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AS-Level Biology (AQA) > 2.1 (3) - Cell Structure > Flashcards

2.1 (3) - Cell Structure Flashcards

Methods of studying cells The electron microscope Microscopic measurements and calculations Eukaryotic cell structure Cell specialisation and organisation Prokaryotic cells and viruses Mitosis The cell cycle

1
Q

What does ‘magnification’ mean?

A

How many times an image is enlarged by under a microscope

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2
Q

What does ‘resolution’ mean?

A

The minimum distance between two objects at which a microscope can distinguish them as separate entities

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3
Q

What are 3 types of microscopes?

A
  • Light microscope
  • Transmission electron microscope (TEM)
  • Scanning electron microscope (SEM)
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4
Q

What are 5 advantages of using a TEM?

A
  • High magnification
  • High resolution (because of short electron wavelengths)
  • Focusses using a condenser
  • Produces a 2D photomicrograph
  • Electrons pass through the specimen, more detail
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5
Q

What are 5 disadvantages of using a TEM?

A
  • Cannot look at living cells
  • Must be in a vacuum
  • Specimen must be really thin
  • Complicated preparation may create an artefact
  • Doesn’t produce a colour image
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6
Q

What are 5 advantages of using a SEM?

A
  • High magnification
  • High resolution
  • Specimen doesn’t need to be thin
  • Focusses using a condenser electromagnet
  • Produces a 3D image using computer analysis
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7
Q

What are 4 disadvantages of using a SEM?

A
  • Cannot look at living cell
  • Must be in a vacuum
  • Complicated preparation may create artefact
  • Doesn’t produce colour image
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8
Q

What is cell fractionation and centrifugation?

A

The process by which cells are broken up and their organelles separated (by size), ready for study

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9
Q

What is it necessary to do before fractionation?

A

Cells are placed into a cold, buffered, isotonic solution

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10
Q

Why does the solution, before fractionation, have to be cold, buffered and isotonic?

A
  • Cold - reduces enzyme activity, which could damage organelles
  • Buffered - maintains constant pH, preventing protein damage
  • Isotonic - prevents organelles from water passing through them via osmosis
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11
Q

Describe the stages of cell fractionation

A

1) Homogenisation - cells are homogenised with a homogeniser (blender). They are broken up to release their organelles
2) The blended cells are filtered through a sieve to separate out the insoluble materials (eg. cell walls)

3) Ultracentrifugation
- The filtrate is put into a centrifuge and spun slowly. The biggest organelles sink to the bottom, forming a pellet
- Fluid at the top (supernatant) is removed from the centrifuge
- Supernatant can be re-spun at a faster speed to gain the next heaviest organelle

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12
Q

What is the equation for magnification?

A

magnification = image size ÷ actual size

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13
Q

What is a eukaryotic cell?

A

Has a nucleus and other membrane-bound organelles

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14
Q

What was electron microscopy developed?

A

1930s

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15
Q

What is the function of the nucleus?

A

Stores genetic information

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16
Q

What is the function of the nuclear envelope?

A

Surrounds the nucleus, encasing genetic information

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17
Q

What is the function of the nuclear pores?

A

Allows molecules to transport across the nuclear envelope

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18
Q

What is the function of the chromosomes?

A

Substance of a cell’s nucleus that contains chromosomes and the nucleolus

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19
Q

What is the function of the nucleolus?

A

Synthesises ribosomes

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20
Q

What is the function of the mitochondria?

A

Aerobic respiration

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21
Q

What is the function of the double (outer and inner) membrane?

A
  • Outer - skin-like layer

- Inner - folded into layered structures, increasing surface area

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22
Q

What is the function of the cristae?

A

Folds of the inner membrane that provide a large SA for enzymes to attach to during respiration

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23
Q

What is the function of the matrix?

A
  • Fluid contained within the mitochondria
  • Has a different set of ribosomes and DNA to other parts of the cell
  • Contains granules, which help with ion concentration
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24
Q

What is the function of the rough endoplasmic reticulum (RER)?

A
  • Site of protein synthesis
  • Transports proteins
  • Contains ribosomes on its surface
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25
Q

What is the function of the smooth endoplasmic reticulum (SER)?

A

Site of lipid and carbohydrate synthesis

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26
Q

What is the function of the golgi apparatus?

A

Where newly-modified proteins are made and packaged into vesicles

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27
Q

What is the function of the vesicles?

A

Transport and secrete newly-made proteins

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28
Q

What is the function of the cytoplasm?

A

Where chemical reactions take place

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29
Q

What is the function of the cell membrane?

A

Controls what enters and exits the cell

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30
Q

What is the function of the lysosomes?

A

Destroys anything unwanted with its enzymes

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31
Q

What is the function of the ribosomes?

A

Protein synthesis

32
Q

What is the function of the cell wall?

A

Gives the cell structure and shape

33
Q

What is the function of the vacuole?

A

Full of sap, keeping the cell structured and turgid

34
Q

What is the function of the chloroplasts?

A

Site of photosynthesis

35
Q

What is the function of the chloroplast envelope?

