Active Cell Physiology

• Define Diffusion


  A concentraion gradient where the movement of molecules move from a high concentraion to a low concentration.
• The movement of diffusion can occur in solids, liquids and gases. This is crucial for movement in cells such as nutrients and waste. 


  Nutrients and Waste
• Define osmosis

  A type of diffusion that involves water molecules across a semi-permeable membrane. This is when lower water concentration moves to a high concentration of solutes until equilibrium is reached.
• Define semi-permeable membrane

  It allows certain particles to move across depending on size, charge and shape.
• The cell membrane divides the body fluid volumes into intracellular and extracellular spaces.
• How will water move across a membrane to balance the tonicity? 


  By Isotonic, hypertonic and hypotonic solutions.
• What is isotonic solution?

  The concentration, which maintains cell volume) of water remain the same on both sides and there is no net movement as the molecules are moving back and forth across the membrane.
• What is Hypertonic Solution

  The concentration of solutes is higher outside the cell, leaving free water molecules outside the cell. This means the water molecules will move across the semi-permeable membrane from a higher concentration to a lower concentration.

  This causes the cell to shrink or undergo crenation.
• What is Hypotonic Solution?

  When the concentration of solutes is lower outside the cell, leaving more free moving water molecules inside the cell. The water molecules will move across the semi-permeable membrane from a high concentration to a lower concentration.

  This causes the cell to swell and burst.
• What is Chemical gradient?

  It is caused by an uneven distribution of molecules across the membrane.

  They drive movements of ions through various channels and transporters to achieve equilibrium, but can't because they are a semi-permeable membrane, so when a passage opens, the ions will quickly move in.
• What is electrical gradient?

  It is the difference in electrically charged ions across a membrane. The difference in charged in determined by the ions.

  Mostly (Na+), (K+), (Cl-), (Ca+).

  They determine the direction and magnitude of ions movement across the membrane. Gradients are actively pumped that use energy.

  The intracellular gradient has more negative charge than the extracellular, which creates the electrical gradient.
• What is resting membrane potential?

  The electrical charge difference between the inside and outside the cell when it is not actively sending signals (mostly negative inside the cell). It is determined by concentration gradients and permeability of ions,

  which is essential for cell functions:

  ion homeostasis, nerve & muscle neuron's and cell communication.
• What is occurring during a depolarisation and repolarisation?

  Changes in electrical potential difference across the cell membrane.
• What is Depolarisation?

  It is the initial of action potential.

  When the traversal reversal of the membrane potential resting

  resting value to a more positive value.

  This occurs when positive charged cons rush through the gate cell voltage channels, which is the interior of cell becomes more less negative or positive compared to the exterior.
• What is repolarisation?

  Process when the cell membrane returns to it's resting membrane potential after depolarisation. it involves the movement of ions (K+) out of the cell gated voltage channels. The result is efflux of positive charged ions become more negative again.

  It prepares cell for depolarisation events, maintains proper cell function.
• What is most likely to result in a depolarization of excitable cell?

  Positive ions move into the cell.