Chapter 5 Flashcards
osmotic equilibrium p123
in which the fluid concentrations are equal on the two sides of the cell membrane.
chemical disequilibrium p123
although the overall concentrations of the ECF and intracellular fluid are equal, some solutes are more concentrated in one of the two body compartments than in the other
electrical disequilibrium p123
The body as a whole is electrically neutral, but a few extra negative ions are found in the intracellular fluid, while their matching positive ions are located in the extracellular fluid.
Steady states p123
the intracellular and extracellular compartments of the body are in osmotic equilibrium, but in chemical and electrical disequilibria, the goal of homeostasis is to maintain these dynamic steady states of the body’s compartments
aquaporin p125
protein that creates special water channels for water to move freely in and out of nearly every cell in the body.
osmosis p125
the movement of water across a membrane in response to a solute concentration gradient.
osmolarity p126
the number of osmotically active particles(ions or intact molecules) per liter of solution. (osmoles per liter or OsM)
Equation
molarity(mol/L) x particles/ molecule (osmol/mol)= osmolarity (osmol/L)
osmolality p127
is concentration expressed as osmoses of solute per kilogram of water. (used interchangeably with osmolarity used in clinical settings for body weight)
isosmotic p127
two solutions containing the same number of solute particles per unit volume
hyperosmotic p127
if solution A has a higher osmolarity (contains more particles per unit volume, is more concentrated) that solution B, we say that the solution A is hyperosmotic to solution B.
hyposmotic p127
if solution A has a higher osmolarity (contains more particles per unit volume, is more concentrated) that solution B, we say that the solution B is hyposmotic to solution A.
tonicity p127
is a physiological term used to describe a solution and how that solution would affect cell volume if the cell were placed in the solution and allowed to come to equilibrium.
hypotonic p127
if a cell placed in the solution gains water at equilibrium and swells
hypertonic p127
if the cell loses water and shrinks at equilibrium
isotonic p127
if the cell in the solution does not change size at equilibrium
3 differences between osmolarity and tonicity
- osmolarity describes the # of solute particles dissolved in a volume of solution. It has until, such as osmoles/liter. The osmolarity of a solution can be measured by a machine called an osmometer, tonicity is only a comparative term.
- Osmolarity can be used to compare any two solutions, and the relationship is reciprocal(ex. solution A is hyper osmotic to solution B; therefore, solution B is hyposmotic to solution A), Tonicity always compares a solution and a cell, and by convention, tonicity is used to describe only the solution(ex. solution A is hypotonic to red blood cells)
- Osmolarity alone does not tell you what happens to a cell placed in a solution. Tonicity by definition tells you what happens to cell volume at equilibrium when the cell is placed in the solution.
Nature of the solutes in the solution (why can’t osmolarity be used to predict tonicity?)
-NOS= whether the solute particles can cross the cell membrane. If can enter are penetrating molecules, if can’t they are non penetrating molecules. Tonicity depends on the concentration of non penetrating solutes only.
penetrating solutes
non penetrating solutes
- solute particles that can enter the cell
- particles that cannot cross the cell membrane
What is the most important non penetrating solute in physiology?
NaCl
Osmolarity table? Hypotonic? Isotonic? Hypertonic?
hypotonic- hyposmotic, isosmotic, hyperosmotic
isotonic- isosmotic, hyperosmotic
hypertonic- hyperosmotic
concentration is? equation?
=osmolarity, solute/volume=concentration (ex. 900mosmol/3L= 300mOsM)
glucose is?
dextrose
Rules or Osmolarity and Tonicity
- Assume that all intracellular solutes are non penetrating
- Compare osmolarities before the cell is exposed to the solution. (at equilibrium, the cell and solution are always isosmotic)
- Tonicity of a solution describes the volume change of a cell at equilibrium
- Determine tonicity by comparing non penetrating solute concentrations in the cell and the solution. Net water movement is into the compartment with the higher concentration of non penetrating solutes.
- Hyposmotic solutions are always hypotonic.
The most general form of biological transport?
bulk flow(the transport of fluids between cells)
What are fluids in physics?
gases and liquids, liquids are not compressible and gases are
Pressure gradient in bulk flow causes what?
fluid to flow from regions of higher pressure to regions of lower pressure.
Selective Permeability
some molecules can cross them but others cannot
Permeable and impermeable
p= substance can pass through membrane i= substance cannot pass through membrane
Why is membrane permeability variable?
can be changed by altering the proteins or lipids of the membrane.
What two properties affect a molecules movement across membranes?
- size of the molecule
- lipid solubility
Passive Transport
does not require the input of energy
Active transport
requires input of energy from some outside source, such as ATP
Transport across membranes chart
see attachment
Diffusion (definition and seven properties)
- is the movement of molecules from an area of higher concentration of the molecules to an area of lower concentration of the molecules.
1. Diffusion is a passive process. (uses only kinetic energy)
2. Molecules move from an are of higher concentration to an area of lower concentration.
3. Net movement of molecules occurs until the concentration is equal everywhere.
4. diffusion is rapid over short distances but much slower over long distances.
5. diffusion is directly related to temperature. ( higher means faster, humans temp. doesn’t change much)
6. Diffusions rate is inversely related to molecular weight and size. (smaller molecules require less energy and diffuse faster)
7. Diffusion can take place in an open system or across a partition that separates two compartments.(open ex. cologne in room, closed ex. btwn extracellular and intracellular compartments)
Concentration/Chemical gradient
difference in concentration of two place
Dynamic equilibrium
state in diffusion when the concentration has equalized throughout the solution but molecules continue to move
time required for diffusion
distance squared, 1 to 2, means 1^2 to 2^2
Ions and movement
ions do not move by diffusion, movement influenced by electrical gradients, so ions move in response to combined electrical and concentrate gradients called electrochemical gradients.
electrochemical gradient
how ions move, combination of electrical and concentration gradients
electrical gradient
gradient formed because of the attraction of opposite charges and repulsion of like charges.
simple diffusion
diffusion directly across the phospholipid bilayer of a membrane.
Simple diffusion properties
- rate of diffusion depends on the ability of the diffusing molecule to dissolve in the lipid layer of the membrane.(how permeable membrane is to the diffusing molecules)
- The rate of diffusion across a membrane is directly proportional to the surface area of the membrane. (larger the surface the more molecules can diffuse per unit time)
ficks law equation
diffusion rate/surface area= concentration gradient x membrane permeability
3 principles of Fick’s Law
- size increases membrane permeability decreases
- lipid solubility increase leads to permeability increase
- composition of lipid bilayer changes permeabiility
flux defintion/equation
flux= concentration gradient x membrane permeability;
-diffusion rate per unit surface area of membrane
mediated transport
the help of membrane proteins to transport solutes across cell membranes
