Chapter Two: Basic component of living systems Flashcards
What are the four types of microscopes?
- light microscopes
- transmission electron microscopes
- scanning electron microscopes
- laser scanning confocal microscopes
What is magnification and resolution?
- Magnification: how big an image appears compared to the original object
- Resolution: the minimum distance between two objects in which they can still be viewed as separate
How is resolution determined in an optical and electron microscope?
- optical: determined by the wavelength of light
- electron: determined by the wavelength of the beam of electrons
What are the four types of slide preparation for light microscopes? explain each.
- dry mount - used when thin or whole specimens are viewed with just the cover slip placed on top
- wet mount - specimens are added to water before lowering the cover slip on with a mounted needle to prevent air bubbles from forming
- squash slide - wet mounts that you push down on the cover slip to squash the sample to make sure that you have a thin layer to let light pass through
- smear slide - created by placing a drop of the sample at one end of the slide and then use another slide at an angle to smear the sample across the first slide to create a smooth, thin, even coated specimen. a cover slip is placed after smearing
What is an eyepiece used for? how do you calibrate it?
- used to measure the size of the objects you are viewing under the microscope
- after changing the objective lens and the magnification, you calibrate the eyepiece by:
- line up the stage micrometer and the eyepiece graticule whilst looking through the eyepiece
- count the amount of divisions on the eyepiece graticule that fit into one division on the micrometer scale
- each division on the micrometer is 10 micrometers. this can be used to calculate what one division on the eyepiece graticule is at that current magnification
What is the formula for measuring structures viewed under a microscope?
Magnification = size of image ➗ size of real object
What is differential staining? what stains are commonly used and how?
- a technique that uses many chemical stains to stain different parts of a cell in different colours
- crystal violet or methylene blue. they are positively charged so the are attracted to and stain negatively charged materials
- nigrosin and congo red are negatively charged so they can’t enter the cells because cytosol repels them which creates a stained background, and the unstained cells stand out
What are the features of an electron microscope? how do they work?
- a beam of electrons are used to make the image, they have a very short wavelength causing the microscope to have a high resolution which allows small organelles and internal structures to be visualised
- the image is created by using an electromagnet to focus the beam of negatively charged electrons
- electrons are absorbed by air so the electron microscope has to be in a vacuum
- because of this only non-living specimens can be examined
- image is in black and white as the samples must be stained
What are the features of a transmission electron microscope? how do they work?
- extremely thin specimens are stained and put inside a vacuum
- an electron gun produces a beam of electrons that passes through the specimen, some parts of the specimen en absorb the electrons which makes them appear darker
- image produced is 2D and shows detailed images of the internal structure of cells
How do scanning electron microscopes work? what are its features?
- specimen dose not need to be thin since the electrons aren’t transmitting through
- electrons are beamed onto the surface and the electrons are scattered in different ways depending on the contours
what is a laser scanning confocal microscope? what are its features? how does it work?
- a type of fluorescent microscope
- the image is created using a very high light intensity to illuminate the specimen stained with a fluorescent dye
- combines the benefits of high-resolution optical imaging with depth selectivity
- allows scientists to view sections of tiny structures that would be hard to section off and creates a 3D image
- the image is made as the microscope scans the specimen point-by-point using a focused laser beam to make a 2D image or a 3D image if different focal planes are used . as the light is emitted from the specimen en is causes fluorescence
what are the 13 organelles in eukaryotic cells that you need to know the structure and function of?
- cell membrane
- nucleus
- mitochondria
-chloroplasts
-golgi apparatus and golgi vesicles - lysosomes
- cytoskeleton
- centriole
- flagella
- cilia
- ribosomes
- rough and smooth endoplasmic reticulum
- cell wall
what are the structure and function of the nucleus?
structure:
- nuclear envelope - double membrane
- nuclear pores
- nucleoplasm
- chromosomes
- nucleolus - smaller sphere inside, site of rRNA production and makes ribosomes
function:
- site of DNA replication and transcription
- holds DNA for each cell
- site of ribosome synthesis
what are the structure and function of the flagella?
- whip like structure
function: for mobility and sometimes as a sensory organelle for chemical stimuli
what are the structure and function of cilia?
- hairlike projections out of cells
function:
- can be mobile or stationary
- mobile cilia help move substances in a sweeping motion
- stationary cilia are important in sensory organs like the nose
