Lecture 1 - Osmosis and Diffusion

Question 1

Define osmosis

Answer 1

Osmosis is the movement of water (the solvent) across a semi-permeable membrane to even the concentration of dissolved particles on either side of the membrane.
*osmosis only cares about the number of particles not their identity

Question 2

Define diffusion

Answer 2

Diffusion is the movement of particles dissolved (the solute) in a solution to even the distribution of that particle in the solution. Occurs when there is a net flow from region of high concentration to region of low concentration

Question 3

Hypertonic

Answer 3

Cells lose water by osmosis and shrink in a hypertonic solution (contains a higher concentration of solutes than are present inside the cells)
= SHRINK

Question 4

State the fluid compartments of the body

Answer 4

1. Extra cellular fluid
   - plasma fluid
   - interstitial fluid
   - 20% of total body weight
2. Intercellular fluid
   - 40% of total body weight
   Plasma has lots of proteins

Question 5

Isotonic

Answer 5

Water moves in and out of cell at same rate and cell maintains structure due to equal concentration of water inside and out of cell

Question 6

Hypotonic

Answer 6

Cells become bloated and possible burst (lyse) due to water coming into cell as concentration of water is greater outside than inside cell

Question 7

What is the difference between osmolarity and concentration

Answer 7

It is quite clear that molarity measures the number of moles of solute per unit volume of solution, while osmolarity measures the number of osmoles of solute particles per unit volume of solution.

Question 8

What is the difference between osmolarity and Tonicity?

Answer 8

Osmolality is a property of a particular solution and is independent of any membrane. Tonicity is a property of a solution in reference to a particular membrane.

Question 9

Define homeostasis

Answer 9

Homeostasis is the maintenance of a stable internal environment notwithstanding changes in the external environment. It is self regulating system

Question 10

Describe the basic reflexes involved in maintaining homeostasis

Answer 10

Autonomic reflex’s such as heart rate, breathing rate, BP and digestion. Uses both negative feedback and positive feedback loops

Question 11

Identify the major components of a reflex arc

Answer 11

Receptors, sensory neurons, inter neurons, motor neurons, muscles

Question 12

Example of endocrine system negative feedback loop

Answer 12

Water levels rise in blood —> osmoreceptors in brain detect —> osmoregulatory centre in hypothalamus—> less ADH is released by pituitary—> water levels decrease

Question 13

Fick’s law of diffusion

Answer 13

1. Thickness of membrane
2. Permeability of barrier
3. Concentration gradient
4. Surface area available