B8 Flashcards
(15 cards)
Where do plants get their food from?
Plants and alge are producers that make food. They use water and carbon dioxide to make sugar and oxygen.
What is photosynthesis?
Photosynthesis is the process where plants use sunlight, carbon dioxide, and water to produce glucose for energy and growth, releasing oxygen as a by-product.
Photosynthesis equation
Carbon dioxide + Water → Glucose + Oxygen
Written as:
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
What does chlorophyll do in photosynthesis?
Green chlorophyll in chloroplasts absorbs the light energy
State where a plant gets the carbon dioxide and water that it needs for photosynthesis.
A plant gets the carbon dioxide from the air through its leaves and the water from the soil through its roots.
State where algae get the carbon dioxide, water, and light they need for photosynthesis.
Algae get the carbon dioxide and water from the surrounding water and absorb light from the sun or artificial sources for photosynthesis.
Describe the path taken by a carbon atom as it moves from being part of the carbon dioxide in the air to being part of a starch molecule in a plant.
A carbon atom in carbon dioxide enters the plant through tiny pores in the leaf called the stomata. It moves to the chloroplasts, where it is used in the Calvin cycle during photosynthesis to form glucose. The glucose molecules are then joined together to form starch, which is stored in the plant for energy.
Explain why a leaf kept in the light for 24 hours will turn an iodine solution blue-black, whereas a leaf kept in the light for 24 hours and then in t h e dark for 24 hours will have no effect on an lodine solution.
A leaf kept in the light for 24 hours will turn iodine solution blue-black because the plant produces starch during photosynthesis, and iodine turns blue-black in the presence of starch.
However, if the leaf is kept in the dark for 24 hours after being in the light, it will have no effect on the iodine solution. This is because the plant cannot photosynthesize in the dark and will use up the stored starch for energy. Without starch, the iodine solution remains unchanged.
Explain why photosynthesis is an endothermic reaction.
Photosynthesis is an endothermic reaction because it absorbs energy from the environment. Specifically, it takes in light energy from the sun, which is needed to convert carbon dioxide and water into glucose and oxygen. Since energy is required and taken in during the process, photosynthesis is classified as endothermic.
Leaf adaptations
• most leaves are broad, giving them a big surface area for light to fall on
• most leaves are thin so diffusion distances for the gases are short
• they contain chlorophyll in the chloroplasts to absorb light
• they have veins, which bring plenty of water in the xylem to the cells of
the leaves and remove the products of photosynthesis in the phloem
• they have air spaces that allow carbon dioxide to get to the cells, and
oxygen to leave by diffusion
• they have guard cells that open and close the stomata to regulate gas
exchange.
What two substances do plants use to make sugar?
Plants use carbon dioxide and water to make sugar (glucose) during photosynthesis.
In which part of the plant does photosynthesis occur?
Photosynthesis occurs primarily in the leaves of the plant, specifically in the chloroplasts found within the leaf cells.
Why does photosynthesis take place only during the day?
Photosynthesis takes place only during the day because it requires light energy from the sun, which is essential for the process. During the day, plants absorb sunlight through chlorophyll in their chloroplasts, enabling them to convert carbon dioxide and water into glucose and oxygen. At night, without sunlight, plants cannot perform photosynthesis, although they can still respire.
CO2 is needed for photosynthesis. How does it enter the plant?
Carbon dioxide (CO₂) enters the plant through tiny openings on the leaves called stomata. These stomata are surrounded by guard cells that regulate their opening and closing, allowing CO₂ from the air to diffuse into the leaf for use in photosynthesis.
In which layer of the leaf does most photosynthesis take place and why?
Most photosynthesis takes place in the palisade mesophyll layer of the leaf. This layer is located just beneath the upper epidermis and contains a high concentration of chloroplasts, which are responsible for capturing light energy. The palisade mesophyll cells are elongated and closely packed, maximizing light absorption and allowing for efficient photosynthesis.
