MCB 2050 Final Exam |371 Questions with Answers
Why are mice used as a model organism? - -- Due to genetic similarity to humans
-Why are yeast used as model organisms? - -- Very simple, not many genes
-Why is C. elegans used as a model organism? - -- Very few cells, used in developmental
biology
-Why is the fruit fly used as a model organism? - -- Breeds quickly and easy to manipulate
genetically
-What is the model plant organism? - -- A. Thaliana
-What is the advantage of using fluorescent proteins in microscopy? - -- To visualize
movement in action
-What is deconvolution? - -- It removes background light and you end up with a sharper
image with better detail
-Describe the pathway of light in bright-field microscopy. - -- Lamp > Condenser Lens >
Specimen > Objective Lens > Intermediate Image > Ocular or projector lens
-Define resolution - -- The minimum distance that can separate two points that still remain
identifiable as separate bonds
-What are the two factors impacting resolving power? - -- Wavelength
- numerical aperture
- mounting medium
-True or False. Using a shorter wavelength (ƛ) will maximize resolution. - -- True
-True or False. Decreasing the numerical aperture (NA) by changing the mounting medium
will result in higher resolution. - -- False. If you increase NA the resolution will be
maximized
-What are fluorophores? - -They are molecules that can re-emit light following excitation
-What are the advantages of using confocal laser scanning microscopy? - -- Lasers can
penetrate into thicker living and moving specimens and the specimen does not need to be
'fixed'
-True or False. TEM is used to magnify internal (cellular) structures. - -- True. An image is
formed from electrons that are transmitted through a specimen
,-True or false. TEM uses lenses. - -- False! TEM uses magnets instead of lenses, very high
powered magnets
-How is an image formed when a beam of electrons in TEM? - -- When electrons strike the
specimen, some are scattered and others are not, the scattering depicts an object
-What are the ways that samples are prepared for TEM? - -- Chemical fixation
- cryofixation
-Why aren't all TEM samples cryofixed? - -- Technically demanding and requires very
expensive equipment
-Why is osmium tetraoxide used to stain TEM samples? - -- It reacts selectively with lipids
in all cellular membranes, making them electron dense
-True or False. An image obtained by TEM is cut into pieces by the laser in the microscope.
- -- False! The sample (in resin) is cut with a ultra-microtome (usually diamond knife)
-What are the components of Bright-Field Microscopy? How is the image captured and
manipulated? - -- light source
- condenser lens
- stage
- objective and ocular lenses
- Image captured by digital camera and can be manipulated by software (deconvolution)
-Bright-Field Microscopy, how - -- Generates dark image over a light background
- Both light diffracted by specimen and undiffracted light can be focused by the objective
lens
-How can resolution for brightfield microscopy be maximized? - -- use shorter wave
lengths
- increase NA by changing mounting medium
- limit is about 200 nm
-What do you understand by principles of fluorescence? - -- certain atom absorb photon of
certain wavelength
- atom excited, up energy state, unstable
- atom comes back, emits energy...light
-Fluorescence microscopy uses principles of ________ and ______ (molecule can re-emit light
after excitation). - -fluorescence and fluorophores
-Fluorophores and other proteins involve: - -- molecules that can re-emit light after
excitation
- GFP
,- Other small organic compounds such as fluorescein, which help staining and
direct/indirect immunofluorescence
-What happens in Confocal Scanning Laser Microscopy (CSLM)? - -- 1 or more lasers allow
only certain wavelength to get into living organism
- can get into thicker organisms, and focus in on one layer
- cuts in Z plane, lets you see the stack of it as a 3D image
-Describe Transmission Electron microscopy (TEM) - -- electrons pass through specimen
- reveals internal structures
- Electrons that pass through easily are grey, and electron dense areas block electrons from
passing through, are black (Scattering)
-Structure of the electron microscope - -- hollow cylindrical chamber
- electron gun
- high voltage, electron speed and high specimen penetration
- decreases wavelength
- high resolution
- electromagnetic lenses, adjust voltage to help focusing
- viewing screen
-Describe the preparation of specimen for TEM - -- chemical fixation
- specimen is placed in glutaraldehyde
- makes cell network insoluble
- this can lead to artifacts, where cells are killed slowly but lipids can still move through cell
- samples stained, making e- dense
- then dehydrated in ethanol and embedded in plastic resin
- cut samples into blocks, then into thin sections, put on grid and stain again with heavy
metals
-Describe Cryofixation - -- specimen flash frozen with nitrogen (l) and high pressure
- results in fewer fixation artifacts
- costly
-What are the primary differences between the Nucleus of a Eukaryote and the nucleus of a
Prokaryote? - -- Eukaryote has a membrane bound nucleus which has a nuclear envelope,
nuclear pores and a organized internal nuclear structure
- Prokaryotes possess a nucleoid with a region where the chromosome is located
-What are characteristics of a nucleus in terms of shape and size? - -- It is irregular in
shape and is typically one cell
- It is the largest structure in the cell
-What are the two main functions of the nucleus? - -- Compartmentalization of the cellular
genome and its activities
, - Coordination of cellular activities
-Give some examples to indicate the nucleus Compartmentalization of the cellular genome
and its activities - -- site of DNA replication
- site of transcription
- site of RNA processing
- site where translation components (ribosomes, mRNA and tRNA) are synthesized
-Give examples of cellular activities coordinated by the nucleus - -- control metabolism
- protein synthesis
-Describe the structure of the nuclear envelope.
