10. Ions and Cells Flashcards
Why are intracelluar ion concentrations different to extracelluar ion concentrations and how do the ions move?
Essential for cell survival - osmosis.
active transport is required to move ions against their concentration gradient
What is an electrical potential difference
A difference in electrical potential on each side of the cell - inside is more negative than the extracelluar side. This is a membrane potential
What is the ionic basis of a membrane potential? Ie how does it change
A very small flow of ions carry a charge to cause a large change in the membrane potential
What is a chemical gradient and an electrical gradient?
chemical gradient: the difference in solute concentratration across a membrane
electrical gradient: difference in charge across a membrane
What is an electrochemical gradient and what is required for it?
the sum of a chemical and electrical gradient. its required for potential energy
What is an electro genie pump?
Electrogenic pumps are primary active transports. They hydrolyse ATP and use the energy released from ATP hydrolysis to transport ions across the membrane
The sodium potassium pump is an electrogenic pump because its going against the concentration gradient and hydrolysing ATP for energy to do so
Why is the sodium potassium pump so important? Three points
- prevents sodium acculation in cell
- preventing swelling of cells due to osmosis
- maintains the sodium/potassium concentration gradients across membrane
- generates electical signals along nerves and muscel cells
- provides energy for ions
What is the difference between primary active transport and secondary active transport?
Primary active transport hydrolysis ATP directly and creates a large concentration gradient
secondary active transport uses the energy stored in the sodium gradient - it isn’t linked to the hydrolysis of ATP
What does uniport and coupled transport (2 types) do?
Uniport: is just one molecule being transported through a protein in the bilayer
coupled transport: two molecules going through the bilayer - symport is when they both go the same direction, antiport is when they are in different diections
What is the difference between the total amount of calcium ICF and ECF and free calcium
The total number of calcium ions ICF and ECF is similar, but inside cells (ICF) calcium is bound to proteins and molecules or hidden. Free ionised calcium inside cells is very low!
Why do cells kept cytosolic Ca2+ at very low levels? 2 points
It stops precipitation of calcium phosphates as they are insoluable.
the Ca2+ concentation can change rapidly so can be used to cell signalling.
How does the cell keep cytosolic Ca2+ at low levels in comparison to extracelluar?
Primary and secondary active transport to pump calcium out, hydrolyse ATP–> ADP then that energy can be used to pump out more calcium ions and sodium ions in.
theres a Ca2+ pump on the ER which stores calcium
What are ion channels made of?
They consist of transmembrane proteins with conducting pores
what are two important features of ion channels?
- There is a high rate of ions passing through them
- when an ion channel is open, the ions more down their electrochemical gradient
What are the two types of ion channels and what are their main features?
Leakage channels: they are always open
gated: can be open or closed, depends on the comformation of the protein that makes the channel
What is hyperpolarisation and depolarisation?
Hyperpolarisation: the stimuli causes the membrane potential to become more negative eg -70mv to -100mv
depolarisation: the stimuli causes the membrane potential to become more positive, eg -70mv to 0
