3.2.1.3 studying cells

Question 1

describe features of the optical microscope

Answer 1

image created using light which passes through the specimen
generates a 2D image
low resolution due to long wavelength
low magnification
can view living organisms
simple preparation
image produced in colour

Question 2

describe features of the transmission electron microscope

Answer 2

image created using electrons which pass through the specimen
generates a 2D image
high resolution due to short wavelength
high magnification
can only view dead organisms
complex preparation and staining process
image produced not in colour

Question 3

describe features of the scanning electron microscope

Answer 3

image created using electrons which bounce off the specimen
generates a 3D image
high resolution due to short wavelength
specimen does not need to be thin
can only view dead organisms
complex preparation and staining process
image produced not in colour

Question 4

describe steps of cell fractionation

Answer 4

homogenise tissue - to break open cells
place in a cold, isotonic, and buffered solution
filter the homogenate - remove large and unwanted debris
ultracentrifugation - separates organelles based on density, remove supernatant between spins

Question 5

why is a cold, isotonic and buffered solution used

Answer 5

cold - reduce enzyme activity so organelles arent broken down
isotonic - maintain water potential so cells dont burst or shrink
buffered - maintain pH so enzymes dont denature