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- Like cellular respiration, photosynthesis also uses an electron transport chain to make a H + concentration gradient, which drives ATP synthesis by chemiosmosis.
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Jul 31, 2024 · The process that forms the electrochemical gradient during photosynthesis is the hydrolysis of ATP. production of water from oxygen in the thylakoid lumen. production of H+ in the stroma during NADPH production. pumping of H+ into the thylakoid lumen. movement of water by osmosis.
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The splitting of carbon dioxide to form oxygen gas and carbon compounds occurs during A) photosynthesis. B) respiration. C) both photosynthesis and respiration. D) neither photosynthesis nor respiration. E) photorespiration.
Photosynthesis uses carbon dioxide and water to assemble carbohydrate molecules and release oxygen as a waste product into the atmosphere. Eukaryotic autotrophs, such as plants and algae, have organelles called chloroplasts in which photosynthesis takes place, and starch accumulates.
Osmosis plays a key role during the germination of seeds. Involved in the movement of water molecules between the cell and cell organelles. In plants, it is involved in the movement of water molecules from the soil into the root nodules.
- 60 min
- Osmosis is the movement of solvent from a region of lower solute concentration to a region of higher solute concentration through a semi-permeable...
- The three types of osmotic conditions include- hypertonic, isotonic, and hypotonic.
- The different types of osmosis include: Endosmosis- when a substance is placed in a hypotonic solution, the solvent molecules move inside the cell...
- Osmosis is important for the cells for many reasons. It helps in the movement of important materials inside and out of the cell. The nutrients, wat...
- Osmosis is a process of movement of solvents through a semi-permeable membrane from a region of lower solute concentration to higher solute concent...
- Yes, dead cells also exhibit osmosis. If a dead cell is placed under a hypotonic solution, water moves inside the cell and it bulges.
- Osmosis helps in stabilizing the internal environment of the organism by balancing the levels of water and intracellular fluids. Also, the nutrient...
- Forward osmosis is a natural phenomenon that occurs around us on a daily basis. It is the type of osmosis that uses a semi-permeable membrane in th...
- The real-life examples of osmosis are: Feeling thirsty after having salty food. Dialysis of kidney in the excretory system. Swelling of resins and...
- Overview
- Introduction
- What is photosynthesis?
- The ecological importance of photosynthesis
- Leaves are sites of photosynthesis
- The light-dependent reactions and the Calvin cycle
- Photosynthesis vs. cellular respiration
Conversion of light energy to chemical energy. Reactions of photosynthesis, where they take place, and their ecological importance.
Have you hugged a tree lately? If not, you might want to give it some thought. You, along with the rest of the human population, owe your existence to plants and other organisms that capture light. In fact, most life on Earth is possible because the sun provides a continuous supply of energy to ecosystems.
All organisms, including humans, need energy to fuel the metabolic reactions of growth, development, and reproduction. But organisms can't use light energy directly for their metabolic needs. Instead, it must first be converted into chemical energy through the process of photosynthesis.
Photosynthesis is the process in which light energy is converted to chemical energy in the form of sugars. In a process driven by light energy, glucose molecules (or other sugars) are constructed from water and carbon dioxide, and oxygen is released as a byproduct. The glucose molecules provide organisms with two crucial resources: energy and fixed—organic—carbon.
•Energy. The glucose molecules serve as fuel for cells: their chemical energy can be harvested through processes like cellular respiration and fermentation, which generate adenosine triphosphate—ATP , a small, energy-carrying molecule—for the cell’s immediate energy needs.
Photosynthetic organisms, including plants, algae, and some bacteria, play a key ecological role. They introduce chemical energy and fixed carbon into ecosystems by using light to synthesize sugars. Since these organisms produce their own food—that is, fix their own carbon—using light energy, they are called photoautotrophs (literally, self-feeders that use light).
