Cell Structure and microscopes

Question 1

comparing microscopes

Answer 1

LSCM:
200nm
2D/3D
coloured

SEM:
3-10nm
3D
black and white

TEM:
0.5nm
2D
black and white

Question 2

Use forceps to place the sample on a glass slide.
* Use a pipette to place two drops of the stain in the centre of the sample.
* Carefully lower a cover slip onto the sample, ensuring that the cover slip is parallel with the
slide as it is lowered.

give two corrections

Answer 2

.place stain at the edge if the sample
.lower cover slip at an angle

Question 3

how is a laser confocal microscope image differ to a EM

Answer 3

.you can see living cells
.lower res
.shows different layers

Question 4

Explain how to measure the diameter of the nucleus of one of the white blood cells, when observing the cells
through a light microscope.

Answer 4

.use eye piece graticule
.calibrate using stage micrometer
.measure diameter of nucleus in epu
.take repeat measurements and calculate mean
.use calibrated epu to calculate in um

Question 5

Suggest three improvements to this method. For each improvement, explain how it would increase the
validity of the slides produced.

Answer 5

.sharp blade- so individual cells are visible
.select thin slides- so the maximum light can pass through the sample
.use a wet mount- prevents dehydration

Question 6

Discuss the benefits of using stains when making slides for light microscopy.

Answer 6

.contrast is higher
.more internal structures are visible
.clear image

Question 7

Explain why it is important to use a differential stain when examining a blood smear under the
microscope.

Answer 7

.to see differences between cells
.to see differences between organelles
.red blood cells visible without stain due to haemoglobin

Question 8

Using Fig. 2, and the information provided, suggest and explain why the cytoplasm of cell C and cell
D reacted differently to the stain.

Answer 8

.C is purple so has nucleic acid
.C has rRNA
.D is red so has more protein
.D has enzyme

Question 9

TEM vs SEM

Answer 9

TEM has 0.05-2nm res
.shows image of cell interior
.shows ultrastructure of cell

.SEM has res of 5-50nm
.3D imahe
.shows cell surface

Question 10

Explain the role of the membrane in the rough endoplasmic reticulum.

Answer 10

.maintains different conditions from cell cyto
.separates proteins from cell cyto

Question 11

features of mito that are similar to bacteria

Answer 11

.similar size
.contain 70s ribosomes
.double membrane

Question 12

Humans use the enzyme α-amylase to break down polysaccharides in food for absorption into the
blood.
The gene for human α-amylase is found on chromosome 1.
The gene is transcribed in the nucleus and translation occurs on the rough endoplasmic reticulum in
cells of the salivary gland.
Describe how the molecule is prepared and secreted by cells of the salivary gland after translation
has taken place.

Answer 12

.transport vesicle from RER
.modification at golgi
.packaged into secretory vesicle
.vesicle move along cytoskeleton
.fuses with plasma membrane
.exocytosis

Question 13

The plasma membrane contains proteins, which are made within the cell.
Outline the process and organelles involved in the translation of these proteins from RNA.

Answer 13

.mRNA transported out of nucleus to ribo
.translation occurs at ribo
.tRNA brings specific amino acids
.peptide bonds form between adjacent amino acids
.polypeptide processed through golgi apparatus

Question 14

Explain how the genetic code in the gene for tubulin codes for the protein tubulin

Answer 14

.3 bases code for one amino acid
.sequence of bases determines sequence of amino acids

Question 15

Describe three other cellular functions of the cytoskeleton.

Answer 15

.mechanical strength
.cell stability
.movement of vesicles within the cell

Question 16

State how the cytoskeleton moves organelles around the cell.

Answer 16

uses motor proteins