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Questions and Answers
What is the primary function of the cell membrane?
What is the primary function of the cell membrane?
What determines whether a molecule can cross the cell membrane?
What determines whether a molecule can cross the cell membrane?
Why can small nonpolar molecules easily cross the cell membrane?
Why can small nonpolar molecules easily cross the cell membrane?
What is the primary mechanism by which molecules like water, oxygen, and carbon dioxide cross the cell membrane?
What is the primary mechanism by which molecules like water, oxygen, and carbon dioxide cross the cell membrane?
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What is the main reason why large polar molecules and molecules with a charge cannot cross the cell membrane?
What is the main reason why large polar molecules and molecules with a charge cannot cross the cell membrane?
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What is true about molecules that are larger or have a charge?
What is true about molecules that are larger or have a charge?
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Study Notes
Cell Membrane Structure and Function
- The cell membrane provides a semipermeable barrier between the inside and outside of the cell, regulating the movement of molecules through the membrane.
Diffusion Across the Membrane
- Molecules tend to spread out, but some are blocked by the semipermeable cell membrane.
- Factors that determine if a molecule can cross the membrane include:
- Size of the molecule
- Polarity or charge of the molecule
- Small nonpolar molecules can easily cross the membrane because they interact favorably with nonpolar lipids.
- Small polar molecules can pass through small temporary holes in the membrane, despite poor interaction with lipids.
- Large polar molecules and molecules with a charge cannot cross the membrane due to their size and poor interaction with lipids.
- Molecules such as water, oxygen, and carbon dioxide can cross the cell membrane using simple diffusion, following their concentration gradient.
- Larger molecules or those with a charge require alternative mechanisms to cross the membrane.
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Description
Learn about the cell membrane's structure and function, and how it regulates molecular movement through diffusion. Understand the concepts of concentration gradients and molecular spread.
