Cell fractionation/Microscopes/ Mitosis Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

What is the equation of magnification?

A

magnification = size of image/ size of real object

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is cell fractionation?

A

the process where cells are broken up and the different organelles they contain are separated out

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe briefly the process of Cell fractionation

A

the tissue is placed in a cold buffered solution of the same water potential as the tissue. It then goes through homogenisation and ultracentrifugation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why is the tissue in Cell fractionation put in a cold, buffered solution (with the same water potential?

A

cold = reduce enzyme activity to prevent self-digestion of organelles

same water potential = prevent organelles from bursting or shrinking as a result of osmotic gain or loss of water

buffered= so that the pH does not fluctuate. Any change to the pH could alter the structure of the organelles or affect the functioning of enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What happens during homogenisation?

A
  • Cells are broken up by a homogenizer (blender), which releases the organelles from the cell
  • this results in homogenate, which is then filtered to remove any complete cells and large pieces of debris
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is ultracentrifugation?

A

the process by which the fragments in the filtered homogenate are separated in a centrifuge.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What happens during ultracentrifugation?

A
  • the tube of filtrate is placed in the centrifuge and spun at a slow peed
  • the heaviest organelles, the nuclei, are forced to the bottom of the tube, where they form a thin pellet
  • the fluid at the top of the tube (supernatant) is removed, leaving just the sediment of the nuclei
  • the supernatant is transferred to another tube and spun in the centrifuge at a faster speed than before
  • the next heaviest organelles, the mitochondria, are forced to the bottom of the tube
  • at each increase in speed, the next heaviest organelle is sedimented and separated out.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Tell me about light microscopes

A
  • use light to form an image
  • The relatively long wavelength of light rays means that light microscopes can only distinguish between two objects if they are 0.2 micrometers or further apart. = poor resolution
  • smaller magnification than electron microscopes
  • image in colour
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Tell me about electron microscopes

A
  • Use beam of electrons instead of light rays
  • higher resolution due to the electron beam having a short wavelength
  • Electrons are negatively charged, so the beam can be focused using electromagnets
  • Electrons are absorbed or deflected by molecules in the air = must be in a vacuum
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How do Transmission electron microscopes (TEMs) work?

A

it consists of an electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.

The beam passes through a thin section of the specimen, which absorbs some electrons and lets some through, producing a black and white image

( the specimen is penetrated from below)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Pros and cons of TEM

A
  • has a magnification up to 1 million and a resolution of 0.1nm
  • can examine really small organelles, as well as virus and bacteria
  • resolving power sometimes not achieved due to difficulties preparing the specimen and a higher energy electron beam being needed, which could destroy the specimen
  • the whole system in a vacuum = needs to be dead
  • a complex staining process is required and the image isn’t in colour
  • the specimen needs to be extremely thin = 2D image only
  • may contain artefacts (things that are a result from the way the specimen was prepared)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How do scanning electrons microscope work?

A

Directs a beam of electrons on the surface of the specimen from above, the beam is then passed back and forth across a portion of the specimen in a regular pattern.

The electrons are scattered by the specimen and the pattern of the scattering depends on the contours of the specimen surface.

A 3D image is produced by a computer analysis of the pattern of scattered electrons and secondary electrons produced.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Pros and cons of SEM

A

Pros :

  • 3D image is produced
  • can be used on thick specimens

Cons:

  • do not produce a colored image
  • has a lower resolving power (20nm)
  • can’t see the internal structure of the cell, because it scans the surface of the object.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the stages of the cell cycle?

A

Interphase, mitosis, cytokinesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What happens during the interphase? (describe all the phases within this phase

A

the cell increases in mass and size and carries out its normal cellular functions

G1 phase = Cells make the RNA, enzymes, and other proteins required for growth (high amount of protein synthesis). Make organelles and grow bigger

S phase = DNA replicated (chromosomes will now consist if two sister chromosomes are held together by chromatids**)**

G2 phase = the cell keeps growing until all of the organelles have duplicated. Proteins needed for cell division are needed

The mitochondria produce more ATP which will provide the energy for cell division

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are checkpoints in the cell cycles and when does it happen?

A

There are two ‘checkpoints’ in the cell cycle - one before S phase and one straight after S phase.

During these checkpoints, the cell is checking its DNA for errors.

This minimises the chances of duplicating any mutated DNA into the replicated cell.

17
Q

What is mitosis?

A

when the eukaryotic cell divides to produce two daughter cells, each with the identical copies of DNA produced by the parent cell during DNA replication

18
Q

What are the 5 stages of mitosis in order?

A

Interphase, prophase, metaphase, anaphase and telophase

19
Q

What happens during the prophase?

A

chromosomes condense getting shorter and fatter ( they become visible)

centrioles move to the opposite poles of the cell. this is where protein spindle fibers are released

The nucleolus disappears and the nuclear envelope breaks down bn

20
Q

What happens during the metaphase?

A

there is no longer a nucleus in the cell, the centrioles move to opposite poles and release spindle fibers

the chromosomes align themselves at the equator of the cell each with a pair of sister chromatids

spindle fibers attach to either the chromatids or centromere

21
Q

What happens during the anaphase?

A

A

the chromosome divide, separating each pair of sister chromatids.

the spindles contract towards the centrioles so the centromere breaks due to the tension created

resulting in the chromatids separating by being pulled to opposite poles of the cell

this stage requires a lot of ATP from respiration

22
Q

what do v-shaped chromosomes show?

A

that the chromatids have been pilled apart at their centromeres

23
Q

What happens during the telophase?

A

the chromatids reach the opposite poles on the spindle

they uncoil and become long and thin again

they’re now called chromosomes again

a nuclear envelope forms around each group of chromosomes, so there are now two nuclei

Division of the cytoplasm (cytokinesis, which starts in anaphase) finishes in telophase

there are now two daughter cells that are genetically identical to the original cell and o each other.

mitosis is finished and each daughter cell starts the interphase part of the cell cycle to get ready for the next round of mitosis

24
Q

Describe what happens in binary fission?

A

circular DNA molecule replicates and both copies attach to the cell membrane

the plasmids also replicate

the cell membrane begins to grow between the two DNA molecules and begins to pinch inward, dividing the cytoplasm into two

A new cell wall forms between the two molecules of DNA, dividing the original cell into two identical daughter cells, each with a single copy of the circular DNA and a variable number of copies of the plasmids

25
Q

Why can’t viruses undergo cell division and how to they replicate?

A

because they are non-living.

They replicate by attaching to their host cell with the attachment proteins on their surface.

Then, they inject their nucleic acid into the host cell.

Genetic information on the injected viral nucleic acid then provides the instructions for the host cell’s metabolic processes to start producing the viral components, nucleic acid, enzymes, and structural proteins, which are then assembled into new viruses.

26
Q

What is the importance of mitosis?

A
  • growth
  • repair
  • reproduction