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A Level Biology > Module 2 - chapter 2 > Flashcards

Module 2 - chapter 2 Flashcards

1
Q

List the parts of a laser scanning confocal microscope.

A

Eyepiece, objective lens, specimen, condenser lens, lamp

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2
Q

List the parts of a light microscope

A

Eyepiece, body tube, coarse adjustment screw, fine adjustment screw, arm, high power objective lens, low power objective lens, stage, condenser, mirror, base

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3
Q

What was the first development to cell theory?

A

The cell was first observed:

Robert Hooke observed the structure of thinly sliced cork using an early light microscope. He described the compartments he saw as ‘cells’. As this was dead plant tissue he was observing only cell walls.

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4
Q

When was the first development to cell theory?

A

1665

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5
Q

What was the second development to cell theory?

A

The first living cells were observed:

Anton van Leeuwenhoek developed a technique for creating powerful glass lenses and used his handcrafted microscope to examine samples of pond water. He was the first person to observe bacteria and protoctista and described them as “little animals” or “animalcules” - today we call them microorganisms. He went on to observe red blood cells, sperm cells, and muscle fibres for the first time.

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6
Q

When was the second development to cell theory?

A

1674-1683

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7
Q

Who made the first development to cell theory?

A

Robert Hooke

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8
Q

Who made the second development to cell theory?

A

Anton van Leeuwenhoek

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9
Q

What was the third development to cell theory?

A

Evidence for the origin of new plant cells:

Barthélemy Dumortier was the first to observe cell division in plants providing evidence against the theories of the time, that new cells arise from within old cells or that cells formed spontaneously from non-cellular material. However it was several more years until cell division as the origin of all new cells became the accepted theory.

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10
Q

When was the third development to cell theory?

A

1832

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11
Q

Who made the third development to cell theory?

A

Barthélemy Dumortier

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12
Q

What was the fourth development to cell theory?

A

Nucleus first observed:

Robert Brown was the first to describe the nucleus of a plant cell.

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13
Q

When was the fourth development to cell theory?

A

1833

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14
Q

Who made the fourth development to cell theory?

A

Robert Brown

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15
Q

What was the fifth development to cell theory?

A

The birth of a universal cell theory:

  • Matthias Schneider proposed that all plant tissues are composed of cells.
  • Jan Purkyne was the first to use a microtome to make ultra-thin sliced of tissue for microscopic examination.
  • Based on his observations, he proposed that not only are animals composed of cells but also that the “basic cellular tissue is clearly analogous to that of plants”.
  • Not long after this, and independently, Theodor Schwann made a similar observation and declared that “all living things are composed of cells and cell products”.
  • He is the scientist credited with the “birth” of cell theory.
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16
Q

When was the fifth development to cell theory?

A

1837-1838

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17
Q

Who made the fifth development to cell theory?

A

Matthias Schleiden, Jan Purkyne, Theodor Schwann

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18
Q

Which scientist is credited with the “birth” of cell theory?

A

Theodor Schwann

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19
Q

What was the sixth development to cell theory?

A

Evidence for the origin of new animal cells:

Robert Remak was the first to observe cell division in animal cells, disproving the existing that new cells originate from within old cells. He was not believed at the time however, and Rudolf Virchow published these findings as his own a decade later in 1855.

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20
Q

When was the sixth development in cell theory?

A

1844

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21
Q

Who was responsible for the sixth development in cell theory?

A

Robert Remak

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22
Q

Who published the findings for the sixth development to cell theory? When?

A

Rudolf Virchow in 1855

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23
Q

What was the seventh development to cell theory?

A

Spontaneous generation disproved:

Louis Pasteur disproved the theory of spontaneous generation of cells by demonstrating that bacteria would only grow in a sterile nutrient broth after it had been exposed to the air.

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24
Q

When was the seventh development to cell theory?

A

1860

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25
Q

Who made the seventh development to cell theory?

A

Louis Pasteur

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26
Q

What does a dry mount entail?

A

Solid specimens are viewed whole or sectioned. Mounting a specimen onto a microscope slide without any stain or liquid. This is used for hair, pollen and dust.

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27
Q

What does a wet mount entail?

A

A wet mount is when a specimen is prepared for being viewed using a stain or liquid. A wet mount is aquatic. The specimen is suspended in a liquid such as water or immersion oil.

