Experiment 7 Properties of Lipids

(Lipid) (diverse) (insolubility) (non-polar solvents)

(_____) is a term given for a (______) group of naturally occurring organic compounds which are grouped together because of their evident (_______) in water and polar solvents, but high solubility in (_______________).

(triacylglycerols) (triester) (3 fatty acids) (condensation reaction)

The most encountered lipids are the (___________). (1) (______________) are structurally defined

as (_______) of glycerol and (_________). In another way of saying it, they contain (3) (_________) bonded to a glycerol molecule covalently by (____________). The general structure of

triacylglycerols is illustrated below. You may not have heard of the term (1) (____________) before,

but you have heard about fats and oils which are found in foods. Fats and oils are mixture of

(1) (___________).

(room temperature) (solid at room temperature) (liquid) (saturated fatty acids) (unsaturated fatty acids) (molecule)

The most noticeable difference between fats and oils are their physical state at (____________). Fats are (______________________), while oils are (_____). This observation is because fats are rich in (_____________) that have no bends in the structure, while oils are rich in (________________) that have a lot of bends in the structure causing disturbances in the forces of attraction between each (_________).

(cholesterol) (bile salts, steroid hormones, and vitamin D) (steroids)

The other most encountered lipid is (___________). You all hear about (1) (_________) as the bad

kind of lipid, but ironically, life won’t be possible without it. It has a lot of physiological

functions, such as being the precursor of (_________________________).

Cholesterol are classified as (_________). (3) (_________) are any molecules containing a 4-ring nucleus,

like the one on the next page.

(Miscibility) (liquid solute and a liquid solvent) (solubility) (solid solute and liquid solvent)

(_________) is the term used to describe the possibility of forming a solution between a (______________). On the other hand, (_________) is between (_____________________). For this experiment, you are going to conduct a simple test of (1)(3) (______________) for both coconut oil and cholesterol using polar and non-polar solvents.

(10 drops) (2 mL) (water) (chloroform) (immiscible) (pinch of cholesterol) (remaining solids)

PROCEDURE:

1. Place (_______) of coconut oil in 2 different test tubes. Label them 1 and 2.

2. Place (______) the following solvent in the corresponding test tubes: a. Test tube 1 – (_____) b. Test tube 2 – (__________)

3. Shake the test tubes carefully. Observe for layer formation. A layer means oil is (__________) in that solvent.

4. Repeat the whole process while using a (________________) instead of drops of oil this time. (In this case, instead of a layer, look for (__________). If there are, then cholesterol is insoluble in that solvent.)

5. Record your observation is Table 1.

(physical property or the chemical property) (fats and oils) (1 glycerol) (3 fatty acids) (Spot test) (translucent) (papers) (non volatile) (high-molecular weight)

II. GENERAL TESTS FOR TRIACYLGLYCEROLS

In recognizing the presence of fats or oils in substances, you can either use a test based on its (_____________________________) of their components. Recall that (_____&______) are triacylglycerols. Triacylglycerols comprise (________) and (________).

(______) is the simplest test for the presence of fats and oils which is based on the fact that fats and oils leave a (________) spot on (_______). This is because triacylglycerols are (________) because they contain (___________) fatty acids.

(twice) (4 quadrants) (coconut oil, glycerol, ethanol, and ether) (dry up)

PROCEDURE:

1. Fold a filter paper (_____) and then unfold to make (_________).

2. Label each quadrant with (_____, _____, _______, _______), respectively.

3. Add 1 drop of (3) (___________________________) into their respective quadrants.

4. Wait for a few minutes until all liquid has (______).

5. Observe for the presence of permanent translucent spot. Record your observation in Table 2.

(Acrolein test) (heating) (dehydrating agent) (potassium bisulfate (KHSO4)

(_________) is used to determine the presence of glycerol. Because fats and oils contain glycerol in their molecules, this test can also be used as a general test for the presence of fats and oils. This test is done by (________) fats or oils with (____________), such as (__________________), which dehydrates the glycerol backbone into an unsaturated aldehyde, (1) (_________) that has characteristic pungent odor of burnt fat. The chemical equation is shown below.

(KHSO4) (directly) (black precipitate)

PROCEDURE:

1. Add 20 drops of coconut oil and 20 drops of glycerol in 2 separate test tubes,

respectively. Label them accordingly.

2. Add a small pinch of (______) into the 2 test tubes.

3. Heat each test tube (______) in open flame until a (_____________) is formed with

characteristic burnt fat smell. Record your observation in Table 3.

(no carbon-carbon double bond) (one carbon-carbon double bonds)

III. CHEMICAL TESTS FOR TRIACYLGLYCEROL

The following tests attempts to identify some functional groups in triacylglycerol and some of its chemical properties when mixed or reacted with other substances.

Test for Unsaturation

Recall that the difference between fats and oils is that fats have a lot of saturated fatty acids, while oils have a lot of unsaturated fatty acids. Saturated fatty acids are fatty acids with (_______________________) in its structure, while unsaturated fatty acids have at least (_____________________).

