Cell Membrane and Homeostasis

The cell membrane is a crucial component in maintaining cellular homeostasis. It functions as a regulator, controlling what can enter and exit the cell, protecting the cell's interior, and enabling cell-to-cell communication. The membrane's selective permeability allows only certain molecules to pass through, which is essential for maintaining the cell's internal balance.

Definition: Homeostasis is the cell's ability to maintain internal balance despite changes in the external environment.

The document introduces three important concepts related to cellular environments:

1. Hypertonic: An environment with a high solute concentration, causing cells to shrink.
2. Isotonic: An environment where solute concentration is equal inside and outside the cell.
3. Hypotonic: An environment with a low solute concentration, causing cells to swell.

Vocabulary: Selectively permeable means that some molecules small enough can pass through the membrane while other larger molecules cannot.

The text then delves into two crucial transport mechanisms:

1. Active transport: This process requires ATP energy and uses channel or carrier proteins to move solutes against the concentration gradient.

Example: The sodium-potassium pump is an example of active transport.

2. Facilitated diffusion: This process doesn't need ATP energy but still requires channel or carrier proteins. It allows solutes or water to move from areas of high concentration to low concentration.

Example: Aquaporins facilitate the movement of water molecules across the cell membrane.

The document also introduces the concept of concentration gradient, which is the gradual change in solute concentration as a function of distance through a solution.

Highlight: The surface area to volume ratio of a cell is crucial for its efficiency in transporting materials. Smaller cells with a higher surface area to volume ratio are more efficient at transporting materials in and out of the cell.