Cell membranes are the gatekeepers of life, controlling what enters and exits cells. They're made of a with embedded proteins, acting as a selective barrier. This structure allows for essential functions like transport and signaling.
Transport across cell membranes occurs through various mechanisms. Passive transport, like , requires no energy, while active transport uses ATP to move substances against concentration gradients. Understanding these processes is crucial for grasping cellular and function.
Cell Membrane Structure and Function
Components of cell membrane
Top images from around the web for Components of cell membrane
Components and Structure | OpenStax Biology 2e View original
Is this image relevant?
The Cell Membrane | Anatomy and Physiology I View original
Is this image relevant?
Components and Structure | OpenStax Biology 2e View original
Is this image relevant?
The Cell Membrane | Anatomy and Physiology I View original
Is this image relevant?
1 of 2
Top images from around the web for Components of cell membrane
Components and Structure | OpenStax Biology 2e View original
Is this image relevant?
The Cell Membrane | Anatomy and Physiology I View original
Is this image relevant?
Components and Structure | OpenStax Biology 2e View original
Is this image relevant?
The Cell Membrane | Anatomy and Physiology I View original
Is this image relevant?
1 of 2
Phospholipid bilayer consists of molecules with heads and tails that form a barrier between intracellular and extracellular environments and provides fluidity and flexibility to the membrane ()
embedded within the phospholipid bilayer include , , and that facilitate transport of molecules (ions, glucose) and cell signaling
attached to the surface of the membrane or to integral proteins serve as enzymes, structural elements, or anchors for the cytoskeleton
helps maintain and stability and regulates membrane permeability
is a layer of carbohydrates attached to membrane proteins and lipids that provides cell recognition and adhesion
are specialized membrane microdomains enriched in cholesterol and sphingolipids that play a role in signal transduction and protein trafficking
Structure and selective permeability
of the phospholipid bilayer prevents passage of polar and charged molecules (ions, amino acids) but allows diffusion of small, nonpolar molecules (oxygen, carbon dioxide)
Size and charge of molecules affect their ability to pass through the membrane, with small, uncharged molecules passing more easily than large, charged, or polar molecules
Membrane proteins, including channel proteins and carrier proteins, facilitate the passage of specific molecules and maintain concentration gradients and cellular homeostasis
Membrane fluidity is influenced by temperature, cholesterol content, and fatty acid composition, affecting the mobility of membrane components and their functions
Transport Mechanisms Across the Cell Membrane
Diffusion through lipid bilayer
Freely diffusible materials include small, nonpolar molecules (oxygen, carbon dioxide, ) and lipid-soluble molecules
Diffusion involves movement of molecules from high to low concentration, requires no energy input, and includes examples like oxygen and carbon dioxide exchange and water movement (osmosis)
involves movement of specific molecules (glucose via , ions through channels) through channel or carrier proteins down the
Active transport
Primary active transport directly uses ATP to power the transport of molecules against the , such as the sodium-potassium pump ()
Secondary active transport uses the electrochemical gradient created by primary active transport and includes examples like (SGLT) and (NCX)
Vesicular transport
involves uptake of extracellular materials by membrane invagination, including:
: uptake of large particles (bacteria, cell debris)
: uptake of fluids and solutes
involves release of intracellular materials by fusion with the membrane, such as neurotransmitter release at synapses
Membrane Electrical Properties
is the electrical potential difference across the , resulting from the unequal distribution of ions
are specialized membrane proteins that allow the selective passage of specific ions, contributing to the establishment and maintenance of membrane potential