Section 1 Flashcards
Who is known as the father of biology and why?
Aristotle; he was one of the first Greek philosophers who used the Scientific Method instead of making assumptions.
Who invented the microscope? How much magnification power did it have?
Hans and Zacharias Janssen; 20x
How many lenses were used in the first microscope? Name them.
Two lenses were used; ocular and objective.
What is a compound microscope?
A microscope that uses more than one lens.
What is a simple microscope?
A microscope that only uses one lens.
What did Robert Hooke add to the microscope?
- A 3rd lens (two lenses in the ocular)
- A light source
Who came up with the term “cells”? How did they come up with it?
Robert Hooke; he was observing cork under his microscope and noticed chambers, which he named cells.
In Latin, what does “cell” mean?
Small compartment.
Name an example of how microscopy affects surgery.
Laparoscopic surgery.
How many lenses did Antoni Van Leeuwenhoek’s microscope have? What was its magnification?
One lens; 250x
Antoni Van Leeuwenhoek was the first person to…
observe the movement of living single celled organisms (eg. bacteria, sperm).
Robert Hooke’s chambers ended up being…
the remnants of living cells.
What is the function of an eyepiece/ocular lens? What is its usual magnification?
Used to observe the specimen. It usually has a magnification of 10x.
What is the function of the coarse adjustment knob?
It moves the stage or objective lens up/down.
What is the function of the fine adjustment knob?
Used to produce a clear, sharp, image.
What is the function of the revolving nosepiece?
It holds the objective lenses: rotates those lenses and helps change the magnification power.
What is the function of the objective lenses? How many do most compound microscopes have?
- Zooms into the specimen
- Can have a low, medium, or high magnification
- Most compound microscopes have three
What is the function of the stage?
It is where the specimen is put for observation.
What is the function of the stage clips?
It holds the slide in place.
What is the function of the diaphragm?
It adjusts the diameter of an opening to control the amount of light passing through the specimen.
What is the function of the lamp/mirror?
The lamp supplies the light required to view the specimen. Sometimes a mirror is used, which directs lights from its surroundings through the diaphragm.
What is the function of the arm?
Used to transport microscopes. Supports the microscope head and attaches it to the base.
What is the function of the base?
Used to transport microscopes. It houses illumination and supports the compound microscope.
What lens improved the amount of detail that could be seen?
The achromatic lens.
What is magnification?
It tells us how much larger (or smaller) the picture is than the real size of the specimen.
Equation:
Magnification =
(power of objective lens) (power of ocular lens)
How many micrometers are in a millimeter?
1000
What is field of view? What can it be referred to as?
Field of view is the entire area that can be seen with a microscope with a particular lens power. It can be referred to as “field diameter” or “field area.”
When the magnification ____________ (increases/decreases), the field diameter decreases.
Increases.
Equation:
higher-power field diameter
————————————— =
Low-power field diameter
low-power magnification/
high-power magnification
Equation:
actual size of an object =
of objects estimated to fit across field of view/field diameter
field diameter/# of objects estimated to fit across field of view
Equation:
scale =
diagram size of object/actual size
Name an example of science contradicting beliefs.
Galileo with his heliocentric model of the universe.
What is spontaneous generation? What is responsible for it? When was it accepted until?
Spontaneous generation is the belief that living things can emerge from non-living matter. People believed that there was a “life force” that caused non-living things to produce/”birth” living things. It was widely accepted until the 19th century.
Explain Francesco Redi’s experiment.
- He questioned spontaneous generation (did not think that maggots appeared spontaneously from raw meat)
- Set out flasks with raw meat, one with access to air, one without
- Maggots were found in the open flasks (flies laid eggs)
Did Francesco Redi’s experiment change the idea of spontaneous generation?
No, it did not, despite the evidence disproving it. Other scientists said that air was an ingredient in life force.
Explain John Needham’s experiment.
- He boiled chicken broth, put it in a flask, and sealed it
- Although it was boiled, micro-organisms still appeared
Did John Needham’s experiment change the idea of spontaneous generation?
Yes, it did. Through his experiment, he suggested that there was a life force that produced spontaneous generation. This became widely accepted.
Explain Lazzaro Spallanzani’s experiment.
