Microscope and Cell Quiz Prep

Objective lens

located on a revolving nosepiece that extends outwards over the stage. There are 3-4 objective lenses, each with a different magnification and working distance. The magnification is written of the lens itself.

Stage translational control knobs

located to one side of the stage, just below the surface. These knows can be used to move the slide from side to side or forward and backward.

Ocular lense

located within the eyepiece and magnifies the object. Typically magnifies 10x.

Electron microscope

microscope that forms an image by focusing beams of electrons onto a specimen use beams of electrons to produce images, 1000 more detailed than light microscope

On/off switch

self-explanatory

Chaos (ameoba)

Chaos feeds on paramecium. Chaos move by shifting their body around to pull themselves forward. Probably doesn't have a cell wall because it needs to ingest food and that would be obstructing.

Volvox

Colonial organism. Each individual cell has a chloroplast, nucleus, and flagella Volvox is free floating fresh water green algae. Volvox grows as planktons on surface of water bodies like temporary and permanent ponds, lakes and water tanks. The green color tells us that it is metabolic as it does photosynthesis. Every single ovoid or spherical cell in volvox colonies possess two flagella. A pair of contractile vacuoles, along with single cup-shaped chloroplasts, are present at the base of these flagella. Flagellar movement of cells present in volvox colonies is used for swimming (rolling motion) and also in changing the direction.

Spirogyra

Colonial organism. Has a nucleus, chloroplast, cell wall, vacuole, cell membrane Does not appear single celled.

Multicellular Organisms: Plants and Animals

Composed of groups of specialized cells that together perform particular functions for the organisms. Cells are grouped into tissues, which are then grouped into organ and organ systems. The potato cell is one example. The part of the plant we usually eat is a specialized portion of the plant's stem (called a stem tuber) that's found underground. Stem tubers are reproductive structures; they can give rise to new, complete potato plants. In addition, stem tubers store energy for the plant, in the form of start molecules. In this activity, you will describe an interesting property of starch that can be observed when it comes into contact with iodine.

Compound light microscope

Compound means that there are at least two magnifying lenses: one ocular and one objective. Light refers to the illumination source.

There are many types of microscopes. In our lab class we will use which two?

compound light and dissecting

Dissecting microscope (stereoscopic microscope)

has a relatively low magnification and is used to view and manipulate the objects that are too large to view under the compound light microscope. is similar to the compound light microscope in two ways: - light is the source of illumination - has an objective lens (and sometimes ocular lenses) it is different in 7 ways.

The dissecting light microscope...

has less resolving power than either the compound light or the electron microscopes

The "Total Magnification" of an object when looking through an oil immersion lens is....

1000x

Numerical aperture of lens

According to google, it's "a dimensionless number that characterizes the range of angles over which the system can accept or emit light." The greater the numerical aperture (NA), the better the resolution. NA is usually indicated on the side of each lens.

Parafocal

An object that is in focus at one magnification should require little focusing when objectives are switched.

heterotroph

An organism that cannot manufacture its own food and instead obtains its food and energy by taking in organic substances, usually plant or animal matter. All animals, protozoans, fungi, and most bacteria are heterotrophs.

Human epithelium

Cell membrane, nucleus, cytoplasm. This human cheek cell is a good example of a typical animal cell. It has a prominent nucleus and a flexible cell membrane which gives the cell its irregular, soft-looking shape. Like most eukaryotic cells, this cell is very large compared to prokaryotic cells. For scale, notice the pair of dark blue bacteria cells sticking to the right edge of the cheek cell. The bacteria are only a fraction of the size of the nucleus, but their tiny size is typical for bacteria.

Electron microscopes resolution over electron beam

Electron microscopes typically have superior resolution because the electron beam has a much shorter wavelength than visible light. Some electron microscopes have a resolution of less than 1.0 nm (0.001 um)

Stage

Flat surface on which the specimen will be placed. Supports the slide being viewed

Fungi

Fungi is eukaryotic, not prokaryotic, because they have organelles, a nucleus, is multicellular, and uses oxygen. Fungi live in moist environments, and play an important ecological role as decomposers; they break down dead organisms, causing the release of nutrient molecules into the environment. The organisms that are classified as fungi are a diverse group, ranging from single-celled organisms (e.g. yeast) to multicellular organisms (e.g. mushrooms, bread mold, and the fungus that causes athlete's foot). Some fungi live symbiotically with other organisms like algae and plants. Multicellular fungi form long, thread-like structures called hyphae. These structures infiltrates the surrounding environment, releasing digestive enzymes; once the nearby nutrient molecules are broken down, they are absorbed by the hyphae. When fungi form many hyphae that form a complex, entangled structure, it's collectively referred to as a mycelium. Fungi can reproduce either sexually or asexually. One way that fungi reproduce asexually is by producing spores, which are reproductive cells that can give rise to new fungi. Fungal spores can be found at the end of a special type of hyphae called aerial hyphae (i.e hyphae that stick up into the air). The portion of mushrooms that we see above ground is actually a large, complex collection of aerial hyphae and spores.

