photosynthesis flashcards

All 30 cards

1. Card 1

   Define photosynthesis and state its primary role in living organisms.

   Photosynthesis is the process by which plants make food (carbohydrates) and oxygen using energy from the sun, water from the soil, and carbon dioxide from the atmosphere. Its primary role is to produce food for plants, which then serves as a food source for animals, and to release oxygen essential for respiration.

2. Card 2

   What is the balanced chemical equation for the overall reaction of photosynthesis?

   The balanced chemical equation for photosynthesis is: 6H₂O + 6CO₂ → C₆H₁₂O₆ + 6O₂. This reaction requires light energy and the presence of chlorophyll to convert water and carbon dioxide into glucose and oxygen.

3. Card 3

   How does light energy initiate the process of electron release in chlorophyll during photosynthesis?

   Light energy is absorbed and trapped by chlorophyll. This absorbed energy then energizes electrons within the chlorophyll, causing them to be released. These high-energy electrons are then passed to electron acceptors, initiating the electron transport pathways.

4. Card 4

   Distinguish between the light-dependent and light-independent stages of photosynthesis.

   The light-dependent stage requires light and takes place in the granum of the chloroplast, producing ATP, NADPH, and oxygen from the splitting of water. The light-independent stage, also known as the Calvin cycle, uses the ATP and NADPH produced in the light stage to reduce carbon dioxide into carbohydrates, and does not directly require light.

5. Card 5

   Explain the role of water in the light-dependent stage of photosynthesis.

   In the light-dependent stage, light energy is used to split water molecules, a process called photolysis. This splitting releases H⁺ ions (protons), electrons, and oxygen. The electrons replace those lost from chlorophyll, the H⁺ ions contribute to the proton pool, and oxygen is released as a waste product.

6. Card 6

   Where is chlorophyll located within a plant cell, and why is this location significant?

   Chlorophyll is found in the chloroplasts of plant cells. This location is significant because chloroplasts are the primary site of photosynthesis, and their structure, particularly the arrangement of chlorophyll in the granum, is optimized for absorbing light energy and facilitating the light-dependent reactions.

7. Card 7

   Why is photosynthesis considered an essential process for the survival of most living organisms?

   Photosynthesis is essential because it produces carbohydrates, which are the primary food source for plants and, indirectly, for animals. Furthermore, it releases oxygen into the atmosphere, which is vital for aerobic respiration in most living organisms to release energy.

8. Card 8

   Describe the journey of carbon dioxide from the atmosphere to the site of photosynthesis within a leaf.

   Carbon dioxide from the atmosphere enters the leaf through small pores called stomata, which are mainly located on the underside of the leaf. Once inside, it diffuses through air spaces within the leaf until it reaches the chloroplasts in the cells, where it is used in the light-independent stage.

9. Card 9

   How do protons (H+ ions) and electrons, derived from the splitting of water, contribute to the formation of carbohydrates?

   The electrons released from chlorophyll and replaced by those from water, along with the protons from water, are used to produce NADPH during the light-dependent stage. Both ATP and NADPH, products of the light-dependent stage, are then utilized in the light-independent stage to reduce carbon dioxide and form carbohydrates.

10. Card 10

    What is the primary function of ATP and NADPH in the light-independent stage of photosynthesis?

    In the light-independent stage, ATP provides the energy, and NADPH provides the reducing power (electrons and protons) necessary to convert carbon dioxide into glucose. ATP is broken down to release energy, while NADPH is oxidized to donate electrons and protons for the synthesis of carbohydrates.

11. Card 11

    Why is the leaf adapted in specific ways to be an efficient structure for photosynthesis?

    The leaf is adapted with features like stomata for gas exchange, air spaces for gas diffusion, a thin structure for rapid diffusion, a cuticle to prevent excessive water loss, and a flattened shape to increase surface area for light absorption. Most chloroplasts are also concentrated in the palisade layer to maximize sunlight absorption.

12. Card 12

    What happens to the oxygen produced during the splitting of water in photosynthesis?

    Most of the oxygen gas produced from the splitting of water is released as a waste product out of the leaf through the stomata into the atmosphere. However, some of the oxygen produced can be used by the cells of the leaf itself for cellular respiration.

13. Card 13

    Explain how light energy is converted to chemical energy during photosynthesis.

    Light energy is absorbed by chlorophyll, energizing electrons. This energy is then used to generate ATP through phosphorylation and to reduce NADP+ to NADPH. These energy-carrying molecules (ATP and NADPH) represent stored chemical energy, which is then used to synthesize glucose, a more stable form of chemical energy.

14. Card 14

    What are the four essential requirements for photosynthesis to occur?

    The four essential requirements for photosynthesis are water, carbon dioxide, light energy, and the presence of chlorophyll. Each plays a crucial role in the overall process of converting light energy into chemical energy in the form of carbohydrates.

15. Card 15

    How does the process of photosynthesis contribute to the formation of fossil fuels?

    Photosynthesis is responsible for forming fossil fuels because it creates organic matter (carbohydrates) from atmospheric carbon dioxide. Over geological timescales, when ancient plants and other photosynthetic organisms died and were buried under specific conditions, this organic matter was transformed into fossil fuels like coal, oil, and natural gas.

