Bio - Unit 1.1

Light Source

The light source is needed to illuminate the specimen for viewing. The light color of light and its intensity can be adjusted using the RED illumination intensity knob on the left side of the microscope.

Condenser

The condenser focuses light on the specimen. The condenser should be positioned in the LOWEST position when focusing the image on the LOWEST level of magnification (40X).

Iris Diaphragm

Used to change the contrast of the image. Partially closing this reduces the amount of light reaching the slide and increases the contrast of the image.

Stage and Stage Clip

The stage holds the microscope slide. The slide is clipped into place by first opening the stage clip and then resting the slide in the expanded space.

Stage Control Knobs

Moves the stage to adjust your field of view on the slide. One knob moves the slide up and down, and the other knob moves the slide left and right.

Coarse Adjustment Knob

This is positioned on the sides of the microscope arm. This knob should be used to focus the image on the LOWEST level of magnification (40x) only.

Fine Adjustment Knob

the smaller knobs attached to the coarse adjustment knobs. It results in a gradual change in the position of the objective lens.

Objective Lenses

The objective lenses magnify the specimen. The levels of magnification from the objective lenses are 4X, 10X, 40X (or 45X), and 100X.

Ocular Lenses

The specimen is observed through the ____ ____ which also magnify the image 10X.

Bright-Field Microscope

Light is produced beneath the stage, passes through the slide and specimen, and is collected and magnified by a series of lenses.

Total Magnification

The total magnification of the sample is determined by multiplying the powers of the two lenses.

Example of Total Magnification

Ocular lens= 10X, Objective lens= 4X, Total Magnification= 10X ● 4X= 40X.

Resolution (Resolving Power)

This is a property of a microscope defined as the minimum distance between two objects when those objects can still be observed as separate entities.

Refraction

the bending of light rays that occurs when light passes from one substance to another of a different refractive index

Refractive index

a measure of the relative velocity of light as it passes through a medium. Note: oil and glass have almost the same refractive index.

Phase-contrast microscope

Amplified differences to create contrast. Therefore, unstained cells are visible.

Fluorescence microscope

UV light is projected through a specimen that is fluorescent (converts UV light into longer wavelength). The fluorescent cells appear illuminated against a dark background.

Scanning electron microscope

a beam of electrons is passed over the surface of metal (often gold) covered cells, producing a 3D image of the surface of the cells.

Transmission electron microscope

cells are 'thin sectioned', a process in which the cell is preserved, embedded into a plastic resin, then sliced. The slices are then exposed to a beam of electrons.

Cell Theory

Every living organism is made up of one or more cells.

Functional units of multicellular organisms

Cells are the functional units of multicellular organisms.

Common Features of Cells

Each cell is surrounded by an extremely thin, rather fluid membrane called the plasma membrane.

Plasma membrane

This membrane consists of a double layer (bilayer) of phospholipids in which proteins are embedded.

Functions of the plasma membrane

• Isolating the cell's contents from the external environment

• regulating the flow of materials into and out of the cell

• allowing interaction with other cells and with the extracellular environment.

Cytoplasm

consists of all the fluid (cytosol) and structures that lie inside the plasma membrane, but outside of the nucleus.

Deoxyribonucleic acid (DNA)

genetic material that serves as an inherited blueprint for making the parts of the cell and for producing new cells.

Ribonucleic acid (RNA)

copies the blueprint of genes on DNA and helps construct proteins based on this blueprint.

Prokaryotic cells

cells that are 'before the nucleus', including Bacteria and Archaea.

Eukaryotic cells

cells that have a 'true nucleus', including animals, plants, fungi, and protists.

Filamentous Appendages

structures found in prokaryotic cells, including flagella and pili.

Flagella

Long protein structures responsible for most types of bacterial motility, spinning like a propeller to move through water.

Pili

considerably shorter and thinner than flagella, with specific forms enabling attachment to surfaces or DNA transfer.

Fimbriae

a specific form of pili that enables a cell to attach to a specific surface.

Sex Pilus

a specific form of pili that joins two bacteria and allows for DNA transfer.

Cell Wall

Rigid structure that determines the shape of the organism and holds the cell together, preventing it from bursting.

Chromosome

Irregular mass within the cytoplasm found in the region referred to as the nucleoid; a single, circular double-stranded DNA molecule containing genetic information required for cell survival.

Plasmid

Small sections of DNA found throughout the cytoplasm, about 1/100-1/10 the size of a chromosome; a circular double-stranded DNA molecule containing genetic information that is not required for cell survival (e.g., Antibiotic Resistance).

Ribosomes

Required for protein synthesis and made up of rRNA and protein.

Cytoskeleton

Proteins that create a framework controlling cell division and cell shape.

Storage Granules

Excess nutrients linked to form polymers for storage (e.g., glycogen); no membrane.

Gas Vesicles

Protein-bound compartments that create buoyancy for aquatic bacteria.

Endocytosis

Process of taking up material from the surrounding environment, creating membrane-bound vesicles.

Phagocytosis

A specific form of endocytosis in which particulate matter or cells are taken up.

Exocytosis

Membrane-bound vesicles inside the cell fuse with the plasma membrane and release contents into the environment.

Nucleus

Membrane-bound organelle that contains DNA, surrounded by the nuclear envelope.

Nucleolus

Site of ribosome synthesis, contained within the nucleus.

Mitochondria

Membrane-bound organelle responsible for ATP generation; outer membrane encloses the matrix and cristae.

Chloroplasts

Found in plants and algae; site of photosynthesis and contains its own DNA and ribosomes.

Endoplasmic Reticulum

Complex internal membrane system; Smooth ER is the site of lipid and carbohydrate synthesis without ribosomes on the outside, while Rough ER has ribosomes on its surface and is where proteins not destined for the cytoplasm are synthesized.

Golgi Apparatus

Series of membrane-bound flattened sacs; site where molecules synthesized in the ER are modified before transport to other destinations; involved in processing, packaging, and shipping.

Lysosomes

Organelles that contain enzymes for digestion of material obtained through endocytosis.

Peroxisomes

Organelles in which oxygen is used to oxidize substances; used for breakdown of lipids and detoxification of certain chemicals.

Vacuoles

Sacs of cell membrane filled with fluid containing water and other molecules; examples include contractile vacuole in Paramecium and central vacuole in plants.

Plasmodesmata

Channels that link plant cells to one another, allowing for cytoplasm, nutrients, hormones, and some organelles to pass between adjacent cells.