1. Name of the enzyme used C4 PHOTOSYNTHESIS

Question

2. Movement of protons across a membrane that is used to drive various cellular processes such as ATP synthesis.
3. Function and structural units of protein complexes involved in the light reaction of photosynthesis

Answer 1

Sure! Here’s a breakdown of each of your three points:

1. Enzyme Used in C4 Photosynthesis:

   • The primary enzyme involved in C4 photosynthesis is phosphoenolpyruvate carboxylase (PEP carboxylase). This enzyme catalyzes the carboxylation of phosphoenolpyruvate (PEP) to form oxaloacetate (OAA) in the mesophyll cells of C4 plants.

2. Movement of Protons Across a Membrane:

   • The process you are referring to is known as proton gradient formation or proton motive force (PMF). This occurs across the thylakoid membrane in chloroplasts and is an essential part of the light reactions of photosynthesis. The movement of protons down their concentration gradient through the enzyme ATP synthase drives the synthesis of ATP from ADP and inorganic phosphate (Pi), a process known as chemiosmosis.

3. Function and Structural Units of Protein Complexes in the Light Reactions of Photosynthesis:

   • The light reactions of photosynthesis involve two main protein complexes: Photosystem II (PSII) and Photosystem I (PSI), along with ATP synthase and the cytochrome b6f complex.

     • Photosystem II (PSII):

       • Function: Captures light energy and uses it to oxidize water, producing oxygen and transferring electrons to the electron transport chain.
       • Structural Units: Consists of a reaction center composed of a special pair of chlorophyll a molecules (P680) and associated proteins, pigments, and accessory pigments (like chlorophyll b and carotenoids).

     • Cytochrome b6f Complex:

       • Function: Facilitates electron transfer from PSII to PSI and contributes to the proton gradient across the thylakoid membrane.
       • Structural Units: Comprised of multiple subunits that include cytochromes and iron-sulfur proteins, it mediates the transfer of electrons and protons.

     • Photosystem I (PSI):

       • Function: Absorbs light energy and drives the reduction of NADP+ to NADPH using the electrons received from the electron transport chain.
       • Structural Units: Contains a reaction center with a special pair of chlorophyll a molecules (P700) and associated proteins and pigments.

     • ATP Synthase:

       • Function: Utilizes the proton gradient created by the electron transport chain to synthesize ATP from ADP and Pi.
       • Structural Units: Composed of two main parts, F0 (membrane-integrating part) and F1 (catalytic unit), where the F0 subunit allows protons to flow through, driving the rotation of the F1 subunit, resulting in ATP synthesis.

These complexes work together to convert light energy into chemical energy during photosynthesis.