Lipids - Triglycerides and Phospholipids

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Questions and Answers

What are the characteristics of lipids?

Insoluble in organic solvents (correct)

Contain Carbon, hydrogen and oxygen (correct)

High proportion of oxygen to carbon and hydrogen

Soluble in water

What are the main groups of lipids?

Triglycerides, phospholipids, waxes

What is a triglyceride?

An individual lipid molecule made up of a glycerol molecule and three fatty acids.

How do lipids serve as an energy source?

They provide more than twice the energy of carbohydrates when oxidized. Signup and view all the answers

What role do lipids play in waterproofing?

Lipids are large non-polar molecules that are insoluble in water. Signup and view all the answers

How do lipids provide insulation?

They are slow conductors of heat and help to retain body heat. Signup and view all the answers

What is the function of lipids as electrical insulators?

They surround the axon of neurons. Signup and view all the answers

How do lipids provide protection?

Fat is stored around delicate organs to act as a shock absorber. Signup and view all the answers

Lipids are soluble in water.

False Signup and view all the answers

What is the role of lipids in hormone production?

Lipids are required for the formation of steroid hormones. Signup and view all the answers

Fats are liquid at room temperature.

False Signup and view all the answers

What type of bond is formed when fatty acids bond with glycerol?

Ester bond Signup and view all the answers

What occurs during a condensation reaction?

Two molecules combine to form a more complex molecule with the elimination of a simple substance. Signup and view all the answers

What is hydrolysis?

The breaking down of large molecules into smaller ones by the addition of water. Signup and view all the answers

What causes variation in the properties of fats and oils?

Differences in the fatty acids. Signup and view all the answers

What characterizes saturated fatty acids?

All carbon atoms are linked to the maximum possible number of hydrogen atoms. Signup and view all the answers

What is a mono-unsaturated fatty acid?

A fatty acid with a single carbon double bond. Signup and view all the answers

What defines a polyunsaturated fatty acid?

A fatty acid with more than one carbon double bond. Signup and view all the answers

What is the result of double bonds in fatty acids?

They cause the molecule to bend, leading to liquids at room temperature. Signup and view all the answers

What defines phospholipids?

They have two fatty acids and one phosphate molecule. Signup and view all the answers

What are the two parts of a phospholipid?

Hydrophilic 'head' and hydrophobic 'tail'. Signup and view all the answers

What are polar molecules?

Molecules with two ends (poles) that behave differently. Signup and view all the answers

How is the test for lipids conducted?

Add ethanol, shake, then add water; a cloudy white color indicates the presence of lipid. Signup and view all the answers

Why does a positive test for lipids result in a cloudy-white color?

Due to lipid droplets being dispersed in water to form an emulsion. Signup and view all the answers

Study Notes

Characteristics of Lipids

Composed of carbon, hydrogen, and oxygen.
Lower oxygen-to-carbon and hydrogen ratio compared to carbohydrates.
Insoluble in water and organic solvents like alcohol and acetone.

Main Groups of Lipids

Triglycerides (fats and oils)
Phospholipids
Waxes

Triglycerides

Comprised of one glycerol molecule linked to three fatty acids.

Role of Lipids as an Energy Source

Fatty acids have long hydrocarbon tails rich in chemical energy.
Lipids yield more than double the energy of carbohydrates per mass and produce valuable water upon oxidation.

Role of Lipids in Waterproofing

Large nonpolar molecules, lipids are effective for waterproofing in plants and insects.
Waxy lipid cuticles help conserve water.

Role of Lipids in Insulation

Serve as poor conductors of heat, aiding in heat retention under the skin.

Electrical Insulation

Lipids form myelin sheaths around neuron axons, preventing premature conduction of nerve impulses.

Protection

Fat surrounding vital organs acts as a shock absorber.

Insolubility of Lipids

Lipids do not dissolve in water, preventing osmotic pressure that could cause cells to swell.

Hormone Production

Lipids are essential for the formation of steroid hormones, including oestrogen and certain plant growth hormones.

State of Fats vs. Oils

Fats are solid at room temperature (10-20°C), in contrast to liquid oils.

Type of Bond in Triglycerides

Fatty acids bond to glycerol via ester bonds.

Chemical Processes

Condensation Reaction: Molecules combine to form a complex one, typically releasing water.
Hydrolysis: Larger molecules break down into smaller units with the addition of water.

Variations in Properties of Fats and Oils

While glycerol is consistent in all triglycerides, differences arise from variations in fatty acids; over 70 distinct fatty acids exist.

Saturated Fatty Acids

Contain maximum hydrogen atoms, no carbon double bonds.

Unsaturated Fatty Acids

Mono-unsaturated Fatty Acids: Feature one carbon double bond.
Polyunsaturated Fatty Acids: Contain multiple carbon double bonds, causing bends in structure.

Effect of Double Bonds

The presence of double bonds prevents tight packing of molecules, resulting in liquids at room temperature.

Phospholipids

Composed of two fatty acids and one phosphate group, exhibiting hydrophilic properties.

Structure of Phospholipids

Hydrophilic "Head": Interacts with water.
Hydrophobic "Tail": Repels water and mixes with fats.

Polar Molecules

Exhibit dual properties (polar ends), leading phospholipids to orient with heads near water and tails away from it.

Test for Lipids

Procedure involves using ethanol to dissolve lipids, followed by adding water to observe for a cloudy white emulsion.

Cloudy White Color in Lipid Test

Result of lipid dispersion in water, creating an emulsion that refracts light, giving a cloudy appearance.

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Description

Explore the essential characteristics and classifications of lipids through flashcards. This quiz covers topics such as triglycerides, phospholipids, and their properties, helping you understand lipid chemistry better.