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Photosynthesis and Ecosystems
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Photosynthesis and Ecosystems
Photosynthesis and Ecosystems
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Question
What raw materials are used in photosynthesis, and what are its main products?
Answer
Photosynthesis uses carbon dioxide, water, and solar energy as raw materials to produce oxygen and carbohydrates, such as 6-carbon sugars (C6H12O6).
Question
What are the two main stages of photosynthesis, and where do they take place in the chloroplast?
Answer
The two stages are light-dependent reactions, which occur in the thylakoid membranes, and light-independent reactions (Calvin cycle), which occur in the stroma of the chloroplast.
Question
What role do NADP+ and NADPH play in photosynthesis?
Answer
NADP+ accepts and holds two high-energy electrons and a hydrogen ion (H+), converting into NADPH, which carries high-energy electrons from light absorption to chemical reactions in the cell, aiding in making carbohydrates like glucose.
Question
Describe the main events occurring in the light-dependent reactions of photosynthesis.
Answer
Light-dependent reactions capture light energy to produce oxygen gas and convert ADP and NADP+ into ATP and NADPH. They involve photosystem II (absorbing light, splitting water into electrons, H+, and oxygen), electron transport chain (moving electrons and pumping H+ into thylakoid), photosystem I (energizing electrons and forming NADPH), hydrogen ion movement creating charge difference, and ATP formation via ATP synthase.
Question
Why is ATP important in photosynthesis and what process produces it during light-dependent reactions?
Answer
ATP stores energy captured from sunlight and is produced when hydrogen ions pass through ATP synthase in the thylakoid membrane, which binds ADP and phosphate to form ATP.
Question
What is the Calvin cycle and why is it called light-independent?
Answer
The Calvin cycle uses ATP and NADPH from light-dependent reactions to convert carbon dioxide into high-energy sugars. It is called light-independent because it does not require light to occur and takes place in the stroma.
Question
Outline the main steps of the Calvin cycle.
Answer
1) Six CO2 molecules enter and combine with six 5-carbon molecules to form twelve 3-carbon molecules; 2) These molecules are converted into higher energy forms using ATP and NADPH; 3) Two of these 3-carbon molecules are used to produce 6-carbon sugars; 4) The remaining ten 3-carbon molecules regenerate the original 5-carbon molecules to continue the cycle.
Question
What is ATP and why is it often called the energy currency of the cell?
Answer
ATP (adenosine triphosphate) is a molecule that stores and transfers energy within cells. It provides usable energy for cellular processes by releasing energy when its phosphate bonds are broken.
Question
Compare photosynthesis and cellular respiration in terms of function, location, reactants, and products.
Answer
Photosynthesis stores energy, occurs in chloroplasts, uses CO2 and H2O as reactants, and produces glucose and O2. Cellular respiration releases energy, occurs in mitochondria, uses glucose and O2 as reactants, and produces CO2 and H2O.
Question
What is a food chain and how does it represent energy transfer in an ecosystem?
Answer
A food chain is a series of steps showing how energy stored by producers is passed through an ecosystem as organisms eat and are eaten.
Question
How does a food web differ from a food chain?
Answer
A food web is a network of feeding relationships linking together multiple food chains, showing the complex interactions among various organisms in an ecosystem.
Question
What is a trophic level, and how much energy is typically transferred from one trophic level to the next?
Answer
A trophic level is each step in a food chain or food web, starting with producers at the first level and consumers at subsequent levels. Only about 10% of available energy at one trophic level is transferred to the next level.
Question
Explain why energy transfer is inefficient in ecosystems with many trophic levels.
Answer
Because only about 10% of energy passes to the next trophic level, much energy is lost as heat at each level, so the more levels that exist between producers and top consumers, the less energy remains for the top level.
Question
What types of organisms carry out photosynthesis?
Answer
Higher plants, phytoplankton, algae, and some bacteria carry out photosynthesis.
Question
Describe the role of chlorophyll and chloroplasts in photosynthesis.
Answer
Chlorophyll is a pigment in chloroplasts that absorbs sunlight to energize electrons. Chloroplasts are organelles where photosynthesis occurs, housing the thylakoid membranes and stroma where the light-dependent and light-independent reactions happen.