Module 11 - Properties and Metabolism of Lipids

Hardness or Firmness

Shorter or more unsaturated fatty acids characterize fats and oils that are soft or liquid at room temperature while solid fats contain large amounts of long chain and saturated fatty acids

Melting point

Fats and oils of shorter and more unsaturated fatty acids melt at lower temperature than those with longer and more saturated fatty acids

Solubility

Fats and oils are not soluble in water but are soluble in organic solvents like ether, chloroform, benzene, hot alcohol, hot acetone and carbon tetrachloride

Odor, taste and color

In the pure state, fats and oils are odorless, tasteless and colorless

Reaction to litmus paper

Fresh fats and oils are neutral to litmus

Greasiness

Neutral fats and oils have a characteristic greasy feel and produce a transluscent spot when in contact with paper

Specific gravity

The specific gravity of all fats and oils is less than 1 g/ml, therefore all fats float in water

Crystallization

Some fats and oils produce characteristic crystals with definite melting points which serves to differentiate them from one another

hydrogenation

This refers to the addition of hydrogen atoms to unsaturated fat molecules converting carbon-to-carbon unsaturated (double) bonds to saturated (single) bonds.

Nickel

In the laboratory, this hydrogenation is done by introducing hydrogen gas bubbles to the heated oil in the presence of a _____ catalyst.

Oxidation of Fats and Oils

other name for randicity

RANCIDITY

A fat or oil becomes rancid when its double bonds are oxidized in the presence of oxygen in air at room temperature turning the unsaturated fatty acids into volatile aldehydes, ketones and carboxylic acids that changes the flavor of these triglycerides and emit disagreeable odors

lipoxidase

The presence of an enzyme, ______ , and such agents like heat, light, moisture and bacteria contribute to the  rapid onset of rancidity

butylated hydroxyanisole

What is BHA

butylated hydroxytoluene

What is BHT

SAPONIFICATION  

Formation of insoluble soaps in the intestinal tract in some abnormal conditions characterized by poor fat absorption such as sprue, can lead to significant calcium losses

SAPONIFICATION

This is the process when a fat is heated with a strong base such as sodium hydroxide or potassium hydroxide. This alkaline hydrolysis will yield glycerol and sodium salts of fatty acids called soaps.

HYDROLYSIS

Fats and oils are readily hydrolyzed by strong acids and digestive enzymes called lipases in the presence of water. The products of hydrolysis are glycerol and three fatty acids. The polar glycerol is soluble in water, but long-chain fatty acids are not.

EMULSIFICATION

It is the process of dispersing fat as tiny fat globules which are suspended in another liquid with the help of an emulsifying agent. Bile salts and lecithins are essential emulsifiers in digestion and absorption.

ACROLEIN FORMATION

Excessive heating of fats leads to the breakdown of glycerol, producing a pungent compound called acrolein (2propenol) which is irritating to the gastrointestinal tract mucosa

60 to 150 g

An adult ingests about _____ of lipids per day,

MOUTH

Hydrolysis of lipids does not occur because the lipids is not yet emulsified but lingual lipase secreted by the salivary glands degrades only the triglycerides at the lipid-water interface to form a fat bolus

lingual lipase

secreted by the salivary glands

Gastric lipase

can only degrade triacyglycerol molecules containing fatty acids of short or medium chain length at neutral pH and is therefore of little or even no use in the adult stomach where the pH is low

SMALL INTESTINES

True digestion of lipids starts at the

bile salts

In the duodenum, triacyglycerol molecules are emulsified or solubilized by mixing with _______

pancreatic lipase

In the jejunum, emulsified fats are then degraded by ________ to produce two fatty acids and monoacylglycerol molecules

Liver

is the main organ which regulates fat metabolism and is largely responsible for the regulation of lipid levels in the body

Lypolysis

This occurs when energy reserves are too low like during fasting, vigorous exercises and in response to stress

LIPOLYSIS

refers to the degradation of fat stores or triglycerides into glycerol and fatty acids by the aid of enzymes known as lipases.

KNOOP’S BETA OXIDATION

refers to the degradation or breakdown of fatty acids into acetyl-coenzyme A that primarily occurs in the mitochondrial matrix of red blood cells and tissue cells.

KETOGENESIS

refers to the synthesis or formation of ketone bodies that occurs during high rates of fatty acid oxidation where large amounts of acetyl-CoA are generated and exceed the capacity of the Kreb’s cycle.

acetoacetate, beta-hydroxybutyrate, and acetone

What are the ketone bodies?

mitochondria

Ketone bodies are produced mainly in the _________ of liver cells when carbohydrates are so scarce that energy must be obtained from breaking down fatty acids

LIPOGENESIS

refers to the synthesis of fats or triglycerides from excess carbohydrate molecules and to a smaller extent, protein. This occurs when there is high carbohydrate intake and the energy demand of the body is too low like in resting.

Adipose cells

The synthesized fat will be store in the ____?

Obesity

Too much lipogenesis can lead to ______?