(Iodine Number) (halides) (slowly disappear) (double bonds)

The test to be used for this is (___________). This is based on the principle that carbon carbon double bonds undergo addition reaction with (_______), such as iodine as illustrated in the reaction below. In return, the color of (2) (______) will (_________). The degree of decolorization is proportional to the number of (___________) present in a triacylglycerol molecule, and therefore to its degree of unsaturation.

(2 mL of chloroform) (I2 in KI solution) (more unsaturated)

PROCEDURE:

1. Add 1 mL each of coconut oil, olive oil, and cottonseed oil in 3 separate test tubes.

2. To each test tube, add (___________) and shake.

3. Then, add 1 drop of (____________) into each test tube.

4. Compare the degree of coloration in each test tube. The lighter the color, the (_____________) the oil is.

5. Record your observations in Table 4.

(Rancidity) (unpleasent smell) (texture and appearance) (hydrolysis) (oxidation) (volatile) (acidic or not)

(________) is the development of (____________) in fats and oils, which are oftend accompanied by changes in their (_________&________). There are 2 chemical reactions that cause this to happen – (__________) which liberates free fatty acids and (_________) which oxidizes carbon-carbon double bonds into (_________) aldehydes and ketones. The test for (1) (_________) is as simple as determining whether an oil or fat sample is (_________).

(fresh coconut oil) (rancid coconut oil)

PROCEDURE:

1. Test both (_________) and (___________) with blue and red litmus paper.

2. Record your observation in Table 5.

(quantitatively or qualitatively)

IV. GENERAL TEST FOR CHOLESTEROL

The following tests are used to determine (____________________) the presence of cholesterol in samples.

(Salkowski’s test) (concentrated sulfuric acid) (1 mL of chloroform) (2)

(____________) is a qualitative test for the presence of cholesterol. This is done by adding (__________________) in a cholesterol solution.

PROCEDURE:

1. Dissolve a small amount of cholesterol crystal in (_____________).

2. Add 1 mL of concentrated sulfuric acid at the side of the test tube.

3. Stand for (__) minutes. Observe the color produced in chloroform layer and sulfuric acid layer. Record your observations in Table 6.

(Liebermann-Burchard test) (acetic anhydride) (concentrated sulfuric acid) (emerald-green color)

(___________________) is a quantitative test for the presence of cholesterol. It is done by adding (___________) and (_________________) in a cholesterol solution.

PROCEDURE:

1. Dissolve a small amount of cholesterol crystal in 1 mL of chloroform.

2. Add 10 drops of (2) (_________________) and 2 drops of (3) (_____________________).

3. Shake mixture and observe for the appearance of (_______________). Record your observations in Table 6.

(dietary) (food) (non-polar) (insoluble) (water) (ether)

V. EXTRACTION OF FATS FROM FOOD

In (______) context, when we talk about fats they are collectively referring to fats and oils present in (_____). For this experiment, when we talk about fats, we really refer to (2) (________) triacylglycerols in food, might it be fats or oils. Like all types of lipids, triacylglycerols are (________) and are, therefore, (_________) in polar solvents, such as (______); and soluble in non-polar solvents, such as (_______).

(exploited) (all polar) (solvent extraction) (crushed food) (filtered out) (evaporation)

The non-polar property of your fats can be (__________) in the procedure for its extraction from food. Most of the macromolecules in foods, such as your carbohydrates and proteins, are (_______). Thus, to separate fats from the other macromolecules, we can use the technique known as (__________). (3) (_________) is a process in which compounds are separated based on their relative solubility. This is done by extracting (____________) sample with a non polar solvent allowing for the dissolution of fats into the solvent, leaving the polar macromolecules behind. The mixture of solvent and extracted fats is then (__________), and the solvent is removed by (____________).

(5 g) (dry Erlenmeyer flask) (25 mL of ether) (5) (filtrate)

Procedure:

1. Weigh (___) of food sample, and crush finely in a mortar and pestle.

2. Transfer the crushed food sample into a clean and (______________). Ensure that

all of the crushed food sample are completely transferred into the flask.

3. Measure (____________) and pour into the Erlenmeyer flask with the crushed food

sample.

4. Cover the flask with a cork, and shake vigorously for (___) minutes. Let it stand.

5. Filter the mixture in the Erlenmeyer flask using a clean beaker as receiving vessel for

the (_______). The filtrate contains fats extracted in ether.

(5 mL ether) (ether washing) (left) (oily substance)

6. Wash the residue in the filter paper with (_________), while collecting the (_________)

in the same beaker.

7. Heat the beaker containing the filtrate on a steam bath for evaporation. The ether solvent will be removed through this process.

8. Stop the heating when the characteristic odor of ether is no longer observable, and an oily liquid is (____) in the beaker. The (_____________) that is left in the beaker is the fat contained in the food.

9. Cool the fat extracted. Characterize its appearance according to viscosity. Record your

observation in Table 7.

10. Once cooled, add 5 mL chloroform into the beaker and mix.

11. Transfer the mixture into a test tube, and add 1 drop of I2 in KI solution. Shake the test

tube. Observe the degree of coloration. Record your observation in Table 7.