Essential Concepts in Biochemistry and Plant Biology

Biological Classification: The Plant Kingdom

Plants are pluricellular, tissue-forming, photosynthetic autotrophs that possess vascular tissue (xylem and phloem).

Non-Vascular Plants (Bryophyta)

Bryophytes live near water (H₂O) due to the necessity for reproduction. They lack vascular tissue and vessels, remaining small. They reproduce through an alternation of generations, involving both sexual and asexual phases.

Vascular Plants (Pteridophytes)

Pteridophytes possess vascular tissue and are cormophytes (having true roots, stems, and leaves).

Seed Plants (Spermatophytes)

Spermatophytes are vascular plants that produce seeds.

Essential Bioelements and Water Properties

Bioelements

These are the elements that form living beings. They are classified as:

• Primary: Carbon (C), Oxygen (O), Nitrogen (N), and Hydrogen (H).
• Secondary: Such as Sodium (Na) and Potassium (K).

Characteristics of Water

Water exhibits several crucial properties:

• High specific heat.
• High surface tension.
• Structural function.
• Mechanical function.
• Excellent solvent for polar substances.
• Acts as a coolant.

Mineral Salts

Mineral salts can be found precipitated, dissolved, or associated with organic molecules. When dissolved, they regulate pH and osmotic processes.

Organic Macromolecules

Carbohydrates

Carbohydrates are compounds formed primarily by Carbon (C), Oxygen (O), and Hydrogen (H). Their primary function is energy storage and/or structural support.

Monosaccharides

These are chains of 3 to 7 Carbon atoms. They function as polyalcohols with an aldehyde (aldose) or ketone (ketose) functional group, depending on whether the carbonyl group is at the end or in the middle of the chain. They are soluble in H₂O and taste sweet.

Disaccharides and Polysaccharides

Disaccharides are formed by two monosaccharide units linked together. Polysaccharides are macromolecules formed by many monosaccharide units. They are generally not soluble in H₂O.

Homopolysaccharides are formed when the monomer is repeated identically. They serve either a reserve/storage function or a structural function, depending on whether the glycosidic linkage is in the alpha or beta configuration.

Key Polysaccharides

• Starch: The primary glucose reserve compound in plants.
• Galactose: A monosaccharide that is part of the disaccharide lactose, as well as various glycoproteins.
• Cellulose: A structural component of plant cell walls, consisting of linear chains of glucose linked by beta (β) bonds.

Lipids (Fats)

Lipids are nonpolar substances that are not water soluble (hydrophobic). They are impermeable, serve as reserve substances, and are composed primarily of C, O, and H. They are divided based on their structure:

• Saponifiable: Contain fatty acids.
• Non-saponifiable: Do not contain fatty acids.

Fatty Acids

Fatty acids are typically long, unbranched hydrocarbon chains, usually containing an even number of carbon atoms. They can be classified as:

• Saturated: If they contain no double bonds.
• Unsaturated: If they contain one or more double bonds.

Some fatty acids are amphipathic, possessing a nonpolar lipid affinity zone and a polar affinity zone for water (H₂O).

Saponifiable Lipids

These lipids contain fatty acids. They can be:

• Simple: Waxes and acylglycerols (e.g., mono-, di-, or triglycerides). They are nonpolar substances that impermeabilize surfaces and often have a high melting point.
• Complex: Phospholipids.

Monoglycerides and Triglycerides

A Monoglyceride is glycerol esterified with one fatty acid. Triglycerides (triacylglycerols) function primarily for energy storage, insulation, and mechanical cushioning.

Hydrolysis

Hydrolysis is a chemical process in which molecular bonds are broken by the addition of a water molecule.