of plants during photosynthesis. It is responsible for converting carbon dioxide from the atmosphere into glucose, a process known as carbon dioxide fixation. This glucose can then be used for energy production or stored as starch. Therefore, carbon dioxide fixation is most closely related to the Calvin cycle.

During photosynthesis, plants use sunlight to convert carbon dioxide and water into oxygen and carbohydrates (such as glucose). Oxygen is released as a byproduct, which is essential for the survival of many organisms, including humans. Carbohydrates, on the other hand, serve as a source of energy for plants and are also important for the growth and development of the plant. Therefore, the correct answer is oxygen and carbohydrate.

Cactus would be a CAM plant because CAM plants, or Crassulacean Acid Metabolism plants, have a unique adaptation to arid environments. They open their stomata at night to reduce water loss through transpiration and store carbon dioxide as organic acids. During the day, the stomata close to conserve water. Cacti are well-known examples of CAM plants as they are able to survive in hot and dry desert conditions by using this specialized mechanism.

Sunlight plays a crucial role in photosynthesis by exciting electrons in chlorophyll. Chlorophyll is a pigment found in chloroplasts, which absorbs light energy. When sunlight hits chlorophyll molecules, it energizes the electrons within them, causing them to become excited. These excited electrons are then used in the process of converting carbon dioxide and water into glucose and oxygen. Thus, the function of sunlight in photosynthesis is to excite electrons in chlorophyll, initiating the process of converting light energy into chemical energy.

The given statement is true. Phosphoenylpyruvate carboxylase (PEPcase) is an enzyme that plays a crucial role in C4 photosynthesis. It catalyzes the fixation of carbon dioxide (C1) to phosphoenolpyruvate (PEP), a three-carbon compound, to form oxaloacetate (C4). This reaction occurs within the mesophyll cells of C4 plants. C4 plants have a specialized carbon fixation pathway that allows them to minimize photorespiration and enhance their efficiency in capturing and utilizing carbon dioxide. Therefore, the given statement is correct.

In the Calvin cycle, the first event is the attachment of carbon dioxide to the five-carbon RuBP molecule. This reaction is assisted by large quantities of RuBP carboxylase enzyme. This enzyme helps to catalyze the reaction and facilitate the attachment of carbon dioxide to RuBP. Therefore, the statement is true.

Fossil fuels are formed from the remains of plants and animals that lived millions of years ago. These organisms absorbed energy from the sun through photosynthesis and stored it in their tissues. Over time, these organic materials were buried and subjected to heat and pressure, which transformed them into fossil fuels such as coal, oil, and natural gas. Therefore, it is true that fossil fuels contain energy that was originally derived from photosynthesis.

The statement is false because the light-dependent reactions of photosynthesis actually occur in the thylakoid membrane of the chloroplast, not in the stroma. The thylakoid membrane contains chlorophyll and other pigments that capture light energy, which is then used to generate ATP and NADPH. These reactions take place in the thylakoid membrane, while the stroma is the fluid-filled space surrounding the thylakoid membrane where the light-independent reactions (Calvin cycle) occur.

The Calvin cycle uses three molecules of CO2 to produce six molecules of G3P. However, only one G3P molecule is used to form a carbohydrate molecule. The other five G3P molecules are used to regenerate more RuBP, which is an important molecule in the Calvin cycle. This regeneration process ensures that the Calvin cycle can continue and produce more carbohydrate molecules.

Chlorophyll c is not a major photosynthetic pigment in plants. The major photosynthetic pigments in plants are chlorophyll a, chlorophyll b, and carotenoid pigments. Chlorophyll c is found in certain algae but is not as prevalent in plants.

Photosystem I passes electrons on to Photosystem II. This statement is not true because in the process of photosynthesis, it is actually Photosystem II that passes electrons on to Photosystem I. Photosystem II is responsible for capturing light energy and using it to split water molecules, releasing electrons in the process. These electrons are then passed on to Photosystem I, where they are further energized and used in the production of ATP and NADPH.

