Forces Acting Across Membranes Flashcards
Describe the basic structure of the cell membrane
Phospholipid bi-layer Selectively permeable Flexible and dynamic Insulating Provides binding sites
What can pass freely between the ECF and the ICF ?
Gasses, nutrients, waste and water
How is total body water (TBW) divided up between the ECF and ICF ?
ECF: 1/3
ICF: 2/3
What is the concentration of Na in the ECF compared to the ICF ?
Na is high in the ECF and low in the ICF
What is the concentration of K in the ECF compared to the ICF ?
K is low in the ECF and high in the ICF
Ions can pass freely between what two compartments ?
The plasma and the interstitial fluid
What are the three types of integral membrane proteins (IMP) ?
Receptors
Transporters
Enzymes
What is the function of receptors on the cell membrane ?
They transmit signals intracellularly
What are the two types of transporter that are found in the cell membrane ? and how do they function ?
Carrier proteins: Open to either ECF or ICF but not simultaneously.
Channel proteins: Allows passage of large molecules that cannot penetrate through diffusion.
What is the function of enzymes with a receptor region ?
The substrate binds to the receptor and an enzymatic reaction will occur within the cell
What type of protein is not integral to the cell membrane ?
Peripheral membrane proteins.
What is diffusion ?
When molecules move from an area of high concentration to an area of low concentration until the concentration is uniform throughout the volume.
What are the three criteria which a molecule must meet in order to diffuse through the cell membrane ?
Small
Lipophillic
Uncharged (Nonpolar)
What is the equation used to calculate net flux across a concentration gradient ?
F = kpA (C1-C2)
What are the three main types of protein channel ? and how do they allow passage of molecules ?
Ion channel: Remain closed until stimulated
Voltage gated channel: Require electrical stimuli
Ligand gated channel: Require a neurotransmitter or hormone to bind
Define electrochemical gradient
A combination of charge of the molecules and also the concentration gradient
What two forms of transport across the membrane require ATP ?
Active transport and facilitated diffusion
What is pumped in and out of the cell for 1 molecule of glucose ?
3Na are pumped out of the cell for 2 K ions pumped into the cell
Define endocytosis
Where the cell creates a vesicle by invagination of a ligand or molecule and takes it into the cell.
Define exocytosis
The opposite of endocytosis where particles are taken out of the cell and recycled or used as waste products
Define osmolarity ?
The total number of particles in a solution
Tonicity
The total number of non-penetrating particles in a solution
What is the human plasma osmolarity ?
300 mOsmol/l
What causes the change in cell volume ?
Tonicity
Define isosmotic
Equal number of particles in solution as plasma
Define Hyposmotic
Total amount of solutes is fewer
Define Hyperosmotic
Total amount of solutes is greater
Define Isotonic
Equal amount of non-penetrating particles as plasma
Define hypotonic
Fewer number of non-penetrating ions
Define hypertonic
Greater number of non-penetrating ions
What is the osmolarity of 1M of glucose ?
1 osmol/l
What is the osmolarity of 1M of NaCl ?
2 osmol/l
Is urea a penetrating or non-penetrating particle ?
Penetrating
What will happen to a RBC placed in a hyperosmotic urea solution ? not in vivo
swell and burst
