cell structure and microscopy

Question 1

describe the role of one named organelle in digestion of bacteria (3)

Answer 1

1. lysosomes
2. fuse with vesicle
3. release hydrolytic enzymes

Question 2

explain why its not possible to see small structures using a optical microscope (2)

Answer 2

1. resolution is too low
2. as wavelength of light is too long

Question 3

give 3 organelles present in all prokaryotic and eukaryotic cells

Answer 3

1. ribosomes
2. cytoplasm
3. cell membrane

Question 4

describe how a sample of chloroplasts can be isolated from leaves (4)

Answer 4

1. break open cells and filter
2. in cold, isotonic, buffered solution
3. spin in centrifuge and remove nuclei
4. spin at faster speed, chloroplasts settle out

Question 5

outline the role of organelles in the production, transport and release of proteins from eukaryotic cells (4)

Answer 5

1. DNA in nucleus is code for protein
2. ribosomes produce proteins
3. mitochondria produce ATP for protein synthesis
4. Golgi apparatus package proteins
5. vesicles transport proteins

Question 6

give an advantage of viewing specimens using a transmission electron microscope rather than scanning electron microscope (1)

Answer 6

has a higher resolution
can view internal structures

Question 7

name an organelle found in both a chloroplast and prokaryotic cell (1)

Answer 7

70s ribosome

Question 8

describe 3 properties of solution used in separating cells (3)

Answer 8

1. cold to reduce enzyme activity
2. buffered to prevent denaturing of enzyme
3. same water potential to prevent bursting of organelle

Question 9

contrast how an optical and transmission microscope work and contrast their limitations (6)

Answer 9

1. TEM use electrons, optical use light
2. TEM allows greater resolution
3. TEM can see smaller organelles
4. TEM only view dead specimens, optical can view live specimens
5. TEM does not show colour, optical shows colour
6. TEM requires thinner specimens
7. TEM focuses using magnets and optical uses glass lenses

Question 10

why are no organelles visible in red blood cells (1)

Answer 10

cytoplasm is filled by haemoglobin

Question 11

name 3 structures in a eukaryotic cell that cannot be viewed using an optical microscope

Answer 11

1. ribosome
2. endoplasmic reticulum
3. lysosome

Question 12

describe how to make a temporary mount of a piece of plant tissue to observe the position of starch grains when using an optical microscope (4)

Answer 12

1. add drop of water to glass slide
2. obtain thin section of plant tissue and place on slide
3. stain with potassium iodide
4. lower cover slip using mounted needle

Question 13

name 2 structures found in ALL bacteria that are not found in plant cells (3)

Answer 13

• murein cell wall
• circular DNA
• 70s ribosomes IN CYTOPLASM

Question 14

name 2 features of HIV particles that are not found in bacteria
don’t include attachment protein (2)

Answer 14

• capsid
• RNA genome
• reverse transcriptase
• lipid envelope

Question 15

give 3 structures found in all prokaryotic cells and all eukaryotic cells

Answer 15

• cell membrane
• cytoplasm
• ribosomes

Question 16

name the biological molecule in the cell membrane of a bacterium cell

Answer 16

phospholipids

Question 17

name the biological molecule in the murein cell wall of bacteria

Answer 17

peptidoglycan

Question 18

Describe how HIV is replicated (4)

Answer 18

1. attachment proteins on HIV bind to RECEPTOR molecules on the T cell
2. virus injects it’s nucleic acid into host cell
3. reverse transcriptase converts RNA into DNA

4.host cell makes viral proteins, they are assembled and released, the cell bursts

Question 19

is RNA present in: bacteria
virus

Answer 19

yes in bacteria and virus

Question 20

is a cell wall present in:
bacteria
virus

Answer 20

yes in bacteria
no in virus

Question 21

are enzyme molecules present in:
bacteria
virus

Answer 21

yes in bacteria and virus

Question 22

is a capsid present in:
bacteria
virus

Answer 22

no in bacteria
yes in virus

Question 23

describe and explain a difference between images produced by a transmission and scanning electron microscope

Answer 23

SEM produces 3D image whereas TEM produces 2D image
because electrons are deflected with SEM but pass through with TEM

Question 24

a student determined the size of a cell from a photograph using a ruler and calculator and gave the answer in micrometres,
describe how (2)

Answer 24

• measured length of structure and divided by magnification
• multiplied by 1000 from mm

Question 25

describe how to use information from calorimeter and calibration curve (2)

Answer 25

• measure light absorption
• draw line to curve

Question 26

explain how the electron microscope is able to resolve objects better than the optical microscope

Answer 26

EM uses electron beam which has smaller wavelength than light beam

Question 27

explain why specimens have to be kept in a vacuum to be viewed effectively with an electron microscope

Answer 27

air would absorb the electrons
would prevent electrons reaching the specimen

Question 28

compare scanning and transmission electron microscopes (6)

Answer 28

• both use electron beam
• both use dead specimens
• both use a vacuum
• both may contain artefacts

transmission
- 2D image
- need thin specimen
- electron beam goes through specimen
- higher resolution

scanning
- 3D image
- don’t need thin specimen
- electrons scattered on surface
- lower resolution

Question 29

explain the advantages and limitations of using a transmission electron microscope (6)

Answer 29

advantages
- can view internal structures
- uses electron beam
- this has short wavelength
- high resolution

limitations
- cant examine living specimens
- need a vacuum
- lots of preparation needed
- may result in artefacts