1.
Which of these types of organisms produce the biosphere's food supply?
Correct Answer
B. AutotropHs
Explanation
Autotrophs are organisms that are able to produce their own food through photosynthesis or chemosynthesis, using energy from the sun or inorganic compounds. They are the primary producers in the biosphere, converting sunlight or chemical energy into organic molecules that serve as food for other organisms. Consumers, on the other hand, rely on the consumption of other organisms for their energy and nutrients. Heterotrophs are a type of consumer that cannot produce their own food and obtain energy by consuming other organisms. Therefore, autotrophs are the correct answer as they are responsible for producing the biosphere's food supply.
2.
How does carbon dioxide enter the leaf?
Correct Answer
C. Through the stomata
Explanation
Carbon dioxide enters the leaf through the stomata. Stomata are small openings on the surface of the leaf that allow gases to enter and exit the plant. When the stomata are open, carbon dioxide from the atmosphere diffuses into the leaf and reaches the chloroplasts where photosynthesis takes place. The vascular system, on the other hand, is responsible for transporting water and nutrients throughout the plant, but it does not directly play a role in the entry of carbon dioxide into the leaf.
3.
Cellular respiration and photosynthesis are similar in that both involve _____.
Correct Answer
B. Redox reactions
Explanation
Cellular respiration and photosynthesis are similar in that both involve redox reactions. Redox reactions, also known as oxidation-reduction reactions, involve the transfer of electrons from one molecule to another. In cellular respiration, glucose is oxidized and oxygen is reduced to produce energy in the form of ATP. In photosynthesis, water is oxidized and carbon dioxide is reduced to produce glucose and oxygen. Both processes rely on redox reactions to transfer electrons and produce energy or organic molecules.
4.
The source of the oxygen produced by photosynthesis has been identified through experiments using radioactive tracers. The oxygen comes from _____.
Correct Answer
B. Water
Explanation
Through experiments using radioactive tracers, it has been determined that the source of the oxygen produced by photosynthesis is water. This means that during the process of photosynthesis, water molecules are split, releasing oxygen as a byproduct.
5.
The wavelengths of light absorbed by pigments in the granum are mainly in which range?
Correct Answer
B. Blue-violet and red-orange
Explanation
The pigments in the granum primarily absorb light in the blue-violet and red-orange range. This means that these wavelengths of light are absorbed by the pigments, while other wavelengths are reflected. This is why plants appear green to us, as green light is not absorbed but rather reflected by the pigments. Additionally, carotenoids also absorb light in a specific range, but the question does not specify that this is the main range of absorption in the granum.
6.
Which one of the following colors is most strongly reflected by chlorophyll?
Correct Answer
D. Green
Explanation
Chlorophyll is the pigment responsible for capturing light energy in plants for photosynthesis. It absorbs light most strongly in the blue and red regions of the electromagnetic spectrum, while reflecting or transmitting green light. This is why plants appear green to our eyes. Therefore, the color green is most strongly reflected by chlorophyll.
7.
When chloroplast pigments absorb light, _____.
Correct Answer
C. Their electrons become excited
Explanation
When chloroplast pigments absorb light, their electrons become excited. This means that the energy from the absorbed light causes the electrons in the pigments to move to a higher energy state. This excited state allows the electrons to participate in various chemical reactions, such as the conversion of light energy into chemical energy through photosynthesis.
8.
The light reactions of photosynthesis generate high-energy electrons, which end up in _____. The light reactions also produce _____ and _____.
Correct Answer
D. NADpH ... ATP ... oxygen
Explanation
During the light reactions of photosynthesis, high-energy electrons are generated. These electrons are then transferred to NADP+ to form NADPH, which is an energy-rich molecule used in the Calvin cycle to produce sugar. Additionally, the light reactions also produce ATP, which is another energy molecule used in the Calvin cycle. Finally, oxygen is released as a byproduct of the light reactions.
9.
During photosynthesis in chloroplasts, O2 is produced from _____ via a series of reactions associated with _____.
Correct Answer
B. H2O ... the water-splitting pHotosystem
Explanation
During photosynthesis in chloroplasts, O2 is produced from H2O via a series of reactions associated with the water-splitting photosystem. This process, known as photolysis, occurs in the thylakoid membrane of the chloroplast. The water-splitting photosystem, also known as Photosystem II, uses light energy to split water molecules into oxygen, protons (H+), and electrons. The oxygen released is a byproduct of this reaction and is essential for sustaining life on Earth.
10.
The _____ of photosynthesis performs a task similar to that of the _____ of cellular respiration.
Correct Answer
C. NADpH ... NADH
Explanation
The correct answer is NADPH ... NADH. During photosynthesis, NADPH is produced in the light-dependent reactions and carries high-energy electrons to the Calvin cycle, where it acts as a reducing agent. Similarly, during cellular respiration, NADH is produced in the Krebs cycle and carries high-energy electrons to the electron transport chain, where it donates these electrons to generate ATP. Both NADPH and NADH play crucial roles in transferring energy during these processes.
11.
Both mitochondria and chloroplasts _____.