A

Similar structure to the mitochondrial double membrane

36
Q

What is the function of the grana?

A
  • Site of light-dependent photosynthesis

- Stacks of thylakoids

37
Q

What is the function of the stroma?

A

Fluid surrounding the grana which contains:

  • enzymes for photosynthesis
  • DNA
  • ribosomes
38
Q

In what 3 ways to cells differ?

A
  • Function
  • Shape
  • Type / number of organelle
39
Q

What is cell differentiation?

A

The process by which cells become specialised for different functions

40
Q

What is a prokaryotic cell?

A

They lack a membrane-bound nucleus (or any other membrane-bound organelles)

41
Q

What is the function of the DNA strand?

A

Contains DNA

42
Q

What is the function of the plasmids?

A

Extra DNA storage

43
Q

What is the function of the capsule?

A

Prevents desiccation and chemical attacks

44
Q

What is the function of the flagella?

A

Aids the cell’s movement

45
Q

What is the function of the pili?

A

Attaches the cell to surfaces

46
Q

Why aren’t viruses considered as non-living?

A

They can’t live without a host cell

47
Q

What is the function of attachment proteins?

A

Attaches the virus to a host cell

48
Q

What is the function of the lipid envelope?

A

Derived from a host cell’s membrane, so that it can become undetectable as a virus particle

49
Q

What is the function of the DNA / RNA in a virus particle?

A

Codes for viral proteins, so that they can replicate themselves

50
Q

What is the function of the capsid?

A

Protein layer that encloses genetic material

51
Q

What is the function of the nucleoproteins?

A

Allow the virus to replicate faster

52
Q

What are the 4 stages of viral replication?

A

1) Virus attaches to host cell and injects genetic material
2) Genetic material used as code to synthesise proteins
3) New virus particles are assembled
4) Viruses burst out of, and destroy, the host cell

53
Q

What are 6 purposes of mitosis?

A
  • Allows for growth of tissues (and whole organelles)
  • Replace lost cells
  • Repairing damages tissues
  • Asexual reproduction
  • Forms clones of T and B lymphocytes
  • Cells abnormally divide uncontrollably to form tumours
54
Q

What is a chromosome?

A

Compact ‘X’ or ‘I’-shaped forms of chromatin formed during cell division

55
Q

What are chromatids?

A

The 2 identical arms of an X-shaped chromosome

56
Q

What is a centromere?

A

Point at which the chromatids join

57
Q

What is a homologous chromosome?

A

2 chromosomes originating from each parent, containing the same genes, but different alleles

58
Q

What is chromatin?

A

DNA when it’s not wound up tightly as a chromosome

59
Q

What are the 6 stages of mitosis?

A

1) Interphase
2) Prophase
3) Metaphase
4) Anaphase
5) Telophase
6) Cytokinesis

60
Q

Describe interphase

A
  • The cell grows and DNA is replicating itself

- Chromosomes aren’t visible yet

61
Q

Describe prophase

A
  • Chromosomes become visible
  • Nuclear envelope disintegrates
  • Nucleolus disappears
62
Q

Describe metaphase

A
  • Mitotic spindle are fully formed

- Chromosomes line up along the equator of the cell, they are pulled by the mitotic spindle

63
Q

Describe anaphase

A
  • Centromeres split, allowing chromatids to separate

- Chromatids move towards poles, pulled by the contracting mitotic spindle

64
Q

Describe telophase

A
  • Mitotic spindle disperses
  • Nuclear envelope reforms
  • Chromosomes aren’t visible anymore
65
Q

Describe cytokinesis

A

A ring of protein filament forms around the equator of the cell, which tightens and splits the cell into 2

66
Q

What are the 3 stages of the cell cycle?

A
  • Interphase
  • Cell/nuclear division
  • Cytokinesis
67
Q

What stage of the the cell cycle takes the longest?

A

Interphase

68
Q

What causes tumours?

A
  • Between each stage of the cell cycle, there are checkpoints that are regulated by control genes
  • Mutated control genes can cause cells to divide uncontrollably, leading to tumours
69
Q

What are some risk factors that make cancer more likely?

A
  • Smoking
  • Diet
  • Obesity
  • Physical activity
  • Sunlight
70
Q

What are the 2 types of tumour?

A

Benign and malignant

71
Q

Describe benign tumours

A
  • Slow growing
  • Don’t spread
  • Not classed as cancer
72
Q

Describe malignant tumours

A
  • Fast growing
  • Often spread
  • Classed as cancer
73
Q

What are 3 treatments for cancer?

A
  • Surgery
  • Radiation
  • Chemotherapy
74
Q

What does surgery do to help the eradication of a tumour?

A

Removal of the tumour

75
Q

What does radiotherapy do to help the eradication of a tumour?

A

Radiation damages the DNA of tumour cells

76
Q

What does chemotherapy do to help the eradication of a tumour?

A
  • Blocks enzymes involved in the DNA synthesis
  • Prevents DNA from unwinding
  • Inhibits synthesis of new nucleotides
  • Prevents development of mitotic spindle

AS-Level Biology (AQA) (11 decks)

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