Oil immersion lens

Has a magnification of 100x. This lens gets its name from the fact that one must add oil to the space between the objective lens and the specimen in order to achieve adequate resolution.

Electron Microscope

It uses a beam of electrons, instead of visible light. The beam has a short wavelength and increases resolution. Lenses are electromagnetic not glass (b/c glass has little effect on electron beams). As a result, they have greater magnification and resolution than light microscopes. But, specimen have to undergo extensive preparation prior to observation with this microscope. The micrographs though are not in color. The ones that appear so have been colorized. There are two types: the SEM and the TEM

Focusing

Lenses are focused by using the coarse and the fine focus adjustment knobs to move the stage (or sometimes the nosepiece) up or down. These knobs are located at the sides of the base of the microscope. One should always begin observation of a specimen with the scanning objective in the HIGHEST position (the largest working distance possible). This may be accomplished by using the COARSE focus adjustment knob. When focusing a specimen, the coarse adjustment knobs will be used ONLY with the scanning objective in place. After moving to other objectives, you will use ONLY the fine focus adjustment knob, which "fine-tunes" the focus. It moves the stage (or nosepiece) only a very small distance. This technique avoids the possibility of "crashing" objective lenses into specimens, given a shorter working distance in the other three lenses. Even with the scanning objective in place, one must use caution when turning the coarse adjustment knob.

Components of the illumination system

Light source (lamp), on/off switch, rheostat, filter, condenser lens, iris diaphragm.

Total magnification

Ocular magnification x objective magnification

Wavelength of light

Passes through the specimen. The shorter the wavelength, the better the resolution. The light microscope's resolution is limited by the wavelengths of visible light

Elodea

Plant cell that has a cell wall, cytoplasm, nucleus, chloroplast, vacuole, cell membrane This Elodea leaf cell exemplifies a typical plant cell. It has a nucleus, and a stiff cell wall which gives the cell its box-like shape. The numerous green chloroplasts allow the cell to make its own food (by photosynthesis). The central vacuole takes up most of the volume of the cell. It is transparent, but you can see where it's pressing the chloroplasts up against the cell wall, especially at the ends of the cell. Like animal cells, the cytoplasm of this plant cell is bordered by a cell membrane. The membrane is so thin and transparent that you can't see it, but it is pressed against the inside of the cell wall. Our observations indicate that plant cells, unlike animal cells, have chloroplasts that let plants differ in their metabolic capabilities since plants can do photosynthesis (and animals cannot). This cell can also take in more fluids without bursting because of the cell wall to mitigate the pressure against it by osmosis.

Two situations when you would choose a dissecting microscope over a compound light one.

Remember that the dissecting microscope is good because: -Better for larger, 3D specimens, such as live termites -Lower Magnification, Greater Resolution -Use transmitted and reflected light -See in 3D because each eye has its own ocular -The dissecting microscope is also known as a stereomicroscope. Because it has a long working distance, between 25 and 150 mm, it has a lower magnification ability. This gives the user the option to manipulate the specimen, even performing small dissections under the microscope. Live specimens can also be observed. A typical student stereoscope can magnify two to 70 times through its one objective lens. With a stereoscope, light can be directed at the specimen from above, creating a three dimensional image. But compound is good because: -Best for small, flat specimens (on a slide) -Greater Magnification -Uses only transmitted light -Compound light microscopes are commonly used to view items that are too small to see with the naked eye. They have several strengths of objective lenses and rely on light shining from beneath the specimen. This requires that a specimen be very thin and at least partly translucent. Most specimens are stained, sectioned and placed on a glass slide for viewing. A compound microscope can magnify up to 1,000 times and provide the ability to see much more detail. The working distance varies from 0.14 to 4 mm. -A compound microscope is used to observe ultra-thin pieces of larger objects. Examples could be the stem of a plant or a cross section of a human blood vessel. In both cases, the specimen is not living. The piece is placed on a slide and stained with dyes to highlight features. A stereoscope can be used for items that light cannot shine through. The actual colors of the specimen will be observed, and the specimen can be manipulated by the observer while being viewed. The intricacy of butterfly wings, the detail of a scorpion claw and the weave in a fabric are a few examples of items that could be viewed. Stereoscopes also might be used to observe some living organisms such as those in pond water.

