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39 Cards in this Set
- Front
- Back
How does a light microscope work? |
-light from a source travels into a condenser -then goes onto stage, illuminating specimen -light goes into objective lens, up the body tube and through eyepiece lens -magnification altered by changing objective lens -focus changed by course and fine focus knobs -worst resolution |
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How does a transmission election microscope work? |
beam of electrons pass THROUGH specimen -these are detected by a fluorescent screen, making a negative image as screen detects electrons that pass through - thin specimen -best resolution |
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how does a scanning electron microscope work? |
electron beam passes OVER specimen -electrons reflected as specimen covered in electron dense metal -detected on fluorescent screen -3D image -20nm resolution |
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how does a laser scanning microscope work |
-light focuses on one point as pin holes used this reduces defraction giving a higher resolution -3D image -confocal |
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what's the difference between magnification and resolution? |
magnification- the enlargement of an image resolution- the smallest distance between two points that they can be distinguished as separate |
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how do you use a stage micrometer and eyepiece graticule? |
-graticule has no units -measure how many graticule units the specimen is -put on an eyepiece micrometer -to calibrate, line up the two scales, take the distance on the SM and divide by the graticule units. times that by the graticule units of the size of the specimen to get the real size - recalibrate at each magnification |
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what type of mount is used for solid specimens or ones suspended in liquid? |
solid- dry mount suspended in liquid- wet mount |
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why is staining used? |
to increase contrast to identify features of a specimen |
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how do you prepare something for staining |
-fixation- preserving specimen as lifelike as possible EM-fixed with acids like osmic acid or glutaraladahyde, immobilising things and staining lipids black LM- non-living things fixed with ethanol and ethanoic acids -dehydration- unnecessary in living things EM&LM- specimen immersed ethano or propano in increasing concentrations to embed them -embedding- supports for sectioning EM- epoxy resin used LM- wax used -sectioning- cutting into thin slices EM- 50-100nm thin, SEM can be thicker LM- microtome cuts 5-10um thin -Staining- makes things easier to see EM- heavy metals used so electrons reflect LM- range of dyes used -Mounting- put on the slide to view it |
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What colour is crystal violet and what does it stain? |
violet gram-positive bacteria |
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what colour is methylene blue and what does it stain? |
blue animal cells |
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what colour is nigrosine and what does it stain? |
white gram-negative bacteria |
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what colour is congo red and what does it stain? |
red amyloid |
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what colour is carbolfuchsin and what does it stain? |
pink mycobacteria |
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what is a gram stain and how is it done? |
-separates bacteria into 2 groups- negative and positive -positive is susceptible to penicillin >crystal violet applied >iodine applied, fixing dye >alcohol wash >positive retains dye and goes purple >negative loses stain as thinner walls and is dyed with safranin red counter dye |
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what is acid fast technique and how is it done? |
-differentiates species of mycobacterium from other bacteria >carbolfuchsin dye carried by lipid solvents into cell >washed by dilute acid-alcohol solution - mycobacteria will be stained red >other bacterium dyed with methylene blue |
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what's the formula for magnification? |
image size= actual size x magnification |
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function of the nucleus, nuclear envelope&pores, nucleoplasm and nucleolus |
nucleus- controls cell activity as it holds genetic information in DNA nuclear envelope- compartmentalises chemical reactions in the nucleus and controls what enters and exits nucleus nuclear pores- regulate transportation of molecules in and out of the nucleus nucleoplasm- contains chromosomes and RNA and makes ribosomes nucleolus- contents of nucleus |
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function of mitochondria |
makes ATP by aerobic respiration double membrane- controls exit and entry of materials cristae- folded to allow maximum volume for matrix matrix- enzymes that form ATP, mitochondrial DNA, ribosomes, tRNA and enables cells to collide |
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function of ribosomes |
site of protein synthesis- tRNA molecules bring it specific amino acids so it can add them to polypeptide chains according to the order of the code on the molecule to make proteins |
