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Alevel Biology [AS] > AS-Cells > Flashcards

AS-Cells Flashcards

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1
Q

Why do optical microscopes have a lower resolution than electron microscopes?

A

Because light rays have a longer wavelength

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2
Q

What is used to focus an optical microscope?

A

Glass lens

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3
Q

What image do optical microscopes produce?

A

-2D (some 3D)
-Coloured images

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4
Q

What do electron microscopes use to focus?

A

Electromagnets

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5
Q

What does the specimen have to be in an electron microscope?

A

Dead in a vacuum and thin

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6
Q

What image do TEMs produce?

A

2D black and white

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7
Q

What image do SEMs produce?

A

3D black and white

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8
Q

What are the steps for measuring cells using a microscope?

A
  1. Measure the cell using an eyepiece graticule.
  2. Calibrate the eyepiece graticule against a stage micrometer.
  3. Take a number of measurements.
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9
Q

What are the steps for setting up a temporary mount?

A
  1. Add a drop of water to a glass slide.
  2. Obtain a thin section of the sample and place it on the slide.
  3. Stain the specimen with iodine in potassium iodide solution.
  4. Lower a cover slip with a mounted needle onto the glass slide.
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10
Q

Give three ways in which the DNA in a chloroplast is different from DNA in the nucleus.

A

1) DNA in chloroplasts is shorter
2) DNA in chloroplasts has fewer genes
3) DNA in chloroplasts is circular not linear

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11
Q

Explain the purpose of boiling agar and transferring the same volume of liquid culture onto each agar plate when doing an experiment.

A

1) So there is no bacteria on the agar
2) So same number of bacteria transferred to allow comparison

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12
Q

Suggest how the Golgi apparatus is involved in the absorption of lipids.

A

1) Modifies triglycerides
2) Combines with proteins
3) Forms vesicles

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13
Q

Contrast how an optical microscope and a transmission electron microscope work and contrast the limitations of their use when studying cells.

A

1) Optical microscope uses light, TEM uses electrons
2) With TEM smaller organelles can be observed
3) TEM has higher resolution than optical microscope
4) TEM uses dead specimen, optical uses live specimen
5) Image from optical is coloured, TEM image has no colour
6) Process for TEM more long and complex than optical
7) TEM uses thinner specimen than optical

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14
Q

What is the function of the Golgi apparatus?

A

1) Assembles products from the SER
2) Modifies products
3) Packages modified products into vesicles

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15
Q

What is the function of the RER?

A

Protein synthesis and transport of proteins

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16
Q

What is the function of the Smooth endoplasmic reticulum?

A

Synthesises and processes lipids

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17
Q

What is the function of the vacuole?

A

Storage of food, water, or waste

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18
Q

What is the function of lysosomes?

A

-contains digestive enzymes
-this helps break down cell/cell parts

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19
Q

Describe the differences between prokaryotic and eukaryotic cells/plant cells?

A

1) Prokaryotic cells are smaller than eukaryotic cells

2) Prokaryotic cells have no membrane-bound organelles eukaryotic cells do

3) Prokaryotic cells have smaller 70S ribosomes
eukaryotic cells have 80S ribosomes

4) Prokaryotic cells have a single circular strand of DNA
eukaryotic cells have double stranded DNA in a double helix

5) Prokaryotic cell walls contain murein
plant cell walls contain cellulose

6) Prokaryotic cells have a flagellum, whereas eukaryotic cells do not

7) Prokaryotic DNA is not associated with histones
eukaryotic DNA have histones

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20
Q

Describe the structure of a virus.

A

-A virus contains genetic material -surrounded by a capsid
-capsid has attachment proteins on it which bind to host cell

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21
Q

How would you calculate the magnification of a microscope?

A

Magnification = Image size/Actual size [AIM]

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22
Q

Why does a solution have to be buffered when doing cell fractionation?

A

Buffered - to maintain pH so enzymes and proteins don’t denature so organelles are not damaged

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23
Q

Why does a solution have to be ice cold when doing cell fractionation?

A

Ice cold - to reduce enzyme activity so organelles are not broken down by enzymes

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24
Q

Why does the solution have to be isotonic when doing cell fractionation?

