Chapter 11: Membrane Transport of Small Molecules and the Electrical Properties of Membranes

Selective Permeability

Selective Permeability

The property of a membrane that allows certain substances to pass while restricting the passage of others, based on factors such as molecular size, charge, and lipid solubility.

Passive Transport

The movement of molecules across a membrane without the input of energy, primarily through diffusion from an area of high concentration to an area of low concentration.

Active Transport

The movement of molecules across a membrane that requires the expenditure of energy, usually in the form of ATP, to transport molecules against their concentration gradient.

Endocytosis

The process by which cells engulf substances from the extracellular environment by forming vesicles.

Exocytosis

The process by which vesicles fuse with the cell membrane, releasing their contents into the extracellular space.

Membrane Potential

The voltage difference across the cell membrane, usually maintained by ion concentration gradients, and important for various cellular functions.

Transporters

Integral membrane proteins that facilitate the movement of specific molecules across the membrane, either through active or passive mechanisms.

Ion Channels

Specialized membrane proteins that allow the selective passage of ions across the cell membrane, playing a crucial role in maintaining the electrical properties of membranes.

Resting Membrane Potential

The electrical potential difference across the cell membrane when the cell is at rest, typically around -70 millivolts (mV), primarily determined by the differential distribution of ions across the membrane.

Action Potentials

Rapid and transient changes in the membrane potential that allow for long-range communication in excitable cells such as neurons and muscle cells.

Synaptic Transmission

The process by which neurotransmitters are released from the presynaptic neuron and bind to receptors on the postsynaptic neuron, leading to changes in the postsynaptic membrane potential.

Endocytosis

bulk transport

Pinocytosis

ingestion of liquid material

Phagocytosis

Ingestion of solid complex materials

Conductance

It refers to the ability of an ion channel to allow the flow of ions.

Permeability

It is the measure of the ease with which ions can pass through a channel.

Ion Selectivity

Ion channels exhibit selectivity for specific ions based on their size, charge, and hydration.

Synaptic transmission

It involves the release of neurotransmitters from the presynaptic neuron, which then bind to receptors on the postsynaptic neuron.

Depolarization

It refers to a change in the membrane potential towards a more positive value, typically caused by the influx of positively charged ions.

Repolarization

It is the process of returning the membrane potential back to its resting state after depolarization.