- Proposed that there were micro-organisms in the air responsible for new growth.
- Repeated Needham’s experiment but drew off the air in the flask
- Nothing grew
Did Lazzaro Spallanzani’s experiment change the idea of spontaneous generation?
No, it did not. Critics suggested that he only proved that air was required for spontaneous generation.
Explain Louis Pasteur’s experiment.
- Set up two flasks with the same boiled meat broth.
- Flasks had bent s shaped necks; open to air, not dust
- Did not become cloudy with microbial growth
- When a neck was removed, bacteria grew.
Did Louis Pasteur’s experiment change the idea of spontaneous generation?
Yes, it was the decisive proof to reject spontaneous generation. It showed that micro-organisms are not generated, but rather carried in the air, too small to see.
What is a controlled variable?
In an experiment, it is something that could have been changed between trials, but was deliberately kept constant.
What is a responding variable?
In an experiment, it is the result of the changes made.
What is a manipulated variable?
In an experiment, it is the thing(s) altered between trials.
What does it mean to have experimental control?
The manipulated variable is not changed in any way.
What did Robert Brown contribute to the cell theory?
He identified the nucleus of the cell and said it was responsible for controlling cell function.
What did Schleiden and Schwann propose?
They proposed that all animals and plants are made up of cells, and that cells are the basic unit of all life.
How did Rudolf Virchow expand on the cell theory?
He proposed that cells must only come from pre-existing cells through cell division (mitosis).
What does the cell theory state? (3 points)
Connect each point to a scientist(s).
- All living things are made up of one or more cells and the materials produced by these cells (Schleiden and Schwann).
- All life functions take place in cells, making them the smallest unit of life (Schleiden and Schwann).
- All cells are produced from pre-existing cells through the process of cell division (Rudolf Virchow).
What is a subcellar particle?
Subcellar particles like viruses and prions fall into a category that is neither living nor non-living. They may exhibit some living cell characteristics.
Explain how staining works.
Chemical preservatives “fix” the specimen (kills the cells) and then colouring agents are attached to particular parts of the cell.
What is the human eye capable of resolving?
Anything 0.1mm or larger.
Explain what contrast is. (4 points)
- The different amount of light absorbed by objects.
- Makes it easier to differentiate cells
- Refers to the variation of shadow and colour
- Helps us register depth
True or false: cells are mostly colourful.
False; cells are mostly colourless.
Why is resolution limited in light microscopes?
They depend on white light illumination, so resolution is limited by the wavelength of the light.
What are the 3 factors that affect the quality of an image?
- Magnification
- Contrast
- Resolution
Microscopic image quality has been improved with…? (2 points)
- New stains and staining techniques
- New methods of illuminating the specimen
What is resolution/resolving power?
The ability to distinguish between 2 structures that are very close together.
Why do fluorescent stains work better with confocal microscopes?
Confocal microscopes eliminate the blurriness of reflected light.
The ___________(higher/lower) the resolution, the clearer the image will be.
Higher
Explain fluorescent microscopy.
- Fluorescent stains called GFP (green fluorescent protein) are introduced to the specimen
- When the specimen is subjected to UV light, it will glow
- Depending on the dye, it will glow either green, yellow, or orange
Does fluorescent microscopy kill the specimen?
Unlike conventional staining, it does not kill the specimen.
Name 5 contrast enhancing techniques.
- Fluorescent microscopy
- Brightfield illumination
- Darkfield illumination
- Phase contrast
- Differential interference contrast
What is brightfield illumination? What resolution does it have?
- Different amounts of light absorbed by the specimen versus the background makes it visible.
- Light passes through the specimen.
- Low resolution (can’t get higher than 0.2um)
Does brightfield illumination kill the specimen?
Yes, the fixing and staining process kills the specimen.
What is darkfield illumination?
The background is darker in contrast to the specimen, making it easier to see.
Does darkfield illumination kill the specimen?
No, it does not.
What is phase contrast?
It allows for more detail to be viewed because of refractive index (ability to bend light).
What is differential interference contrast?
A complicated lighting scheme that helps to show the depth and structures of a specimen that would otherwise be invisible.
Explain how a confocal microscope works.
- It uses lasers + computers to focus light.
- A laser concentrates light onto a specimen, then the laser reflects off the object, back to the eyepiece.