Chemiosmotic ATP synthesis does not occur in the cytosol of the cell. It actually occurs in the mitochondria, specifically in the inner mitochondrial membrane. This process involves the movement of protons across the membrane, creating an electrochemical gradient, which is then used by ATP synthase to generate ATP.

Plants that conduct C-4 metabolism are desert plants because C-4 metabolism is an adaptation that allows plants to efficiently use carbon dioxide in environments with high temperatures and limited water availability, such as deserts. C-4 plants have specialized leaf anatomy and biochemical pathways that enable them to minimize water loss and maximize carbon fixation, making them well-suited for arid conditions. Therefore, it is true that desert plants often employ C-4 metabolism.

In the Calvin cycle, the first event is the attachment of carbon dioxide to the five-carbon RuBP molecule. This forms a six-carbon molecule, which then immediately breaks down into two three-carbon PGA molecules. Therefore, the statement that the attachment of carbon dioxide forms a six-carbon molecule that immediately breaks down into three-carbon PGA molecules is true.

G3P (glyceraldehyde 3 phosphate) is a molecule that plays a crucial role in the process of photosynthesis in plants. It is used in the formation of fatty acids, amino acids, and sucrose. However, it is not involved in the production or formation of oxygen. Oxygen is a byproduct of photosynthesis and is released into the atmosphere as plants convert carbon dioxide and water into glucose and oxygen. Therefore, G3P is not used by plants for the formation of oxygen.

Glyceradehyde-3-phosphate (G3P) is a product of the Calvin Cycle that is used to form glucose phosphate, amino acids, or fatty acids. G3P is an important molecule in photosynthesis as it serves as a precursor for the synthesis of various organic compounds. It can be converted into glucose phosphate, which is used in the production of glucose, a vital energy source for cells. G3P can also be used in the synthesis of amino acids, the building blocks of proteins, and fatty acids, which are essential components of cell membranes and energy storage molecules.

The given answer states that all of the choices are correct. This means that C-4 plants indeed store carbon dioxide temporarily as oxaloacetate, are found in hot, dry climates, and have a higher net photosynthetic rate compared to C-3 plants. Therefore, all the statements provided in the options are accurate.

In the Calvin cycle, the first event involves the attachment of carbon dioxide to the five-carbon RuBP molecule. This process decreases the levels of carbon dioxide in the cell, which in turn increases the diffusion gradient. This means that there is a higher concentration of carbon dioxide outside the cell compared to inside, leading to the movement of carbon dioxide into the cell. Therefore, the statement is true.

The graph would appear just like the action spectrum with peaks at violet/blue and orange/red and a trough at yellow/green. This is because the action spectrum indicates the wavelengths of light that are most efficiently absorbed by chlorophyll for photosynthesis. Therefore, when narrow bands of unicolored light are shown on the aquatic plant, the highest rate of photosynthesis, indicated by the number of oxygen bubbles produced, would be observed for the violet/blue and orange/red light, while the lowest rate would be observed for the green/yellow light.

During electron transport between photosystems I and II, protons accumulate in the thylakoid space. These excess protons then move from the thylakoid space to the stroma through an ATP synthase complex channel that generates ATP. This movement of protons is essential for the production of ATP, which is a form of energy that can be used by the cell. Therefore, this process allows for the conversion of light energy into chemical energy in the form of ATP.

Glucose is the correct answer because it is a product of photosynthesis and serves as the chief source of energy for most organisms. Through cellular respiration, glucose is broken down to release energy that is used for various metabolic processes in cells. Oxygen is produced as a byproduct of photosynthesis, but it is not the chief source of energy. Sucrose is a disaccharide that can be broken down into glucose and fructose, so it is not the direct product of photosynthesis. Therefore, the correct answer is glucose.

