Electrical Functions Of Plant And Animal Cells

A voltage-gated sodium ion channel opens when there is a change in the voltage of the membrane and allows sodium ions to flow across its electrochemical gradient. These voltage-gated channels are made up of amino acids and they aid in generating and moving an action potential down a membrane or axon (Brooker, Robert, 106).

Change in pH concentrations increases permeability of beetroot (‎Beta vulgaris) cell membranes indicated through color intensity using the spectrophotometer

Water diffuses across the membrane from the region of lower solute concentration (higher free water concentration) to that of higher solute concentration (lower free water concentration) until the solute concentrations on both sides of the membrane are equal. The diffusion of free water across a selectively permeable membrane, whether artificial or cellular, is called osmosis. The movement of water across cell membranes and the balance of water between the cell and its environment are crucial to organisms. ("Diffusion And Osmosis - Difference And Comparison | Diffen"). A semi-permeable membrane known as the cell membrane surrounds the living cells of both plants and animals. Both solute concentration and membrane permeability are

During osmosis, solvents move across a semipermeable membrane in order to regulate the solute balance within the cell (Campbell Biology). Experiment 5.5 was conducted to further research osmotic activity, particularly in potato cells in different osmolarities of a NaCl solution. The goal of the experiment was to find out whether the potato slices used would be hypotonic or hypertonic to the different osmolarities. This process is relevant because without osmosis, the passage of solvents would not be possible. To perform the experiment, seven potato slices were soaked in 5cm of a different osmolarity level of a NaCl solution (0M – 0.6M) to determine whether each slice was hypotonic or hypertonic to the NaCl solution it was placed in, based on percent weight change. The prediction that the potato slices soaked in solutions with lesser osmolarities (0M – 0.1M) of NaCl would be hypotonic to their solutions, and the potato slices soaked in solutions with higher osmolarities (0.2M – 0.6M) would be hypertonic to their solutions was supported by this experiment because the slices soaked in (0.2M – 0.6M) had

The objective of this experiment is to develop an understanding of the molecular basis of diffusion and osmosis and its physiological importance. Students will analyze how solute size and concentration affect diffusion across semi-permeable membranes and how these processes affect water potential. Students will also calculate water potential of plant cells.

Diffusion, osmosis and active transport of substances in and out of the membrane is very important for all types of cells. One example is the root hair cell. These cells are the exchange surface in plants which are responsible for the absorption of water and mineral ions so without osmosis and active transport this would not be possible. The water is taken up by osmosis through the partially permeable membrane. The root hair cells are surrounded by a soil solution which contains small quantities of mineral ions but mainly water, so has a high water potential (slightly less than zero). The root hair cells themselves contain a high quantity of amino acids, mineral ions and sugars inside them (low water potential). Therefore water will move by osmosis from the soil solution and into the root hair cells, going down the water potential gradient.

This experiment seeks to analyze how the resting membrane potential of Orconectes rusticus muscle cells changes in response to increasing [K+]o solution concentrations. By recording the intracellular voltage of the DEM, DEL1, and DEL2 crayfish muscle cells at six concentrations of [K+]o solution, we determined whether the observed resting membrane potentials (Vrest) were significantly different from the predicted Nernst equilibrium potential values. We hypothesized that the Vrest of the crayfish muscles at each concentration would not significantly differ from the Nernst potential, which solely considers the permeability of potassium ions to the cell membrane. However, our findings suggested differently, and results indicated that the Nernst equation did not accurately predict the obtained values of the resting membrane potential. The differences in muscle cell Vrest reveal instead that the membrane is differentially permeable to other ions.

___The concentration of extracellular K+ ions would be high and this would prevent more K+ ions from diffusing out of the cell.

Despite its importance osmosis may also damage cells by causing them to; a) shrink from water loss or b) burst from too much water gain. Plant cells [fig 3] have adapted themselves to ensure that these factors do not affect them, by forming a ridged wall, known as the cell wall, around their cells. The cell wall maintains the shape of the cell, and prevents the cell from bursting in a hypotonic medium by resisting water pressure. Plant cells have also adapted a larger vacuole, which occupies 80% or more of the cells cytoplasm (Davidson, 2004); allowing plants to store more water and nutrients per cell. Vacuoles also play a structural role in plant cells; by swelling when liquids contact them, plant vacuoles are able to control turgor pressure within the cell. This helps maintain the structural integrity of the cell as well as providing the plant with suitable amounts of water and nutrients; however the cell will never burst because the vacuole is contained within the cell wall. If plant cells are deprived of water their vacuole will begin to shrink, yet due to the cell the wall, the plant cell will be able to maintain its shape. [fig.4] Animal cells [fig 5] on the other hand do not have this

b. Describe the role of primary active transport with regard to potassium (K+) and hydrogen (H+) ion movement.

-If the potassium transport pump was blocked the leakage channels would still be open allowing Na+ to

are pore forming proteins which allow the passage of ions that are charged into and out of the cell

When a membrane is excited depolarization begins. When the membrane depolarizes the resting membrane potential of -70 mV becomes less negative. When the membrane potential reaches 0 mV, indicating there is no charge difference across the membrane. the sodium ion channels start to close and potassium ion channels open. By the time the sodium ion channels finally close. The membrane potential has reached +35 mV. The opening of the potassium channels allows K+ to flow out of the cell down its electrochemical gradient ( ion of like charge are repelled from each other). The flow of K+ out of the cell causes the membrane potential to move in a negative direction. This is referred to as repolarization. ( Marieb & Mitchell, 2009). As the transmembrane potential comes back down towards its resting potential level and the potassium channels begins to close, the trasmembrane potential level goes just below -90mV, causing a brief period of hyperpolarization (Martini, Nath & Bartholomew, 2012). Finally, as the potassium channels close, the membrane turns back to its resting potential until it is excited or inhibited again.

The fact that potassium is indeed the most influential determinant of crayfish resting membrane potential can be seen through the analysis of Figure 2. This table shows that the obtained resting membrane potential follows the same trajectory as the Nernst calculated one. The initial concentration elicited a resting membrane potential that was significantly more positive than

To study the effects of hypotonic, hypertonic and isotonic solutions on plant and animal cells.