Topic 4

• Magnesium ions are essential in the production of chlorophyll molecules, which are required for photosynthesis.
• Glucose, produced in photosynthesis, is needed for growth and to produce cellulose in cell walls.
• Magnesium ions deficiency limits the production of chlorophyll, resulting in less photosynthesis, and a lack of glucose.
• Plants with magnesium ions deficiency may have yellow leaves or stunted growth.
• Calcium ions are essential in the production of calcium pectate in the middle lamella, which acts as a glue between cells and cements them together.
• Calcium ions deficiency limits the production of calcium pectate in the middle lamellae, preventing new leaves from growing fully.
• Nitrate ions are essential in the production of amino acids (for protein synthesis) and nitrogenous bases in nucleotides (for nucleic acids synthesis).
• Proteins are required for growth and repair.
• Cellulose is a polysaccharide made up of β-glucose monomers joined together by 1,4 glycosidic bonds, in a condensation reaction.
• Alternate β-glucose monomers are inverted in the chain of cellulose molecules.
• Cellulose molecules are long, straight chains.
• Many cellulose molecules, held together by hydrogen bonds, form cellulose microfibrils.
• In primary cell walls, the cellulose microfibrils are embedded in a matrix of hemicellulose and pectin.
• Cell wall is reinforced with lignin in xylem and sclerenchyma (secondary cell wall).
• Lignin provides structural support/ tensile strength (the pulling force the fibre can withstand before breaking).
• Lignin holds the cellulose microfibrils together and keeps them parallel; layers arranged in a net.
• Lignin makes the walls waterproof.
• Xylem vessels function to transport water and mineral ions and provide structural support.
• Xylem vessels consist of cells with no end walls and no cytoplasm, no cell contents, forming hollow, light tubes.
• The hollow tubes allow water and mineral to move vertically.
• Lignified cell walls in xylem vessels allow water and mineral ions to move horizontally between cells through pits (no secondary cell walls).
• Sclerenchyma provides structural support.
• Sclerenchyma consists of light, hollow tubes and a thickened, lignified cell wall.
• Phloem vessels transport organic solutes (amino acids and sucrose).
• Phloem vessels consist of sieve tube elements and companion cells.
• Sieve tube elements (ST) are connected end-to-end by sieve end plates, which allow solutes to move from one cell to the next; they have very little cytoplasm and few or no organelles (no nucleus - no transcription, no ribosomes, no rER - no translation).
• Accompanied by a companion cell (CC) containing a nucleus and mitochondria, supplying energy to the ST for actively loading solutes.
• Production of products made of plant fibres is sustainable as plants are a renewable resource and more plants can be grown.
• Products made of plant fibres are biodegradable.
• Preclinical trial involves testing on cell culture/ tissue culture/ animals to determine toxicity.
• Benefits of a medicine must outweigh harm done to animals during clinical trials.
• Phase 1 of clinical trials involves testing on healthy volunteers to determine safe dose, side effects, and how drug is metabolised.
• Phase 2 of clinical trials involves testing on a small number of individuals with the medical condition to see whether drug is effective in treating the medical condition and to determine less-common side effects.
• Phase 3 of clinical trials involves testing on a large number of individuals with the medical condition to gather more data for statistical analysis for effectiveness and safety.
• Placebo is used as a control in comparison with the actual drug to ensure the active drug is causing the effect/ improvement is not due to a psychological effect.
• Double-blind trial involves neither patients nor doctors knowing whether the treatment contains the new drug or placebo to remove bias from results.
• William Withering’s digitalis soup involved using a foxglove extract (digitalis soup), not pure digitalis, on individuals with the medical condition.
• Antimicrobial property is the ability to kill or inhibit the growth of microorganisms.
• Antibacterial property is the ability to kill or inhibit the growth of bacteria.
• Zone of inhibition is a clear area; the larger the diameter/ area of the zone of inhibition/ the stronger the antibacterial property.