chapter 2- Basic components of living systems Flashcards
max resolutions?
light microscope= 0.2um
TEM=0.0005um
SEM=0.003um- 0.01um
lower resolution= better image quality
Max magnification
light microscope= x1500
TEM= more x1,000,000
SEM= less than x1,000,000
higher magnification the better
how does staining enable cell components to become visible?
- resolution is limited by wavelength of light as it passes through the sample
- most cell structures have low contrast and do not absorb light
- stains increase contrast as different cell components take up the stain by different amounts
Give examples of stains
- Crystal violet/ methylene blue= positively charged dye, attracted to negatively charged materials in the cytoplasm, stains RNA/DNA.
- Nigrosin/ Congo red= negatively charged dye, repels negatively charged cytosol. These dyes stay outside of the cell, leaving the cell unstained so it can stand out against a stained background.
units of measurement
1000nm= 1um
1000um= 1mm
1000mm= 1m
10mm=1cm
what are the 4 different ways a specimen can be prepared for light microscopy?
- dry mount
- wet mount
- squash slides
- smear slides
stages involved in the production of slides
- fixing= used to preserve the specimen
- sectioning= specimens are dehydrated with alcohols then placed in a mould with wax, which can be thinly sliced
- staining= specimens are treated with multiple stains to show different structures
- mounting= specimens are secured to a microscope slide with a cover slip on top
describe the acid- fast technique
- used to identify bacteria
- carbolfuchsin dye is carried into specific cells
- the cells are then washed with a dilute acid alcohol solution
- bacteria will retain the carbolfuchsin dye which is bright red
- other bacteria will lose stain and appear blue*
what is the acid fast technique used for?
- used to differentiate species of mycobacterium from other bacteria.
describe the gram stain technique.
- crystal violet is added to the bacterial specimen on the slide, then iodine which fixes the dye
- the slide is then washed with alcohol
- the gram positive bacteria retain the crystal violet stain and will appear blue/ purple
- the gram negative bacteria have thinner cell walls, and therefore lose the stain. so they are stained with a counter stain (e.g. safranin dye), which will make the bacteria appear red.
what is the gram stain technique used for?
- used to separate bacteria into 2 groups, gram positive and gram negative bacteria.
describe the features of a laser micoroscope
- also known as a confocal microscope
- laser scans objects point by point to assemble an image
- can focus on different structures at different depths
- more expensive than light microscopes
- can study whole living organisms
what are the structures of a prokaryotic cell?
it is a bacteria cell and contains:
- cell wall( made of peptidoglycan)
- cell membrane= to allow transport of substances in an out of the cell
- slime capsule= to protect the bacteria from detection
- cytoplasm= for chemical reactions
- no nucleus= DNA in a loop
- ribosomes
- mesosome= help in the synthesis of the cell membrane, replication of DNA, and protein synthesis.
- flagella= for movement
- cytoskeleton= contains microtubules involved in cell division
- contains plasmids
- glycogen granules as energy stored
- pili= made of protein, for attachment (adhesion) to host cells
what is ultrastructure?
the detailed structure of cells visible only with an electron microscope
describe the mitochondria.
- oval shaped organelle
- matrix contains enzymes needed for respiration
- needed for ATP production
- inner membrane folded to form the cristae
describe the Golgi apparatus
- fluid filled, flattened sacs.
- processes and packages new lipids and proteins into vesicles
- makes lysosomes
describe the function of the SER
- synthesis and processes new lipids
describe the function of the RER
- folds and process proteins made by ribosomes
describe the chloroplast
- site of photosynthesis
- small, flattened structure
- surrounded by a double membrane, filled with a thick liquid called stroma
- contains thylakoid membranes which stack up to form grana (linked together by lamellae).
is sucrose a reducing sugar?
Sucrose is not a reducing sugar because it lacks an aldehyde group.
what are some examples of reducing sugars?
- glucose
- fructose
- galactose
what is a reducing sugar?
A reducing sugar is a type of sugar that can donate electrons to another substance. This happens in the Benedict’s test, where reducing sugars react with the Benedict’s solution and cause a color change. Reducing sugars have a free aldehyde (-CHO) or ketone (-C=O) group.
define magnification
magnification is the number of times larger the image is compared to the object
describe how the ultrastructure (can only be seen with a high magnification) of a neutrophil is specialised to enable it to perform this function. (4)
- many microfilaments/microtubules
- many ribosomes
- many mitochondria
- lots of Golgi
- many receptor sites on plasma membrane
- many lysosomes
