🧪 Unit 1: Chemistry of Life
1.3Introduction to Biological Macromolecules
1.4Properties of Biological Macromolecules
1.5Structure and Function of Biological Macromolecules
🧬 Unit 2: Cell Structure and Function
2.1Cell Structure: Subcellular Components
🔋 Unit 3: Cellular Energetics
🦠 Unit 4: Cell Communication and Cell Cycle
4.0Unit 4 Overview: Cell Communication and Cell Cycle
4.2Introduction to Signal Transduction
👪 Unit 5: Heredity
👻 Unit 6: Gene Expression and Regulation
🦍 Unit 7: Natural Selection
🌲 Unit 8: Ecology
8.4Effect of Density of Populations
👏 General Review
✍️ Free Response Questions (FRQ)
Biology Long Essay Free Response Questions
Biology Short Essay Free Response Questions
🧐 Multiple Choice Questions (MCQ)
Biology Multiple Choice Questions
⏱️ 1 min read
June 8, 2020
Thanks to the structure of the membrane, with the hydrophobic tails and hydrophilic heads, the cellular membrane has selective permeability. This allows some substances to cross easily, while others may not be able to cross or may require a special transport protein to do so.
The membrane acts like a barrier separating the inside of the cell from the external environment of the cell.
Small, non-polar molecules are able to freely cross the cell membrane, while polar or charged molecules require transport proteins to cross. If a molecule is small, polar, and uncharged (like water!) it may be able to pass through the membrane in small quantities but requires a transport protein to move across in any larger quantities.
The hydrophobic fatty acid tails are what controls the movement of substances described above. They repel charged and polar molecules and make it very challenging for them to come across.
Image courtesy of WikiMedia Commons.
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