CHAPTER 5 - MEMBRANE DYNAMICS

define osmolarity

number of particles in a solution

what is osmosis

movement of water across a membrane in repsonse to a solute concentration gradient

conversion between molarity and osmolarity

molarity (mol/L) x particles/molecule (osmol/mol)

= osmolarity (osmol/L)

what is isosmotic osmolarities

2 solutions contain same number of solute particles per unit volume

what are hyperosmotic osmolarities

solution A has higher osmolarity (contains more particles per unit volume, is more concentrated) then solution B. Solution A is hyperosmotic

what are hyposmotic osmolarities

less concentrated

unit for osmolarity

osmoles/ 1 L solution

unit for osmolality

osmoles/1kg solvent

define tonicity

physiological term used to describe a solution and how that solution would affect cell volume if cells were placed in the solution and allowed to come to equilibrium

define selective permeability

movement of substance across membrane depends on permeability of the membrane to the substance

eg. cell membrane

define diffusion

passive movement of molecules down a chemical concentration gradient from an area of higher concentration to lower.

how much total body water volume is intracellular fluid

2/3

how much total body water volume is extracellular fluid

1/3

how much extracellular volume is plasma

25%

how much extracellular volume is intersticial fluid

75%

what molecules can cross through diffusion

• H2O

• O2

• CO2

• lipids

what membrane transportation systems require ATP (4)

1. primary active transport

2. endocytosis

3. exocytosis

4. phagocytosis

what membrane transportation systems use molecular motion (no ATP)

1. diffusion

• simple diffusion

• facilitated diffusion

what are carrier proteins

carrier proteins never form an open channel between the two sides of the membrane

two kinds of cotransports

1. symport - carries in same direction

2. antiport - carries in opposite directions

what is a uniport carrier

only carries one kind of substrate

define specificity

Specificity refers to the ability of a transporter to move only one molecule or a group of closely related molecules

define competition

molecules both meet transportation requirements

define saturation

occurs when a group of membrane transporters are working at their maximum rate

define chemical disequilibriumsam

solutes are more concentrated in one of the 2 body compartments

defines electrical disequilibrium

negative ions found in ICF, positive ions in ECF

define osmotic equilibrium

water moves freely between cells and ECF, equilibrium on both sides

what are the kinds of active transport

1. vesicular transport (endocytosis, exocytosis, phagocytosis)

2. direct or primary active transport

3. indirect or secondary active transport

what are the passive transport

1. facilitated diffusion

2. ion channel (electrochemical gradient)

3. aquaporin channel (osmosis)

4 functional roles of membrane proteins

1. structural proteins

2. membrane-associated enzymes

3. receptor proteins

4. transport proteins

what are channel proteins

from water-filled channels that link intracellular and extracellular compartments

what are gated channels

regulate the movement of substances through channel proteins by opening and closing. It may be regulated by ligands, the electrical state of the cell or by physical changes such as pressure

define carrier proteins

never form a continuous connection between ICF and ECF they bind to substrates then change conformation

what is facilitated diffusion

protein mediated diffusion

2 kinds of active transport

1. primary active transport

2. secondary active transport

what is the sodium- potassium - ATPase

most important primary active transporter.

pumps Na+ out of cell and K+ into cell