Biological Membranes Flashcards
(21 cards)
What is the fluid mosaic model?
The fluid mosaic model describes the structure of cell membranes as a flexible, dynamic bilayer of phospholipids with embedded proteins, cholesterol, glycoproteins, and glycolipids.
What are the roles of phospholipids in membranes?
Phospholipids form the bilayer, providing a barrier that separates the cell from its environment. The hydrophobic tails prevent polar substances from passing through easily.
What are the roles of proteins in membranes?
Proteins facilitate transport (e.g., channels and carriers), act as enzymes, or function as receptors.
What is the role of cholesterol in membranes?
Cholesterol regulates membrane fluidity, maintaining stability at high temperatures and preventing rigidity at low temperatures.
What are the roles of glycoproteins in membranes?
Glycoproteins act in cell recognition, signaling, and adhesion.
What are the roles of glycolipids in membranes?
Glycolipids are involved in cell recognition and act as receptors.
What are the key roles of membranes within cells?
Within cells, membranes separate organelles from the cytoplasm, maintain conditions for specific reactions, and enable vesicle formation for transport.
What are the key roles of membranes at the surface of cells?
At the surface, membranes regulate the entry and exit of substances, facilitate cell communication (e.g., via receptors), and provide structural support.
How do membranes control the movement of substances?
The phospholipid bilayer is selectively permeable, allowing small, non-polar molecules to diffuse through while restricting large, polar molecules and ions.
What is diffusion?
Diffusion is the passive movement of molecules from a high to low concentration without energy or proteins.
What is facilitated diffusion?
Facilitated diffusion is the passive transport of molecules via channel or carrier proteins down their concentration gradient.
What is active transport?
Active transport is the movement of molecules against their concentration gradient using carrier proteins and ATP.
Selective process as only certain molecules can bind to the receptor site on carrier proteins. ATP will bind to the protein on the inside of them membrane- is hydrolysed into ADP and Pi.
What is osmosis?
Osmosis is the passive movement of water molecules through a semi-permeable membrane from a region of high water potential to low water potential.
What is endocytosis?
Endocytosis is the active process of engulfing substances into the cell via vesicle formation.
What is exocytosis?
Exocytosis is the active process of vesicles fusing with the membrane to release substances outside the cell.
How does temperature affect membrane permeability?
High temperatures increase kinetic energy, causing phospholipids to become more fluid, leading to gaps and higher permeability.
How does alcohol affect membrane permeability?
Alcohol disrupts the phospholipid bilayer by dissolving lipids, increasing permeability.
How do you measure the permeability of a cell membrane experimentally?
Use beetroot cells, place samples in solutions with different temperatures or alcohol concentrations, and measure pigment leakage using a colorimeter.
What is an isotonic solution?
When water potential of the solution is the same in solution and the cell within the solution
What is a hypotonic solution
When water potential of a solution is more positive (closer to zero) than the cell
What is a hypertonic solution
When the water potential of a solution is more negative than the cell.
