How do plants recycle carbon during photosynthesis?
1. The carbon in oxygen molecules is recycled during photosynthesis.
2. The carbon in glucose is recycled during photosynthesis.
3. The carbon in water is recycled during photosynthesis.
4. The carbon in carbon dioxide is recycled during photosynthesis.
4. The carbon in carbon dioxide is recycled during photosynthesis.
During photosynthesis, plants absorb carbon dioxide (CO2) from the air. The carbon in carbon dioxide is then used to create glucose (C6H12O6) and other organic molecules in a process known as the Calvin cycle. Oxygen (O2) is produced as a byproduct and released back into the atmosphere. Thus, carbon is continuously recycled as plants convert carbon dioxide into organic compounds and the ecosystem uses these compounds for various purposes, including respiration which releases CO2 back into the atmosphere.
How do plants recycle hydrogen during cellular respiration?
Plants and all other organisms that perform cellular respiration do not specifically recycle hydrogen in an isolated manner; rather, hydrogen atoms are involved as part of the biochemical processes that convert glucose and oxygen into ATP (adenosine triphosphate), water, and carbon dioxide.
Here's a simplified version of what happens during cellular respiration:
1. **Glycolysis:** The process starts in the cytosol with glycolysis, where one molecule of glucose (which contains hydrogen atoms as part of its chemical structure) is broken down into two molecules of pyruvate (pyruvic acid). This process also releases a small amount of ATP and transfers hydrogen atoms to the carriers NAD+ to form NADH.
2. **Citric Acid Cycle (Krebs Cycle):** The pyruvates enter the mitochondria (in eukaryotic cells) and are converted into acetyl CoA, which contains hydrogen. During the citric acid cycle, more hydrogen atoms are transferred to NAD+ and another carrier called FAD (flavin adenine dinucleotide), forming NADH and FADH2.
3. **Oxidative Phosphorylation and Electron Transport Chain:** The NADH and FADH2 then donate the electrons from these hydrogen atoms to the electron transport chain in the inner mitochondrial membrane. As the electrons move through the chain, the energy from the electrons is used to pump protons (which are hydrogen ions, H+) across the membrane, creating a proton gradient.
4. **Chemiosmosis and ATP Synthesis:** The protons flow back into the mitochondrial matrix through the enzyme ATP synthase due to the gradient created, and this flow of protons generates the energy needed to synthesize ATP from ADP and inorganic phosphate.
5. **Water Formation:** At the end of the electron transport chain, the electrons, protons, and molecular oxygen (O2) combine to form water (H2O). This is the step where hydrogen is "recycled" in the sense that the hydrogen atoms from glucose and other substrates end up combining with oxygen to form water, which is a byproduct of cellular respiration.
Thus, hydrogen from the breakdown of glucose and other molecules is effectively transferred and utilized throughout the cellular respiration process, ending up as part of water molecules. Plants release some of this water back into the environment via transpiration, continuing the natural cycles of elements.
The answers are
1. The hydrogen in glucose is recycled when hydrogen gas is formed.
2. The hydrogen in water is recycled when glucose is formed.
3. The hydrogen in glucose is recycled when water is formed.
4. The hydrogen in hydrogen gas is recycled when glucose is formed.
The correct answer is:
3. The hydrogen in glucose is recycled when water is formed.
During cellular respiration, the hydrogen atoms that are originally part of glucose are eventually transferred to oxygen, forming water as one of the end products. This occurs as part of the oxidative phosphorylation stage of cellular respiration, during which electrons (from hydrogen) are passed down the electron transport chain and finally combine with oxygen to produce water.
How many molecules of water are recycled when one molecule of glucose is created during photosynthesis?
During photosynthesis, water molecules are not "recycled" to form glucose; they are split during the light-dependent reactions to provide electrons necessary for the photosynthetic process.
Here's how photosynthesis works in two main stages:
1. **Light-dependent reactions:** These occur in the thylakoid membranes of chloroplasts. When light is absorbed by chlorophyll, water molecules (H2O) are split in a process known as photolysis. This splitting produces oxygen (O2), protons (H+), and electrons (e-):
\[ 2H_2O \rightarrow 4H^+ + 4e^- + O_2 \]
These electrons are then used to reduce NADP+ to NADPH and to contribute to the production of ATP via the electron transport chain and chemiosmosis.
2. **Calvin cycle (light-independent reactions):** During this stage, which occurs in the stroma of chloroplasts, ATP and NADPH produced in the light-dependent reactions are used to convert carbon dioxide (CO2) into glucose (C6H12O6). The actual number of water molecules used in the Calvin cycle to reduce CO2 and form glucose is not typically specified because water is not directly incorporated into the glucose molecule. The hydrogens from water originally contribute to forming NADPH during the light-dependent reactions, which subsequently provides the reducing power to help transform CO2 into glucose.
So, for your question, we consider the water molecules split during the light-dependent reactions. For each molecule of glucose produced, six carbon dioxide molecules are required, and hence six turns of the Calvin cycle are necessary. Each turn fixes one carbon dioxide molecule, so for the entire glucose molecule (which contains six carbon atoms), you have:
\[ 6CO_2 + 12NADPH + 12H^+ + 18ATP \rightarrow C_6H_{12}O_6 + 12NADP^+ + 18ADP + 18Pi + 6H_2O \]
The equation shows that in the Calvin cycle, water is actually produced as a byproduct rather than consumed. Therefore, it's not accurate to say that water molecules are recycled to form glucose; instead, water is both split and produced during different stages of photosynthesis.
3,6,12 or 1
To calculate the number of water molecules used during the photosynthesis process to produce one molecule of glucose, we can refer to the balanced overall equation for photosynthesis:
\[ 6CO_2 + 6H_2O + light \ energy \rightarrow C_6H_{12}O_6 + 6O_2 \]
This equation simplifies the full process and represents what happens during both the light-dependent reactions (where water is split to provide electrons) and the Calvin cycle (where the carbon fixation occurs).
From the equation, we can see that six molecules of water (6H2O) are consumed along with six molecules of carbon dioxide (6CO2) to produce one molecule of glucose (C6H12O6) and six molecules of oxygen (6O2).
So, the answer to the question of how many molecules of water are used when one molecule of glucose is created during photosynthesis is:
6 water molecules (6H2O).
Scientist used radioactive hydrogen to make water. They grew plants using the radioactive water. What happened to the radioactive hydrogen during photosynthesis?
1. It was recycled when glucose was formed.
2. It was recycled when light energy was formed.
3. It was recycled when hydrogen gas was formed.
4. It was recycled when water was formed.