BIO101 ‒ Topic 6: Cell Membrane and Transport Systems
Course Code: BIO 101
Course Name: General Biology
© Lesuyai Organic Guides (Original ¦ Educational ¦ Professional ¦ Plagiarism-Free ¦ A4
Format)
6.1 Structure of the Cell Membrane
The cell membrane, also called the plasma membrane, is a thin, flexible barrier that
surrounds the cell, separating the internal cytoplasm from the external environment. It is
essential for maintaining homeostasis and controlling what enters and exits the cell.
Key Features of the Cell Membrane:
- **Phospholipid Bilayer:** Composed of two layers of phospholipids with hydrophilic
heads facing outward and hydrophobic tails inward.
- **Proteins:** Embedded within the bilayer; include integral proteins (span the
membrane) and peripheral proteins (attach to surfaces).
- **Cholesterol:** Provides stability and fluidity to the membrane.
- **Carbohydrates:** Attached to proteins or lipids, forming glycoproteins and glycolipids
for cell recognition and communication.
Text-Based Diagram Description: Imagine the membrane as a sea of lipids with
proteins floating like islands. Hydrophilic heads face outward to water, tails inward away
from water, proteins span across or sit on the surface, and carbohydrate chains extend
outward for signaling.
6.2 Properties and Functions of the Cell Membrane
**Properties:**
1. Selective Permeability: Allows only specific substances to enter or exit the cell.
2. Fluidity: Lipids and proteins can move laterally within the membrane, allowing
flexibility.
3. Dynamic Nature: Continuously adapts during cell growth, division, and
endocytosis/exocytosis.
**Functions:**
- Regulates movement of materials into and out of the cell.
Course Code: BIO 101
Course Name: General Biology
© Lesuyai Organic Guides (Original ¦ Educational ¦ Professional ¦ Plagiarism-Free ¦ A4
Format)
6.1 Structure of the Cell Membrane
The cell membrane, also called the plasma membrane, is a thin, flexible barrier that
surrounds the cell, separating the internal cytoplasm from the external environment. It is
essential for maintaining homeostasis and controlling what enters and exits the cell.
Key Features of the Cell Membrane:
- **Phospholipid Bilayer:** Composed of two layers of phospholipids with hydrophilic
heads facing outward and hydrophobic tails inward.
- **Proteins:** Embedded within the bilayer; include integral proteins (span the
membrane) and peripheral proteins (attach to surfaces).
- **Cholesterol:** Provides stability and fluidity to the membrane.
- **Carbohydrates:** Attached to proteins or lipids, forming glycoproteins and glycolipids
for cell recognition and communication.
Text-Based Diagram Description: Imagine the membrane as a sea of lipids with
proteins floating like islands. Hydrophilic heads face outward to water, tails inward away
from water, proteins span across or sit on the surface, and carbohydrate chains extend
outward for signaling.
6.2 Properties and Functions of the Cell Membrane
**Properties:**
1. Selective Permeability: Allows only specific substances to enter or exit the cell.
2. Fluidity: Lipids and proteins can move laterally within the membrane, allowing
flexibility.
3. Dynamic Nature: Continuously adapts during cell growth, division, and
endocytosis/exocytosis.
**Functions:**
- Regulates movement of materials into and out of the cell.
