Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Biology aqa biology > 2.1.3 methods of studying cells > Flashcards

2.1.3 methods of studying cells Flashcards

1
Q

What is the magnification formula with a scale bar?

A

Actual length of scale bar / representative length of scale bar.

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

What is the magnification formula without a scale bar?

A

Image size / actual size.

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

What is magnification?

A

The degree to which an image is bigger than the object (specimen) being viewed under the microscope.

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

What is resolution?

A

The clarity of an image; the greater the resolution, the ability to distinguish between 2 points that are closer together.

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

How are specimens illuminated in an optical (light) microscope?

A

Using light.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How is the image produced in an optical microscope?

A

Some parts of the specimen absorb more light than others.

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

What state do specimens need to be in an optical microscope?

A

They can be living or dead.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How can you make specimens more visible in an optical microscope?

A

By staining the specimen with a coloured dye.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the maximum useful magnification of a light microscope?

A

x 1500.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the maximum resolution of a light microscope?

A

0.2 micrometers.

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

Can you view organelles with an optical microscope?

A

NO - only cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How do transmission electron microscopes (TEM) work?

A

TEMs use electromagnets to focus a beam of electrons, which is transmitted through the specimen; denser parts absorb more electrons and appear darker.

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

What is the thickness of the specimen like in the TEM?

A

Must be very thin slices - 100nm or less.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Can specimens be living in a TEM?

A

NO - they must be dead; they are put in a vacuum, chemically fixed and dehydrated.

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

Is the image produced in a TEM black and white or colour?

A

Black and white.

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

Is the image produced in an optical microscope black and white or colour?

A

Colour.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Is a TEM expensive to use?

A

YES.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the resolution of a TEM?

A

1nm.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the magnification of a TEM?

A

x500,000.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the steps of using an electron microscope?

A
  • Fix the specimen.
  • Dehydrate the specimen.
  • Cut into thin slices.
  • Stain.
  • Mount onto a copper grid.
  • Place in a vacuum.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the magnification of a scanning electron microscope (SEM)?

A

x 250000.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the resolution of a SEM?

23
Q

How is a specimen prepared for SEM?

A
  • Coated in a thin layer of gold.
  • Put in a vacuum.
24
Q

Can the specimens be living in a SEM?

A

No - they must be dead.

25
Is the image produced in colour in a SEM?
No - black and white.
26
Are SEMs cheap or expensive to use?
Expensive.
27
How does a SEM work?
- Beam of electrons onto surface of specimen from above, not below. - Beam passed back and forth across portion of specimen in a regular pattern. - Electrons scattered by specimen; then can build up 3D image by computer analysis based on pattern and secondary electrons produced.
28
Describe how to use a micrometer.
- Reference EPU. - Unknown scale. - Use micrometer. - Known 1mm. - Line up. - Work out EPU equivalent to number of micrometers.
29
What is the role of organelles in the production, transport and release of proteins from eukaryotic cells?
- DNA in nucleus is code for protein. - Ribosomes/rough endoplasmic reticulum produce protein. - Mitochondria produce ATP for protein synthesis. - Golgi apparatus package/modify.
30
What is one advantage of using a transmission electron microscope compared with a scanning electron microscope?
Higher resolution/view internal structures.
31
Describe how to make a temporary mount of a piece of plant tissue to observe starch grains.
- Add drop of water to glass slide. - Obtain thin section of plant tissue and place on slide. - Stain with potassium iodide. - Lower cover slip using mounted needle.
32
What is the function of a mitochondrion?
Aerobic respiration.
33
Describe the steps of ultracentrifugation. (6 steps)
Tube of filtrate is placed in centrifuge and spun at a low speed. The heaviest organelles (nuclei) are forced to the bottom, forming a sediment or pellet. The fluid at the top, called the supernatant, is removed, leaving just the sediment of nuclei. The supernatant is transferred to another tube and spun in the centrifuge at a faster speed. The next heaviest organelles (mitochondria) are forced to the bottom. The process is continued with the supernatant transferred each time so that progressively less heavy organelles are separated (until only cytoplasm is left).
34
Explain why a homogenate is filtered before spinning at low speed in the centrifuge. (2)
removes debris / intact cells / sand; which would contaminate the 1st sediment / interfere with the results;
35
An optical light microscope cannot be used to see a plasma membrane. Explain why.
Does not have the resolution / cannot distinguish between points this close together; As light has longer wavelength;
36
Contrast how an optical microscope and a transmission electron microscope work and contrast the limitations of their use when studying cells.
TEM uses electrons vs light TEM- uses a greater resolution TEM - can see smaller organisms LM - see living specimens TEM - dead TEM can’t see in colour LM can TEM - longer process to prepare sample LM - quick don’t need to be skilled TEM - thinner specimens
37
Describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells.
Cell Homogenisation - to break open cells Filter to remove whole cells Isotonic solution - to prevent damage to mitochondria Cold - prevents enzymes activity Buffered solution - prevents enzymes denaturing Spins - centrifugation -at low speed - separates out nuclei into pellet Left over stiff - supernatant - re-spin to get pellet Centrifuge again at higher speed to get mitochondria
38
Describe how to determine size and structure with microscope of an organisms
1- measure and divide by magnification 2- Micrometers to cm x10000 or 1- measure and divide by length of scale bar 2- Multiply by actual length of scale bar
39
Describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells when using an optical light microscope. (4marks)
Add a drop of water to a glass slide Place a section of a thin tissue sample onto a glass slide Put onto drop of water Add iodine solution to stain it And add cover slip lower with mounted needle - prevents air bubbles
40
Describe the limitations of a light microscope.
low magnification low resolution 2D
41
How can the size of an object under a light microscope be measured?
Focus lens with specimen underneath. Remove specimen and replace with stage micrometer (without changing magnification) Use the stage micrometer to find the value that each division on the eyepiece graticule holds Remove the stage micrometer and replace with specimen. Measure the size of object with eyepiece graticule divisions. Multiply the number of divisions by the value for one division.
42
In the preparation for cell fractionation, why is the tissue placed in a buffered solution?
to maintain a constant pH so that structure of organelles and enzyme activity is not altered
43
In the preparation for cell fractionation, why is the tissue placed in a cold solution?
to reduce enzyme activity which may break down organelles
44
In the preparation for cell fractionation, why is the tissue placed in a isotonic solution?
to prevent organelles bursting/shrinking due to osmosis
45
What are the advantages of a light microscope?
specimen can be alive easier to use (than electron microscopes) can use stains can see natural colour
46
What are the advantages of SEM?
3D image (shows contours) very detailed
47
What are the advantages of TEM?
highest resolution (out of light and SEM) highest magnification (out of light and SEM)
48
What are the two stages of cell fractionation?
Homogenation Ultracentrifugation
49
What is the order of organelle fractionation?
Nuclei Chloroplasts Mitochondria Lysosomes Endoplasmic Reticulum Ribosomes
50
What is the preparation for cell fractionation?
tissue is placed in a cold, isotonic buffer solution
51
Why do electron microscopes produce high resolution images?
the beam of electrons has a short wavelength (shorter wavelength than light)
52
Why is a buffer solution used when homogenising cells?
keep pH the same / controls pH; prevent change to / denaturing of proteins/enzymes;
53
why is the Resolution in Electron microscopes higher?
shorter wavelength between electrons longer wavelength In light rays

Biology aqa biology (54 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions