Lipids Overview

Study Notes

Lipids are organic substances including fats and fat-like substances (phospholipid, wax, steroid, sphingolipid)
Regardless of structure, they have large amounts of C-H bonds (hydrocarbon chains) which enable grouping
Lipids are important components of cell membranes, aiding in fat digestion, providing water resistance and protection
Lipids include phospholipids, waxes, steroids, and triglycerides
- Phospholipids are major components of cell membranes.
- Waxes provide water resistance and protection.
- Steroids have hormonal signaling, cell response and growth functions.
- Triglycerides are involved in energy storage, thermal insulation and carrying fat-soluble vitamins
Main elements of lipids include carbon, hydrogen, and oxygen.
Some lipids contain other elements like phosphorus, sulfur, and nitrogen
Triglycerides consist of one glycerol molecule bonded to three fatty acids.
- Glycerol is a three-carbon chain bonded to hydrogen atoms and alcohol groups.
- Fatty acids are hydrocarbon chains with a carboxyl group at one end.

There are two types of fatty acids: saturated and unsaturated
- Saturated fats have all carbon atoms bonded to other carbon and hydrogen atoms, mostly solid at room temperature.
- Unsaturated fats have some carbon atoms bonded via double bonds to other carbon atoms. These cause kinks in the molecule, leading to liquid form at room temperature.

Phospholipids are composed of fatty acid chains attached to a glycerol backbone.
Phospholipid molecules are amphipathic, meaning they have a polar head and a nonpolar tail. This arrangement is crucial to cell membrane structure.

Steroids are small lipids where the hydrocarbon backbone is linked into four rings.
Cholesterol is an important steroid, providing structure to cell membranes and aiding in digestion of dietary fats.

Waxes are components of organisms such as cuticles, covering leaves and stems of plants and protective coverings on skin and fur of animals.

Lipids act as solvents for fat-soluble vitamins and hormones.
They prevent water loss from the skin.
They are crucial components of cell structures, including cell membranes.
They provide insulation and protection against extreme cold.
Lipids store energy, and provide twice as much energy per pound as carbohydrates.

Nucleic acids are organic compounds that store genetic information, transmitting it from one generation to the next.
Nucleic acids function during protein synthesis by carrying the code needed to form specific proteins.
Two main types: Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA)
- DNA is a double-stranded helix.
- RNA is a single-stranded structure (sometimes a double helix)

DNA replicates and stores genetic information. It acts as a blueprint for all genetic information.
RNA converts genetic information from DNA to a format used to build proteins, then moves it.

Nucleotides are the building blocks of nucleic acids. Each nucleotide contains a phosphate group, a five-carbon sugar (deoxyribose in DNA, ribose in RNA), and a nitrogenous base.
DNA consists of two strands arranged in a double helix, while RNA has a single strand (sometimes a double helix).
DNA is a much longer polymer than RNA.

DNA is more stable than RNA due to its deoxyribose sugar.
RNA is more reactive and not stable in alkaline conditions, meaning it's more easily susceptible to enzyme attack.