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28
Q

What is a squash mount?

A

A squash mount is when a soft sample is squashed using a cover slip in preparation for viewing with the microscope. A wet mount is prepared first then the sample is squashed using lens tissue. This is used for onion cells.

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29
Q

What is a smear mount?

A

When a specimen is smeared across the microscope slide before being covered with a cover slip and studied. This is used for blood and other bodily fluids. The edge of a slide is used to smear the sample - creating a thin, even coating on another slide.

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30
Q

How do you prepare a slide for a light microscope?

A

1) Take a thin slice of the specimen and place it onto a clean microscope slide.
2) Add a drop of water or a drop of stain onto the specimen.
3) Take a clean cover slip and lower it slowly onto the specimen, taking care to avoid air bubbles.

For a specimen that is in solution add a drop of specimen onto the slide and then add a drop of stain. You can then cover the specimen with a cover slip.

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31
Q

What are some uses of staining?

A
  • To highlight a particular organelle.
  • To distinguish between different cell types.
  • To distinguish different tissue types.
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32
Q

What are photographs of specimens taken down the microscope called?

A

Micrographs

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33
Q

What is the definition for resolution?

A

The degree to which it is possible to distinguish between two objects that are very close. In order to see greater detail.

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34
Q

What is the maximum resolution for a light microscope?

A

200nm

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35
Q

What are the charges of crystal violet and methylene blue?

A

Positively charged dyes

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36
Q

How do positively charged dyes work to stain cell components?

A

The positively charged dyes are attracted tot the negatively charged materials in the cytoplasm. This stains the cell components.

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37
Q

What are the charges of nigrosin, Congo red and cytosol dye?

A

Negatively charged

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38
Q

What is a negative stain technique?

A

when negatively charged dyes are repelled from each other and so stay outside the cells, leaving the cells unstained. This makes the cells stand out against a stained background

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39
Q

What is differential staining?

A

When staining is used to distinguish between two types of organisms which would otherwise be hard to identify. It can also differentiate between different organelles of a single organism within a tissue sample.

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40
Q

What is gram staining technique?

A

When staining is used to separate bacteria into two groups: Gram-positive and Gram-negative bacteria.

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41
Q

How is gram staining carried out?

A
  • Crystal violet is applied to a bacterial specimen on a slide, then iodine which fixes the dye.
  • The slide is then washed with alcohol and the gram-positive bacteria retain the crystal violet stain and will appear blue or purple under a microscope.
  • Gram negative bacteria have thinner cell walls and so lose the stain.
  • The bacteria are then stained with safranin dye which is a counterstain. The bacteria appear red.
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42
Q

What colour does safranin dye stain?

A

Red

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43
Q

What is sectioning?

A

When solid specimens are cut into very thin slices with a sharp blade. Specimens are dehydrated with alcohols and then placed in a mound with sac or resin to form a hard block which is then sliced using a microtome.

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44
Q

What is brightfield microscopy?

A

When the sample is illuminated from below with white light and observed from above.

45
Q

What is wide-field microscopy?

A

When the whole sample is illuminated at once.

46
Q

Why do the images of wide-field microscope tend to have low contrast?

A

Because most cells do not absorb a lot of light

47
Q

How is resolution limited in light microscopes?

A

By the wavelength of light and diffraction of light.

48
Q

What is diffraction?

A

The bending of light as it passed close to the edge of an object.

49
Q

What is cytosol?

A

The aqueous interior of cells

50
Q

How do stains increase contrast?

A

The different components within a cell take up stains to different degrees.

51
Q

How is a sample prepared for staining?

A

The sample is placed on a slide and allowed to air dry. This is then heat-fixed by passing through a flame. The specimen will adhere to the microscope slide and will then take up the stains.

52
Q

What does safranin act as in gram staining?

A

A counterstain

53
Q

How does penicillin affect gram-positive bacteria?

A

Inhibits the formation of cell walls

54
Q

How does penicillin affect gram-negative bacteria?

A

It doesn’t, the bacteria have much thinning cell walls that aren’t susceptible to penicillin

55
Q

What is acid-fast technique?

