Water as a solvent of "solid" solutes - the basics

Question 1

these solutes include…
and what do they all contribute too

Answer 1

ionic solutes - salts, acids, bases
colloids - high MW organic molecules
“substrate” organic molecules - amino acids, glucose, urea etc

All contribute to osmolarity of body fluids
all participate in physiological processes

Question 2

what is colloid?

Answer 2

a general term for large particles (from 1-100 nm in diameter) maintained in a suspension

Question 3

what do all colloidal solutes posess?

Answer 3

a surface charge
- include high molecular weight proteins, nucleic acids and carbohydrates

Question 4

Do colloidal solutes have small or large hydration spheres?

Answer 4

very large hydration spheres with gegenions in the sphere

Question 5

what is the most fundamental organic compounds in animals

Answer 5

colloidal solutes

Question 6

what is osmosis?

Answer 6

the movement of water across a semi- or selectively permeable membrane, from an area of low solute concentration to high

Question 7

what is a semi-permeable membrane?

Answer 7

permits passage of water, not solutes

Question 8

what is a selectively permeable membrane

Answer 8

permits water and some solutes to pass through but not others
- most biological membranes are selectively permeable - plasma membrane, tissue layers, skin etc

Question 9

Diffusion vs osmosis

Answer 9

Diffusion:
no selectively permeable membrane
solute particles move by diffusion
follow ficks equation

Osmosis:
selectively permeable membrane
water moves to area of high [solute]
movement of water greater than predicted from ficks equation
follows van’t hoff equation
colligative properties of solutions

Question 10

what is
hypotonic
hypertonic
isotonic

Answer 10

swell
shrink
stay the same

Question 11

is osmosis reversible?

Answer 11

yes it can be reversed
ie. when put into a piston device for direct measurement of osmotic pressure
- is the solution is placed under hydrostatic pressure that exactly opposed osmosis, by putting force back on the water creating energy, or stopping water movement

Question 12

what is osmotic pressure?

Answer 12

mechanical pressure required to prevent movement of water across a semipermeable membrane

Question 13

osmotic pressure can be predicted by the van’t hoff equation
what is that equation

Answer 13

Π = CRT
Π = osmotic pressure
C = osmolarity or concentration
R= universal gas constant 8.314 J/K/mol
T = absolute temperature

Question 14

which equation is the van’t hoff related too?

Answer 14

RV=nRT

Question 15

what does van’t hoff equation predict

Answer 15

all colligative properties, ficks does not since osmosis is not the diffusion of water

Question 16

what is the cause of osmolarity

Answer 16

osmosis is faster than diffusion
- there must be the bulk flow of water driven by something other than kinetic motion

Question 17

osmosis occurs at every membrane in the body when…

Answer 17

membrane is selectively permeable to at least one solute
- and there is a concentration gradient for the solute

membranes include all cellular membranes, any tubule in the body, and the skin

Question 18

Nature of the capillary wall:

Answer 18

made of membranes - endothelial cells & basement membrane
- interstitial fluid comes from blood plasma via intercellular clefts

Question 19

how permeable is the capillary wall

Answer 19

it is selectively permeable (especially through the pores between cells, the intercellular clefts)
- this means large proteins do not cross the membrane
- water, ions, small organic molecules do

Question 20

what is C.O.P

Answer 20

this sets up a colloid osmotic pressure
- gradient across the capillary wall

Question 21

what pressures acting at arterial side of capillary:

Answer 21

BP, neg IFP (negative interstitial fluid pressure), IF COP (interstitial fluid colloid osmotic pressure), P COP

Question 22

Starling-Landis model

Answer 22

capillary fluid flow, where osmotic and mechanical fluid pressures interact
- is a net pressure forcing fluid out of capillary, and this fluid forms the interstitial fluid
- interstitial fluid hydrates cells helps deliver nutrients, carry away wastes etc.

Question 23

The disrupting of Starling - Landis model may cause what

Answer 23

cause tissue swelling (edema)

Question 24

The Second Law & Osmosis of Aqueous Solutions

Answer 24

-pure water is a very ordered substance due to extensive H-bonds
- creates a low entropy in pure water ( entropy = randomness thus less randomness)
- solutes in water decrease order
ie. increased entropy in solutions

Question 25

During osmosis, water moves…
from ___ toward ___
from ___ entropy to ____ entropy

Answer 25

-From ordered toward disordered
- From low entropy to high entropy

Question 26

When you think of osmosis and other colligative properties, think of…

Answer 26

the 2nd law of thermodynamics
from low to high [solutes]
- DO NOT THINK DIFFUSION OF WATER

Question 27

General Functions of Plasma/Cellular Membranes:

Answer 27

1. Compartmentalization & Isolation
   - separates cell contents from “environment”
   - subdivides cell into specialized regions
   - concentrates reactants for biochemistry
2. Generation & Conduction of Bioelectricity
3. Reception & Transduction of Information
   - to & from the extracellular environment

All are dependent on membrane chemistry/structure