B2.1 Flashcards
membranes and membrane transport (20 cards)
What are membranes essential for in cells?
They form the border between a cell and its environment.
What is the function of membranes within a eukaryotic cell?
Compartmentalize processes, regulate transport, and create distinct environments for functions like energy production.
What is the basic structure of a phospholipid molecule?
A phosphate head and two hydrocarbon tails.
How do phospholipids arrange themselves in a membrane?
The hydrophilic heads face outwards and the hydrophobic tails face inwards.
What is diffusion?
Movement from high concentration to low concentration.
What types of molecules diffuse easily through the phospholipid bilayer?
Non-polar molecules like oxygen.
Why do ions and polar molecules diffuse at slower rates through membranes?
The hydrophobic center of the membrane repels them.
Define integral proteins.
Hydrophobic proteins that may fit in one of the two phospholipid layers or extend across both.
What are peripheral proteins?
Hydrophilic proteins attached to the surface of integral proteins, often reversibly.
What role do aquaporins play in cell membranes?
They are water channels that facilitate the movement of water molecules.
Explain osmosis.
Movement of water from low solute concentration to high solute concentration through a semipermeable membrane.
What is facilitated diffusion?
A type of diffusion that allows ions and polar molecules to pass through membranes with the help of channel proteins.
What distinguishes pump proteins from diffusion channel proteins?
Energy requirement, direction of transport, and selectivity.
What is the energy requirement for pump proteins?
They require energy to function.
What is selective permeability in cell membranes?
The ability to allow passage of particular particles but not others.
What are glycoproteins?
Conjugated proteins with carbohydrates as the non-polypeptide component.
What are glycolipids?
Molecules consisting of carbohydrates linked to lipids.
What do glycoproteins and glycolipids contribute to?
Cell recognition and forming a carbohydrate-rich layer.
What is the fluid mosaic model of membrane structure?
A model describing the membrane as made of layers of various lipids and proteins allowing lateral movement.
Fill in the blank: The model of the membrane that is now accepted is known as the _____________.
fluid mosaic model.
