Cell membrane

Definition

The cell membrane is a thin, flexible barrier that surrounds the cell, providing structural support and regulating the movement of substances in and out of the cell. It plays a critical role in maintaining cellular homeostasis by controlling the internal environment and facilitating communication between cells. The cell membrane is primarily composed of a phospholipid bilayer with embedded proteins, which help in transport and signaling.

5 Must Know Facts For Your Next Test

1. The cell membrane is often described as a 'fluid mosaic model' because it consists of various proteins floating in or on the fluid lipid bilayer.
2. Integral proteins span the membrane and assist in transporting molecules across the membrane, while peripheral proteins are located on the surface and play roles in signaling.
3. The cell membrane contains cholesterol molecules that help to stabilize its structure and maintain fluidity, particularly in varying temperatures.
4. Receptors on the cell membrane bind to signaling molecules (like hormones) and trigger specific cellular responses, playing a key role in communication between cells.
5. Endocytosis and exocytosis are processes that allow larger molecules to enter or exit the cell by enveloping them in portions of the cell membrane.

Review Questions

• How does the structure of the cell membrane contribute to its function in regulating what enters and exits the cell?
  • The structure of the cell membrane, primarily composed of a phospholipid bilayer with embedded proteins, is crucial for its function as a selective barrier. The hydrophobic interior of the bilayer restricts the passage of polar molecules, while integral proteins facilitate transport for specific substances through channels or carriers. This organization allows the membrane to effectively control the internal environment of the cell, maintaining homeostasis by regulating nutrient uptake and waste removal.
• Discuss the role of membrane proteins in facilitating communication and transport across the cell membrane.
  • Membrane proteins play essential roles in both communication and transport across the cell membrane. Receptor proteins bind specific signaling molecules, triggering intracellular responses that affect cellular activity. Meanwhile, transport proteins assist in moving substances into and out of the cell through various mechanisms such as facilitated diffusion and active transport, ensuring that essential nutrients enter while waste products are expelled. This coordination between transport and signaling supports overall cellular function and homeostasis.
• Evaluate how changes in cell membrane permeability can impact cellular homeostasis and overall health.
  • Changes in cell membrane permeability can significantly disrupt cellular homeostasis and lead to health issues. For example, if the membrane becomes too permeable due to damage or disease, it may allow harmful substances to enter or essential ions to leak out, disrupting ionic balance and metabolic processes. Conversely, reduced permeability may hinder nutrient uptake, impairing cellular function. Therefore, maintaining proper permeability is vital for cell health and overall physiological stability.

Related terms

Phospholipid Bilayer: A double layer of phospholipids that makes up the cell membrane, with hydrophilic heads facing outward and hydrophobic tails facing inward.

Diffusion:

The process by which molecules move from an area of higher concentration to an area of lower concentration, often occurring across the cell membrane.

Selective Permeability: The property of the cell membrane that allows certain substances to pass through while blocking others, crucial for maintaining homeostasis.