Humans, and other organisms that can’t convert carbon dioxide to organic compounds themselves, are called heterotrophs, meaning different-feeders. Heterotrophs must get fixed carbon by eating other organisms or their by-products. Animals, fungi, and many prokaryotes and protists are heterotrophs.
[Read more about autotrophs and heterotrophs.]
Besides introducing fixed carbon and energy into ecosystems, photosynthesis also affects the makeup of Earth’s atmosphere. Most photosynthetic organisms generate oxygen gas as a byproduct, and the advent of photosynthesis—over 3 billion years ago, in bacteria resembling modern cyanobacteria—forever changed life on Earth1 . These bacteria gradually released oxygen into Earth’s oxygen-poor atmosphere, and the increase in oxygen concentration is thought to have influenced the evolution of aerobic life forms—organisms that use oxygen for cellular respiration. If it hadn’t been for those ancient photosynthesizers, we, like many other species, wouldn't be here today!
Plants are the most common autotrophs in terrestrial—land—ecosystems. All green plant tissues can photosynthesize, but in most plants, but the majority of photosynthesis usually takes place in the leaves. The cells in a middle layer of leaf tissue called the mesophyll are the primary site of photosynthesis.
Small pores called stomata—singular, stoma—are found on the surface of leaves in most plants, and they let carbon dioxide diffuse into the mesophyll layer and oxygen diffuse out.
Photosynthesis in the leaves of plants involves many steps, but it can be divided into two stages: the light-dependent reactions and the Calvin cycle.
•The light-dependent reactions take place in the thylakoid membrane and require a continuous supply of light energy. Chlorophylls absorb this light energy, which is converted into chemical energy through the formation of two compounds, ATP —an energy storage molecule—and NADPH —a reduced (electron-bearing) electron carrier. In this process, water molecules are also converted to oxygen gas—the oxygen we breathe!
•The Calvin cycle, also called the light-independent reactions, takes place in the stroma and does not directly require light. Instead, the Calvin cycle uses ATP and NADPH from the light-dependent reactions to fix carbon dioxide and produce three-carbon sugars—glyceraldehyde-3-phosphate, or G3P, molecules—which join up to form glucose.
Overall, the light-dependent reactions capture light energy and store it temporarily in the chemical forms of ATP and NADPH . There, ATP is broken down to release energy, and NADPH donates its electrons to convert carbon dioxide molecules into sugars. In the end, the energy that started out as light winds up trapped in the bonds of the sugars.
At the level of the overall reactions, photosynthesis and cellular respiration are near-opposite processes. They differ only in the form of energy absorbed or released, as shown in the diagram below.
At the level of individual steps, photosynthesis isn't just cellular respiration run in reverse. Instead, as we'll see the rest of this section, photosynthesis takes place in its own unique series of steps. However, there are some notable similarities between photosynthesis and cellular respiration.
For instance, photosynthesis and cellular respiration both involve a series of redox reactions (reactions involving electron transfers). In cellular respiration, electrons flow from glucose to oxygen, forming water and releasing energy. In photosynthesis, they go in the opposite direction, starting in water and winding up in glucose—an energy-requiring process powered by light. Like cellular respiration, photosynthesis also uses an electron transport chain to make a H+ concentration gradient, which drives ATP synthesis by chemiosmosis.
If those things don't sound familiar, though, don't worry! You don't need to know cellular respiration to understand photosynthesis. Just keep reading and watching, and you'll learn all the ins and outs of this life-sustaining process.
Key points: Many organisms make their own food through photosynthesis. Plants, algae, and some unicellular organisms do photosynthesis. Photosynthesis is powered by energy from sunlight. This energy is used to rearrange atoms in carbon dioxide and water to make oxygen and sugars. Carbon dioxide and water are inputs of photosynthesis.
Photosynthesis consists of two stages: the light-dependent reactions and the light-independent reactions or Calvin cycle. The light-dependent reactions occur when light is available. The overall equation for photosynthesis shows that is it a redox reaction; carbon dioxide is reduced and water is oxidized to produce oxygen: