Lipids are one of the four major groups of organic molecules; the other three being proteins, nucleic acids (DNA), and carbohydrates (sugars). Lipids are made up of the same elements as carbohydrates: carbon, hydrogen, and oxygen. However, lipids tend to contain many more hydrogen atoms than oxygen atoms.

Lipids include fats, steroids, phospholipids, and waxes. One main characteristic of lipids is that they do not dissolve in water. Lipids play an important role in living organisms. Some of their main functions include energy storage, hormones, and cell membranes.

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Types of Lipids

Fats

Fats are composed of a glycerol molecule and three fatty acid molecules. Just like all lipids, fat molecules are made up of the elements carbon, hydrogen, and oxygen. Fat is used as energy storage in our bodies. Fats are needed by our bodies to be healthy. We couldn’t live without some fats in our diet. Most people need to get around 20%-30% of their food from fats. However, too much fat can be bad. It can cause you to be overweight and clog up your arteries.

Types of Fats

There are two main types of fats: saturated fats and unsaturated fats.

• Saturated Fats – Saturated fats are solids at room temperature. These fats tend to come from foods like red meat, cheese, and butter. Saturated fats are sometimes called “bad” fats because they have been known to cause higher cholesterol, clog arteries, and even increase the risk for some cancers.
• Unsaturated Fats – Unsaturated fats are liquids at room temperature. These fats tend to come from foods like nuts, vegetables, and fish. Unsaturated fats are considered much better for you than saturated fats and are sometimes called “good” fats.

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Waxes

Waxes are similar to fats in their chemical makeup, however, they only have one long fatty acid chain. Waxes are soft and plastic at room temperatures. They are produced by animals and plants and are typically used for protection. Plants use waxes to help prevent water loss. Humans have wax in our ears to help protect our eardrums.

Steroids

Steroids are another major group of lipids. Steroids include cholesterol, chlorophyll, and hormones. Our bodies use cholesterol to make the hormones testosterone (male hormones) and estrogen (female hormones). Chlorophyll is used by plants to absorb light for photosynthesis.

Not all steroids are bad. Our bodies need steroids like cholesterol and cortisol to survive, so some steroids are good for us. There are also many steroids that doctors use to help sick people.

However, the type of steroids you hear about in sports, anabolic steroids, can be very bad for you. They can cause all sorts of damage to your body including strokes, kidney failure, blood clots, and liver damage.

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Phospholipids

Phospholipids make up the fourth major group of lipids. They are very similar to fats in their chemical makeup. Phospholipids are one of the main structural components of all cell membranes.

Interesting Facts about Lipids

• When a compound is not water soluble it is called “hydrophobic.”
• Honeybees use wax to make their honeycombs.
• Waxes are used in all sorts of everyday applications including chewing gum, polishes, and candles.
• Fats help us to dissolve and store some important vitamins including A, D, E, and K.
• Cortisol is a type of steroid that our bodies use to regulate energy and fight off diseases.

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The noble gases are a group of elements in the periodic table. They are located to the far right of the periodic table and make up the eighteenth column. Elements in the noble gas family have atoms with a full outer shell of electrons. They are also called the inert gases.  The elements that make up the family of noble gases include helium, neon, argon, krypton, xenon, and radon.
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What are the similar properties of noble gases?

Noble gases share many similar properties including:

• A full outer shell of electrons. Helium has two electrons in its outer shell and the rest have eight electrons.
• Because of their full outer shells, they are very inert and stable. This means they don’t tend to react with other elements to form compounds.
• They are gases under standard conditions.
• They are colourless and odourless.
• Their melting and boiling points are close together giving them a very narrow liquid range.

Abundance

Radon

• Because helium is non-flammable it is much safer to use in balloons than hydrogen.
• Krypton gets its name from the Greek word “kryptos” meaning “the hidden one.”
• Many of the noble gases were either discovered or isolated by Scottish chemist Sir William Ramsay.
• Helium has the lowest melting and boiling points of any substance.
• All of the noble gases except for radon have stable isotopes.
• Neon signs do not use just neon gas, but a mixture of different noble gases and other elements to create bright lights of different colours.
• Noble gases are often used to create a safe or inert atmosphere due to their stable nature.
• Xenon gets its name from the Greek word “xenos” which means “stranger or foreigner.”
• Sir William Ramsay (1852-1916) was a British chemist, and was the first to successfully isolate all of the noble gases, except radon. He also discovered 4 of them, namely neon, argon, krypton, and xenon.
• Pierre Janssen discovered helium in 1868 during a solar eclipse in the spectrum of the corona of the sun. However, Ramsay was the first to isolate it.
•  Ramsay and the British physicist Lord Raleigh found that nitrogen removed from the atmosphere was denser than nitrogen formed by the decomposition of ammonium nitrate. This led to the discovery of argon in 1894.
• Helium was discovered by Janssen in 1895. Through the attempts of Ramsay and his assistant Morris Travers, krypton, neon and xenon were found from the atmosphere by fractional distillation.
• Radon was discovered by a German chemist, Friedrich Ernst Dorn in 1900.