Molecules - Carbohydrates and Lipids P43

Molecules Overview

• Four primary types of biological molecules:
  • Carbohydrates (CHO)
  • Lipids (CHOP)
  • Proteins (CHONS)
  • Nucleic acids (CHONP)
• Cells are predominantly composed of water, which serves as a medium for biochemical reactions.
• Carbohydrates and proteins show variability depending on the cell type, while lipids maintain more consistency.

Organic vs. Inorganic Compounds

• Carbon Dioxide (CO2) is considered inorganic due to the absence of covalent H-C or C-C bonds.
• Structural diagrams like skeletal formulas represent carbon atoms at line ends and vertices.

Polymer Formation

• Monomers combine to form polymers via dehydration reactions, removing water to form covalent bonds.
• Hydrolysis is the reverse process, adding water to break down polymers into monomers.
• Branching is possible in polymers, facilitating energy storage.

Carbohydrates

• Types of carbohydrates:
  • Monosaccharides (e.g., glucose, fructose)
  • Disaccharides (e.g., sucrose formed from glucose and fructose)
  • Oligosaccharides
  • Polysaccharides (e.g., glycogen, starch)
• Monosaccharides are polyhydroxy aldehydes or ketones and often exist in ring structures, particularly 5 or 6-membered rings.
• Alpha and beta glucose are isomers distinguished by the orientation of the hydroxyl group.

Polysaccharide Characteristics

• Glycogen serves as short-term carbohydrate storage in animals (found in liver and muscles) and consists of alpha 1-4 and alpha 1-6 linkages.
• Starch, the plant storage form of glucose, has two types:
  • Amylose: linear structure (alpha 1-4)
  • Amylopectin: branched structure (alpha 1-6 branching)
• Cellulose is the most abundant natural polymer, providing structural support in plants, and is indigestible.
• Chitin, a structural component in exoskeletons and fungal cell walls, is composed of N-acetylglucosamine (NAG) units.

Lipids

• Lipids are organic molecules that are non-polar and insoluble in water.
• Key types of lipids include fatty acids, triglycerides, phospholipids, steroids, waxes, and glycolipids.
• Fatty acids can be saturated (no double bonds) or unsaturated (one or more double bonds).
• Triglycerides consist of glycerol and three fatty acids, serving as the main form of energy storage.

Fat and Oil Properties

• Fats are saturated, solid at room temperature, and have higher melting points (e.g., butter).
• Oils are liquid at room temperature due to the presence of unsaturated fatty acids.
• Cis isomers have bent structures, while trans isomers are straight due to the positioning of hydrogen atoms.

Phospholipids

• Phospholipids contain a hydrophilic phosphate head and hydrophobic fatty acid tails, forming bilayers in aqueous environments essential for cell membranes.
• Their structure influences fluidity; unsaturated tails result in lower melting points and greater fluidity.

Steroids and Other Lipids

• Steroids, such as cholesterol, play critical roles in signaling (e.g., testosterone, estradiol).
• Waxes are hydrophobic lipids used by organisms for protection against dehydration.
• Glycolipids consist of sugars, glycerol, and fatty acids, crucial for immune responses and blood type differentiation.

Lipopolysaccharides

• Found in the cell walls of some bacteria, providing structural integrity and protection.
• Lipid A is linked to pathogenicity through its sugar components, which face the external environment.

This quiz focuses on the structural aspects of molecules, specifically carbohydrates and lipids, as detailed on page 43. You will explore concepts such as the composition of carbohydrates, lipids, and other biological molecules, including their stability and variation in different cells. Test your understanding of organic versus inorganic compounds.