Plasma Membrane Lecture 2

Study Notes

Understanding basic cell structures and their functions is fundamental to cell biology.
The plasma membrane is a lipid bilayer incorporated with proteins that plays a crucial role in cellular functions.
Key functions of the plasma membrane include selective permeability and communication with the external environment.
Distribution of phospholipids and proteins significantly affects the membrane's permeability to ions and compounds.
Carbohydrate components of the plasma membrane are vital for cell recognition and interaction.
Protein components of the plasma membrane have diverse functions, including substance transport and signal transduction.

Plasma membrane: A fluid lipid bilayer with embedded proteins, forming the outer boundary of the cell.
Cytoplasm contains:
- Membranous organelles: Such as endoplasmic reticulum, Golgi complex, lysosomes, peroxisomes, mitochondria.
- Nonmembranous organelles: Including ribosomes, proteasomes, vaults, and centrioles.
- Cytoskeleton: A protein scaffold that maintains cell shape and facilitates movements.
- Cytosol: A gel-like liquid that hosts various cellular processes.
Nucleus: Contains genetic material and directs protein synthesis, ensuring proper cell replication and function.

The plasma membrane regulates the movement of molecules between intracellular fluid (ICF) and extracellular fluid (ECF).
Endoplasmic reticulum serves as the primary site for protein and lipid synthesis.
Golgi complex processes, packages, and distributes proteins synthesized in the cell.
Mitochondria are critical for ATP production, functioning as energy organelles.
The cytoskeleton provides structural support and aids in intracellular transport.

Comprises phospholipids and cholesterol that contribute to fluidity and stability.
Membrane carbohydrates serve as recognition markers for cell identity and interaction.

Creates a boundary that houses the cell's internal environment, maintaining differences in ion concentrations vital for electrical activity.
Facilitates cell adhesion to form tissues and organs.
Enables cellular responses to environmental chemical signals.

Main structural element of the plasma membrane, creating a hydrophobic barrier to water-soluble substances.
Fluidity of the membrane allows for dynamic cellular functions, and cholesterol enhances both fluidity and stability.

Act as self-identity markers for cells, influencing growth and maintaining tissue boundaries to prevent overgrowth.
Different cell types express unique carbohydrate markers for recognition.

Carrier Proteins: Transport specific substances that cannot cross the membrane unaided; can function as uniport, symport, or antiport.
Channel Proteins: Create water-filled pathways, allowing water-soluble substances to pass through; includes leak channels and gated channels.