- Reflection goes through a tiny opening called the confocal pinhole and an electronic detector converts the light into an image.
- Only the light returning from an exact plane of focus can pass through the pinhole to the detector.
- Software can be used to build a 3D image.
Confocal microscopes allow us to see a _________(thin/thick) section with a ________________(low/high) resolution.
Thin, high
Who invented the first electron microscope?
James Hillier and Albert Prebus
What is an electron-dense material?
It does not allow electrons to pass through because of its density.
How does electron microscopy work?
- Uses a fine beam of electrons from an electron gun instead of light
- Instead of lenses, it will use electromagnets
- To focus an image, magnetic fields will be adjusted
What is the receiver of a light microscope?
The eye or a digital image.
What is the receiver of an electron microscope?
A fluorescent screen or a digital image.
What does TEM stand for?
Transmission Electron Microscope.
What does SEM stand for?
Scanning Electron Microscope.
How does a TEM work?
- Beam of electrons pass through a very thin section of fixed and stained tissue
- Black and white photographs are produced when the electrons fall on a fluorescent screen or photographic film
What is an advantage of a TEM? What is its usual magnification and resolution?
- 100x better resolution than a light microscope
- Magnification: up to
1 500 000x - Resolution: about 2.5nm
What are some disadvantages of a TEM?
- Hard to produce 3D images
- Cannot have live specimen
- Must be operated in a vacuum
Confocal technology gives opportunities for…?
(give an example)
The use of other techniques to study the cell.
eg. the use of GFPs
How does an SEM work?
- Specimen are fixed and coated in gold
- Electrons bounce/reflect off the gold an produce a 3D image
- Computers can move the specimen and reveal different angles
What is an SEM normally used for?
They are normally used for seeing surfaces of specimen.
What are some advantages of the SEM?
- 2x better image quality than the TEM
- Can produce a 3D image
- New SEMs permit the use of live material
What is the usual magnification and resolution of an SEM?
Magnification: 300 000x
Resolution: 20nm
What is a disadvantage of the SEM?
It has less magnification and resolution power than the TEM.
What are the photographs taken through electron microscopes called?
Electron micrographs
New imaging techniques results in?
News possibilities for research at the cellular level.
What is gene mapping?
Gene mapping is the decoding of a species’ genome.
What is a genome?
All of the information contained in a species’ DNA.
In 2001, the H__________ G___________P______ published a map of the entire h_________ g ___________
Human Genome Project, human genome
What can the knowledge of the human genome do?
It can help us understand where cancer and other diseases come from/how to treat them.
What can the gene mapping of crop plants result in? Does everyone agree with it?
It can result in new varieties of plants, which more resistance to certain environments. No, not everyone agrees with it; ethical issues have been raised about how this can be used in the future and the dangers of genetically modified food.
What is an open system?
It must interact with its environment to maintain its existence; it can exchange both matter and energy with its surroundings.
What type of system is a cell?
An open system.
Explain the process of cell-to-cell communication. What are transmitters? Receptors?
Messenger molecules (transmitters) from other cells travel through the bloodstream and attach to specialized molecules on the surface of the target cell (called receptors).
Explain how transmitters and receptors can resemble a lock and key.
Only transmitters with the right shape can dock at a particular receptor.
What is a hormone? What kind of chemical is it? Give an example.
Hormones are a transmitter chemical that are produced somewhere in your body and act on a different part.
Eg. adrenaline is produced in your brain but acts all over your body.
True or false: certain viruses/bacteria can mimic harmless molecules.
True
How can an immune system fight invaders?
It must identify them based on the markers on their cell membranes.
The understanding of cell communication allows us to…? (3 points)
- Diagnose diseases carried by viruses/bacteria
- Diagnose diseases of the immune system
- Make more targeted, more effective medications
What is x-ray crystallography? How has it helped to advance biology?
It uses x-rays, computers, and sensors to allow scientists to learn the details of molecular structure and help understand how molecules work. It was essential to the studies that led to the model of the DNA molecule.
How is GFP technology advancing genetic studies?
It is being used to study degenerative diseases like Huntington’s, Alzheimer’s, and Parkinson’s. Scientists compare healthy tissue and tissue affected by these diseases.
