The Structural Organization of Human Cells (Plasma Membrane)

Cytology

The study of single body cells and their internal structures (microscopic anatomy)

General Functions of Human Body Cells

Cover external and internal structures, lining, storage, movement, connection, defense, communication, reproduction

3 basic parts of a human cell

Plasma membrane, cytoplasm, nucleus

Plasma Membrane (cell membrane or plasmalemma)

Extremely thin, outer border of the cell that separates the intracellular and extracellular fluid compartments

Composition and Structure of plasma membrane

Primarily a phospholipid bilayer with proteins interspersed throughout

Functions of plasma membrane

Communication, intercellular connection, physical barrier, selective permeability, protecting the cell from the outside

Plasma membrane general transport mechanisms

Passive transport: Materials move down with their concentration gradients high to low

Active transport: Materials move against their concentration gradients (low to high) or large in size or quantity

Two general types of membrane transport

Passive transport and active transport

Passive transport mechanisms

Simple diffusion, osmosis, and facilitated diffusion

Simple diffusion

Small, non polar molecules move from high to low concentration

Osmosis (special time of simple diffusion)

Diffusion of water

Facilitated diffusion

Transport proteins, help move molecules across membrane (Large molecules move down with concentration gradient)

Active Transport

Requires energy in the form of ATP to move substances across the membrane

Bulk Transport

A type of active transport. Move large molecules or bulk structures across the plasma membrane

Types of Bulk transport

Exocytosis and Endocytosis

Exocytosis

Material packaged into vesicles and secreted out of the cell when vesicles fuse with the plasma membrane

Endocytosis

Materials are taken into the cell, packaged into vesicle

Forms of endocytosis

Phagocytosis and pinocytosis

Phagocytosis

Nonspecific uptake of particles by formation of membrane extensions (pseudopodia) that surround and engulf particles

Pinocytosis

Nonspecific uptake of cellular fluid