Which of the following statements regarding the events in the functioning of photosystem II is FALSE?
Light energy excites electrons in an antenna pigment in a photosynthetic unit
The excitation is passed along to a molecule of P680 chlorophyll in the photosynthetic unit
The P680 chlorophyll donates a pair of protons to NADPH, which is thus converted to NADP+
The electron vacancies in P680 are filled by electrons derived from water
The splitting of water yields molecular oxygen as a by-product
Well, well, well, let's clown around with these options!
The statement that is absolutely FALSE is: "The P680 chlorophyll donates a pair of protons to NADPH, which is thus converted to NADP+."
Now, I hate to burst your bubble, but P680 chlorophyll doesn't donate protons to NADPH. It actually donates electrons to the primary electron acceptor, which helps form an electron transport chain that eventually leads to the production of NADPH. No proton donation, my friend, just some electron shuffling.
The statement that is FALSE regarding the events in the functioning of photosystem II is:
"The P680 chlorophyll donates a pair of protons to NADPH, which is thus converted to NADP+."
In photosystem II, the electron vacancies in P680 are filled by electrons derived from water, not from the donation of protons by P680 chlorophyll. The splitting of water yields molecular oxygen as a by-product.
To determine which statement is false regarding the events in the functioning of photosystem II, let's analyze each statement:
1. Light energy excites electrons in an antenna pigment in a photosynthetic unit: This statement is true. During the light reaction of photosynthesis, light energy is absorbed by antenna pigments, such as chlorophyll, which excite electrons.
2. The excitation is passed along to a molecule of P680 chlorophyll in the photosynthetic unit: This statement is also true. The excited electrons move from the antenna pigments to the reaction center chlorophyll, called P680 in photosystem II.
3. The P680 chlorophyll donates a pair of protons to NADPH, which is thus converted to NADP+: This statement is false. In photosystem II, the P680 chlorophyll does not donate protons to NADPH. Instead, it donates electrons to an electron transport chain.
4. The electron vacancies in P680 are filled by electrons derived from water: This statement is true. After P680 donates electrons, it becomes positively charged and is replenished by electrons derived from the splitting of water molecules. This process is called photolysis.
5. The splitting of water yields molecular oxygen as a by-product: This statement is true. When water molecules are split during the process of photolysis, molecular oxygen (O2) is released as a by-product.
Therefore, the false statement is statement 3.