Study "photosynthesis", a flashcard deck on FORKSAI.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.