2.03 Cell Membranes and Homeostasis Essay

895 Words Apr 30th, 2014 4 Pages
Title: Ms. K
Cell Membrane and Homeostasis Experiment
Objective(s): The reason for this experiment is to see how starch and iodine affect each other and how a plastic bag works similar to a membrane in certain situations.
Introduction: I know prior to doing this experiment that iodine mixed with starch creates a dark color and that most objects, organic and inorganic, naturally experience isotonic reactions.
Hypothesis: I think that the potato will absorb more starch than the sweet potato and they will both absorb relatively similar amounts of water.
Procedure: Variables: Controlled- water and size of potatoes. Manipulated variables- potatoes growth based on contents of solution.
Data and Observations
Bag Content Initial
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Those cells must receive nutrients and gases in order to undergo the metabolic processes that maintain homeostasis. In paragraph form, explain how you think the nutrients and gases enter the cell. Distinguish between the molecules that can enter by diffusion by simply moving across the membrane and those that must expend energy to cross the cell membrane.
- Nutrients enter cells in to major ways, through active and passive transport. When a molecule uses diffusion or other processes that require no energy, they are using passive transport. An example molecule for this would be water or glucose. Other molecules, that need to use energy to enter a cell use active transport. Many molecules that use this are macromolecules, like proteins. Molecules use one of these two transports to enter a cell.
8. List three criteria cells use to select materials to enter or leave the cell. Then explain the role of each criterion in determining the type of transport a cell will use for different sized molecules. For instance, small molecules move across the membrane by diffusion, given they are moving with the concentration gradient.
- Water can enter the cell in order to balance the amount inside to the amount of the environment. This is passive due to the fact that it happens without any external energy.
- Some molecules can pass into the cell by facilitated diffusion. This is passive due to the nature of diffusion and because the solute is moving down its

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