Describe the process chemiosmosis in chloroplasts, tracing the flow of energy from sunlight to ATP?

Answer 1

Light energy strikes Photosystem II, where it excites 2 electrons into a system similar to the elctron transport chain in cellular respiration. The electrons travel down this chain which includes a b6-f cytochrome complex, which pumps hydride ions against their concentration gradient into the intermembrane space. These hydride (H+) ions then diffuse down their concentration gradient through ATp Synth(et)ase, phosphorylating ATP. (That's how the ATP is made; the electrons don't stop there, but I just wanted to answer your specific question.)

Awigman

Answer 2

Light energy is fixed into chemical energy in glucose through the process of photosynthesis. During cellular respiration, mitochondria break down glucose, extracting the chemical energy and creating ATP.

Answer 3

In the light-dependent reactions of photosynthesis, photons energize electrons in photosystem II. In the electron transport chain associated with photosystem II, these energetic electrons lose energy as they move from carrier to carrier. The electron transfers do not directly drive ATP synthesis; rather, the energy they release is used to pump hydrogen ions (H+) from the stroma across the thylakoid membrane into the thylakoid space. Like charging a battery, active transport of (H+) stores energy by creating a concentration gradient of (H+) across the thylakoid membrane. Then, in a separate reaction, the energy stored in this gradient powers ATP synthesis.

The gradient of (H+) is used to synthesize ATP. Hydrogen ions in the thylakoid interior can move down their gradients into the stroma only through special (H+) channels linked to ATP-synthesizing enzymes. The enzymes linked to (H+) channels capture the energy liberated by the flow of (H+) and use it to drive ATP synthesis from ADP plus phosphate. About one ATP molecule is synthesized for every three hydrogen ions that pass through the channel.

Answer 4

The energy released as electrons pass down the gradient between photosystem II and photosystem I is harnessed by the cytochrome b6/f complex to pump protons (H+) against their concentration gradient from the stroma of the chloroplast into the interior of the thylakoid (an example of active transport). As their concentration increases inside (which is the same as saying that the pH of the interior decreases), a strong diffusion gradient is set up. The only exit for these protons is through the ATP synthase complex.

Answer 5

First there is the light dependent stage called 'Photolysis.

Light energy is absobed by pigments, these include Chlorophyll A & B(both green), Xanthophyll and carotine(orange/yellow). This light energy is used to separate water into oxygen(which is released) and hydrogen which is accepted by NADP to become NADPH2 and carried to the 'Calcin Cycle'. Some ADP+Pi is also turned into ATP using spare energy.

Calvin Cycle/Carbon Fixation(Takes place in stoma of chloroplast)

Carbon Dioxide becomes six 3-carbon glycerate phosphates(GP) then the hydrogen joins from NADPH2(which then becomes NADP again) and some ATP is used as the three glycerate phosphates become three triose phosphates. One of which becomes ribulose biphosphate using ATP and the other two create glucose for respiration.

In respiration there are three stages glycolysis, The Kreb's Cycle and the cytochrome system. In glycolysis the six carbon compound is broken down into two three-carbon Pyruvic Acid molecules(this takes place in the cytoplasm) Hydrogen is released in the Kreb's cycle and then used to create ATP from ADP in the cytpchrome system before being accepted by oxygen to create water.

Answer 6

There is no such things called flow of ATP. But for ATP synthesis, electrons are transferred from one protein to other in the ETC to the terminal acceptor O2 to make ATP in mitochondria. Thus produced ATP are used in biochemical pathways to give energy to reaction by dephosphoryation.

Answer 7

from the motion of hydrogen ions