number of layers and arrangement - -- Made of 2 parallel phospholipid bilayers separated
by inter membrane space
- Outer membrane binds ribosomes and is continuous with the RER
- The inner membrane contains unique protein composition distinct from the outer
membrane. It also contains integral membrane proteins that connect to the nuclear lamina
- The intermembrane space is continuous with the ER lumen
- Inner and outer membranes join at nuclear pores
-The Nuclear envelope is made up of: - -- Nuclear membrane
- Nuclear lamina
- Nuclear pores
-The Nuclear content are: - -- Chromatin
- Nucleoplasm
- Nuclear matrix (maybe?)
- Nucleolus
-Describe four functions of the nuclear envelope - -1. Separates nuclear content from
cytoplasm
- separating the genome from the cytoplasm, as well as transcription from translation
2. Acts as a selective barrier, thus allowing regulated passage of molecules (i.e. RNA and
proteins) between the nucleus and the cytosol
3. Establishes the composition of the nucleus and regulates gene expression
4. Binds the nuclear lamina, thus providing the structural framework for the nucleus
Why are mice used as a model organism? - -- Due to genetic similarity to humans
-Why are yeast used as model organisms? - -- Very simple, not many genes
-Why is C. elegans used as a model organism? - -- Very few cells, used in developmental
biology
-Why is the fruit fly used as a model organism? - -- Breeds quickly and easy to manipulate
genetically
-What is the model plant organism? - -- A. Thaliana
-What is the advantage of using fluorescent proteins in microscopy? - -- To visualize
movement in action
-What is deconvolution? - -- It removes background light and you end up with a sharper
image with better detail
-Describe the pathway of light in bright-field microscopy. - -- Lamp > Condenser Lens >
Specimen > Objective Lens > Intermediate Image > Ocular or projector lens
-Define resolution - -- The minimum distance that can separate two points that still remain
identifiable as separate bonds
-What are the two factors impacting resolving power? - -- Wavelength
- numerical aperture
- mounting medium
-True or False. Using a shorter wavelength (ƛ) will maximize resolution. - -- True
-True or False. Decreasing the numerical aperture (NA) by changing the mounting medium
will result in higher resolution. - -- False. If you increase NA the resolution will be
maximized
-What are fluorophores? - -They are molecules that can re-emit light following excitation
-What are the advantages of using confocal laser scanning microscopy? - -- Lasers can
penetrate into thicker living and moving specimens and the specimen does not need to be
'fixed'
-True or False. TEM is used to magnify internal (cellular) structures. - -- True. An image is
formed from electrons that are transmitted through a specimen
,-True or false. TEM uses lenses. - -- False! TEM uses magnets instead of lenses, very high
powered magnets
-How is an image formed when a beam of electrons in TEM? - -- When electrons strike the
specimen, some are scattered and others are not, the scattering depicts an object
-What are the ways that samples are prepared for TEM? - -- Chemical fixation
- cryofixation
-Why aren't all TEM samples cryofixed? - -- Technically demanding and requires very
expensive equipment
-Why is osmium tetraoxide used to stain TEM samples? - -- It reacts selectively with lipids
in all cellular membranes, making them electron dense
-True or False. An image obtained by TEM is cut into pieces by the laser in the microscope.
