2.1- bacteria and disease Flashcards
measuring lengths of cells- SI units of distance
km= 1 (103m)
cm= 1 (10-2m)
mm=1 (10-3m)
um=1 (10-6m)
nm=1 (10*-9m)
magnification definition
measure of how much bigger the image you see is than the real object
resolution definition
measure of how close two objects can be before they are seen as one
step by step- how to use a eyepiece graticule
1.place stage micrometer on top of stage
2.link up one division on eyepiece graticule with a fixed point on stage micrometer
3. count number of divisions on eyepiece graticule that correspond with a set measurement on stage micrometer
4. calculate distance in micrometres of one division on eyepiece graticule
5.The eyepiece graticule needs to be calibrated with the stage micrometer (the true ruler). By calibrating the two, you can determine what each length on the eyepiece graticule corresponds to in terms of actual micrometer measurements on the stage micrometer. After calibration, you can measure the length
about a light microscope
-uses a beam of light
-beam reflected by a mirror through specimen
- beam then passes through lens to magnify the image
SEM microscope
-emits an electron beam
-electrons bounce off surface of specimen and received at senor
TEM microscope
-emits an electron beam
-electron passes through specimen
-harder for electrons to pass through thicker parts which gives contrast in the 2D image produced
-electrons have smaller wavelength, so better resolution than SEM
advantages and disadvantages of using a light microscope
adv= —-can see living plants and animals directly
-relatively cheap, light and portable
dis=
-preservation and staining tissue can produce artefacts which makes us see things we have created
-limited magnification and resolution
advantages and disadvantages of using an electron microscope
adv=
huge magnification and resolution power, many details seen for first time
dis=
-all examined in a vacuum as air would make if fuzzy, so impossible to see living things
-extremely expensive
-specimens undergo severe treatment likely to result in artefacts
-large, must be kept at certain temp and pressure and maintain vacuum
3 jobs of cell surface membranes
- control what substances enter/ leave the cell
2.allow recognition by other cells e.g. immune system
3.allow cells to communicate
what is the phospholipid bilayer made up of
-Phosphate heads facing aqueous solution (extracellular space)
-phospholipid bilayer
-Hydrophobic tails facing inwards
fluid mosaic model- function of the membrane
-plasma membrane forms a barrier between cell and external environment
-offers mechanical support
-flexible to allow cells to grow, move and divide
-self sealing to stop bursting
-controls material passage
-recognition of other cells
-receptors for hormones and neurotransmitters
fluid mosaic model- function of intracellular membrane
-similar to plasma membranes
-acts as a reaction surface
-Provides intracellular compartments so isolating different chemical reactions.
components of the membrane- phospholipid bilayer
-Each consists of a hydrophobic tail (2 fatty acids) and hydrophilic head (phosphate).
-arranged with tails pointing in
-oily to give membrane flexibility and fluidity
-allows passage of certain lipid soluble substances
components of the membrane- intrinsic proteins
-span the width of the membrane
-act as protein channels to transport substances across membrane
-carrier proteins bind to ions or other molecules then change shape to move molecule across
components of the membrane- extrinsic proteins
-on outer and inner surfaces
-give mechanical support by attaching to cytoskeleton to anchor membrane
-many combine with carb groups to form glycoproteins
-some lipid molecules join with carb to form glycolipid
-glycolipids act as chemical receptors
components of membrane- cholesterol
-strengthens bilayer
-hydrophobic to prevent water loss
-helps decrease permeability
-makes membrane less fluid at high temps
-reduces lateral movement of other molecules
