Lab 1: Pharmacognosy - Maize Starch and Light Microscopy

Vocabulary flashcards covering the components of light microscopes, plant cell contents, and the physical, chemical, and microscopical properties of maize starch (Zea mays).

Cell content

Substances present inside the plant cell, identified by physical and chemical tests or microscopical examination.

Active constituent

Cell contents that produce a pharmacological effect, such as alkaloids and glycosides.

Storage product

Cell contents stored for nutritional use, such as carbohydrates (e.g., starch), proteins, and lipids.

End product of metabolism

Metabolic waste products or byproducts within a plant cell, such as calcium oxalate.

Eyepiece lens

Also known as the 'ocular lens', it provides the first point of magnification, usually $10\times$ or $15\times$.

Barrel

Also known as the 'bodytube', it connects the eyepiece lens to the objective lenses.

Arm

The part of the microscope that raises the objective lenses above the stage and is used for carrying the microscope.

Objective lenses

The second point of magnification, usually $4\times$, $10\times$, $40\times$, and $100\times$, featuring standard color-coding of red, yellow, blue, and grey.

Stage

The platform where the slide is placed for viewing, attached via 'slide clips' and movable in four directions using stage controls.

Diaphragm

A rotating disk under the stage that varies the intensity of light projected upwards into the slide.

Coarse & fine focus knobs

Focus controls where the coarse focus brings the specimen into view and fine focus fine-tunes the focus to increase specimen detail.

Lamp

The light source for the microscope whose brightness can be adjusted with a dimmer.

Base

The bottom part of the microscope used for structural support.

Starch

Reserved food material that is polysaccharide in nature, stored as granules in higher plants (not present in lower plants like fungi and algae).

Medicinal uses of starch

Includes serving as a skin emollient, an antidote for iodine poisoning, a dusting powder in forensic medicine, and a pharmaceutical excipient (filler, binder, glidant, diluent, and disintegrant).

Maize starch origin

Polysaccharide granules obtained from the endosperm of seeds of Zea mays, belonging to the family Gramineae.

Maize powder condition and touch

Appears as a fine, homogenous white powder that is odorless with a starchy taste and smooth touch.

Maize starch solubility

Insoluble in cold water; soluble in hot water, forming a gel upon cooling (gelatinization).

Maize starch hilum

Present, distinct, fissured (x or y shaped), and centric.

Maize starch microscopical description

Medium-sized polyhedral shape with rounded angles, indistinct striations, and mostly simple (rarely compound) aggregations.

Iodine test for starch

A chemical test where starch plus iodine yields a blue color due to adsorption; warming causes the blue color to fade due to desorption.

Differentiation of starch granules

Since all starch granules are chemically and physically identical, microscopical examination is the only method to differentiate between them.