Cell Structure and Microscopy Lecture Notes

Flashcards covering microscope slide preparation, staining, magnification calculations, cell organelles, and the differences between prokaryotic cells, eukaryotic cells, and viruses.

Dry Mount

A slide preparation method for solid specimens where thin slices, called sectioning, are taken and a coverslip is placed on top; used for hair, pollen, dust, and tissues.

Wet Mount

A slide preparation where specimens are suspended in water or immersion oil with a coverslip placed at an angle; used for aquatic samples and living organisms.

Squash Slides

A slide preparation for soft specimens where a wet mount is squashed between the slide and coverslip, often used to observe cell division in root cells.

Smear Slides

A slide preparation where the edge of a slide is used to smear the sample into a thin, even coating, such as in blood smears to view erythrocytes.

Crystal Violet

A stain used in Gram staining that stains cell walls purple.

Methylene Blue

A stain used to provide contrast by staining the nuclei in animal cells.

Congo Red

A negative stain that is not taken up by the cell, providing contrast between the cell and the background.

Magnification

How many times bigger the image of a specimen is compared to its actual size, calculated as $\text{Magnification} = \frac{\text{Image Size}}{\text{Actual Image}}$.

Total magnification

The product of the eyepiece lens magnification and the objective lens magnification ($\text{eyepiece lens magnification} \times \text{objective lens magnification}$).

Resolution

The ability to distinguish between two separate points, defined as the minimum distance apart two objects can be to appear as separate items.

Light microscope

A microscope that shines light through a specimen, suitable for specimens above $200\,nm$ with a maximum magnification of $\times 1500$.

Electron microscope

A microscope that uses a beam of electrons, allowing for high resolution and a maximum magnification of $\times 500\,000$ for specimens above $0.5\,nm$.

Stage Micrometre

A slide with a very accurate calibrated scale in micrometres ($10$ units, $100$ mini stage units) used to calibrate the eyepiece graticule.

Eyepiece Graticule

A disc with $100$ divisions placed in the eyepiece that has no scale (is not calibrated until compared with a stage micrometre).

Cell surface membrane

A partially permeable phospholipid bilayer containing proteins that controls the exchange of materials between the internal and external environment.

Nuclear envelope

A double membrane containing nuclear pores that separates the nucleus from the cytoplasm and allows the passage of large molecules like mRNA and ribosomes.

Nucleolus

The center of the nucleus responsible for producing and assembling ribosomes.

Mitochondria

The site of aerobic respiration and ATP production, containing cristae, matrix, small circular DNA, and $70S$ ribosomes.

80S Ribosomes

Ribosomes composed of $60S$ and $40S$ subunits found in eukaryotic cells; they are the site of protein synthesis.

70S Ribosomes

Smaller ribosomes composed of $50S$ and $30S$ subunits found in prokaryotes, mitochondria, and chloroplasts.

Rough endoplasmic reticulum (RER)

A network of flattened sacs (cisternae) covered in $80S$ ribosomes involved in the synthesis, transport, and modification of proteins.

Smooth endoplasmic reticulum (SER)

A tubular structure lacking ribosomes involved in the production and synthesis of lipids such as cholesterol.

Golgi body

Flattened sacs of membrane called cisternae that collect, process, and modify proteins and lipids before packaging them into vesicles.

Lysosomes

Vesicles containing hydrolytic enzymes responsible for breaking down unwanted structures, old organelles, dead cells, and bacteria via hydrolysis.

Microtubules

Tiny tubules made of alpha and beta tubulin that form the cytoskeleton and the spindle used in mitosis.

Centrioles

Structures made of $27$ microtubules (nine triplets) found only in animal cells; two centrioles at right angles form a centrosome.

Cilia

Hair-like projections made from microtubules that use whip-like movements to move substances, such as mucus, over the cell surface.

Microvilli

Finger-like extensions of the cell surface membrane found in animal cells that increase surface area for absorption.

Chloroplasts

Organelles in plants containing thylakoids (stacked as grana) and stroma; they are the site of photosynthesis and contain $70S$ ribosomes and circular DNA.

Plasmodesmata

Pore-like structures that connect the cytoplasm of adjacent plant cells, allowing substances to pass through without crossing the cell membrane.

Tonoplast

The selectively permeable single membrane that surrounds the large permanent vacuole in plant cells.

Prokaryotic cells

Cells with no true nucleus, naked circular DNA, peptidoglycan cell walls, and $70S$ ribosomes.

Eukaryotic cells

Cells with a distinct nucleus, linear DNA associated with histone proteins, double membrane-bound organelles, and $80S$ ribosomes.

Viruses

Non-cellular infectious particles ($20$ to $300\,nm$) consisting of a nucleic acid core (DNA or RNA) and a protein coat called a capsid.