Cells and microscopes Flashcards
What is differential staining?
can distinguish between 2 types of organisms that would otherwise be hard to see
what is the… size, DNA, ribosomes, cell wall, flagella in prokaryotic cells?
Size- 0.1-10 micrometres,
DNA- one main molecule, circular, additional DNA found in plasmids
ribosomes- 70S
Cell wall-made of peptidoglycan (also known as murein)
Flagella- not movement by ATP but move by chemiosmosis, no 9+2 arrangement, thinner and smaller than in eukaryotes
why is a microscope set to the lowest magnification first?
To see largest area of slide ad focus more easily using course focus
how does fixation work in electron microscopes?
stabilises sample, prevents decomposition
how does dehydration work in electron microscopes?
prevents vaporisation of water in the vacuum as this would damage the sample
how does embedding work in electron microscopes?
allows for thin slices to be obtained
how does staining with heavy metals work in electron microscopes?
allows for contrast in electron beams
what does a plant cell wall do?
Plant cell walls are a strong barrier acting as a defensive mechanism against the outside (invading pathogens). It is composed of a complex carbohydrate called cellulose.
Cell walls allow substances to pass in and out as they are permeable and also allow the cells to keep their shape.
contents of cell press against cell wall making it rigid
What is the function of the nucleus/what is it
contains genetic information in the DNA molecules. DNA directs protein synthesis required by the cell. contains nucleolus which produces rRNA
contained within nuclear envelope to protect the cytoplasm from damage
contains nuclear pores, contains chromatin
conversions of length
T,G M,K m, mm, μm,nm,
why would it be necessary to recalibrate the eyepiece graticule if a higher power objective lens was then used.
eyepiece unit has different values for each calibration
Thin stem and thin cell walls do not provide much support for the leaf. Suggest how the leaf is supported
air spaces giving buoyancy, supported by surrounding water.
why preparing a wet mount the refractive index of the medium should be roughly the same as glass
reduce the diffraction between the liquid and the glass therefore preventing the distortion of the image
what magnifies the image first the objective lens or the eyepiece lens
objective first then eyepiece
how do you prepare a smear slide
edge of slide used to smear the sample creating a thin even coating on another slide
blood is an example
what is a wet mount and what are examples of when we would use this
specimens are suspended in a liquid such as water of an immersion oil, a coverslip is then placed over at an angle
example- aquatic samples
discuss how the structure of microfilaments and microtubules means these components of the cytoskeleton are involved in the movement of cells but the intermediate fibres aren’t
microfilaments are composed of actin which is contractile. Microtubules are composed of tubulin, which polymerises. Contraction and polymerisation lead to change in length resulting of movement in the cell. Intermediate fibres have fixed length, for stablility.
how can potential coverslip damage be prevented in squash slides
squashing sample between 2 microscope slides
Explain how to do a dry mount and what examples are used
solid spears viewed whole or cut into thin slices. The specimen is placed on the centre of the slide an and a coverslip is placed on it at an angle
exapmles; plants, muscle tissue, hair
can mitochondria produce their own enzymes
yes
can mitochondria reproduce themselves
yes
what are the cell walls of prokaryotic cells made of
peptidoglycan
what are the cell walls of fungal cells made of
chitin
why are plasmids important in bacteria
small number of genes but these can contain genes which make the bacterium resistant to antibiotics
