Lecture7-Osmosis Flashcards
Understand the terms "diffusion" and "osmosis". Predict how water will move across a membrane to balance tonicity. Understand chemical and electrical gradients and define the term "Resting Membrane Potential" Briefly describe what is occurring during a depolarization and repolarization.
whats a Hypotonic solution explain the concept as well.
high water conc outside cell, water moves into the cell
cell swells becomes turgid.
EXPLANATION:
Remember that whether a solution is hypertonic, or hypotonic is referenced from the ECF. So a hypotonic cell means that the ECF has very low conc( lots of water), so the water will move to the ICF to equalise conc. So the water volume would decrease from ECF and go into the cell(ICF)( TO EQUALISE CONC) this WILL THUS CAUSE SWELLING( Gummy bear example.
Isotonic solution
equal water conc
no net movement of water
cell size remains unchanged.
Explanation: ECF and ICF have some conc of solute, evenly spread
hypertonic cell
low conc of water compared to the inside of the cell.
water moves out the cell
cell shrinks/becomes flaccid
Explanation.
Remember whether a solution is hypertonic, or hypotonic is referenced from the ECF.
In a hypertonic cell, the ECF has a very high solute concentration compared to ICF. so the water will move from ICF into the ECF to equalise the concentrations by Diluting ECF. THIS DECREASES THE VOLUME IN THE ICF, and the cell shrinks, and becomes flaccid.
whats osmosis
movement of water across a membrane to equalise solute conc.
cell membrane divides our body fluid volumes into intracellular and extracellular spaces.
water conc is dynamic on both sides and so is the conc of solutes and ions.
Osmosis works to balance tonicity between the intracellular and extracellular spaces.
water in human body
females=50% of body mass
Males-60% of body mass
Distribution-
Intracellular fluid=2/3 of TBW
extracellular fluid=1/3 of TBW
- interstitial fluid=4/5 ECF
-plamsa- 1/5 ECF
Resting membrane potential
Resting membrane potential is the diff in charge on the outside of the membrane compared to the inside. ie more negative charges in the cell compared to outside. NA+ and K+ are important for RMB.
ions stop moving around at one point, this is called the RMP.
At rest, the intracellular space is more negatively charged than the
extracellular space. The electrical gradient when the cell is at rest is
known as the resting membrane potential.
Depolarisation
Positive ions enter the cell during depolarization, which acts as a
signalling event for excitable cells.
Depolarization occurs when the membrane potential becomes less negative (e.g., Na+ channels open, allowing Na+ into the cell).
Repolaraistaion
The positive ions are then
removed during repolarization to return to the resting membrane
potential.
Repolarization occurs when the membrane potential returns to its resting state (e.g., K+ channels open, allowing K+ out of the cell).
What is osmosis, give a definition and explain the concept.
Osmosis is the movement of water across a membrane to equalise solute concentration.
The cell membrane divides our body fluid volumes into extracellular space and intracellular space. water conc in dynamic on both sides.
concept:
The semi-permeable membrane doesn’t let the solutes go through, so the concentrations of solute are equal in ECF and ICF. So to equalise concentration, water moves instead, to balance the solute conc on both sides
Whats a chemical gradient
The uneven distribution of molecules across the membrane creates a chemical gradient.
there are 2 gradients that are opposite to each other present.
- ECF has high Na and ICF low NA
- ECF has low k and ICF has high K
both the NA+ and K+ are imbalanced.
remember bananas in the cell, bananas have potassium.
whats an electrical gradient
The uneven distribution of charges across the membrane creates an electrical gradient.
CELLS ARE NEGATIVE INSIDE, this is because of the sodium-potassium pump, it pumps 2 K+ inside the cell for every 3Na+ out of the cell, so overall cell is more negative.
Describe and explain the sodium-potassium pump
The sodium-potassium exchange pump maintains the chemical and electrical gradients across the cell membrane
The sodium-potassium exchange pump is an ACTIVE pump, meaning it uses energy (ATP) to move molecules.
It has to be active because it’s working against chemical and electrical gradients!
It moves three sodium (Na⁺) ions out of the cell and brings two potassium (K⁺) ions in for every ATP used.
This creates chemical gradients for both sodium and potassium, as well as maintaining the electrical gradient (more positives leaving the cell means the inside becomes more negative). SO IT MAINTAINS THE INSIDE OF THE CELL TO BE NEGATIVE WHICH IS ITS RESTING MEMBRANE POTENTIAL.
How do the chemical and electrical gradients allow rapid signalling in excitable cells?
Chemical and electrical gradients allow rapid
signalling in excitable cells
Ions are highly driven to move down their concentration ( high to low) and electrical gradients…to
equalise the inside and the outside of the cell.
But they can’t! The cell membrane is semi-
permeable and won’t allow the ions through.
SO the moment a pathway opens, the ions will
rush in/out along their gradient.
The bigger the gradient, the faster and stronger the signal!