- -- False! The sample (in resin) is cut with a ultra-microtome (usually diamond knife)
-What are the components of Bright-Field Microscopy? How is the image captured and
manipulated? - -- light source
- condenser lens
- stage
- objective and ocular lenses
- Image captured by digital camera and can be manipulated by software (deconvolution)
-Bright-Field Microscopy, how - -- Generates dark image over a light background
- Both light diffracted by specimen and undiffracted light can be focused by the objective
lens
-How can resolution for brightfield microscopy be maximized? - -- use shorter wave
lengths
- increase NA by changing mounting medium
- limit is about 200 nm
-What do you understand by principles of fluorescence? - -- certain atom absorb photon of
certain wavelength
- atom excited, up energy state, unstable
- atom comes back, emits energy...light
-Fluorescence microscopy uses principles of ________ and ______ (molecule can re-emit light
after excitation). - -fluorescence and fluorophores
-Fluorophores and other proteins involve: - -- molecules that can re-emit light after
excitation
- GFP
,- Other small organic compounds such as fluorescein, which help staining and
direct/indirect immunofluorescence
-What happens in Confocal Scanning Laser Microscopy (CSLM)? - -- 1 or more lasers allow
only certain wavelength to get into living organism
- can get into thicker organisms, and focus in on one layer
- cuts in Z plane, lets you see the stack of it as a 3D image
-Describe Transmission Electron microscopy (TEM) - -- electrons pass through specimen
- reveals internal structures
- Electrons that pass through easily are grey, and electron dense areas block electrons from
passing through, are black (Scattering)
-Structure of the electron microscope - -- hollow cylindrical chamber
- electron gun
- high voltage, electron speed and high specimen penetration
- decreases wavelength
- high resolution
- electromagnetic lenses, adjust voltage to help focusing
- viewing screen
-Describe the preparation of specimen for TEM - -- chemical fixation
- specimen is placed in glutaraldehyde
- makes cell network insoluble
- this can lead to artifacts, where cells are killed slowly but lipids can still move through cell
- samples stained, making e- dense
- then dehydrated in ethanol and embedded in plastic resin
- cut samples into blocks, then into thin sections, put on grid and stain again with heavy
metals
-Describe Cryofixation - -- specimen flash frozen with nitrogen (l) and high pressure
- results in fewer fixation artifacts
- costly
-What are the primary differences between the Nucleus of a Eukaryote and the nucleus of a
Prokaryote? - -- Eukaryote has a membrane bound nucleus which has a nuclear envelope,
nuclear pores and a organized internal nuclear structure
- Prokaryotes possess a nucleoid with a region where the chromosome is located
-What are characteristics of a nucleus in terms of shape and size? - -- It is irregular in
shape and is typically one cell
- It is the largest structure in the cell
-What are the two main functions of the nucleus? - -- Compartmentalization of the cellular
genome and its activities
, - Coordination of cellular activities
-Give some examples to indicate the nucleus Compartmentalization of the cellular genome
and its activities - -- site of DNA replication
- site of transcription
- site of RNA processing
- site where translation components (ribosomes, mRNA and tRNA) are synthesized
-Give examples of cellular activities coordinated by the nucleus - -- control metabolism
- protein synthesis
-Describe the structure of the nuclear envelope.
number of layers and arrangement - -- Made of 2 parallel phospholipid bilayers separated
by inter membrane space
- Outer membrane binds ribosomes and is continuous with the RER
- The inner membrane contains unique protein composition distinct from the outer
membrane. It also contains integral membrane proteins that connect to the nuclear lamina
- The intermembrane space is continuous with the ER lumen
- Inner and outer membranes join at nuclear pores
-The Nuclear envelope is made up of: - -- Nuclear membrane
- Nuclear lamina
- Nuclear pores
-The Nuclear content are: - -- Chromatin
- Nucleoplasm
- Nuclear matrix (maybe?)
- Nucleolus
-Describe four functions of the nuclear envelope - -1. Separates nuclear content from
cytoplasm
- separating the genome from the cytoplasm, as well as transcription from translation
2. Acts as a selective barrier, thus allowing regulated passage of molecules (i.e. RNA and
proteins) between the nucleus and the cytosol
3. Establishes the composition of the nucleus and regulates gene expression
4. Binds the nuclear lamina, thus providing the structural framework for the nucleus
