A&P Lab - Class 3: The Behaviour of Living Cells

All molecules that enter or leave the cell must either:

- Pass directly through the cell membrane
- Pass through channels that exist in the cell membrane

What is the permeability of the cell membrane?

Selectively permeable/semipermeable

What is diffusion?

The movement of molecules from a high concentration level to a low concentration level until equilibrium is attained.

What did the orcein crystal experiment demonstrate?

Diffusion (throughout the lab period, we observed the crystals diffusing at room temperature - in water)

How does temperature affect the rate of diffusion?

(Water example):
Cold water: Molecules are moving slower, resulting in much slower diffusion.
Hot water: Molecules are moving quicker, resulting in much quicker diffusion.

What is osmosis?

Similar to diffusion.
The dispersion of particles from high concentration to low concentration until equilibrium is achieved. But, it is through water, and there is a semi-permeable membrane.

What is starch?

A polysaccharide (large organic molecule) composed of many glucose units (monosaccharides).

What happens when starch reacts with iodine?

A dark blue colour is produced.

What is iodine?

A small inorganic molecule.

What did the dialysis bag represent in the dialysis tubing exercise?

The selectively permeable membrane of a cell.

Isotonic solution

"The same"

Hypertonic solution

"Too much"

Hypotonic solution

"Too little"

Which de-calcified egg (previously sitting in 5% acetic acid) gains weight after sitting in the following solutions:

De-calcified egg soaked in 42% sucrose solution.

De-calcified egg soaked in distilled water.

- Which solution is hypertonic to egg contents?
- Which solution is hypotonic to egg contents?

42% sucrose solution: Loses weight

Distilled water: Gains weight

- 42% sucrose solution is hypertonic to egg contents
- Water is hypotonic to egg contents

What word is used when a red blood cell is placed in a hypotonic solution (such as distilled water)?

Blood cells will burst, called hemolysis (this name only applies to red blood cells).

What word is used when a red blood cell is placed in a hypertonic solution (such as concentrated salt water)?

Red blood cells will shrivel, called crenation (this name only applies to red blood cells).

What is the salt solution (%) of a red blood cell and its environment?

0.9% salt solution

What happens to a red blood cell if we add it to a 10% salt solution?

It will shrivel up (crenate).

What happens to a red blood cell if we add distilled water to it?

It will absorb lots of water and burst (haemolyze).

When you're cooking beets, why does the red dye exit the beet?

Heat while cooking denatures the cell membrane of a beet, and pigment is released into the water.

Heat denatures _________________ of the cell.

Acetone denatures _________________ of the cell.

How do these affect cell wall permeability?

Heat denatures the cell wall.

Acetone denatures lipids.

This means that the cell membrane is no longer selectively permeable.

In a solution that biuret is added to, the biuret suddenly turns purple.
What substance is in the solution that caused the biuret to turn purple?

Protein.