Cell Membrane Transport Processes

Movement of substances across a cell membrane without requiring energy. This type of transport occurs down a concentration gradient, from a region of high concentration to a region of low concentration.

Movement of substances across a cell membrane requiring energy. It occurs against a concentration gradient, from a region of low concentration to a region of high concentration.

Active transport that directly utilizes ATP for energy. This type of transport uses transport proteins to move substances against their concentration gradients.

A primary active transport protein that pumps sodium ions out of the cell and potassium ions into the cell. This process uses ATP energy and maintains the concentration gradients of these ions.

Active transport that utilizes the energy stored in the electrochemical gradient of another substance to move a second substance against its concentration gradient. It indirectly relies on ATP, using the energy established by primary active transport.

The movement of molecules from a region of high concentration to a region of low concentration, driven by the kinetic energy of the molecules.

The rate of diffusion is influenced by several factors, including the concentration gradient, temperature, surface area, and the type of molecule or ion diffusing.

The movement of molecules directly across the cell membrane without the assistance of transport proteins. This occurs for small nonpolar molecules and some ions.

The movement of molecules across the cell membrane with the help of transport proteins. This is necessary for larger polar molecules that cannot cross the membrane directly.

Protein pores in the cell membrane that allow specific ions to pass through. They are gated, meaning they can be opened or closed.

Ion channels can be classified based on their activation mechanism:

Ion channels that open or close in response to changes in the electrical potential across the cell membrane.

Ion channels that open or close in response to the binding of a specific molecule, called a ligand, to the channel.

SGLT1 is a protein found in the gut and kidneys that helps transport glucose across cell membranes. It uses sodium to move glucose, either in the same direction (symport) or in the opposite direction (antiport).

In the kidney, SGLT1 helps reabsorb glucose back into the bloodstream. It uses sodium to transport glucose from the kidney tubules into the cells lining the tubules, and then glucose moves into the blood via another transporter called GLUT2.

Symport is when two molecules are transported in the same direction across a membrane, while antiport is when they are transported in opposite directions.

The cell membrane is a thin, flexible barrier that encloses every cell, separating its internal environment (cytoplasm) from the external environment. It's vital for cell function, controlling what enters and exits, allowing communication with other cells, and providing structural support.

Secondary active transport is a type of membrane transport that uses the energy from the movement of one molecule down its concentration gradient to move another molecule against its gradient.

GLUT2 is a protein that facilitates the movement of glucose across cell membranes. It allows glucose to move down its concentration gradient, from areas of high concentration to low concentration, without requiring energy.

The fluid mosaic model describes the cell membrane's structure. It's a dynamic, fluid arrangement of phospholipids and proteins, like a constantly moving sea. The phospholipids form a bilayer, with hydrophilic heads facing outward and hydrophobic tails in the middle. Proteins are embedded within this bilayer, acting as channels, receptors or carriers.

The cell membrane regulates the transport of substances across it, ensuring essential molecules like nutrients and oxygen enter the cell, while waste products exit. This control is vital for maintaining the cell's internal environment and function.

Endocytosis is a process where cells engulf molecules or particles from the outside by forming vesicles that bud inward from the plasma membrane.

Transmembrane proteins are integral membrane proteins that span the entire membrane, with parts extending into both the intracellular fluid (ICF) and extracellular fluid (ECF). These proteins play crucial roles in communication, transport, and anchoring.

There are three main types: fluid endocytosis (pinocytosis) where the cell takes in fluid, phagocytosis where cells engulf large particles, and receptor-mediated endocytosis where cells take in specific molecules by binding to receptors on their surface.

Integral membrane proteins are embedded within the phospholipid bilayer, held in place by hydrophobic interactions. They are tightly bound to the membrane. Peripheral membrane proteins, on the other hand, are loosely associated with the membrane surface through electrostatic interactions.

Exocytosis is the process by which cells export molecules or particles outside the cell by forming vesicles that fuse with the plasma membrane and release their contents.

The cell membrane is selectively permeable because it controls which substances can pass through. It allows some molecules to enter while blocking others, based on size, charge, and chemical properties. This selectivity is essential for maintaining the cell's internal environment.

The cell membrane has several crucial roles: separating the cell's internal environment from the external environment, regulating the passage of substances, receiving chemical signals (communication), linking adjacent cells, and anchoring cells to the extracellular matrix.

The cell membrane ensures that the composition of the intracellular fluid (ICF) is different from the extracellular fluid (ECF). This difference is vital for normal cell function. Maintaining distinct compositions allows for processes like nutrient uptake, waste removal, and communication between cells.