Question

Lipids

1. Describe the building-block molecules, structure, and biological importance of fats, phospholipids, and steroids.
2. Why are lipids classed together?
3. Do lipids have monomers?
4. Distinguish between saturated and unsaturated fats.
5. Distinguish between cis and trans fat molecules.
6. What are some of the health risks associated with trans fats?
7. Describe how phospholipids orient to form membranes.
8. Which part of a phospholipid is hydrophobic? Which part is hydrophilic?
9. What are the three classes of lipids?
10. List two important biological functions of a steroid.
11. What is the structure of a steroid?
12. How do anabolic steroids cause an increase in muscle mass?

Answer 1

Fats : are esters of fatty acid with glycerol

Biological Importance :

• Fats are the storage form of energy in animals.
• Act as a fuel source in body.
• Contribute to a major proportion of our daily calories.
• Provides insulation to body and act as a shock absorber.
• Important component of vitamins.

Phospholipids : are important class of lipids with phosphate groups and major building block of cellular membranes.

Phospholipids consist of a glycerol molecule, two fatty acids and a phosphate group. The structure of a phospholipid is composed of two hydrophobic fatty acid tails and a hydrophilic head with glycerol and phosphate. The phosphate group is usually modified by organic molecules such as choline, ethanol amine or Serine.

Biological Importance :

• Major component of cell membranes.
• Phospholipids can form lipid bilayers due to the amphiphilic nature. The hydrophobic tails are buried inside the bilayer and hydrophilic heads are oriented outside.
• Important in nano-formulations and material science.
• Used in the synthesis of liposome for efficient drug delivery.

Steroids : are bioactive compounds derived from a ring structure and involved in mediating several biological processes in our body.

All steroids are composed of a ring structure called cyclopentano perhydrophenanthrene ring.

Biological Importance :

• Important components of cell membranes.
• Regulate the fluidity of plasma membranes.
• Important for the synthesis of sexual hormones.
• Decrease inflammation.
• Act as signaling molecule.

All lipids are insoluble in water and soluble in non-polar solvents such as chloroform, ether, acetone etc.

Glycerol and fatty acids are the monomers of lipids.

Saturated Fats	Unsaturated fats
Fatty acid chains have single bonds and saturated with hydrogen molecules.	Fatty acid chains have double or triple bonds.
Solid at room temperature	Liquid at room temperature in oil form.
Increase blood cholesterol level	Reduces harmful LDL and improves lipid profile.

Cis Fat	Trans Fat
Typical form of Unsaturated fatty acid found in nature	A byproduct of hydrogenation which turns healthy oils into solids and prevents rancidity.
High energy configuration	Low energy configuration
Beneficial than trans fat	Trans fat is considererd unhealthy

• Trans fat increases harmful LDL cholesterol level and reduces beneficial HDL cholesterol.
• Creates inflammation thereby promoting heart disease, stroke and diabetes.
• Contributes to insulin resistance and leads to type 2 diabetes.

The three important classes of lipids are triglycerides (fats and oils), diglycerides (Phospholipids) and steroids.

Anabolic steroids increase the protein production by muscle cells and allows the cells to produce more ATP.