module 2 Flashcards
how does a compound light microscope work
objective lens and eyepiece lens
combination of the two allows for higher magnification and reduced chromatic aberration
what is the difference between preparing a dry mount and a wet mount
dry mount
specimen placed on centre of the slide and place cover slip over the sample
wet mount
cover slip is placed on at an angle
what do we do to wet mounts
squash slides
smear slides
why are electron microscopes better than light
electrons have a smaller wavelength than light waves
what is the resolution and max mag of a TEM
res = 0.5nm
max mag =
what is the resolution and max mag of a SEM
res = 3-10nm
max mag =
define an artefact
visible structural detail caused by processing the specimen
describe the function of DNA helicase
unwinding and separation of DNA double helix
describe the function of DNA polymerase
catalyses the formation of phosphodiester bonds between nucleotides
what are the characteristics of DNA
universal
degenerate
triplet
non-overlapping
what does the degenerate code mean
many amino acids can be coded for by more than one codon
describe the ‘fluid mosaic’ model
phospholipids are free to move within the layer relative to each other
proteins embedded in the bilayer
define glycoprotein
branched carb portion of a protein that acts as a recognition site for chemicals
define glycolipid
acts as a recog site
define intrinsic proteins
proteins embedded through both layers of a membrane
have hydrophobic R-groups on their surface which interact with hydrophobic core of membrane, keeps them in place
give two examples of intrinsic proteins
channel proteins
carrier proteins
glycoproteins
glycolipids
describe channel protiens
provide hydrophilic channel allowing diffusion of polar molecules and ions
describe carrier proteins
role in passive and active transport
involves protein shape changing
define extrinsic proteins
present in one side of the bilayer
have hydrophilic R-groups
what are the 2 factors affecting membrane structure
temperature
solvent
how does temperature affect membrane structure
phospholipids have more kinetic energy and move more
membane more fluid
how do solvents affect membrane structure
many organic solvents less polar than water
organic solvents dissolve membrane
or they can disrupt the membrane (making it more fluid and permeable)
how do neuronal membranes become disrupted by alcohol and what is the effect
alcohol molecules between the phospholipid disrupts the permeability of the membrane
nerve impulses can’t be normally transmitted
how can scientists observe the route taken by a dye through the stem
cutting series of sections at intervals along stem
transverse sections
taking from above and below site of injection
using a microscope
how does high light intensity require more water than shaded plants
high light intensity increases rate of photosynthesis
more stomata open to allow gas exchange
high light intensity increases transpiration so more water vapour is lost
how would you use a colorimeter
zero the colorimeter
use known concentration of solutions
plot calibration curve
measure absorance of unknown sample
compare absorbance of sample with calibration graph
use appropriate filter for the colour
what is human therapeutic cloning
DNA of embryo is replaced with the DNA from patient
describe uses of stem cells for research
grown into different tissues to test effectiveness of new medicinal drugs and side effects
how does a bud form
nucleus divides by mitosis
cell swells on one side
nucleus, cytoplasm and organelles move into bud
bud pinches off
cell wall forms so bud becomes separate cellw
what is the type of speciation that occurs when two populations live in the same location
sympatric
what is allopatric speciation
where populations become geographically isolated from each other to an extent that prevent or interferes with gene flow