Photosynthesis is the process by which plants convert sunlight into energy, and oxygen is produced as a byproduct. Photosystem one and photosystem two are both involved in capturing light energy and converting it into chemical energy. The splitting of water is a crucial step in photosynthesis that provides electrons and protons for the production of oxygen. Therefore, the correct answer is photosystem one, as it is an essential component in the process of oxygen production during photosynthesis.

Photorespiration is not the process by which light is used to release the stored energy in carbohydrate molecules. Instead, it is a wasteful process that occurs in plants when there is a shortage of carbon dioxide. During photorespiration, instead of fixing carbon dioxide, plants use oxygen, resulting in the release of carbon dioxide and the consumption of energy. Therefore, the given statement is false.

Photorespiration is a process that occurs in plants when there is a shortage of carbon dioxide. It involves the breakdown of organic compounds in the presence of light, leading to the release of carbon dioxide. C3 plants, which include the majority of plant species, are more prone to photorespiration compared to C4 and CAM plants. C4 plants have adapted mechanisms to minimize photorespiration, while CAM plants have a different carbon fixation pathway that reduces the occurrence of photorespiration. Therefore, the correct answer is C3 plants.

When chlorophyll is extracted and exposed to red or blue light, it fluoresces brightly. However, when chlorophyll is inside chloroplasts and exposed to the same light, there is no fluorescence. This suggests that the excited electrons in chlorophyll are being transferred to electron acceptors in the chloroplast, rather than being emitted as fluorescence.

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The cyclic electron pathway is a process in photosynthesis that involves only Photosystem I. It produces ATP by generating a proton gradient across the thylakoid membrane, but it does not produce NADPH. NADPH is produced in the non-cyclic electron pathway, which involves both Photosystem I and Photosystem II. In the cyclic pathway, electrons lost from Photosystem I return to Photosystem I, completing a closed loop.

The noncyclic electron pathway does not produce carbohydrates through carbon dioxide fixation. This pathway is responsible for producing ATP and NADPH, which are used in the Calvin cycle to fix carbon dioxide and produce carbohydrates. However, the actual fixation of carbon dioxide occurs in the Calvin cycle, not in the noncyclic electron pathway.

The given answer accurately describes the reactions involved in the reduction of CO2 in the Calvin cycle. It states that energy in the form of ATP is required and is hydrolyzed to ADP. The substrate BPG is reduced, while the coenzyme NADPH is oxidized. This explanation aligns with the information provided in the question and accurately characterizes the reactions involved in the Calvin cycle.

If plants were only able to undergo the cyclic pathway, more NADPH would not be produced during the cyclic electron pathway. The cyclic pathway only produces ATP and does not generate NADPH. NADPH is produced during the non-cyclic pathway, also known as the linear electron pathway.

In the Calvin cycle, the first event is not the attachment of carbon dioxide to the five-carbon RuBP molecule. The first event is the attachment of carbon dioxide to a three-carbon molecule called ribulose-1,5-bisphosphate (RuBP), forming an unstable six-carbon molecule. This six-carbon molecule then breaks down into two molecules of a three-carbon compound called 3-phosphoglycerate, which is the base for starch, sucrose, cellulose, and other organic molecules. Therefore, the statement that the attachment of carbon dioxide immediately becomes a six-carbon sugar is false.

CAM plants have carbon dioxide fixation and carbon dioxide uptake separated by time. Unlike C-4 plants, which have these processes separated by location within the plant, CAM plants open their stomata at night to take in carbon dioxide and store it as an organic acid. During the day, the stomata remain closed to prevent water loss, and the stored carbon dioxide is used for photosynthesis. This adaptation allows CAM plants to survive in arid environments with limited water availability. Therefore, the correct answer is "have these processes separated by time."

The given correct answer states that all of the options provided are correct except for the nutrient conversion. This means that the additional experiment that would provide evidence for the rest of the story is not related to the conversion of nutrients in the soil. However, without further information, it is not clear what specific experiment would provide evidence for the rest of the story.