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Questions and Answers

Which of the following is a characteristic of lipids?

They are soluble in water.

They are polar molecules.

They are hydrophilic.

They are largely hydrophobic. (correct)

Triglycerides are composed of two fatty acid chains bonded to one glycerol molecule.

False

What is the primary function of fats in the body?

Efficient energy storage

Fats are also known as ___________.

triglycerides Signup and view all the answers

Match the types of lipids with their characteristics:

Fats = Efficient energy storage Phospholipids = Major component of cell membranes Steroids = Hormones and signaling molecules Waxes = Waterproofing and protection Signup and view all the answers

Which type of fat is solid at room temperature?

Saturated Signup and view all the answers

All unsaturated fats contain one or more double bonds in their structure.

True Signup and view all the answers

Name a source of trans-fats.

Fried foods Signup and view all the answers

_________ fats are primarily sourced from plants.

Unsaturated Signup and view all the answers

Match the type of fat with its characteristic:

Saturated = Solid at room temperature Monounsaturated = Contains one double bond Polyunsaturated = Contains more than one double bond Trans-fats = Created by hydrogenation process Signup and view all the answers

Which of the following fats is more likely to increase the risk of heart disease?

Trans-fats Signup and view all the answers

Canola oil is a source of saturated fat.

False Signup and view all the answers

What is the structure of saturated fats characterized by?

No double bonds Signup and view all the answers

What is the structure of a phospholipid primarily characterized by?

Two fatty acid chains and a phosphate group Signup and view all the answers

Cholesterol is an example of a steroid.

True Signup and view all the answers

What is the primary function of phospholipids in cells?

To form cell membranes Signup and view all the answers

Waxes are primarily used in plants to coat the leaves and prevent _________ from entering.

water Signup and view all the answers

Which of the following statements is true about fats?

Healthy fats can be a naturally occurring energy source. Signup and view all the answers

Explain why fat is considered a more efficient energy storage option compared to carbohydrates.

One gram of fat stores twice the energy of carbohydrates. Signup and view all the answers

Lipase is an enzyme produced by the liver that digests triglycerides.

False Signup and view all the answers

Match the substances with their primary function or characteristic:

Phospholipids = Form cell membranes Steroids = Hormonal regulation Waxes = Water protection and prevention Triglycerides = Energy storage Signup and view all the answers

Study Notes

Lipids

Lipids are mainly non-polar hydrocarbons and therefore hydrophobic.
They are a diverse group including fats, phospholipids, steroids, and waxes.

Fats

Also known as triglycerides.
Composed of three fatty acid chains bonded to a glycerol molecule through ester bonds.
Function as efficient energy storage due to their compact structure and high energy density.
One gram of fat stores more than twice the energy of one gram of carbohydrates.
The body prefers to use carbohydrates as an energy source and only uses fats after carbohydrate stores are depleted.

Types of Fats

Saturated Fats: Contain only single bonds in the fatty acid chains, leading to straight chains and tight packing. They are solid at room temperature and typically found in animal fats.
Unsaturated Fats: Contain one or more double bonds in the fatty acid chains, leading to kinks in the chains and loose packing. These are usually liquid at room temperature and predominantly found in plant fats.
- Monounsaturated Fats: Have one double bond.
- Polyunsaturated Fats: Have more than one double bond.
Trans-fats: Formed through a synthetic process that changes the configuration of double bonds in unsaturated fats from cis to trans. These fats are solid at room temperature and have been linked to increased risk of heart disease.

Phospholipids

Similar to triglycerides, but one fatty acid chain is replaced with a phosphate functional group.
This creates an amphipathic molecule with a polar, hydrophilic head and a non-polar, hydrophobic tail.
Major components of cell membranes forming a phospholipid bilayer with the hydrophilic heads facing the aqueous environment and the hydrophobic tails facing each other in the interior of the membrane.

Steroids

Characterized by a four-ring carbon skeleton with different functional groups attached.
Examples include cholesterol, a key component of cell membranes, and sex hormones like estrogen and progesterone.

Waxes

Long hydrocarbon chains that are solid at room temperature, non-polar, and hydrophobic.
In plants, waxes coat leaves and fruits to prevent water loss and protect against insects.
In animals, waxes coat fur, feathers and skin to repel water. Examples include earwax, beeswax, and spermaceti wax.

Lipid Practice Questions

Question 1: Some fats are healthier than others because of their structure and potential impact on health.
- Healthy Fats: Naturally occurring and provide an efficient energy source.
- Unhealthy Fats: Trans fats are artificially produced and associated with a higher risk of heart disease.
Question 2: Fat is a more efficient energy storage than carbohydrates because one gram of fat stores more than twice the energy of carbohydrates while occupying a smaller volume.