Generalized Plant vs Animal Cell Differences

Structurally, plant and animal cells are very similar because they are both eukaryotic cells. They both contain membrane-bound organelles such as the nucleus, mitochondria, endoplasmic reticulum, golgi apparatus, lysosomes, and peroxisomes. Both also contain similar membranes, cytosol, and cytoskeletal elements. The functions of these organelles are extremely similar between the two classes of cells (peroxisomes perform additional complex functions in plant cells having to do with cellular respiration). However, the few differences that exist between plant and animals are very significant and reflect a difference in the functions of each cell. Plant cells can be larger than animal cells. The normal range for an animal cell varies from 10 to 30 micrometers while that for a plant cell stretches from 10 to 100 micrometers. Beyond size, the main structural differences between plant and animal cells lie in a few additional structures found in plant cells. These structures include: chloroplasts, the cell wall, and vacuoles. Chloroplasts In animal cells, the mitochondria produces the majority of the cells energy from food. It does not have the same function in plant cells. Plant cells use sunlight as their energy source; the sunlight must be converted into energy inside the cell in a process called photosynthesis. Chloroplasts are the structures that perform this function. They are rather large, double membrane-bound structures (about 5 micrometers across) that contain the substance chlorophyll, which absorbs sunlight. Additional membranes within the chloroplast contain the structures that actually carry out photosynthesis. Chloroplasts carry out energy conversion through a complex set of reactions similar to those performed by mitochondria in animals. The double membrane structure of chloroplasts is also reminiscent of mitochondria. The inner membrane encloses an area called the stoma, which is analogous to the matrix in mitochondria and houses DNA, RNA, ribosomes, and different enzymes. Chloroplasts, however, contain a third membrane and are generally larger than mitochondria. The Cell Wall Another structural difference between in plant cells is the presence of a rigid cell wall surrounding the cell membrane. This wall can range from 0.1 to 10 micrometers thick and is composed of fats and sugars. The tough wall gives added stability and protection to the plant cell. Vacuoles Vacuoles are large, liquid-filled organelles found only in plant cells. Vacuoles can occupy up to 90% of a cell's volume and have a single membrane. Their main function is as a space-filler in the cell, but they can also fill digestive functions similar to lysosomes (which are also present in plant cells). Vacuoles contain a number of enzymes that perform diverse functions, and their interiors can be used as storage for nutrients or, as mentioned, provide a place to degrade unwanted substances.

Low power lens

The next longest lens and has a magnification of 10x

Resolution

The ability to distinguish between two points, a certain distance apart, as separate points. The better the resolution, the "sharper" the image appears. When describing resolution, use of the terms "greater" or "smaller" may be misleading. The smaller the limit of resolution, the better the resolution.

Iris Diaphragm

This is an adjustable opening controlled by a flattened lever that protrudes right below the condenser. This allows the user to easily adjust the amount of light passing upward through the CONDENSER LENS toward the specimen.

Magnification

The degree to which the specimen is enlarged by a microscope. For instance, a compound light microscope may magnify a specimen anywhere from 40 times its original size to 100 times its original size. Magnification is accomplished by one or more lenses which refract (bend) the light.

High power (high dry lens)

The lens that is just a bit longer than the lower power lens and has a magnification of 40x, 44x, or 45x

Limit of Resolution (Resolving Power)

The limit of resolution of my eye is approximately 0.1 mm, meaning that my eyes can distinguish two objects that are 0.1 mm apart as two separate objects If two points are only 0.05 mm apart, your eye would "see" them as a single point. this distance would be beyond the limit of resolution of my eyes. The limit of resolution of a compound light microscope is approximately 0.2 um (micrometers) Resolving power depends on wavelength of light and the numerical aperture of the lens

Condenser Lens

The purpose of the condenser lens is to focus the light onto the specimen This lens lies between the stage and the light source. It focuses light from the light source by refracting (bending) the light rays. The height of the condenser (and therefore its ability to focus light) may, in some microscopes, be adjusted using its own adjustment knob. .

Scanning lens

The shortest lens is called the scanning lens. It typically has magnification of 4x. This lens should be pointing down and "clicked" in place as you begin working with the microscope (and before you return the microscope to storage).

Transmission Electron Microscope

This is what he had in lab(?) The transmission electron microscope (TEM) projects an electron bean THROUGH the specimen. For the electrons to penetrate, the specimen must be VERY thin. To produce such specimen, they need to do some work on them. The TEM is used to view the internal structures of cells, viruses, and cellular components. It can achieve magnifications up to 1,000,000x and a resolution of less than 1.0nm.