A

Isotonic - so there is no net movement of water by osmosis so the organelles do not shrink/burst

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25
Describe the process of cell fractionation and ultracentrifugation.
1) Homogenise a tissue sample in a blender - breaks open cells (kept in a cold, buffered, isotonic solution) 2) Filter the homogenate to remove large debris 3) Centrifuge the filtrate (spining tubes at low to higher speeds) 4) Remove supernatant from pellet and centrifuge supernatant 5) Repeat step 4 but centrifuge supernatant at increasing speeds until pellet containing desired organelle is obtained
26
What is meant by the supernantant in cell fractionation
The remaining organelles suspended in the liquid
27
Why do scientists use cell fractionation
Allows scientists to isolate cellular components for further study.
28
What is the order of organelles that settle at the bottom of the centrifuge from HIGHEST to LOWEST density
-Nuclei -Chloroplasts -Mitocondria -Lysosomes -Endoplasmic reticulum -Ribosomes
28
What is the order of organelles that settle at the bottom of the centrifuge from HIGHEST to LOWEST density
-Nuclei -Chloroplasts -Mitocondria -Lysosomes -Endoplasmic reticulum -Ribosomes
29
What is the function of the Rough endoplasmic reticulum (RER)?
Folds and processes protiens made at ribososmes
30
What is the function of the smooth endoplasmic reticulum (SER)?
synthesis & processes lipids
31
Why do organelles have different shapes under the microscope?
different shapes depend on how the cell has been cut
32
How many chloroplasts do algae have?
1 massive chloroplast
33
What are fungal cell walls made of?
Chitin
34
Define Magnification
How large the image is compared to real life
35
Define resolution
Ability to distinguish between two close objects on an image - how detailed an image is
36
How can you tell a picture is SEM?
- image has depth - 3D image
37
Why is a transmission electron microsope used?
- to view internal structure of organelles - using high resolution
38
Why is staining used?
- provides contrast - denser organelles stain darker - helps to identify organelles
39
Why is the specimen pressed down firmly under the cover slip?
- ensures single layer of cells - so light passes through specimen
40
convert 1 micrometre (up)to milimeter
0.001 mm
41
convert 1 nanometre (mm) to 1 milimetre
0.000001mm
42
heavy organelle which are are at the bottom of the tube are called
pellets
43
How do prokaryotes repoduce?
Binary Fission
44
How do Viruses repliate?
Via Host cells
45
What is the function of attachment protiens on viruses?
Allows viruses to bind to receptors on cells
46
What are the function of Caspid on viruses?
protien coat that surrounds DNA/RNA
47
What does the genetic material do in viruses?
Contains all viruses DNA/RNA e.g RNA reverse transcription
48
What is the function of the capsule in prokaryotes?
Layer of slime protection
49
Function of plasmids in prokaryotes?
Small loop of DNA containing celles genes
50
Function of circular DNA in prokaryotes
Contains most of genes in the cell
51
disadvantages of transmission electron microscopes
- can only be used with thin specimin - needs to be in a vacume so can see living organelles only 2d image created - high posibility of artefacts seen
52
what are the advantages of transmission electron microscopes
has a high resolution
53
what are the advantage and disadvantages of scanning electron microscopes
advantage- can use thick specimen 3d image formed dis- vacumm needed only look at non living specimin has a lower resolution than SEM
54
How do you calibrate eyepiece graticule?
1) Line up the stage micrometer and eyepeice graticule 2) Count how many divisions on the eyepeice graticule fit into 1 division on the micrometer scale 3) each division on the micrometer scale / division from the eyepeice lgraticule (multiply this answer by how long the cell is (under the microscope for the ACTUAL SIZE)
55
Recall the order of the cell cycle
-G1 (growth) -S (DNA synthesis) -G2 (growth) -M (Mitosis/meiosis) -CK (cell splits into two) -G0 (exit of cell cycle)
56
What makes good microscope drawing?
1) your drawing and labels must drawn in sharp pencil (not pen) 2) your drawing should take up at least half the page 3) lines should be clear (no shading) 4) Rule the label lines 5) make sure the label lines touch the part that you are labeling 6) don't let the label lines cross each other 7) ensure correct proportions 8) label all the different parts you have drawn as shown
57
What is meant by the ultrastructure?
