The rate of simple diffusion is always proportional to the solute concentration, while facilitated diffusion reaches a maximum rate.
Proton (H+) pumps and sodium-potassium (Na+-K+) pumps.
Proteins are scattered in a 'patchwork' arrangement within the bilayer.
It maintains structural relationships with neighboring cells for tissue formation.
The ability of phospholipids and proteins to move laterally within a monolayer.
The process where a cell takes up droplets of extracellular fluid in tiny vesicles, not selective in substances.
They are involved in physiological phenomena like cell-to-cell recognition for immune responses.
The Fluid Mosaic Model.
Carrier proteins for active transport bind with their molecules or ions on one side of the membrane only, while those for facilitated diffusion can bind on both sides.
It regulates the passage of substances, allowing only certain molecules to enter or exit.
They act as recognition/receptor sites for cell-to-cell recognition and immune response.
Cholesterol helps maintain membrane fluidity by acting as a buffer against temperature changes.
A process that transports substances down the concentration gradient using transport proteins, but does not require energy.
Water-soluble substances, such as ions.
The diffusion of water across a selectively permeable membrane, occurring down the concentration gradient without energy.
In a bilayer due to their amphipathic nature.
The intake of materials into cells.
Active processes that require expenditure of energy by the cell.
Carbohydrates attached to lipid and protein molecules, respectively.
They facilitate electron transport in the inner membrane of mitochondria.
To act as a barrier between the contents of a cell and the external environment.
An input of energy, specifically from the hydrolysis of ATP.
They maintain the structural integrity of a cell.
Because they are insoluble in lipids and cannot pass through the hydrophobic core of the phospholipid bilayer.
The transport of material into or out of a cell by enclosing the material within a fluid-filled, membrane-bound sac called a vesicle.
Lipids (phospholipids, cholesterol), proteins, and carbohydrates.
Phospholipids.
A cell engulfs large particles, such as bacteria, by extending pseudopodia to surround the particle.
It means they allow only certain molecules to pass through.
Cholesterol maintains membrane fluidity by increasing it at low temperatures and decreasing it at high temperatures.
Yes, it requires transport proteins.
Small, non-polar or hydrophobic substances such as oxygen, carbon dioxide, and lipids.
They are specific and can transport only one substance or a group of structurally similar ones across the membrane.
Concentration gradient, distance, area, size and nature of the molecule, and temperature.
Substances like proteins and polysaccharides that are too large to cross the membrane via transport proteins.
Exocytosis and Endocytosis.
Active transport moves substances against the concentration gradient and requires energy in the form of ATP.
The release of materials to the outside of the cells.
About 7.5 nm, typically ranging from 5 to 10 nm.
They are strongly attached.
Hydrophilic regions that interact with phospholipid heads and hydrophobic regions that interact with hydrocarbon tails.
Yes, it requires energy in the form of ATP.
By interactions between the hydrophilic and hydrophobic R groups of their amino acids with phospholipids.
Water molecules.
It slows down nervous transmission.
The polar heads interact with the aqueous environment via hydrogen bonds, ensuring stability.
Both involve net movement of particles down a concentration gradient and do not require energy from ATP hydrolysis.
They shield charged and polar particles from the hydrophobic core of the plasma membrane.
They are highly hydrophilic and help orient glycoproteins and glycolipids to face the exterior, forming hydrogen bonds with water to stabilize the membrane structure.
Some proteins serve as receptors for the attachment of signal molecules (e.g., hormones).
Phospholipids, cholesterol, proteins, carbohydrates.
They act as 'glue' for the adhesion of cells to neighboring cells for tissue formation.
They facilitate communication, transport, and protection.
They move through the membrane via carrier proteins, channel proteins, or protein pumps.
They vary between different types of cells.
As the length of the hydrocarbon chain increases, fluidity decreases due to increased intermolecular interactions between the hydrocarbon chains.
Fat-soluble substances and small molecules like carbon dioxide and oxygen.
The process by which cells expel materials to the outside environment.
The rate reaches a maximum (V max).
They attach to the cytoskeleton or extracellular matrix, strengthening the cell membrane framework.
Different conditions can be set up in organelles for enzyme activity.
It increases fluidity by disrupting the close packing of phospholipids, lowering the temperature at which the membrane solidifies.
A process that involves the movement of large quantities of substances across the membrane, often requiring energy.
Phospholipids, proteins, and cholesterol.
Temperature, cholesterol content, and the presence of unsaturated fatty acids.
Membranes become more fluid as the kinetic energy of the phospholipids increases, resulting in a reduction of intermolecular interactions and bonds.
Vesicles from phagocytosis are generally >250 nm in diameter, while pinocytic vesicles are about 100 nm.
The tendency of water molecules to leave the solution by osmosis.
Integral proteins that transport substances across the membrane.
Through a conformational change that exposes binding sites to different sides of the membrane.
By molecules that resemble the normal diffusing substances, which compete for the transport protein.
