Lab Notes and Procedures-03 Biology 1004
North Arkansas College
Topic: Chemical Basis of Life
(Experiment 2)
Lipids
- Compounds are not soluble in water (non-polar) but are soluble in organic solvents such as ether, acetone, etc.
- There are several types of lipids:
- Phospholipids - membranes
- Steroids - hormones
- Cholesterol
- Spingo lipids
- Neutral fats - most common lipid group
- Neutral fats are composed of two chemical components:
- Glycerol
- Fatty acids
Condensation synthesis forms bond between fatty acid and glycerol. These are also called triglycerides. Neutral lipids are stored in the body as connective tissue (in the form of adipose) - observe an adipose tissue slide.
- The bond between the glycerol and the fatty acid causes the (neutral fat) resulting fatty acid to be covalent (share electrons) and non-polar (non-charged) and not soluble in water.
- If placed in water, you must use an emulsifier to create a suspension between a neutral fat and a water molecule. Emulsifiers have a covalent end that combines with the neutral fat, and a polar end that combines with H2O.
- When lipids are spotted on brown paper, they tend to form oily spots that do not readily dry.
(See Pages 30-31)
- Spot drop of water and a drop of vegetable oil onto brown paper (let stand 5-10 min.).
- Two Tubes
- Add 2 cm water and 1 cm oil (let stand 5-10 min.).
- Add 2 cm water, 1 cm oil, and 1 cm emulsifier (let stand 5-10 min.).
- Make slide.
Results of Lab Experiment
| Substance |
Protein |
Carbo |
Starch |
Lipid |
|
Milk |
+++++ |
+++ |
0 |
0 |
|
OJ |
0 |
++++ |
0 |
0 |
|
Diet Soda |
0 |
+ |
0 |
0 |
|
Bitter Candy |
0 |
+ |
0 |
+ |
|
Flour |
+++++ |
++++ |
+++++ |
0 |
Starch - 2 cm sample, and 1 drop of iodine (blue-black).
Fat - Spot test on brown paper.
Protein - 2 cm sample, and 2 cm Biuret (violet).
Free Sugar - 2 cm sample, and 2 cm Benedicts; heat 5-7 min.
Various Shades: Red - high; Orange - medium; and Green - low.
Record as: +++++ (high), +++ (medium), ++ (low), + (slight change).