16. Card 16

    What is the role of electron acceptors in the light-dependent stage of photosynthesis?

    Electron acceptors receive the high-energy electrons released from chlorophyll. They then pass these electrons along a series of other electron acceptors in an electron transport chain. As electrons move through this chain, they lose energy, which is harnessed to produce ATP and NADPH.

17. Card 17

    Describe the two pathways of electron flow in the light-dependent stage (cyclic and non-cyclic).

    In cyclic electron flow (Pathway 1), electrons from chlorophyll return to chlorophyll after passing through a series of electron acceptors, generating ATP. In non-cyclic electron flow (Pathway 2), electrons leave chlorophyll and do not return, instead being used to form NADPH, while ATP is also produced, and lost electrons are replaced by those from water.

18. Card 18

    How does the source of water for photosynthesis reach the leaves?

    Water for photosynthesis is absorbed by the roots of the plant from the soil. It then travels upwards through the plant stem to the leaves via specialized vascular tissues called xylem vessels, which are found in the veins of the leaf.

19. Card 19

    What are the main products of the light-dependent stage of photosynthesis?

    The main products of the light-dependent stage of photosynthesis are ATP (adenosine triphosphate), NADPH (nicotinamide adenine dinucleotide phosphate), and oxygen. ATP and NADPH are energy carriers used in the next stage, while oxygen is a byproduct.

20. Card 20

    Why is it important for plants to remove carbon dioxide from the air through photosynthesis?

    Photosynthesis removes carbon dioxide from the air, which is crucial for regulating Earth's climate and for the carbon cycle. By converting atmospheric CO₂ into organic compounds, plants help mitigate the greenhouse effect and provide the carbon necessary for their own growth and the food chain.

21. Card 21

    What is phosphorylation, and how is it relevant to ATP production in photosynthesis?

    Phosphorylation is the process of adding a phosphate group to a molecule. In photosynthesis, light energy is used in the light-dependent stage to add a phosphate group to ADP (adenosine diphosphate) to form ATP (adenosine triphosphate), storing energy in the chemical bonds of ATP.

22. Card 22

    Why is the light-independent stage also referred to as the 'dark stage,' even though it doesn't necessarily occur in darkness?

    The light-independent stage is called the 'dark stage' because it does not directly require light energy. Instead, it relies on the ATP and NADPH produced during the light-dependent stage. While it can occur in the dark, it typically happens concurrently with the light-dependent stage during daylight hours.

23. Card 23

    Explain how light energy causes electrons to be released by chlorophyll.

    When chlorophyll absorbs light energy, this energy excites electrons within the chlorophyll molecule to a higher energy level. These energized electrons become unstable and are then released from the chlorophyll, ready to be passed to an electron acceptor.

24. Card 24

    What is the primary site of photosynthesis within a plant cell?

    The primary site of photosynthesis within a plant cell is the chloroplast. These specialized organelles contain chlorophyll and the necessary enzymes and structures to carry out both the light-dependent and light-independent stages of photosynthesis.

25. Card 25

    How does the splitting of water contribute to the common pool of protons in the chloroplast?

    The splitting of water molecules (photolysis) during the light-dependent stage releases H⁺ ions, also known as protons. These protons are released into the thylakoid lumen, contributing to a concentration gradient that is then used to drive ATP synthesis, forming a 'common pool' of protons.

26. Card 26

    Why is the light-dependent stage of photosynthesis considered 'light-dependent' and what are its key products?

    The light-dependent stage is called 'light-dependent' because it requires the presence of light to occur. During this stage, light energy is absorbed by chlorophyll pigments, leading to the production of ATP and NADPH, and the splitting of water, which releases oxygen.

27. Card 27

    Distinguish between cyclic and non-cyclic electron flow in the light-dependent stage of photosynthesis.

    In cyclic electron flow (Pathway 1), electrons energized by light return to the chlorophyll molecule after passing through a series of electron acceptors, generating ATP. In non-cyclic electron flow (Pathway 2), energized electrons leave the chlorophyll and do not return, instead combining with NADP+ and H+ to form NADPH, while also producing ATP and obtaining replacement electrons from the splitting of water.

28. Card 28

    How does the splitting of water (photolysis) contribute to the overall process of photosynthesis during the light-dependent stage?

    Photolysis, the splitting of water using light energy, is crucial because it provides electrons to replace those lost by chlorophyll in non-cyclic electron flow. It also releases protons (H+) that contribute to the formation of NADPH and produces oxygen as a byproduct, which is either released or used in respiration.

29. Card 29

    Explain the role of ATP and NADPH, produced in the light-dependent stage, in the subsequent light-independent stage of photosynthesis.

    ATP provides the necessary energy for the reactions in the light-independent stage, specifically for the conversion of carbon dioxide into carbohydrate. NADPH supplies the hydrogen ions and electrons required to reduce carbon dioxide, facilitating its transformation into glucose.

30. Card 30

    Why is the light-independent stage also known as the 'Dark Stage' or 'Calvin Cycle', and where does it occur within the chloroplast?

    The light-independent stage is called the 'Dark Stage' or 'Calvin Cycle' because it does not directly require light to proceed, although it can occur in the light. This stage takes place in the stroma of the chloroplast, where carbon dioxide is reduced to sugar using the ATP and NADPH produced in the light-dependent stage.

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