A
  • When a lipid solvent is used to carry carbon fuchsia dye into the cells being studied.
  • the cells are then washed with a dilute acid-alcohol solution.
  • Mycobacterium are not affected by the acid-alcohol and retain the carbolfuchsin stain which is bright red.
  • other bacteria lose the stain and are exposed to methylene blue.
56
Q

What is fixing as part of sample preparation?

A

Chemicals like formaldehyde are used to preserve specimens in as near-natural a state as possible.

57
Q

What must be included for a good biological drawing?

A
  • title
  • state magnification
  • use a sharp pencil
  • use white, unlined paper
  • use as much of the paper as possible for the drawing
  • draw smooth, continuous lines
  • do not shade
  • draw clearly defined structures
  • ensure proportions are correct
  • label lines should not cross and should not have arrow heads
  • label lines should be parallel to the top of the page and drawn with a ruler
58
Q

Is the wavelength of light longer or shorter than electrons? How does this affect resolution?

A

Longer, makes resolution worse

59
Q

What are the two types of electron microscopes?

A

TEM - Transmission Electron Microscope

SEM - Scanning electron microscope

60
Q

How do the electrons move about the specimen in TEM?

A

The electrons move through and around the specimen

61
Q

How do the electrons move about the specimen in SEM?

A

The electrons move around and reflect off the specimen

62
Q

Do TEM microscopes produce a 2D or 3D image?

A

2D

63
Q

Do SEM microscopes produce a 2D or 3D image?

A

3D

64
Q

What is the maximum magnification of TEM?

A

x500 000

65
Q

What is the maximum magnification of SEM?

A

x100 000

66
Q

Compare light microscopes and electron microscopes.

A
  • light: sample prep doesn’t usually distort material, electron: sample prep often distorts material.
  • light: no vacuum required, electron: requires vacuum
  • light : allows viewing of the natural colour of the sample (or colour of stain if used), electron: only black and white images produced so images are often coloured digitally
  • light: up to x2000 magnification, electron: over x500 000 magnification
  • light: resolving power of 200nm, electron: TEM = 0.5 nm, SEM = 3-10nm
  • light: live or dead specimens can be viewed, electron: dead specimens only
67
Q

What can electron microscopes only produce black and white images?

A

Because electrons are only emitted by one wavelength

68
Q

Advantages of electron microscopes

A
  • resolution is 0.2nm (1000x more than light)
  • structured, detailed images of organelles inside cells are visible
  • SEM produces 3D images that can uncover details of contorts and cellular tissue arrangement (not possible with light)
69
Q

Disadvantages of electron microscopes

A
  • electron beams are deflected by air molecules so the sample has to be in a vacuum
  • preparing slides and samples requires high level training and skills because the slides must be very thin
70
Q

Why must the specimen be dead with electron microscopes?

A

Because the sample has to be in a vacuum

71
Q

What are some uses of staining?

A
  • to highlight a particular organelle
  • to distinguish between different cell types
  • to distinguish different tissue types
72
Q

What can you stain red blood cells with?

A

Eosin

73
Q

What can you stain white blood cells with?

A

Haematoxylin

74
Q

What is the structure of the nucleus?

A
  • Contains genetic material in the form of DNA molecules
  • DNA contained within a double membrane called a nuclear envelope containing nuclear pores.
  • contains chromatin which condenses into chromosomes
75
Q

What is the function of the nucleus?

A
  • DNA directs the synthesis of proteins required by the cell.
  • The DNA controls the metabolic activities of the cell.
  • The nucleus houses nearly all of the cell’s genetic material
76
Q

What is the structure of the nucleolus?

A

An area in the nucleus responsible for producing ribosomes. Composed of proteins and RNA

77
Q

What is the function of the nucleolus?

A
  • The nucleolus makes RNA and ribosomes which pass into the cytoplasm and proteins are assembled at them.
  • RNA is used to produce ribosomal RNA which is combined with proteins to form ribosomes
78
Q

What is the structure of the rough endoplasmic reticulum?

A

A network of membranes enclosing flattened sacs called cisternae. The ER is connected to the outer membrane of the nucleus. The rough ER has ribosomes bound to the surface.

79
Q

What is the function of the rough ER?

A

The rough ER is responsible for the synthesis and transport of proteins

80
Q

What is the function of the smooth ER?

A

The same as the rough ER but without ribosomes: a network of membranes enclosing flattened sacs - cisternae.

81
Q

What is the function of the smooth ER?

