2.1 Cell structure and magnification

Question 1

compare and contrast structure of chloroplasts and mitochondria (4)

Answer 1

both double membrane bound organelle

both contain circular DNA

both contain ribosomes

pigments in chloroplast but not in mitocondria

Question 2

describe how a sample of chloroplast could be isolated from leaves

Answer 2

break cell open and filter
centrifuge to remove nuclei in cold, isotonic, pH buffered soloution
centrifuge at a higher speed to seperate chloroplast

Question 3

explain the advantages and limitations of using a TEM to investigate cell structure

Answer 3

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

Question 4

contrast the structre of a bacteria cell and a human cell

Answer 4

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

Question 5

mitochondria

Answer 5

site of aerobic respiration

Question 6

chloroplast

Answer 6

site of photosynthesis
has its own DNA and ribosomes for protein synthesis of proteins needed for photosynthesis

Question 7

ribsosomes

Answer 7

made from rRNA and proteins
80s in eukaryotes
70s in prokaryotes
site of translation (of protein synthesis)

Question 8

rough endoplasmic reliculum (RER)

Answer 8

surface covered in ribosomes
processes proteins made by ribosomes

Question 9

smooth endoplasmic resticulum

Answer 9

site of production of lipids

Question 10

golgi apparatus

Answer 10

sorts, modifies and packages proteins
makes lysosomes

Question 11

lysosomes

Answer 11

produced by golgi apparatus
sacs that contain digestive enzymes that can destroy unwanted organelles

Question 12

light microscope

Answer 12

poor resoloution due to long wavelength of light
can view living cells
2D images
in colour

Question 13

electron microscope

Answer 13

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

Question 14

cell wall in prokaryotes

Answer 14

made from murein

Question 15

DNA in prokaryotes

Answer 15

circular

Question 16

DNA in eukaryotes

Answer 16

linear

Question 17

plasmids

Answer 17

only in prokaryotes
extra DNA containing genes for things such as antibiotic resistance

Question 18

flagellum

Answer 18

only in prokaryotes
long hair like structure that rotates tto make cell move

Question 19

Binary fission

Answer 19

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

Question 20

why use ice cold soloution for ultracentrifugation

Answer 20

reduces kinetic energy and rate of reaction of enzymes

Question 21

why use isotonic soloution for ultracentrifugation

Answer 21

means soloution has same water potential as organelle
prevents osmosis which could cause cells to burst

Question 22

why use pH buffered soloution for ultracentrifugation

Answer 22

keeps pH constant and prevents proteins denaturing