Plant Metabolism and Compound Production Flashcards
How many systems are in the flowering Plant Structure? What are their names?
- shoot system
- root system
what is the Fx of the cell wall?
protection and structure
fx of chloroplasts
energy production and carbon assimilation
What are the 3 tissue cells?
- dermal
- vascular
- ground
Dermal Cells
outer covering modified for protection and water absorption
what are trichomes?
outgrowth of epidermis on leaves, secrete secondary compounds
- ex. tomato plants, cannabis (where CBD and THC is located)
Vascular cells
provides long distance transport of material within the plant
- includes xylem and phloem
Ground
between dermal and vascular tissues
- within the vascular tissue forms ‘pith’
- external to vascular tissue forms ‘cortex’
Translocation
movement in the phloem
Transpiration
movement in the xylem
Xylem Tissue Transport
- xylem moves water and dissolved minerals from roots into shoots
- xylem derived form greek word for wood
- tissue contains water conducting cells
- xylem is comprised of dead cells
- tracheids and vessel elements
- primary and secondary cell walls (hardened with lignin) reinforce cell structure and prevent cells from collapsing during high water tension
Phloem Tissue Transport
- phloem transports sugars (photosynthates) from their site of synthesis to where they are needed
- phloem is formed of live cells
- sieve tubes and plasmodemata
Sieve Tubes
chains of sieve-tube members
- lack organelles
- connected at ends by sieve plates through which fluid moves
Plasmodemata
connect nearby companion cells to sieve tubes
Anabolize vs. Catabolize
- anabolize = create
- catabolize = breakdown
Studying metabolic pathways (1950s, 1970s, 1990s)
- 1950: radioisotopes to label precursors (follow radioactivity to identify sequence of products)
- 1970: use plant cell cultures to produce pathway enzymes (provides abundant material to isolate, purify, and characterize enzymes - Hairy Root Culture)
- 1990: use molecular techniques (isolate, characterize and manipulate genes encoding biosynthetic enzymes
Virus Induced Gene Silencing (VIGs)
- ideal for use non-model organisms
- utilized plants own defence machinery to silencing genes of interest
- has been employed to see how metabolism re-arranges without the production fo the GOI
Primary Metabolic Pathways
- create molecules that are essential for life
- used in normals cells functioning
- these compounds are not toxic to predators
Secondary Metabolic Pathways
- processes that create molecules that are NOT required for the general fx of the organsim
- molecules produced used for defence
- often the compounds of medicinal interest that are produced by plants
Carbohydrates (sugars)
- primary metabolic pathway
- energy store (short and long term) - starch
- structural integrity - cellulose
- specialized compounds - complex polysaccharides, alginic acid, carrageenan, agar, Gum arabic
Medically relevant carbohydrates
- Panax quinquefolius: polysaccharides in Echincea species stimulate the immune system
- aloe barbadensis: used for skin conditions
- many medicinal compounds are glycosides
Photosynthetic pathways produce carbohydrates used…
- as energy resources
- to build more complex like glycosides or cellulose
- to generate ATP through cellular respiration
Production of Lipids
- long chain hydrocarbons (fatty acids) attach to glycerol to form triglycerides
- carbon rings combine to form phytosterols - energy sources (oils/fats) , components of cell membranes
- can form the basis of specialized molecules
- not found in defensive or medically relevant plant compounds
Amino acids
- aa are the precursors form many secondary plant metabolites
- rarely have medicinal or defensive action on their own
- aa have different chemical properties based on their structures
Production of Proteins
- produced as polymer chains of amino acids
- multiple function: structure, enzymes, defense, transport, etc.
What are Secondary Metabolites
- pharmacologically active compounds found in plants are usually produced form secondary metabolic pathways
- primary and secondary pathways are directly connected
- derived from precursors made from primary metabolic pathways
- not essential for the basic fx of the plants
Characteristics of Secondary Metabolites
- small, organic molecules
- contain oxygen, nitrogen, sulfur
- structures may be simple or complex - do not reach the size of polymer primary macromolecules
- immense structural diversity/complexity
- exhibit hyrdophobic or hydrophilic behavior
MEP/DOXP pathway
- plants and bacteria and some protists
- terpenes
Shikimate Pathway
- produces aromatic amino acids
- phenylalanine, tryptophan, tyrosine
- are precursors for alkaloids and phenolics
- this pathway does not occur in animal cells
Malonic acid pathway
- phenolics
- more prevalent in fungi and bacteria that in plants
Terpenes
- largest class of secondary metabolites
- some act as primary metabolites for the plant and are necessary for cell fx (cell growth modulation, light harvesting, photoprotection, control of membrane fluidity)
- components of essential oils (smell, pain, relief, cough suppression)
disease and health (anti-malarial, anti-cancer, regulation of heart rate, antioxidants - soap properties and hormone precursors
Terpene Synthesis (MVA pathway & MEP pathway)
- MVA pathway (cystol): acetyl CoA is coneverted into mevalonic acid, melavonic acid is coverted into isopenanyl diphosphate and its isomer dimethylallyldiphosphate (DMAPP)
- MEP pathway (plastid): pyruvate and glyceraldehyde 3-P
Structure of Terpene
- structurally, there are linear terpenes and cyclic terpenes
- geraniol: non-cyclic terpene
- limonene: cyclic terpene
Opium Poppy identification and use
- Friedrich Wilhelm Serturner (1806) pain relieving compounds in opium poppy
- extracts crystals of a bitter alkaline substance that puts animals to sleep without coma/death (uses it on himself for toothache)
- he calls the active compound morphine (first alkaloid identified, named after the greek God of dreams Morpheus)
What is a Alkaloid?
