Membrane Physiology Flashcards
Identify 4 Roles of the cell membrane
- Defines boundaries of the cell.
- Encloses the cell’s organelles.
- Enables the cell to create an internal environment that promotes the normal functions of the cell.
- Creates an internal environment that is different from outside of the cell.
Describe the structure of the cell membrane
- Made up of 2 layers of phospholipids.
- Each phospholipid is made up of a hydrophilic head (form the outer and hydrophobic tail.
What is the main purpose of the phospholipid bilayer arrangement
The membrane is impermeable to any particles that are hydrophilic.
What 2 things happen as a result of the structural features of the cell membrane
- Intracellular and extracellular environments are created
- Membrane is able to control the composition of the intracellular environment (cannot affect the extracellular environment).
How are optimum environments that enable cells to thrive achieved by cell membranes
They selectively concentrate various combinations of charged particles in the intracellular compartment
What kinds of species are concentrated in the intracellular environment to achieve optimum conditions
Organelles of the cells
Proteins
Combinations of specific anions and cations
What happens when specific species are concentrated in the intracellular environment
- Creates a concentration difference between the intracellular and extracellular environments.
- The difference in charged particles creates a rising electric potential between the intracellular and extracellular environments
What are the concentration gradients for a typical nerve cell (Na+)
- Inside cell 15mM
- Outside cell 150mM
What are the concentration gradients for a typical nerve cell (K+)
- Inside cell 150mM
- Outside cell 5.5mM
What are the concentration gradients for a typical nerve cell (Cl-)
Inside cell 9mM
Outside cell 125mM
What are the concentration gradients for a typical nerve cell (Ca2+)
Inside cell <10-7 mM
Outside cell Ca2+ 1.8 mM
What is a concentration gradient also known as
A chemical gradient
What is a standing electro-chemical gradient
A combination of the electrical and chemical gradients between the intracellular and extracellular environments. Also known as electro-chemical gradient
What is the standard resting potential of a nerve cell
-65mV to -70mV inside the cell (with respect to outside the cell)
What is a defining characteristic of electrically excitable tissue
They are able to momentarily discharge the standing electrical potential between the intracellular and extracellular environments.
In nervous tissue what is the process of discharging the standing electrical potential also a mechanism of?
Electrical communication between cells
What does the membrane do after discharging the standing potential between the intracellular and extracellular environments?
It works to restore the resting membrane potential of the cell.
Give 2 examples of biologically excitable tissues
Nerve Cells
Muscle Cells
Identify 4 factors that determine whether or not a particle is able to cross the cell membrane
- The size of the particle
- The electrical charge on the particle
- The solubility of the particle in water
- Whether the particle uses specialised transport systems to cross the membrane
Identify 4 factors that determine whether or not a particle is able to cross the cell membrane
- The size of the particle
- The electrical charge on the particle
- The solubility of the particle in water
- Whether the particle uses specialised transport systems to cross the membrane
Name the 3 types of ion channels present in the membrane
- Selective ion channels
- Nonselective ion channels
- Leak Channels
What is an ion channel
A protein assembly that is lodged in the cell membrane. It spans the full thickness of the cell membrane. They facilitate PASSIVE movement of ions across the cell membrane
What is it called when a protein spans the full thickness of the membrane
Trans-membrane spanning proteins
Describe the structure of an ion channel
A water filled central pore that passes from the inside to the outside of the cell (or vice-versa)
What sets an ion channel apart from others
- Which species of ions they conduct
- how their ion conductance is governed
- the gating mechanism of the ion channel
N
A
Give 5 examples of the most commonly studied ion channels
- Voltage-gated channels (Na+ and K+)
- Ligand-gated channels (neurotransmitters)
- Mechanically-gated channels
- Non-gated ion channels
- Leak channels
What is an ion pump?
Protein lodged in the cell membrane. Main function is to maintain the resting membrane potential. THEY HAVE NO IMPACT ON SETTING UP THE RESTING MEMBRANE POTENTIAL.
What do ion pumps need to maintain the resting membrane potential?
energy in the form of ATP
What are ion pumps also known as?
Ion-exchange pumps. Some poisons specifically target these pumps.
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