Cells (studying, Mitosis)

Question 1

Limitations of TEM

Answer 1

thin slice of specimen
Vacuum
Artefacts
Black and white image
Complex staining process

Question 2

Magnification

Answer 2

How much larger a sample appears to be compared to its actual size

Question 3

Resolution

Answer 3

Ability to distinguish between two objects that are close together

Question 4

Cell fractionation
(Followed by filtration)

Answer 4

Breaking cells open
Ice cold to prevent enzyme activity
Isotonic to prevent osmosis
Buffer to keep pH same
(Then filter homogenate to remove debris and whole cells)

Question 5

Ultracentrifugation order of pellets (first/ heaviest to last/ lightest)

Answer 5

Nuclei
(Chloroplasts)
Mitochondria
Lysosomes
Endoplasmic reticulum
Ribosomes

Question 6

Artefacts vs cell organelles (history)

Answer 6

Repeatedly prepare specimen in different ways using different techniques
If they saw a particular object in a specimen prepared using one preparation technique but not another, the object was more likely to be an artefact than an organelle

Question 7

What an optical microscope cannot see

Answer 7

Ribosomes
ER
lysosomes
Mitochondria in limited detail

Question 8

G1

Answer 8

Cell grows
New organelles and proteins manufactured

Question 9

S phase

Answer 9

DNA replication generates sister chromatids attaches by a centromere

Question 10

G2

Answer 10

Centrosomes/ centrioles replicate
Start to move to opposite poles
More cell growth
Prep; spindle fibres

Question 11

Prophase

Answer 11

Chromosomes condense
Centrosomes move to opposite poles
Spindle fibres begin to emerge from centrosomes
Nuclear envelope breaks down into small vesicles
Nucleolus breaks down

Question 12

Centrosome vs centriole

Answer 12

Centrosome is an organelle made up of two centrioles in animal cells

Question 13

Metaphase

Answer 13

(Centrosomes reach opposite poles)
Spindle fibres extend
Chromosomes line up at equator of spindle which attach to centromeres (each sister chromatid attached to a spindle fibre originating from opposite poles)

Question 14

Anaphase

Answer 14

Sister chromatids separate at centromere (centromere splits/ divides in two)
Spindle fibres shorten
Sister chromatids pulled to opposite poles and are now called chromosomes

Question 15

Telophase

Answer 15

Chromosomes arrive at opposite poles and begin to decondense
Nuclear envelope begins to reform around each set of chromosomes
Spindle fibres break down
Cytokinesis

Question 16

Chemical drugs (cancer)

Answer 16

Prevent synthesis of enzymes (G1) needed for dna replication (S)
Cell never reaches S phase
Cell kills itself

Question 17

Radiation and some drugs (cancer)

Answer 17

Can damage dna
At several points in the cell cycle, dna is checked for damage, if severe damage is detected, the cell kills itself which prevent further tumour growth

Question 18

Binary fission

Answer 18

Circular loop of dna replicates and move to opposite poles of cell, plasmids also replicate
Cytoplasm divided to produce two daughter cells each with a single copy of the circular dna and a variable number of plasmids

Question 19

Root tip squash

Answer 19

Remove root/shoot tip
Use a fixative (HCl)
Stain dna with methylene blue
Push cover slip down firmly, without pushing it sideways
(Rest of microscope set up)

Question 20

Reason for use of root and shoot

Answer 20

Dividing cells only found here
Roots don’t have chlorophyll so it’s easier to see stained chromosomes

Question 21

Reason for use of fixative

Answer 21

Prevent enzyme action to preserve cells
Breaks down plant cell walls to form a single layer of cells

Question 22

Reason for wet mount

Answer 22

Prevents dehydration or cell

Question 23

Reason for staining dna

Answer 23

Makes condensed chromosomes visible so stages of mitosis can be identified

Question 24

Reason for firmly pushing cover slip but don’t slide it

Answer 24

Squash tissue into a single layer of cells so light can pass through
Avoid rolling cells together and breaking chromosomes