The Chemical Basis of Life - Organic Molecules

Lipids

• Lipids are diverse organic compounds, including fats, oils, phospholipids, and cholesterol.
• Composed mainly of carbon, hydrogen, and oxygen; have a higher ratio of hydrogen to oxygen than 2:1.
• Building blocks are fatty acids and glycerol; lipids do not form polymers.

Functions of Lipids

• Fats and oils serve primarily as energy storage.
• Fats provide thermal insulation.
• Waxes and oils act as protective coatings and water barriers.
• Phospholipids are crucial for cell membrane structure and function.
• Carotenoids assist in light absorption for photosynthesis.
• Steroids and modified fatty acids serve regulatory roles as hormones and vitamins.
• Myelin acts as electrical insulation around nerves.

Fatty Acids

• Fatty acids consist of a long hydrocarbon chain and a carboxyl group (COOH).
• Saturated fatty acids have only single bonds between carbon atoms; unsaturated fatty acids contain one or more double bonds.
• Saturated fats (often from animals) are solids at room temperature, while unsaturated fats (from plants and fish) are liquids.

Triglycerides

• Comprised of one glycerol and three fatty acids linked by ester bonds, formed through dehydration synthesis.
• Triglycerides are non-polar and insoluble in water, leading to clumping when introduced to water.

Phospholipids

• Made from glycerol, two fatty acids, and a phosphate group.
• Phosphate group is hydrophilic (water-attracting), while fatty acid tails are hydrophobic (water-repelling).
• Key components of cell membranes; form bilayers in aqueous environments by orienting hydrophilic heads outward and hydrophobic tails inward.

Steroids

• Function as signaling molecules and components of cell membranes.
• Testosterone and estrogen regulate sexual development in vertebrates.
• Cholesterol is synthesized in the liver and is a precursor for steroid hormones.

Nucleic Acids

• Nucleic acids (DNA and RNA) are vital for genetic information storage, transmission, and use.
• Composed of nucleotides, which include a pentose sugar, phosphate group, and nitrogenous base.

Differences Between DNA and RNA

• DNA contains deoxyribose, is double-stranded, and uses thymine as a nitrogenous base; while RNA contains ribose, is single-stranded, and uses uracil instead.
• Both have nitrogen bases: purines (adenine and guanine) and pyrimidines (cytosine and thymine or uracil).

Nucleotide Structure

• Nucleotides link via phosphodiester bonds, connecting the 5' phosphate of one nucleotide to the 3' hydroxyl of another.
• Nucleic acids grow in the 5' to 3' direction.

Digestibility of Starch vs. Cellulose

• Both are polymers of glucose but differ in structure: starch is branched, making it more digestible than linear cellulose.

Energy Storage

• Fats are more energy-dense than carbohydrates and can provide energy when carbohydrates are depleted.

Summary

• Life is based on a limited number of chemical elements, with specific ones being essential for biological processes.
• The chemicals of life are fundamentally similar across all living organisms.

This quiz focuses on the study of organic molecules, specifically lipids and nucleic acids. It explores the chemical structures and functions of these vital components of life. Additionally, it includes discussions on protein structure and assembly processes.