It allows cells to take up nutrients when external concentrations are lower and to eliminate waste when external concentrations are higher.
By regulating the passage of substances into and out of the cell.
Protein molecules embedded in the plasma membrane.
They allow cells to respond to chemical messengers like hormones.
It transports substances down the concentration gradient without requiring energy or transport proteins.
The patchwork distribution of proteins within the phospholipid bilayer.
The net movement of water molecules from a region of higher water potential to a region of lower water potential through a selectively permeable membrane.
Hydrophobic portions of proteins and the hydrocarbon tails of phospholipids.
Fluidity allows membranes to fuse, which is important for self-repair, fusion of transport vesicles, binding of metabolites and hormones, and activity of membrane-bound enzymes.
The more unsaturated the hydrocarbon chains are, the more fluid the membrane will be, as unsaturated chains prevent tight packing of phospholipids.
0.
It refers to the ability of a living cell membrane to allow certain substances to pass while blocking others.
It means there is a maximum rate of transport when all transport protein molecules are utilized.
Movement of ions or molecules across a membrane from a region of lower concentration to a region of higher concentration, using specific transport proteins and energy from ATP.
Cell surface (plasma) membrane and internal membranes (like nuclear membrane, ER).
The two sides of the membrane differ in lipid and protein composition.
Proteins that partially penetrate or span the entire membrane.
Simple diffusion, facilitated diffusion, osmosis, active transport, and bulk transport.
Cholesterol provides mechanical stability, preventing membranes from breaking easily.
Transport proteins allow water-soluble ions, glucose, amino acids, and proteins to be transported into or out of the cells.
Secretion of extracellular enzymes, hormones, antibodies, and removal of waste products of digestion.
A bilayer structure due to their amphipathic nature.
An 'antennae' layer formed by carbohydrates on the exterior surface of the cell membrane.
Channels that can open and close in response to specific signals.
Adenylyl cyclase is an enzyme that converts ATP to cyclic AMP (cAMP), involved in signal transduction pathways.
Oxygen and glucose for respiration.
Pinocytic vesicles are much smaller than phagocytic vesicles.
Lateral movement.
They form a water-filled pore in the membrane that allows water-soluble substances to pass through.
The net movement of molecules from a region of high concentration to a region of lower concentration until equilibrium is achieved.
It is a form of passive transport that does not require energy expenditure by the cell.
Cells that require higher water permeability, such as proximal kidney tubule cells.
The movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration.
They separate cell content from the surrounding environment, allowing compartmentalization.
They act as receptors, binding with chemicals like hormones to allow cells to respond to external stimuli.
Protein pumps.
It decreases fluidity by hindering the movement of phospholipids through interaction with hydrocarbon chains.
Hydrophilic and hydrophobic interactions.
Proteins that are loosely attached at the polar surfaces of phospholipids or proteins.
Phospholipids.
The process by which cells engulf substances from the outside environment.
Transport of substances down a concentration gradient via carrier proteins.
They allow for compartmentalization and formation of organelles.
Seymour Singer and Garth Nicolson in 1972.
Pinocytosis, phagocytosis, and receptor-mediated endocytosis.
Transmembrane proteins.
A food vacuole called a phagosome, which fuses with lysosomes to form a phagolysosome.
Hydrophilic portions of proteins and phosphate groups of phospholipids with the aqueous medium.
Variations in the type of phospholipids, such as length and saturation of hydrocarbon chains.
Through the lipid bilayer and through water channels called aquaporins.
Cholesterol has a hydrophilic region (-OH group) and a hydrophobic region, fitting between phospholipids.
Clathrin forms a coated pit that helps in the formation of a coated vesicle within the cytoplasm.
Integral membrane proteins that act as water channels.
A process where extracellular macromolecules bind to cell surface receptors, allowing the uptake of specific substances.
Due to the polar nature of water, despite its small size.
A vesicle pinched off from the Golgi apparatus moves toward the cell surface, fuses with the plasma membrane, and opens to release its contents outside the cell.
They are involved in the activity of various metabolic processes and transport of enzymes.
To move substances against their concentration gradient, requiring energy.
Energy transducer proteins, like electron carriers and ATP synthase, facilitate the transport of electrons and protons for ATP synthesis during respiration and photosynthesis.
Simple diffusion, osmosis, facilitated diffusion, active transport, endocytosis, and exocytosis.
An appropriate signal such as a change in voltage or binding of a hormone or ligand.
-200 kPa.
Short carbohydrate chains (oligosaccharides) attached to proteins and lipids, respectively.
They move from an area of higher concentration to an area of lower concentration.
Pressure (kPa).
The hydrophobic core of the phospholipid bilayer.
It triggers a conformational change that allows the solute to be released on the other side of the membrane.
One state exposes binding sites to the outside of the cell, and the other exposes them to the inside.
More solute binds to the carrier protein, resulting in net transport down its concentration gradient.
