Active Cell Physiology - Lecture 7 Flashcards
What is diffusion
Movement of molecules from high to low concentration gradient
What is osmosis
Movement of water across a membrane to equalise solute concentration
Semipermeable membrane
Only allowing some molecules through
Don’t like large molecules or sugars or polar molecules and dislike ions
They like water
What does the Cell membrane do
It divides our body fluid volumes into intracellular and extracellular spaces, and this is where osmosis needs to happen as the cell membrane is a semipermeable membrane, it is preventing movement of a lot of different types of molecules in and out of cells. This is where we move water by diffusion in a process known as osmosis.
Isotonic
If the concentration of solute molecules on both sides (intracellular and extracellular ) are the same. And NO PRESSURE IS NEEDED
Hypertonic
Water loss from the extracellular fluid decreases volume and makes the solution hypertonic with respect to the intracellular fluid
An osmotic water shift from ICF into the ECF will restore osmotic equilibrium but decrease the ICF volume
Hypotonic
This is when the concentration of the ECF is low as there is more water, this means that there is low tonicity.
The cell will swell in hypotonic solution
Hypotonic solution affecting the intergrity of cells
Water molecules would move into the blood cell and the cell would swell up
Hypertonic solution effecting the integrity of cells
The cell will shrivel and die
Chemical gradient
Uneven distribution of MOLECULES across the membrane
Electrical gradient
Uneven distribution of CHARGES across the membrane
What can we do if ions are imbalanced on both sides
We can move ions down a chemical gradient through passive ion channels this makes it easy to try equalise concentration on each side. The channels don’t need energy to work
What does active pump do
Working against concentration gradient, it needs to use energy ( ATP )
Moving Na+ out of cells and K+ into cells
How are the potassium and sodium gradient maintained
They are maintained by active pumps that use energy to move ions against their concentration gradient
Resting membrane potential
When the cell is at rest, the intercellular space has more negative charge than the extracellular space, creating an electrical gradient
It’s typical value is around -70mV
What is sodium potassium pump
Ensuring that the resting membrane potential is at a level that enables an action potential to be possible at any time. The cell membrane needs more negative intracellular for this to be accomplished
Permeability of K+
The energy ( ATP to ADP ) realised drives the pump to ensure that internal Na+ is exchanged for external K+ ( 2K+ for 3Na+ ions ). This allows the intercellular charge to reach -70mV to 80mV or resting membrane potential to set an environment for action potentials to occur with proper simulation and release of neurotransmitter
Why are ions distributed unevenly across the cell membrane at rest
To create chemical and electrical gradients
What happens to the intracellular space at rest
It is more negatively charged.
What is the electrical gradient called when the cell is at rest
Resting membrane potential
Does positive or negative ions enter the cell during polarisation
Positive ions, which act as a signalling event for excitable cells, the positive ions are then removed during repolorization to return to the resting membrane potential
What happens during depolarisation
Positive ions enter the cell, which acts as a signalling event for excitable cells. The positive ions are then removed during repolorization to return to the resting membrane potential
What creates the electrical gradient known as the resting membrane potential
Uneven distribution of ions across the cell membrane
What is the function of active pumps
Maintains the sodium and potassium gradients by using energy to move ions against their concentration gradient
During depolarisation, what occurs in excitable cells
Positive ions enter the cell, creating an electrical gradient
Higher solute concentration compared to another solution
Hypertonic
What is the term for the state where a cell has lost water due to being placed in hypertonic solution
Plasmolysis
What is the primary driving force for the movement of ions during depolarisation
Chemical gradients
What ion is more abunedent in the extracellular space compared to the intercellular space
Na+
What maintains the resting membrane potential in excitable cells
Movement of ions through passive channels
What best describes resting membrane potential
The difference in electrical charge between the inside and the outside of the cell at rest
Main function of ion channels in excitable cells
To provide a pathway for ions to move down their concentration gradient
What channels open, allowing positive ions to enter the cell
Sodium channels
What is the main function of ion channels in a cell membrane
Provide passive pathway for ions to move down their concentration gradient
During repolorization, what channels open to allow positive ions to exit the cell
Potassium channels
What is the primary force driving the movement of ions during depolarisation
Electrical gradients
