STOMACH CONTENTS ANALYSIS

What do you look for?• Drugs• Type of food that was

ingested: can test for the presence of fats, sugars, proteins, etc.; this will give an indication of the type of food that was ingested

• Degree of breakdown: food takes anywhere from 2 to 6 hours to pass through the stomach

Carbohydrates• Includes sugars, starches, and cellulose• Function to store energy and to provide

shape to organisms• Composed of carbon, hydrogen, and oxygen

Carbohydrates (cont.)• Can be divided into 3 groups

based on their size:– Monosaccharides: simple

sugars like glucose (blood sugar) and fructose

– Disaccharides: double sugars like sucrose (table sugar) and lactose (milk sugar)

– Polysaccharides: chains of sugars like starch, glycogen, cellulose and chitin

Carbohydrates (cont.)• Simple sugars are also called reducing sugars

and can be identified using the Benedict’s test• Benedict’s solution is a light blue color

(contains copper II)• In the presence of a reducing sugar, the

Benedict’s solution will change color ranging from green to yellow to red, depending on the amount of reducing sugar present

BENEDICT'S TEST

• To perform the test, place about 30 drops of your sample into a test tube. Add about 30 drops of Benedict's. Place the test tube into a hot water bath for 5 minutes and observe any changes.

A positive test results in a color change from light blue to orange, green, yellow, or red.

A negative test results in NO color change. The solution will remain light blue.

Carbohydrates (cont.)

• Starch can be tested for using the iodine test• Iodine is a yellow/orange color• In the presence of starch, the iodine changes

color ranging from royal blue to purple to black

IODINE TEST

• To perform the test, add about 30 drops of your sample to a test tube. Add 2-3 drops of iodine. Observe any color changes.

A negative test results in no color change.

A positive test results in a color change from yellow/brown to blackish/purple.

Proteins

• Make up ½ of the dry body weight• Structure is a complex molecule composed of 20

different, smaller molecules called amino acids• The presence of protein in foods can be

identified using the biuret test• Biuret solution (blue in color) contains copper

sulfate dissolved in a strong base• Protein causes the solution to change color

ranging from lavender to purple depending on the nature and amount of protein present

BIURET'S TEST

• To perform the test, put about 30 drops of your sample into a test tube. Add 2-3 drops of Biuret's. Observe any color changes.

A negative test is seen here. The color stays blue.

A positive result is seen here. The color changes to purple.

Lipids

• Include fats, phospholipids and steroids• Insoluble in water• Functions include:– Provide long-term energy storage – Act as insulators– Important in cell membranes– Act as hormones

Lipids (cont.)

• Structure: – Fats: a glycerol and 3

fatty acids– Phospholipids: a

glycerol, a phosphate group and 2 fatty acids

– Steroids: four fused rings with various side groups

Lipids• Lipids are insoluble in water• The presence of lipids can be identified using

the Sudan III test• Sudan III is a pink dye that is attracted to and

dissolves in non-polar compounds• Sudan III does not dissolve in water or other

polar solvents• In the presence of lipids, Sudan III changes

color from pink to yellow/white

SUDAN III TEST

• This is the test for lipids.

This is a positive test result.

You can also do the brown paper test.

Vitamin C• Ascorbic acid, commonly called Vitamin C, is

important in the body for collagen production (an important component of bone, cartilage, and other connective tissues)

• Vitamin C deficiency results in the disease scurvy which causes bleeding gums and a tendency to bruise easily

Vitamin C (cont.)• High concentrations of Vitamin C can be

found in citrus fruits (oranges, limes, grapefruits, etc.), tomatoes, potatoes, and leafy green vegetables

• Vitamin C is water soluble and a reducing agent (gives up electrons)

• 2,6-dichloroindophenol is a blue color indicator that turns colorless in the presence of Vitamin C