Membranes and membrane transport Flashcards
(22 cards)
How does fatty acid composition affect membrane fluidity
Length of Fatty Acid Chains: Shorter fatty acid chains increase fluidity because they have fewer interactions with neighboring chains. Longer chains tend to be more rigid due to increased van der Waals interactions.
Degree of Saturation: Unsaturated fatty acids (which have one or more double bonds) introduce kinks in the hydrocarbon chain, preventing tight packing and enhancing fluidity. Saturated fatty acids, which lack double bonds, pack more closely together, reducing fluidity.
How does cholesterol affect membrane fluidity
Cholesterol is interspersed within the phospholipid bilayer
At high temperatures, cholesterol stabilizes the membrane, reducing fluidity by limiting the movement of phospholipids.
At low temperatures, cholesterol prevents the fatty acid chains from packing too closely, thus maintaining fluidity.
How does temperature affect membrane fluidity
As temperature increases, membrane fluidity also increases because the kinetic energy of molecules is higher, allowing them to move more freely.
Conversely, lowering the temperature decreases fluidity as molecular movement slows, potentially leading to phase changes.
What are the important components of membrane fluidity
protein mobility (facilitates lateral movement), cell communication (ensures receptors and signaling), and membrane fusion (allows merging of lipid bilayers)
Role of lipids in the fluid mosaic model of membrane
Lipids (primarily phospholipids and cholesterol) form the bilayer that serves as the fundamental barrier
- stable due to amphipathic nature
- fluidity and stability through cholesterol
Role of proteins in the fluid mosaic model of membrane
Membrane proteins are interspersed throughout the lipid bilayer
These proteins are involved in various functions, including:
transport (channels and carriers)
signaling (receptors)
cell recognition (glycoproteins)
Explain integral proteins
Permanently embedded within the hydrophobic core of the cell membrane.
Often have both hydrophilic (water-loving) regions exposed to the extracellular fluid and cytoplasm, and hydrophobic (water-hating) regions spanning the membrane.
Function as channels, transporters, receptors, and enzymes that facilitate movement of molecules across the membrane.
Explain Peripheral proteins
Non-covalently attached to the surface of the membrane, interacting with the polar head groups of phospholipids or with integral proteins through electrostatic interactions.
Can easily dissociate from the membrane.
Often involved in cell signaling pathways and cytoskeletal anchoring.
Explain Lipid-anchored proteins
Attached to the membrane by a lipid molecule covalently linked to the protein.
The lipid tail is embedded within the phospholipid bilayer, anchoring the protein to the membrane.
Can be located on either the inner or outer leaflet of the membrane depending on the lipid anchor.
Define diffusion
Passive movement of molecules from an area of high concentration to an area of low concentration, directly through the membrane.
Define Facilitated diffusion
Passive transport where molecules move across the membrane with the help of a specific transport protein, still following the concentration gradient.
Requires channels and transporters
Define Osmosis
The movement of water across a semipermeable membrane from a region of low solute concentration to a region of high solute concentration.
Define Active transport
Requires energy to move molecules against their concentration gradient, often using pumps powered by ATP.
Define endocytosis
Type of Vesicular Transport: Process where the cell engulfs large particles by forming vesicles from the plasma membrane.
Define exocytosis
Type of Vesicular Transport: the release of substances from the cell by fusing vesicles with the plasma membrane
Define passive diffusion
The movement of molecules from an area of higher concentration to an area of lower concentration without the input of energy
- down the concentration gradient
- no membrane proteins required, relies on permeability of lipid bilayer
Define Primary Active Transport
Directly uses energy from ATP hydrolysis to move substances against their gradient.
Example: The Na⁺/K⁺ pump, which moves sodium out of the cell and potassium into the cell.
Define Vesicular Transport
The process by which substances are transported in membrane-bound vesicles
Define channels
Facilitate the passive movement of ions and small molecules across the membrane.
Define transports/carriers
Mediate facilitated diffusion and active transport by binding to substrates and changing conformation.
Define pumps
Actively transport ions and molecules against their concentration gradient using energy.
