MEMBRANE TRANSPORT MECHANISM

OBJECTIVES

• Understand factors that influence membrane permeability

• Know types of membrane transport and proposed mechanisms

MEMBRANE PERMEABILITY

Cell Membranes Are Selectively Permeable:

– Membranes allow flow of crucial materials in & out of cell while keeping out the unnecessary

TRANSPORT MECHANISMS

Permeability Depends on

Characteristics of Solute:

MEMBRANE PERMEABILITY: TRANSPORTED SUBSTANCE

TRANSPORT MECHANISMS• Active Transport

• Passive Transport

NOTE: Movement of substance can be into or out of cell!!!

PASSIVE TRANSPORT

MECHANISMSPassive Transport:

• Simple Diffusion

PASSIVE TRANSPORT

MECHANISMSPassive Transport

• Osmosis:

OSMOREGULATION• Cell survival depends on

balancing water uptake and loss

TONICITYTonicity• Compares solute

concentrations of two solutions – Hypertonic solution

– Hypotonic solution

– Isotonic solution

TONICITY

NOTE: Solute particles cannot move across membrane!!!

PASSIVE MECHANISMS

Passive Transport:

• Facilitated Diffusion:

ACTIVE TRANSPORT

MECHANISMSActive Transport

TRANSPORT OF LARGE MOLECULESBulk Transport Mechanisms:

• Endocytosis

TRANSPORT OF LARGE MOLECULESBulk Transport Mechanisms:

• Exocytosis