Question

1. tonicity (2.8) define osmosis. create a chart and define hypotonic, hypertonic and isotonic. diagram and explain how water will move in each case.
2. water potential (2.8) what is water potential? give the equation and explain its

Explanation:

1. Membrane potential or polarity: It is the electrical potential difference across a cell membrane. This is due to an unequal distribution of ions (such as sodium, potassium) across the membrane. The resting membrane potential of a typical cell is around -70 mV, with the inside of the cell being more negative relative to the outside.
2. Osmosis: Osmosis is the diffusion of water across a semi - permeable membrane from an area of high water potential to an area of low water potential.

Tonicity	Definition	Water movement
Hypertonic	A solution with a higher solute concentration compared to the cell.	Water moves out of the cell, causing it to shrink or crenate (in animal cells).
Isotonic	A solution with the same solute concentration as the cell.	There is no net movement of water.

1. Water potential: Water potential ($\Psi$) is a measure of the potential energy of water in a system relative to pure water. The equation for water potential is $\Psi=\Psi_s+\Psi_p+\Psi_g+\Psi_m$, where $\Psi_s$ is the solute potential (lowered by the presence of solutes), $\Psi_p$ is the pressure potential (positive in turgid plant cells), $\Psi_g$ is the gravitational potential (usually negligible in small systems), and $\Psi_m$ is the matric potential (due to adhesion of water to surfaces). In most cases, for plant cells, $\Psi=\Psi_s+\Psi_p$ as $\Psi_g$ and $\Psi_m$ are often not significant factors.

Answer:

1. Membrane potential or polarity is the electrical potential difference across a cell membrane due to unequal ion distribution.
2. Osmosis is the diffusion of water across a semi - permeable membrane from high to low water potential. Hypotonic: lower solute concentration than cell, water moves in. Hypertonic: higher solute concentration than cell, water moves out. Isotonic: same solute concentration as cell, no net water movement.
3. Water potential ($\Psi$) measures water's potential energy. Equation $\Psi=\Psi_s+\Psi_p+\Psi_g+\Psi_m$ (simplified to $\Psi=\Psi_s+\Psi_p$ in many cases), where $\Psi_s$ is solute potential, $\Psi_p$ is pressure potential, $\Psi_g$ is gravitational potential, and $\Psi_m$ is matric potential.