2.1 Cell structure and magnification Flashcards
compare and contrast structure of chloroplasts and mitochondria (4)
both double membrane bound organelle
both contain circular DNA
both contain ribosomes
pigments in chloroplast but not in mitocondria
describe how a sample of chloroplast could be isolated from leaves
break cell open and filter
centrifuge to remove nuclei in cold, isotonic, pH buffered soloution
centrifuge at a higher speed to seperate chloroplast
explain the advantages and limitations of using a TEM to investigate cell structure
ADVANTAGES
high resolution
small objects can be seen
LIMITATIONS
specimen must be in a vacuum
cannot look at living cells
only thin specimen can be viewed
contrast the structre of a bacteria cell and a human cell
bacteria has a cell wall, human doesn’t
bacteria cell is smaller than human
70s ribosomes in bacteria 80s in human
bacteria have no nucleus human cells do
DNA in bacteria is circular human DNA linear
mitochondria
site of aerobic respiration
chloroplast
site of photosynthesis
has its own DNA and ribosomes for protein synthesis of proteins needed for photosynthesis
ribsosomes
made from rRNA and proteins
80s in eukaryotes
70s in prokaryotes
site of translation (of protein synthesis)
rough endoplasmic reliculum (RER)
surface covered in ribosomes
processes proteins made by ribosomes
smooth endoplasmic resticulum
site of production of lipids
golgi apparatus
sorts, modifies and packages proteins
makes lysosomes
lysosomes
produced by golgi apparatus
sacs that contain digestive enzymes that can destroy unwanted organelles
light microscope
poor resoloution due to long wavelength of light
can view living cells
2D images
in colour
electron microscope
high resolution due to short wavelength of electrons
cells must be dead as in a vacuum
with tranmission electron microscopes images are 2D
scanning electron microscopes images are 3D
images are in black and white
cell wall in prokaryotes
made from murein
DNA in prokaryotes
circular
DNA in eukaryotes
linear
plasmids
only in prokaryotes
extra DNA containing genes for things such as antibiotic resistance
flagellum
only in prokaryotes
long hair like structure that rotates tto make cell move
Binary fission
circular DNA and plasmids replicate
cell enlargens
DNA loops move to opposite poles of cell
cytoplasm begins to divide and new cell wall forms and two daughter cells form each containing one copy of circular DNA but random number of plasmids
why use ice cold soloution for ultracentrifugation
reduces kinetic energy and rate of reaction of enzymes
why use isotonic soloution for ultracentrifugation
means soloution has same water potential as organelle
prevents osmosis which could cause cells to burst
why use pH buffered soloution for ultracentrifugation
keeps pH constant and prevents proteins denaturing
