Medicinal Plants (PG101) Lecture 1

Study Notes

Course title: Medicinal plants (PG101)
Academic year: 2024/2025
Lecture 1
Lecturers: Dr. Amal F. Soliman (Associate Professor of Pharmacognosy) and Dr. Walaa Safwat (Lecturer of Pharmacognosy)

Pharmacognosy is the study of medicinal drugs derived from plants and other natural sources.
Medicinal plants (PG101) is a course taught by the department.
Other courses offered include Pharmacognosy 1 & 2, Phytochemistry 1 & 2, and Phytotherapy.

Students will learn about dusting powders, plant anatomy, physiology, and the taxonomy of medicinal plants.
The course will cover the importance of natural products, preparation of natural product-derived drugs, including collection, storage, preservation, and avoiding adulteration.

Plant anatomy details the structure and organization of plant cells, tissues, and organs in relation to their development and function, including cell and tissue structures.
Images of plant parts, such as axillary buds, terminal buds, petioles, vegetative branches, vascular tissue, nodes, taproots, lateral roots, flowers, and internodes, were shown.
The parts of a plant cell have various shapes, arrangements, and margins, (e.g., linear, ovate, obvate, lobed, pinnately compound, simple, entire, crenate, alternate).

The plant cell wall is semi-rigid, external, and non-living.
It’s present in plants but absent in animal cells.
It provides protection and support to the living plasma membrane.
The cell wall is primarily composed of polysaccharides (cellulose, hemicellulose, pectin), and lignin.
The cell wall is divided into three parts: middle lamella, primary cell wall, and secondary cell wall.

Middle Lamella: The layer between two cells, primarily composed of calcium and magnesium pectate.
Primary Cell Wall: The second layer, mainly made of cellulose, which can expand as the cell grows.
Secondary Cell Wall: The inner layer, formed after cell growth ceases, containing cellulose, hemicellulose, lignin, and suberin. It supports cells like fibers and vessel cells.

Pits are areas in cell walls where no secondary wall is deposited. Types include simple, bordered, and half-bordered pits.
Bordered pits are mainly located in conducting and mechanical cells of xylem, like vessels and tracheids.
Simple pits can be found in parenchyma cells, phloem fibers, and sclereids.
Plasmodesmata are small pores in adjacent cell walls. Cytoplasmic strands pass through these pores connecting protoplasts of adjoining cells facilitating material movement.

Nucleus: The large, spherical structure controlling cell activities and hereditary character transmission. Enclosed by a nuclear envelope and containing chromatin, chromosomes, and a nucleolus.
Endoplasmic Reticulum (ER): Rough ER has ribosomes synthesizing proteins for export, while smooth ER synthesizes lipids and phospholipids.
Ribosomes: Round, spherical organelles responsible for protein synthesis, made of RNA and protein.
Golgi Apparatus (Golgi body): Flattened sacs involved in packaging and secretion of proteins, receiving proteins from the ER and transporting them to various organelles or the cell surface. It's involved in cell wall formation.
Mitochondria: Rod-shaped organelles known as the "powerhouse" of the cell, producing much of the cell's energy (ATP) through cellular respiration.
Plastids: Found only in plant cells. Three types: leucoplasts (colorless), chromoplasts (colored), and chloroplasts (responsible for photosynthesis).
Chloroplasts: Contain chlorophyll and are surrounded by two membranes (outer and inner). Thylakoids (stacks called grana) are within stroma (fluid). Photosynthesis occurs in grana.
Lysosomes: Sacs containing digestive enzymes responsible for intracellular digestion.

Mature plant cells have vacuoles, which occupy a significant space.
Filled with cell sap, they're surrounded by a lipoprotein membrane (the tonoplast).
Vacuoles may contain pigments such as anthocyanin, found in colored petals.

Question 1: What is a plant cell wall primarily composed of? (Answer: polysaccharides)
Question 2: Which organelle is responsible for cell wall formation? (Answer: Golgi Apparatus)
Question 3: Which of the following are considered non-living components of a plant cell? (Answer: cell wall, vacuoles)
Question 4: What color are lignified elements when stained with phloroglucinol and hydrochloric acid? (Answer: red)