Cell Membrane Structure and Function

Overview

• All cells are surrounded by a membrane, also known as the plasma membrane.
• Acts as a barrier, regulating entry and exit of substances.
• Described as semi-permeable or selectively permeable.

Membrane Composition

Phospholipids

• Main component of the membrane.
• Composed of a phosphate head (hydrophilic) and two fatty acid tails (hydrophobic).
• Form a phospholipid bilayer:
  • Hydrophilic heads face watery environments (external and cytoplasm).
  • Hydrophobic tails face inward, away from water.
• Responsible for the semi-permeable nature of the membrane.

Cholesterol

• Stabilizes the membrane.
• Enhances membrane's ability to control substance passage.

Proteins

• Facilitate transport of materials across the membrane, especially larger or charged molecules.
• Perform various functions critical to cell operation.

Carbohydrates

• Involved in cell identification.
• Example: Membrane carbohydrates determine blood types.
• Attached to proteins, help distinguish own cells from foreign invaders.

Importance

• The plasma membrane is essential for life, serving as a critical barrier.

Additional Learning Resources

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