Draw a phospholipid, identifying polar and nonpolar regions and describe how phospholipids behave in water. Draw a cell membrane with its four primary components. Rank the ability... Draw a phospholipid, identifying polar and nonpolar regions and describe how phospholipids behave in water. Draw a cell membrane with its four primary components. Rank the ability of the following substances to cross a phospholipid bilayer - large versus small molecules; polar versus nonpolar molecules; charged versus uncharged molecules. Predict the direction of movement of substances across membranes based on relative concentrations. Contrast the fluidity and permeability of a membrane composed of mostly saturated versus unsaturated phospholipids. Predict how the addition of cholesterol would alter membrane permeability.
Understand the Problem
The questions are asking for detailed explanations and drawings related to the structure and behavior of phospholipids in water, cell membranes and their components, the ability of substances to cross phospholipid bilayers, concentration gradients affecting substance movement, and the impact of saturated versus unsaturated phospholipids and cholesterol on membrane properties.
Answer
small nonpolar > small polar > large nonpolar > large polar > charged
To cross a phospholipid bilayer: small nonpolar molecules cross most easily, followed by small polar, large nonpolar, large polar, and charged molecules.
Answer for screen readers
To cross a phospholipid bilayer: small nonpolar molecules cross most easily, followed by small polar, large nonpolar, large polar, and charged molecules.
More Information
Phospholipids form bilayers in aqueous environments, creating the basic structure of cell membranes. The amphipathic nature of phospholipids drives this process.
Tips
A common mistake is assuming all polar molecules can cross the membrane easily. Remember, the lipid bilayer is more permeable to nonpolar molecules.
Sources
- Fluid mosaic model: cell membranes article - Khan Academy - khanacademy.org
- 3.1 The Cell Membrane – Anatomy & Physiology - open.oregonstate.education
- Structure of the plasma membrane (article) | Khan Academy - khanacademy.org