A

Responsible for lipid and carbohydrate synthesis and storage.

82
Q

What is the structure of the Golgi apparatus?

A

A compact structure of cisternae without any ribosomes - similar to the structure of the smooth ER

83
Q

What is the function of the Golgi apparatus?

A

Modifies proteins (may add sugar to them) and packaged them into vesicles - Secretory vesicles if the proteins are destined to leave the cell or lysosomes if staying in the cell

84
Q

What is the structure of mitochondria?

A
  • Has a double membrane, the inner membrane is highly folded to form Cristae and the fluid interior is the matrix.
  • the membrane forming Cristae contain enzymes used in aerobic respiration
  • mitochondria Cornish mitochondrial DNA also
85
Q

What is the function of the mitochondria?

A

The site of the final stages of cellular respiration where the molecule ATP is produced.

ATP stands for adenosine triphosphate

86
Q

What is the structure of lysosomes?

A

Specialised vesicles containing hydrolytic enzymes.

Membrsneous sacs consisting of a single membrane with fluid inside

87
Q

What is the function of the lysosomes?

A

Responsible for breaking down water material in cells.
Additionally, lysosomes are responsible for breaking down pathogens ingested by phagocytic cells.
Contains powerful digestive enzymes and the role is to break down materials

88
Q

What is the structure of the ribosomes?

A

Not surrounded by a membrane, made of RNA molecules made in the nucleolus of the cell.

Each ribosome consists of two subunits

89
Q

What is the function of the ribosomes?

A

The site of protein synthesis

90
Q

What is the structure of the centrioles?

A

Composed of microtubules. Only found in animal cells

91
Q

What is the function of the centrioles?

A

Two associated centrioles from the centrosome, involved in the assembly and organisation of the spindle fibres during cell division.

92
Q

What is the structure of the flagella and cilia?

A

Flagella are longer than cilia

Each cilium contains 2 central microtubules surrounded by 9 pairs of microtubules arranged as a wheel

Pairs of the parallel microtubules slide over each other, causing the cilia to move

93
Q

What is the function of the flagella?

A

Flagella used primarily to enable cells mobility. Sometimes used as a sensory organelle.

94
Q

What is the function of the cilia?

A

Cilia can be mobile or stationary.

Mobile cilia beat in a rhythmic manner, creating a current and causing fluids/objects adjacent to the cell to move.

95
Q

Describe the process of protein production

A

1) mRNA copy of the instructions gene is made in the nucleus
2) mRNA leaves the nucleus through a nuclear pore
3) mRNA attaches to a ribosome attached to endoplasmic reticulum. The ribosome reads the instructions to assemble the protein.
4) The assembled proteins are separated into vesicles and travel to the Golgi apparatus.
5) the vesicles dude with the Golgi apparatus
6) the Golgi apparatus processes and packages the protein molecules ready for release
7) the packaged proteins are separated in vesicles from the Golgi apparatus and move to the cell surface membrane
8) the vesicle fuses with the cell membrane
9) the cell membrane opens to release the protein

96
Q

What is a prokaryotic cell?

A

Single-cellular, without a nucleus and has no membrane bound organelles. Can survive in extreme environments.

97
Q

What are extremophiles?

A

Prokaryotic cells which can survive in extreme environments

98
Q

What are eukaryotic cells?

A

Multi cellular, has membrane-bound organelles

99
Q

How large are the ribosomes in eukaryotic cells?

A

80 Svedberg

100
Q

How large are the ribosomes in prokayotic cells?

A

70 Svedberg

101
Q

In prokaryotic cells how do flagella generate energy?

A

From chemiosmosis rather than ATP as in eukaryotic cells

102
Q

What do vacuoles consist of?

A

A tonoplast membrane filled with cell sap

103
Q

What is cell sap?

A

A watery solution of different substances including sugars, enzymes and pigments

104
Q

What is the cell wall made out of?

A

Polysaccharide cellulose which can function as a carbohydrate store by varying the amount of cellulose it holds

105
Q

What are the pores in the cell wall called?

A

Plamodesmata

106
Q

What is the process of proteins being released out of the cell?

A

Exocytosis

107
Q

What is the site of ATP synthesis?

A

Cristae

108
Q

Do mitochondria produce or release energy?

A

RELEASE

A Level Biology (8 decks)

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