Ion Channels and Cellular homeostasis Flashcards
what is the fluid mosaic model ?
- embedded proteins in phospholipid bilayer can float lipids
what do structural proteins do in the plasma membrane ?
- Provide support and shape to the cell
what is the role of receptor proteins in cell membranes?
- facilitate communication with external signals (e.g., hormones, neurotransmitters).
what do channel proteins allow to pass through the cell membrane?
- allow passive flow of water, ions, and small molecules.
what are glycoproteins, and what is their function?
- proteins with carbohydrate chains that aid in cell signalling and adhesion.
how do hydrophobic substances move across the plasma membrane?
- they passively diffuse through the phospholipid bilayer.
what do hydrophilic substances require for transport across the membrane?
- carrier proteins
what substances can and cannot pass through membrane ?
- can = lipid soluble
- cannot = water soluble eg. glucose
how does water diffuse through the plasma membrane?
- water diffuses easily via aquaporins, which are specialized proteins forming always-open pores.
what is passive diffusion?
- the movement of molecules from high to low concentration without energy.
what is active transport?
- the movement of molecules from low to high concentration using energy (ATP) through protein carriers.
what is a hypertonic solution + what happens to cells ?
- has low water conc (high sugar conc) so water moves out of cell
- causes shell to shrink
what is a hypotonic solution + what happens to cells ?
- has high water conc so water moves into cell
- causes cell to swell
what is an isotonic solution + what happens to cells ?
- equal solute concentration to inside cells
- no net movement of water
- cell shape is normal / sam e
How does the Na-K pump work ?
- uses ATP to actively pump 2 K+ in and 3Na + out of the cell
What is the electrochemical driving force of Na⁺?
- chemical = higher conc of Na+ outside cell so wants to move in
- electrical = inside of the cell is slightly negative compared to the outside, attracting positively charged Na⁺ ions
- strong ECF provides source of potential energy
Why does Na+ not move into cells if there is a large electrochemical driving force ?
- plasma membrane has low permeability to Na+
What is secondary active transport?
- Na+ coupled simport allows cells to take up glucose
- Na+ and glucose move into cell
- uses energy from ECG
what is facilitated diffusion?
- molecules move down conc gradient with channel /carrier protein
what is electrochemical driving force on K+ ?
- high conc of K+ inside cell so wants to move to outside
- electrical force = K+ positive so still wants to move in since inside is slightly negative
- opposite forces
What does the Ca2+ pump do?
- actively pumps Ca2+ out of the cell, maintaining a steep gradient
- using ATP
What do ionotropic receptors do?
- allow Na+ and Ca2+ to flow into cells, evoking cellular responses.
what is the direction of Ca2+ driving force ?
- inwardly directed
- higher conc outside so wants to enter cell