Cells and microscopes

Question 1

What is differential staining?

Answer 1

can distinguish between 2 types of organisms that would otherwise be hard to see

Question 2

what is the… size, DNA, ribosomes, cell wall, flagella in prokaryotic cells?

Answer 2

Size- 0.1-10 micrometres,
DNA- one main molecule, circular, additional DNA found in plasmids
ribosomes- 70S
Cell wall-made of peptidoglycan (also known as murein)
Flagella- not movement by ATP but move by chemiosmosis, no 9+2 arrangement, thinner and smaller than in eukaryotes

Question 3

why is a microscope set to the lowest magnification first?

Answer 3

To see largest area of slide ad focus more easily using course focus

Question 4

how does fixation work in electron microscopes?

Answer 4

stabilises sample, prevents decomposition

Question 5

how does dehydration work in electron microscopes?

Answer 5

prevents vaporisation of water in the vacuum as this would damage the sample

Question 6

how does embedding work in electron microscopes?

Answer 6

allows for thin slices to be obtained

Question 7

how does staining with heavy metals work in electron microscopes?

Answer 7

allows for contrast in electron beams

Question 8

what does a plant cell wall do?

Answer 8

Plant cell walls are a strong barrier acting as a defensive mechanism against the outside (invading pathogens). It is composed of a complex carbohydrate called cellulose.
Cell walls allow substances to pass in and out as they are permeable and also allow the cells to keep their shape.
contents of cell press against cell wall making it rigid

Question 9

What is the function of the nucleus/what is it

Answer 9

contains genetic information in the DNA molecules. DNA directs protein synthesis required by the cell. contains nucleolus which produces rRNA
contained within nuclear envelope to protect the cytoplasm from damage
contains nuclear pores, contains chromatin

Question 10

conversions of length

Answer 10

T,G M,K m, mm, μm,nm,

Question 11

why would it be necessary to recalibrate the eyepiece graticule if a higher power objective lens was then used.

Answer 11

eyepiece unit has different values for each calibration

Question 12

Thin stem and thin cell walls do not provide much support for the leaf. Suggest how the leaf is supported

Answer 12

air spaces giving buoyancy, supported by surrounding water.

Question 13

why preparing a wet mount the refractive index of the medium should be roughly the same as glass

Answer 13

reduce the diffraction between the liquid and the glass therefore preventing the distortion of the image

Question 14

what magnifies the image first the objective lens or the eyepiece lens

Answer 14

objective first then eyepiece

Question 15

how do you prepare a smear slide

Answer 15

edge of slide used to smear the sample creating a thin even coating on another slide
blood is an example

Question 16

what is a wet mount and what are examples of when we would use this

Answer 16

specimens are suspended in a liquid such as water of an immersion oil, a coverslip is then placed over at an angle
example- aquatic samples

Question 17

discuss how the structure of microfilaments and microtubules means these components of the cytoskeleton are involved in the movement of cells but the intermediate fibres aren’t

Answer 17

microfilaments are composed of actin which is contractile. Microtubules are composed of tubulin, which polymerises. Contraction and polymerisation lead to change in length resulting of movement in the cell. Intermediate fibres have fixed length, for stablility.

Question 18

how can potential coverslip damage be prevented in squash slides

Answer 18

squashing sample between 2 microscope slides

Question 19

Explain how to do a dry mount and what examples are used

Answer 19

solid spears viewed whole or cut into thin slices. The specimen is placed on the centre of the slide an and a coverslip is placed on it at an angle
exapmles; plants, muscle tissue, hair

Question 20

can mitochondria produce their own enzymes

Answer 20

yes

Question 21

can mitochondria reproduce themselves

Answer 21

yes

Question 22

what are the cell walls of prokaryotic cells made of

Answer 22

peptidoglycan

Question 23

what are the cell walls of fungal cells made of

Answer 23

chitin

Question 24

why are plasmids important in bacteria

Answer 24

small number of genes but these can contain genes which make the bacterium resistant to antibiotics

Question 25

which is bigger, what mitocondria or chloroplast

Answer 25

chloroplasts

Question 26

do prokaryotic cells contain mitochondria

Answer 26

no

Question 27

what do nuclear pores do

Answer 27

allow molecules to move in and out of the nucleus as DNA itself too large to leave to the site of protein synthesis. in the cytoplasm. so it is transcribed into RNA molecules which are exported via the nuclear pore

Question 28

what does chromatin do

Answer 28

dna and protein’s called histones form a complex called chromatin. chromatin forms chromosomes

Question 29

what is detail about microscope and why is an electron one better

Answer 29

detail is about resolution
electrons better due to electrons having a shorter wavelength than light

Question 30

how do the following get their energy
eukaryotic cells
prokaryotic cells

Answer 30

E: ATP
P: chemiosmosis

Question 31

what does it mean that dna is linear molecule

Answer 31

ends of the dna molecule in a chromosome a not joined together to form a loop

Question 32

what is the limiting factor of a light microscope

Answer 32

resolution

Question 33

how do the electron microscopes work (simple)

Answer 33

a beam of electrons with a wavelength of less than 1nm are used to illuminate the specimen

Question 34

how do you prepare a squash slide

Answer 34

a wet mount is first prepared ten lens tissue is used to gently press down on the coverslip to se cell division
example- soft samples like root tips

Question 35

what do centrioles do

Answer 35

component of the cytoskeleton

compared to microtubules. involved in organism of spindle fibres

Question 36

what is cell theory

Answer 36

both plant and animal cell tissue is composed of cells
cells are the basic building block of life
cells only develop from existing cells