Correct Answer
D. Use an H+ gradient to produce ATP
Explanation
Mitochondria and chloroplasts both use an H+ gradient to produce ATP. This process, known as chemiosmosis, involves the movement of protons across a membrane, which creates a gradient of H+ ions. This gradient is then used by ATP synthase to generate ATP. Mitochondria use this process during cellular respiration, while chloroplasts use it during photosynthesis.
12.
In photosynthesis, what is the fate of the oxygen atoms present in CO2? They end up _____
Correct Answer
C. In sugar molecules and in water
Explanation
During photosynthesis, the oxygen atoms present in CO2 are utilized to form sugar molecules and water. This process involves the conversion of carbon dioxide and water into glucose and oxygen through the use of sunlight and chlorophyll. Oxygen atoms from CO2 are released as molecular oxygen (O2) into the atmosphere, while others are incorporated into sugar molecules and water, which are essential for the plant's growth and energy production.
13.
In an experiment, a plant was given _____ containing radioactive 18O, and the radioactive oxygen atoms were used to make sugar.
Correct Answer
B. Carbon dioxide
Explanation
Plants undergo a process called photosynthesis where they convert carbon dioxide and water into glucose (sugar) and oxygen using energy from sunlight. In this experiment, the plant was given carbon dioxide containing radioactive 18O, which means that the oxygen atoms in the carbon dioxide were radioactive. These radioactive oxygen atoms were then used by the plant to synthesize sugar through photosynthesis.
14.
In photosynthesis, plants use carbon from _____ to make sugar and other organic molecules.
Correct Answer
A. Carbon dioxide
Explanation
Plants use carbon dioxide in photosynthesis to make sugar and other organic molecules. During photosynthesis, plants capture carbon dioxide from the atmosphere and convert it into glucose, which is used as a source of energy. This process takes place in the chloroplasts of plant cells, where sunlight provides the energy needed to drive the chemical reactions. Water is also required in photosynthesis, but it is used to provide hydrogen atoms for the synthesis of glucose, while carbon dioxide is the source of carbon atoms. The sun is necessary for photosynthesis to occur, but it does not directly provide the carbon needed for sugar production.
15.
What effect does photosynthesis have on the greenhouse effect?
Correct Answer
A. It reduces atmospHeric carbon dioxide and thus reduces greenhouse warming.
Explanation
Photosynthesis is the process by which plants convert carbon dioxide into oxygen, reducing the amount of carbon dioxide in the atmosphere. Since carbon dioxide is a greenhouse gas that contributes to the greenhouse effect and global warming, reducing its concentration helps to mitigate the greenhouse effect. Therefore, photosynthesis reduces atmospheric carbon dioxide and thus reduces greenhouse warming.
16.
Carbon dioxide makes up about _____ of the air we breathe.
Correct Answer
A. 0.03%
Explanation
Carbon dioxide makes up about 0.03% of the air we breathe. This is a relatively small percentage, indicating that carbon dioxide is a minor component of the Earth's atmosphere. Despite its low concentration, carbon dioxide plays a crucial role in the Earth's climate system and is a greenhouse gas that contributes to global warming.
17.
Why is NADP+ needed in photosynthesis?
Correct Answer
E. It forms NADpH to be used in the Calvin cycle.
Explanation
NADP+ is needed in photosynthesis because it is converted into NADPH, which is an essential molecule in the Calvin cycle. The Calvin cycle is the second stage of photosynthesis where carbon dioxide is converted into glucose. NADPH provides the necessary electrons and hydrogen ions for this process. Without NADP+, the Calvin cycle would not be able to proceed, and glucose production would be hindered. Therefore, NADP+ plays a crucial role in photosynthesis by forming NADPH to be used in the Calvin cycle.
18.
The Calvin cycle is a series of reactions that _____.
Correct Answer
D. Assemble sugar molecules by incorporating carbon
Explanation
The Calvin cycle is a series of reactions that assemble sugar molecules by incorporating carbon. This process occurs in the stroma of chloroplasts and is an essential part of photosynthesis. The cycle uses carbon dioxide, ATP, and NADPH to produce glucose, which is a form of chemical energy. The Calvin cycle does not directly produce oxygen gas or NADPH, although it relies on the products of the light-dependent reactions, which produce oxygen gas and NADPH. Therefore, the correct answer is "assemble sugar molecules by incorporating carbon".
19.
The "photo-" part of the word "photosynthesis" refers to _____, whereas "-synthesis" refers to _____.
Correct Answer
C. The light reactions that occur in the thylakoids ... the incorporation of carbon dioxide
Explanation
The "photo-" part of the word "photosynthesis" refers to the light reactions that occur in the thylakoids, whereas "-synthesis" refers to the incorporation of carbon dioxide.
20.
The photosynthetic event known as the Calvin cycle occurs in the _____.
Correct Answer
A. Stroma
Explanation
The Calvin cycle, which is a series of biochemical reactions that take place in the chloroplasts of plants, occurs in the stroma. The stroma is the fluid-filled space within the chloroplasts, where the enzymes and other molecules necessary for the Calvin cycle are located. This is where carbon dioxide is converted into glucose using the energy from sunlight, and it is an essential part of the process of photosynthesis. The thylakoid membrane, nucleus, and stomata are not directly involved in the Calvin cycle.