- second largest more structurally diverse, most medically important group of plant compounds
- plant compounds containing a N atom in a ring structure
- many have chemical characteristics as bases
- many are bitter
- in plants, human blood and the human stomach, the nitrogen atom has a positive charge making molecules polar and water soluble
Synthetic Pathways for Alkaloids
- usually synthesized from precursor compounds like amino acids
- aliphatic amino acids via Krebs/TCA cycle
- aromatic amino acids via Shikimate pathway
- may also be synthesized from or with terpenes, purines, polyketides and others
Naming of Alkaloids
- related alkaloids by the common name of one that is well known (e.g., morphine alkaloids)
- latin name of plant from which alkaloids were originally isolated (e.g., lobelia alkaloids)
- refer to chemical name of the nitrogen ring as a descriptor (e.g., tropane alkaloids)
What are Phenolics?
- weakly acidic, simple, aromatic molecules with a hydroxyl group attached to an aromatic ring
- sometimes the hydroxyl group is ‘lost’
- phenolic compounds account for 40% of organic compound found in the biosphere
Phenolic Characteristics
- phenolics are a plant adaptation that allow for survival on land
- most phenolic compounds have cell wall structural roles
- provide wood and bark characteristics
- provide wood and bark characteristics
- roles in flower color, plant taste and odor
- roles in plant defence
Synthesis of Phenolic Compounds
- derived from aromatic amino acids made in the shikimate pathway
- tyrosine, phenylalanine, tryptophan
Phenolic Compounds
- flavonoids (anthoxanthins, flavanones, flavanonols, flavans, anthocyanidins)
- stilbenes (resveratrol)
- coumarins (gingerol)
- tannins (derived from gallic acid or flavonoids)
Why did scientists originally think that secondary compounds were a ‘waste’?
because they did not play a major role in plant metabolism
What were some arguments against the thinking that secondary compounds were a waste?
- compounds are energtically expensive to produce, story, and transport
- made in specific cellular and tissue areas
- expression is regulated
What factors does the amount and distribution of compounds depend on?
- plant Genera
- part of plant
- stage of development
- stage of growing season
- weather
- time of day
- plant injury/attack
Storage and Synthesis of Secondary Compounds
- location of secondary compounds vary
- organ level: compounds generally stored in roots, leaves, stems, flowers, fruiting bodies, seeds (leaves are the most frequent site)
- tissue level: nonliving wood and bark cells, epidermal hairs (trichomes), living cell cytoplasm
- cellular level: vacuoles
Examples of where different plant store and synthesize compounds (organs)
- not always stored in leaves
- morphine produced and stored in seed capsule
- ginsenosides produced and stored in the root
- nicotine is synthesized in the roots, but transported and stored in leaves
Plant compound synthesis and storage in Tissues
- synthesis of plant volatiles often occurs in flower epidermal cells (easy escape to atmosphere)
- in vegetative organs, plant volatiles are synthesized in surface glandular trichomes
- some plant volatiles are made in specialized cells structures
Example of Plant Compound Synthesis and Storage in Tissue (catharanthus roseus)
- aka madagascar periwinkle
- produces anti-cancer drugs (terpenoid indole alkaloids)
- enzymes in the biosynthetic pathway were localized using in situ hybridization techniques
- enzymes are specifically localized to at least three cell types - internal phloem parenchyma, epidermis, laticifers
- synthesis of terpenes may involve steps where intermediated are transported from cell-to-cell
Example of Plant Compound Synthesis and Storage in Tissues (Papaver Somniferum)
- aka opium poppy
- morphine is found in the latex
- latex is found in the cytoplasm of laticifers; cells associated with phloem tissue
- key enzymes int eh biosynthesis of morphine are not found in latex
Define Synteny
physical co-localization of genetic loci on the same chromosome within an individual or species
Proteome Regulation - Cellular
- induce conformational changes (e.g., protein activation)
- create sites for protein-protein interactions
- induce changes in subcellular localization
Example of Regulation of Secondary Compound Synthesis
- time of day regulation
- the circadian clock allows plants to anticipate day and night - correspondingly, they time when they perform specific tasks
- ‘timed attack’ is met with ‘times defense’
