Chapter 6: Production of Chemicals from Plants

Chapter 6: Production of Chemical from Plants

• Metabolism & Metabolites:
  • Metabolism encompasses the chemical processes within a living organism to sustain life
  • Metabolites are the intermediates and products of metabolic processes
  • Generally, metabolites are small molecules with varied functions like structure, signalling, stimulation, and defence.

Metabolic Engineering in Plants

• Prolific Factories: Plants produce a wide array of small molecules.
• Vast Catalogue: Over 100,000 metabolites have been identified, though this likely represents only 10% of the total.
• Rich Source: Plants are the most abundant source of secondary metabolites (5,000 - 25,000 per plant).

Plant Metabolism

• Photosynthesis, Respiration, and Photorespiration: These processes demonstrate the plant's metabolic activity, involving the intake of CO2 and release of O2. Energy from light is converted to chemical energy (sugars), which is stored and used in different plant parts. Water and minerals are absorbed to support these processes.

Plant Metabolism Outline

• Photosynthesis: Uses light energy, CO2, and water to produce sugars. These sugars are then stored as starch/sugar.
• Respiration: A process which uses the starch/sugar for energy through the breakdown of sugars. This is necessary for plant function.
• Interconnectedness: Both photosynthesis and respiration are linked, forming an outline of plant metabolism.
• Product Synthesis: The products of photosynthesis and respiration provide the building blocks for other plant molecules.

Primary Metabolites

• Essential Role: Primary metabolites are crucial for plant growth, development, and reproduction.
• Major Categories: Carbohydrates, proteins, nucleic acids, and lipids.
• Precursors: Some primary metabolites act as precursors for secondary metabolites' production.

Secondary Metabolites

• Non-Essential Role: Secondary metabolites aren't directly involved in growth and reproduction, but have ecological functions.
• Functions: Defence, attraction of pollinators, seed dispersal.
• Examples: Lignin, anthocyanin, phytoalexin, alkaloids.

Carbohydrates

• Sugars (Isomers): Carbohydrates are sugars, including glucose and its isomers.
• Various Sizes: They exist in monosaccharides, disaccharides, and polysaccharides.
• Monosaccharides: Single sugar units (e.g., glucose, fructose)
• Disaccharides: Two sugar units combined (e.g., sucrose, a combination of glucose and fructose)
• Polysaccharides: Polymers with more than two sugar units (e.g., cellulose, starch)

Polysaccharides

• Structural Support: Structural polysaccharides (e.g., cellulose) provide structural support to the plant.
• Energy Storage: Storage polysaccharides (e.g., starch) store energy for the plant.
• Cellulose: Widely distributed structural polysaccharide found in cell walls.
• Cellulose Composition: Long chains of beta-glucose molecules (100 to 15,000) give cell walls strength.

Proteins

• Essential Components: Proteins constitute a significant portion of plant biomass.
• Polypeptide Structure: Proteins consist of one or more polypeptides formed by amino acids.
• Synthesis: Plants produce amino acids from the photosynthetic process, a complex sequence involving nitrogen acquisition (often as NH3) and energy.

Enzymes

• Catalysts: Enzymes catalyze biochemical reactions within living cells.
• Protein Basis: Many enzymes are proteins.
• Human Health: Some plant-derived enzymes are useful for human health.
• Commercial Importance: Pure, plant-derived enzymes, which maintain activity when isolated, are often commercially valuable.

Nucleic Acids

• Complex Polymers: Nucleic acids are incredibly complex biological polymers, including RNA and DNA.
• Fundamental Bases: All plants share similar base constituents (adenine, thymine, guanine, and cytosine)

Lipids

• Non-Polar Solvents: Lipids dissolve in nonpolar solvents like ether, chloroform, and acetone, but not in water.

• Energy Storage: Several types of lipids store energy.

• Membrane Components: Some lipids are primary components of cell membranes.

• Other Functions: Lipid roles include hormones, antioxidants, pigments, etc.

• Hydrocarbon Backbone: Most lipids consist of non-polar hydrocarbon groups (CH3, CH2, CH).

• Major Lipid Classes: Fatty acids, triacylglycerols, waxes, phospholipids.

• Fatty Acids:

  • Stearic acid
  • Oleic acid
  • Linoleic acid
  • Palmitic acid

Plant Secondary Metabolites (Part 2)

• More Diverse Distribution: Secondary metabolites encompass less widespread, diverse chemicals than primary compounds, such as morphine, caffeine, nicotine, and rubber.
• Selective Production: Specific plants uniquely produce particular secondary metabolites, influencing their ecological characteristics.
• Essential Ecological Roles: Secondary metabolites play vital roles in plant-to-plant interactions and with other organisms (e.g., pollination, defense).
  • Examples include alkaloids, terpenoids, phenolics
• Additional Info: These compounds are often found in combination with sugars (forming glycosides).

Plant Secondary Metabolites (Part 3)

• Categorization: Grouping based on similarities in structure, biosynthetic pathways.
• Largest Classes: Alkaloids, terpenoids, phenolics.
• Combination with Sugars: Frequent occurrence with sugars (e.g., glucose, galactose, rhamnose, apiose).
• Flavonoids: A specific type of phenolic with prominent pigments for flower coloration, and vitamin C.

Functions of Secondary Metabolites

• Pigments: Many secondary metabolites, like anthocyanins, provide color.
• Defense: Toxic compounds like alkaloids or toxins protect plants from herbivores and microbes.
• Structural Support: Lignin builds up strength to vascular tissues.

Alkaloids

• Basic Compounds: Naturally occurring compounds containing nitrogen atoms, usually possessing basic properties.
• Often Toxic: Notably, many alkaloids are toxic to other organisms, while some possess pharmacological effects and medicinal or recreational drug use, making them extremely important to study.
• Extensive Variety and Use: Over 6500 alkaloids are known.

Terpenoids (Isoprenoids)

• Isoprene Unit Structure: Dimers and polymers of isoprene, producing varied compounds (C5H8).
• Natural Aromatic Compounds: Common in plants, contributing variety to scents, flavors, and colors (e.g., scents of eucalyptus, ginger, cinnamon flavor).

Phenolics

• Aromatic Hydrocarbon Structures: Chemical compounds with a hydroxyl group directly attached to an aromatic ring (or six-carbon ring).
• Common Component: Salicylic acid, a simple phenolic and important biologically, contributes to the pain-relieving properties in aspirin.
• Various Functions: Phenolic compounds may flavor foods, create dyes, contribute to water coloration, and provide protection against herbivores (e.g., tannins). Lignin is a complex polymer that gives support to wood and other plant structures. Also, important in flavour of nutmeg

Enhancing Product Yield in Major Crop Through Biotechnology

• Breeding Strategies: Selecting varieties with high-yield traits, molecular markers, and reverse breeding.
• Plant Cloning (Tissue Culture): Generating exact copies of plants for commercial use.
• Genetic Engineering: Modifying plants to enhance yield or introduce beneficial traits not present in natural varieties.
• Biofertilizers: Encouraging specific organisms that support essential soil nutrients to the host plant, thus improving crop yield.
• Biocontrol Agents: Suppressing plant pests and pathogens through biological means.