Study Notes
The structure of cell membranes is primarily composed of a phospholipid bilayer due to the amphipathic nature of phospholipids, which have both hydrophilic and hydrophobic regions. Membrane proteins are diverse and serve various functions, including transport and communication. Cholesterol is a component of animal cell membranes that influences fluidity and permeability.
- Phospholipid bilayer — A double layer of phospholipids that forms the backbone of the cell membrane. Example: The hydrophilic heads face outward towards water, while the hydrophobic tails face inward.
- Amphipathic — Molecules that have both hydrophilic and hydrophobic parts. Example: Phospholipids have a hydrophilic head and hydrophobic tail.
- Integral proteins — Proteins that are permanently embedded in the membrane, often spanning its entire width. Example: Channel proteins that allow substances to pass through the membrane.
- Peripheral proteins — Proteins temporarily associated with the membrane surface. Example: Enzymes that catalyze reactions on the membrane surface.
- Cholesterol — A lipid that modulates membrane fluidity and permeability in animal cells. Example: It prevents the membrane from becoming too rigid or too fluid.
Exam Tips
Key Definitions to Remember
- Phospholipid bilayer
- Amphipathic
- Integral proteins
- Peripheral proteins
- Cholesterol
Common Confusions
- Confusing the roles of integral and peripheral proteins
- Misunderstanding the function of cholesterol in plant vs. animal cells
Typical Exam Questions
- What is the role of cholesterol in animal cell membranes? It modulates membrane fluidity and reduces permeability to some solutes.
- How do phospholipids arrange themselves in water? They form a bilayer with hydrophilic heads facing outward and hydrophobic tails inward.
- What is the fluid mosaic model? It describes the membrane as a fluid structure with a mosaic of proteins embedded in or attached to a bilayer of phospholipids.
What Examiners Usually Test
- Understanding of the fluid mosaic model
- Functions of different types of membrane proteins
- Role of cholesterol in maintaining membrane integrity