Cell Transport Mechanisms Flashcards
(21 cards)
What does it mean when the plasma membrane is described as semi-permeable?
It allows selective molecules to pass while restricting others, based on membrane characteristics.
What determines the permeability of the plasma membrane?
The type of molecules, membrane proteins, and lipid solubility of substances.
What are the three main types of transport across the plasma membrane?
Diffusion (passive), Carrier-mediated (passive or active), and Vesicular transport (active).
What is diffusion?
The passive movement of molecules from an area of high concentration to low concentration due to random motion.
What factors influence the rate of diffusion?
Distance, molecule size, temperature, concentration gradient, and electrical forces.
What types of molecules use simple diffusion?
Lipid-soluble molecules like alcohols, fatty acids, steroids, and gases (O₂, CO₂).
How does facilitated diffusion differ from simple diffusion?
It requires protein channels or carrier proteins to help transport molecules across the membrane.
What is the role of carrier proteins in facilitated diffusion?
They bind to specific molecules, change shape, and transport them across the membrane.
What is osmosis?
The movement of water across a semi-permeable membrane from a lower solute concentration to a higher solute concentration.
What protein channels allow water movement during osmosis?
Aquaporins.
What is osmolarity?
The total solute concentration of a solution, measured in osmoles per liter (Osmol/L).
What happens to a cell in an isotonic solution?
No net water movement; the cell remains the same size.
What happens to a cell in a hypotonic solution?
Water moves into the cell, causing it to swell and possibly burst (lysis).
What happens to a cell in a hypertonic solution?
Water moves out of the cell, causing it to shrink (crenation).
Why would the infusion of pure water into the bloodstream be dangerous?
It would create a hypotonic environment, causing red blood cells to swell and burst.
What is the transmembrane potential?
The electrical difference across a cell’s plasma membrane.
What is the typical resting membrane potential of neurons?
Approximately -70mV.
What contributes to the transmembrane potential?
Unequal distribution of ions (Na⁺ and K⁺) and differences in membrane permeability.
How is the transmembrane potential important for neurons?
It allows for the transmission of nerve impulses.
What forces act on sodium (Na⁺) and potassium (K⁺) ions?
The chemical gradient (concentration differences) and the electrical gradient (charge differences).
Are there more sodium ions or potassium ions inside the cell?
- More potassium (K+ kk all good)
- Less sodium (Na+ no no)
