Exam 2 (A&P) Flashcards
Osmotic equilibrium
The state where fluid concentrations are equal on the two sides of the cell membrane
Chemical disequilibrium
Solutes are more concentrated in one of the two sides of a compartment
Electrical disequilibrium
body as a whole is neutral, distribution of charges is unequal (across compartments like cell membrane and neurons)
Intracellular fluid (within cell) concentrations
Na, Cl, and HCO3 are low
K and proteins are high
Interstitial fluid concentrations
K and HCO3 are low
Na, Cl are high
Plasma concentrations
Na, Cl, and proteins are high
K and HCO3 are low
Intracellular Fluid
2/3 of total body water, water contained in all cells of body
Extracellular Fluid
1/3 of total body water, water contained between cells is interstitial fluid and water portion of blood (plasma)
What fluid content can the body regulate
ECF is regulated but NOT ICF
Osmosis
The movement of water across a membrane due to a difference in solute concentration.
The movement stops when the 2 compartments are equal in concentration; water wants to move from low to high SOLUTE concentration
Movement occurs through aquaporins
Osmotic pressure
Pressure that is needed to oppose the osmotic movement of water
Molarity
Number of moles of ONE TYPE of dissolved solute per liter of solution (mol/L).
Osmolarity
Number of osmotically active particles (all particles added together) per liter of solution (osmol/L or mOsM)
Osmolarity can be used to compare concentrations of two different solutions
Isomotic
A comparison of osmolarity; 2 solutions contain the same number of solute particles per unit of volume
Hyperosmotic
A comparison of osmolarity; a solution contains a higher number of solute particles per unit of volume
Hyposmotic
A comparison of osmolarity; a solution contains a lower number of solute particles per unit of volume
Tonicity
Physiological term to describe how a solution affects CELL volume.
Depends on osmolarity of solution and the nature/type of solutes in the solution; Compare non-penetrating solute concentrations between cell and the solution
Hypotonic
If a cell placed in the solution gains water it will swell and the solution is hypotonic to the cell
(Solute concentration is greater in the cell)
Hypertonic
If the cell loses water and shrinks the solution is hypertonic to the cell (solute concentration is less in the cell)
isotonic
if the cell in the solution does not change size the solution is isotonic to the cell (equal concnetrations)
How does tonicity differ from osmolarity
Osmolarity compares two SOLUTIONS. Tonicity allows us to predict how a solution affects CELLS. Osmolarity has units for # of particles per volume and tonicity has no units it is strictly comparative.
Why do we care about water movement
Administration of drugs, dealing with dehydration and swelling.
Penetrating solutes
Freely cross the membrane and enter/exit the cell
ex: urea and gases
Non-penetrating solutes
Unable to cross the membrane freely and need a transport; only enter via specific transport. Most particles are non-penetrating
ex: ions, proteins, biomolecules
Biological transport
Transport of biological components require help to cross the cell membrane
Bulk flow
Most general form of transport; driven by pressure, temp, or chemical gradients. Move from high to low. May or may not cross cell membrane
ex: movement of blood via pressure gradient
gas movement between lungs and cells
Membrane permeability
Cell membranes are selectively permeable (the degree in which things can cross); permeability can be altered
Depends on: molecule’s lipid solubility, molecule’s size, lipid comp of membrane
Molecule properties that alter permeablity
size: the larger the molecule the less permeable
Lipid solubility: lipid and lipid-like substances are more permeable.
water and some gases move freely
Passive transport
Broad category of movement; uses potential energy stored in concentration gradients, does NOT need energy from outside source.
Uses kinetic energy of molecules bouncing off each other and potential E from CG
Active transport
Broad category of movement; REQUIRES input of energy from outside source (often from ATP or another molecule moving down its CG and bringing something with it)
Diffusion
Movement of molecules from an area of higher concentration to an area of lower concentration; does NOT require outside energy
Occurs in open or closed system, across a membrane or within.
Smaller diffuses faster
7 properties of diffusion
- No energy needed
- Molecules move from high to low concentration
- Net movement occurs until equilibrium (if possible)
- Rapid over short distance
- Directly related to temp (high temp = high diffusion)
- Inversely related to molecular weight/size (smaller diffuse faster)
- Can take place in open or across separate compartments
Rate of diffusion is faster if…
Membrane’s surface area is larger, membrane is thinner, the CG is larger, the membrane is more permeable to given molecule
simple diffusion
movement of a substance directly across the phospholipid bilayer. Rate depends on molecule dissolving in lipid layer (lipophobic vs lipiphilic, lipid content/charge) and the larger the surface area of membrane the faster things will move
Fick’s law
Summarizes simple diffusion
Rate proportional to (SA)(CG)(Membrane permeability)
with membrane perm proportional to (lipid solubility/molecular size)
Protein-mediated transport
Proteins help move lipophobic/charged across membrane
Can be passive or active
Passive transport
No energy required
facilitated diffusion, ion channels, aquaporins
Active transport
Energy required, moves substances AGAINST their CG, maintains or creates disequilibrium
primary (direct) active transport
secondary (indirect) active transport
Structural proteins
Create cell junctions to hold tissue together, connect membrane to cytoskeleton, attach cells to ECM
Enzymes
Catalyze chemical reactions on or near cell membrane
Receptors
Chemical signaling, receptor-ligand binding triggers intracellular response
transport proteins
specialized proteins that allow substances to cross;
2 types: Channel and carrier
Channel proteins
Transport, create water filled passageways, link intracellular and extracellular fluid
Specificity is important; can be open or gated (chemical, voltage, or mechanical gate) which allows for control
ex: aquaporin
Carrier proteins
transport, only exposed to intracellular or extracellular fluid at one time.
Uniport, antiport, symport
specificity is important and direction of fluid it faces can change
Molecule binds, carrier changes shape, protein opens to other side fluid
Uniport carrier protein
transports only one kind of substrate
Symport carrier protein
Move two or more substrates in the same direction across the membrane