1)Animal cells prefer to be in isotonic solution, while plant cells prefer to be in hypotonic solution.

Explain what this means and why it is so.

2.) In terms of Gibbs free energy, what does “unstable” mean? Also, give at least two additional ways to say that a molecule is unstable.

3.) Red algae are photosynthetic eukaryotes that contain the pigment phycoerythrin in their chloroplasts, which causes the algae to appear pink or red. Would you expect the photosynthetic action spectrum for red algae to differ from the action spectrum for green plants? If so, how?

4.) The P680 chlorophyll a molecule splits water molecules, but the P700 chlorophyll a does not. Explain why this is so.

5.)briefly explain when and why a second messenger is sometimes needed during cellular communication.

Ha fellow Jjay student

1) Animal cells prefer to be in an isotonic solution because it ensures that the concentration of solutes inside and outside the cell is balanced. In an isotonic solution, there is no net movement of water across the cell membrane. This is beneficial for animal cells because it helps maintain their shape and prevents excessive water intake or loss, which could cause cell bursting or shrinking respectively.

On the other hand, plant cells prefer to be in a hypotonic solution, which means the concentration of solutes outside the cell is lower than inside the cell. This allows water to enter the cell through osmosis, creating turgor pressure and helping maintain the rigidity of the plant cell wall. The cell wall provides support to the plant, so being in a hypotonic solution allows the plant cell to maintain its shape and stay upright.

2) In terms of Gibbs free energy, "unstable" refers to a molecule that has a high energy state. It means that the molecule has the potential to undergo spontaneous reactions to reach a lower energy state. At a molecular level, instability can arise from factors such as high internal energy, large structural strain, or the presence of reactive functional groups.

Additional ways to say that a molecule is unstable include:
- High reactivity: Unstable molecules tend to readily participate in chemical reactions due to their reactive nature.
- High energy state: Unstable molecules have excess energy, making them prone to undergoing transformations to attain a more stable state.

3) Yes, the photosynthetic action spectrum for red algae is expected to differ from that of green plants. The action spectrum refers to the efficiency of light absorption at different wavelengths by photosynthetic pigments. Red algae contain the pigment phycoerythrin, which absorbs light in the blue and green spectrums more effectively than chlorophyll. Therefore, the photosynthetic action spectrum for red algae would show an increased absorption in the blue and green regions, resulting in a different shape compared to the action spectrum for green plants.

4) The P680 chlorophyll a molecule, present in photosystem II of photosynthesis, is responsible for splitting water molecules. On the other hand, the P700 chlorophyll a molecule, present in photosystem I, does not have this capability.

The difference arises from the specific arrangement of pigments and proteins in each photosystem. Photosystem II has a reaction center consisting of P680, which absorbs light energy and transfers it to an electron acceptor. This electron acceptor has a strong oxidative potential, allowing it to extract electrons from water molecules and releasing oxygen as a byproduct.

In contrast, photosystem I (with P700) has a different reaction center that accepts electrons from another electron donor molecule, not water. This difference in reaction center composition and electron flow pathways explains why P680 can split water molecules, while P700 cannot.

5) In cellular communication, a second messenger is sometimes needed to amplify the initial signal and transmit it to the appropriate cellular targets. This is necessary because the extracellular signaling molecules, such as hormones or neurotransmitters, cannot directly enter the cells. They bind to specific cell surface receptors and trigger the activation of intracellular signaling pathways.

The role of second messengers is to relay the signal from the cell surface receptor to the intracellular targets. They act as intermediaries, carrying the signal from the receptor to amplify and distribute it to multiple downstream effectors simultaneously.

Second messengers like cyclic adenosine monophosphate (cAMP) and calcium ions (Ca2+) are commonly used in cellular signaling. They can diffuse throughout the cell, activating protein kinases, ion channels, or gene transcription factors, triggering a wide range of cellular responses.

The need for a second messenger is essential to ensure efficient and coordinated cellular responses to extracellular signals by involving multiple downstream components in the signaling pathway.