Depth of field

The thickness (or depth) of the specimen that may be focused at a given time. the low power lens has the greatest depth of field. As one increases magnification, the depth of field increases.

Unicellular organisms

These have all living functions within one cell. Each cell is an individual organism. Unicellular prokaryotic organisms are bacteria. Unicellular eukaryotic organisms are in the kingdom Protista, which includes protozoans and some algae.

Protists

They are considered to be all eukaryotic organisms that are not fungi, plants, or animals. Examples of protists include diatoms (single-celled photosynthetic organisms that have cell walls made of silicon dioxide), algae (e.g. kelp), and Plasmodium (the parasite that causes malaria). Even though protists may differ quite a bit in structure and metabolism, one thing they all have in common is that they live in aquatic environments. Examples of characteristics that may vary between protists include cellular respiration (some are unicellular, other are multicellular), cellular structure, size (some are microscopic, others can grow to several feet in length), reproduction (some are sexual, others are asexual), and the ability to perform photosynthesis. Another example of how protists can vary is in the way they acquire nutrient molecules. Some protists can ingest entire cells. For example, some protists "eat" bacterial cells; others "eat" other protists. Chaos feeds on paramecium.

Scanning Electron Microscope

This projects an electron beam ONTO the specimen (as opposed to THROUGH). As electrons bounce off the specimen, they are focused by a series of electromagnetic lenses. That focused image appears on the screen of the SEM and can be photographed. The specimen take prep work. The SEM is most useful in examining surface features of specimens, and provides a three-dimensional image similar to that of the dissecting light microscope, but with greater resolution. Magnifications are typically 200-500,000x, with resolution of 5-10nm.

Paramecium

Unicellular eukaryotic organism. Has a cilia, food vacuole, ectoplasm, endoplasm, contractile vacuole, cell membrane, nucleus notice how it has a nucleus that bacteria do not. Differences from Euglena: 1. Euglena is a flagellate while Paramecium is a ciliate. 2. Paramecium shows animal characteristics, whereas Euglena shows both animal and plant characteristics. 3. Euglena has chloroplasts but not Paramecium does. 4. Paramecium is a heterotroph while Euglena is both a heterotroph and an autotroph. 5. Euglena can survive long droughts without water or light, but Paramecium cannot. 6. Pellicle in Euglena enables them the flexibility, but there is no pellicle in Paramecium. Similarities to Euglena: 1. They are single celled. 2. They ingest food through openings (oral groove) 3.They have projections for movement (Cillia & Flagella)

Euglena

Unicellular eukaryotic organism. Has a flagellum, cell membrane, eyespot, nucleus, chloroplast notice how it has a nucleus that bacteria do not. Like algae and plants, Euglena cells contain chloroplasts that allow them to create food through photosynthesis, but they can also take in nutrients from other organisms when light is not available. Euglena are a unique group of single-cell organisms that have some of the same functions as both plants and animals

Colonial organisms

Unlike unicellular organisms which live independently of one another, colonial organisms are cells that live in groups. Each cell still exists independent of others, although in some cases there is some evidence of interaction.

Mechanical Stage

Used when delicate movements of the slide are required for better viewing Spring lever that hold the slide in place

Light source (lamp)

a light bulb located in a housing at the base of the microscope

Microbiology is the study of living things that cannot be resolved with the lens of the naked eye. Small eukaryotic organisms can be clearly seen with the 40x (high power) objective lens of the compound light microscope. The smallest single-celled organisms which require oil immersion for visualization are called....

bacteria

The term "parfocal" refers to which of the following?

objective lenses should require no coarse adjustment as you increase magnification from one objective to another

Transmission electron microscopy (TEM) is especially useful for...

resolving intracellular organelles and really small things like viruses

Rheostat

rotating knob adjusts the AMOUNT OF LIGHT passing out the LIGHT SOURCE

"Working distance" refers to the amount of room between the specimen and the objective lens. Which lens has the greatest working distance?

scanning (4x)

Filter

some microscopes have a filter that lies on top of the light source. This filter may allow only light of a particular wavelength (e.g., blue) to improve resolution

The term "resolution" in microscopy specifically refers to...

the ability to distinguish two distinct points from each other

With the compound light microscope, light is "focused" on the object by bending light through....

the condenser lens

Working distance

the distance between the objective lens and the specimen.

Field of view

the visible area of the specimen seen through the eyepiece of a compound microscope

Resolution by the compound light microscope is limited by the two key factors...

visible wavelengths of light and numerical aperture of the objective lens