Excitable cells Part 1 (6/16/15) Flashcards
Electrical events provides a mechanism for what 2 things?
A mechanism for sensing environmental changes
A mechanism for triggering intracellular events (activation of muscle)
What are the 3 components of Cell Excitation?
- Extracellular fluid (High NaCl content)
- Membrane (Phospholipid bilayer and with proteins)
- Intracellular fluid (Predominant salt is KCl)
_____ is random diffusion down an electrical or concentration gradient (Organic molecules or ions).
Simple diffusion
______ diffuse rapidly through the membrane (No energy required)
Non-polar, organic molecules
________ cross membrane through channels which are proteins.
Ions (K-channels & Na-channels)
What are some examples of Nonpolar substances?
O2, Co2 = crosses membrane easily for breathing
Fatty acids = Heart needs these
Steroid hormones = synthesized as needed and can quickly enter cells to meat metabolic demands
_____ is the amount of a substance crossing a surface per unit of time.
Flux *Flux is bidirectional
____ is the difference between the two directional fluxes.
Net flux
When net flux = 0 the system is referred to as being _______.
In a state of diffusion equilibrium (Does not mean flux has stopped, just means it is balanced)
What are the 2 types of Mediated Transport?
- Facilitated diffusion = No ATP needed, uses membrane protein to serve as a carrier. (Transports glucose and other large polar molecules.)
- Active Transport = ATP required, Molecule or ion is bound to transporter and moves UP concentration/electrical gradient.
What can Energy input in active transport affect?
Affinity of transport for the ligand on one side of the membrane more than the other.
Rate of transporter conformational change.
Describe the process of PRIMARY active transport…
Energy source is hydrolysis of ATP –> Transporter becomes phosphorylated –> changes affinity for solute (ligand) –> increases transport rate.
Active Transport of Na is almost always ______ the cell.
out of the cell. Because the concentration gradient for Na is going into the cell.
Describe the process of SECONDARY active transport…
uses energy in ION CONCENTRATION GRADIENT (no ATP needed) *Transporter has two binding sites and s the primary transporter of amino acids.
What are the 3 basic steps of mediated transport?
Ligand binds to transporter, Transporter undergoes conformational change, ligand is released on the other side of membrane.
What are the 3 factors that determine the rate of flux?
- Number of transporters in the membrane
- Extent of transporter saturation, which will affect Transporter affinity and ligand concentration.
- Rate of transporter conformational change.
What are the three types of transport channels?
Ligand sensitive
Voltage sensitive
Mechanosensitive
_____ is bulk flow of water across a membrane (swelling or shrinkage if flow is large).
Osmosis
Water diffuses through channels called ______.
Aquaporins *Water is polar therefore needs to use channels.
Osmolarity of ECF = ?
300 mOsm
What are the 3 types of External solutions?
Isotonic = 300 mOsm of non-penetrating solutes = np change in cell volume
Hypotonic = 300 most of non-penetrating solutes = cells shrink
What is Isoosmotic?
= 300 mOsm of non-penetrating PLUS penetrating solutes.
What is Hypoosmotic?
What is Hyperosmotic?
> 300 mOsm of non-penetrating PLUS penetrating solutes.
T or F, A solution can be Hyperosmotic and Isotonic at the same time?
True, For example, it has 300 mosm of non-penetrating solute and 100 mosm of penetrating solutes!
What are the 2 types of endocytosis?
Pinocytosis = Cell drinking (Engulfment of small particles and fluid) *can be preformed by any cell. Phagocytosis = engulfment of large particles or cellular debris, preformed by specialized cells- phagocytes.
What is Exocytosis?
Reverse of Endocytosis, replaces membrane patches internalized through endocytosis!
K+ is found more _______ the cell.
Inside the cell.
Na+ is found more _______ the cell.
Outside the cell.
Electrical charge difference between the inside and outside of the cell is called _____.
Voltage
The plasma membrane must have ______. (in regards to voltage)
Resistance
Current is described as what?
Movement of Ions across membrane
What is Ohms law?
V = IR (Voltage = Current X Resistance)
What is Nernst Equation and what does it Describe?
Ex = (58/z) log10 ([X1]/[X2])
It Relates Equilibrium voltage (E) between 1 and 2 and the concentration difference between 1 & 2.
Log10 0.1 =
-1
Log10 1 =
0
Log10 10 =
1
Log10 100 =
2
What is a Diffusion potential?
A Transient (temporary potential) that is due to the asymmetric ion flow, an imbalance in the flow of an ion or several ions between two compartments.
Can a diffusion potential be maintained at a steady level over time?
Yes
What is resting membrane potential?
Describes the conditions of the living, resting cell.
- Higher K+ inside
- Higher Na+ outside
- The membrane of resting cell favors K+ permeability 60 times more than Na+