Internal structure of a cell as reveled by microscopes
58
What happens at the G1 of the cell cycle?
cell prepares for the S phase -duplicates organelles -grows in size -makes protiens
59
What happens at the S phase of the cell cycle?
DNA synthesis -more important DNA sequences are coded first -all DNA+ chromosomes doubled
60
What happens at the G2 phase of the cell cycle?
cell prepares for mitosis -grows in size -makes protiens
61
What happens at the M phase of the cell cycle?
-Mitosis/meiosis occurs- nuclear division
62
What happens at the CK phase of the cell cycle?
Cytokenesis- cell division
63
What happens at the G0 phase of the cell cycle?
Exit of the cell cycle -These cells can differentiate -die -senescence (no longer divide)
64
What type of reproduction is binary fission?
Asexual reproduction
65
what organisms carry out binary fission?
prokaryotes & single celled eukaryotes
65
what organisms carry out binary fission?
prokaryotes & single celled eukaryotes
66
Describe binary fission (3)
-circular DNA and plasmid DNA are replicated -circular DNA and plasmid DNA move to opposite sides of the cell -each daughter cell inherits single copies of DNA (genetically identical)
67
How does binary fission differ from mitosis?
-no nucleus -no chromatids -no spindle fibers
68
Why can't viruses undergo cell division?
VIRUSES ARE NON-LIVING
69
Explain viral replication
1) attachment protein on virus attaches to receptor on cells 2) Virus injects viral DNA into cell 3) DNA injected transcribed (by reverse transcriptase) into RNA into Viral proteins 4) Viral proteins copied allowing new viruses to assemble 5) New viruses over run host cell & burst free killing the cell *Then the process repeats*
70
What is the cell cycle?
cycle of division with intermediate growth periods
71
What stage of the cell cycle is G1, S and G2 also known as?
The interphase
72
Why doesn't the cell cycle occur in all cells?
some cells loose the ability to divide after G0 phase e.g. after differentiation
73
What is the difference between the cell cycle and mitosis?
-cell cycle includes growth periods between divisions -mitosis is only 10% of the cycle referring to only nuclear division
74
What is the purpose of mitosis?
-growth and repair -reproduction
75
Name the stages of mitosis [remember PMAT]
P-prophase M- metaphase A-anaphase T-telophase
76
Outline what happens during PROPHASE
-chromosomes condense and become visible -centrioles separate -nuclear envelop breaks down
77
Outline what happens during METAPHASE
-sister chromatids line up in the equator of the cell -spindle fibres formed and attach to chromatids
78
Outline what happens during ANAPHASE
- requires ATP -sister chromotids are pulled to the poles of the cell -chromosomes pulled to poles
79
Outline what happens during the TELOPHASE
-nuclear envelope forms -cytoplasm divides
80
What are the products of mitosis
-genetically identical daughter cells -diploid cells
81
What are tumour suppressor genes
Genes that code for proteins that trigger apoptosis (programmed cell death)
82
What are proto-oncogenes?
genes that codes for protiens to stimulate cell cycle from one stage to the next stage
83
How can a mutation to tumour suppressor genes and proto-oncogenes cause cancer?
TS genes-no production of the protein needed to slow the cell cycle PO genes-form permanently-actively oncogenes This combined causes a disruption in the cell cycle, uncontrolled cell division causing a tumour
84
How can cancer treatments control the rate of cell division?
They disrupt the cell cycle: -preventing DNA replication -inhibit the Metaphase/anaphase HOWEVER they can also damage healthy cells
85
Why is it so hard to develop effective treatments against viruses?
-Viruses replicate inside cells -difficult to kill viruses without killing host cells
86
What are membranes used for?
-regulating transport of substances in and out -separating cell content from outside -separating organelles from cytoplasm -cell recognition & signalling -surface for metabolic pathways
87
Why is the cell membrane referred to as a 'fluid mosaic' (2)
-molecules are moving 'fluid' -the structure is made up of a range of proteins and phospholipids
88
What is the role of cholesterol in the cell membrane?
-gives stability -lives water passing through
89
What is the role of glycolipids and glycoproteins in the cell membrane?
-signalling -allow the immune system to recognise its own cells
90
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Alevel Biology [AS] (5 decks)

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