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function of the rough endoplasmic reticulum |
transports and keeps together proteins made by ribosomes- they're threaded through pores and accumulate in ER lumen with enzymes |
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function of smooth endoplasmic reticulum |
site of steroid production- has enzymes that detoxify organic materials. storage site for calcium for skeletal cells |
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function of Golgi apparatus |
synthesising and modifying proteins, carbohydrates and lipids. sometimes adds non-protein elements. labels them and sends to correct destination |
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function of lysosomes |
digests unwanted materials and worn out organelles |
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function of centriols |
forms spindle fibres in cell division- site of formation of cytoskeleton network |
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function of cell surface membrane |
controls what enters and exits cell to compartmentalise reactions |
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function of cell wall |
provides rigidity and strength to plant cell making it strong enough to resist expansion allowing it to become turgid. Due to arrangement of fibrils, it forces the cell to grow in a certain way/shape |
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function of chloroplast |
site of manufacture and storage of amylose/amylose pectin as it is the site of photosynthesis |
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function of vacuole |
storage site of sap, made of mineral salts, sugars and water. stores pigment for colour. is strong and turgid to provide rigidity. accumulates waste products of metabolism |
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function of cilia and flagella |
cilia- lines trachea and inside of oviducts to waft out unwanted materials and aid movement of egg. flagella- moves cel/organism |
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function of plasmodesmata |
provides living connection between neighbouring plant cell walls by strands of cytoplasm |
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function of microtubules |
supports and gives shape to cell. pathway for organelles to move. helps chromosomes split in cell division |
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Give example of division of labour in a cell |
protein synthesis- >nucleus- transcription of gene in DNA onto mRNA to leave nuclear pore and bring specific amino acids to ribosome >ribosome- translation of amino acids into polypeptide chain >vesicles- transport to Golgi apparatus >Golgi apparatus- post translation modification >vesicles- secretes out of cell in exocytosis |
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what is the cytoskeleton |
A network of protein fibres that allow the cell to move. It's an internal framework that preserves the shape and holds organelles in position |
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What's the structure of the cytoskeleton in eukaryotic cells |
-proteins arranged as microfilaments and microtubules (made of a protein called Tubulin and microtubule motor proteins) -has actin filaments - Has undulipodia and cilia
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what's the structure of the cytoskeleton in prokaryotic cells |
-has actin filaments -has flagella with an internal spiral of protein attached to the base which spins to move the cell |
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what's the importance of the cytoskeleton |
-preserves shape of cell and holds organelles in position to perform their functions -helps organelles move to perform functions e.g. vesicles transporting proteins in protein synthesis -change in shape of white blood cells to engulf pathogens -moves things in environment of cell e.g. cilia wafts mucus out of lungs on ciliated epithelial cells |
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give organelles unique to prokaryotes and their functions |
capsule- not always present, protects cell and stops them sticking together free chromosomal DNA- has restriction enzymes to cut viral DNA and controls activity of cell and passes on genetic information mesosome- respiratory enzymes held here, large surface area 70S ribosomes- protein synthesis (eukaryotes have 80S) plasmid- extra DNA to aid survival in adverse conditions flagellum- moves cell pili- pathway of passing on genetic information and hooks onto other prokaryotes glycogen granules- carbohydrate storage lipid droplets- long term lipid store for conversion to carbohydrates
photosynthetic lamellae- enzymes and chlorophyl for photosynthesis |
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give 9 differences between eukaryotes and prokaryotes |
P- no membrane bound organelles E-membrane bound organelles P-no nucleus or nucleolus E- distinct nucleus and nucleolus P-DNA free in cytoplasm and plasmids E-DNA in chromosomes P-no chloroplasts, only photosynthetic lamellae in some bacteria E-chloroplasts in plant cells P-smaller ribosomes 70S E-larger ribosomes 80S P-flagella rotates, no 9+2 arrangement E-flagella, if present, as 9+2 arrangement P-no ER, Golgi, or lysosomes E- has ER, Golgi, and lysosome P-cell wall made of peptidoglycan E- cell wall, if present, made of cellulose or chitin |