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George Biology > Foundations in biology chapter 2 > Flashcards

Foundations in biology chapter 2 Flashcards

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1
Q

when was spontaneous cell generation disproved and how was it disproven

A
  • 1860 by Louis Pasteur
  • proved it by demonstrating that bacteria would only grow in a sterile nutrient broth after it had been exposed to the air
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2
Q

what path does the light take in a light microscope

A
  • light bulb
  • stage
  • specimen
  • objective lens
  • eyepiece lens
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3
Q

what is a dry mount in sample preparation

A
  • a sectioned specimen is placed directly on the slide.
  • A cover slip may be used to keep the specimen in place and to help protect the objective lens.
  • suitable for specimens such as samples of pollen, hair, feathers or plant materials.
  • called a dry mount as no chemicals or solvents are used
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4
Q

what is a wet mount in sample preparation

A
  • specimens are suspended in a liquid such as water or an immersion oil (this is why called wet)
  • a cover slip is placed on from an angle.
  • Aquatic samples and other living organisms can be viewed this way
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5
Q

How are squash slides prepared and when would they be used

A
  • A wet mount is first prepared, then a lens tissue is used to gently press down the cover slip.
  • Squash slides are a good technique to use when you have soft samples
  • care needs to be taken to not brake the cover slip during the process.
  • Root tip squashes are used to look at cell division
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6
Q

How are smear slides prepared, what is an example of a smear slide

A
  • The edge of a slide is used to smear the sample, creating a thin, even coating on another slide.
  • A cover slip is then placed on over the sample.
  • An example of a smear slide is a blood smear, which is a good way of viewing the cells in the blood
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7
Q

what’s the difference between gram positive and negative bacteria

A
  • Gram-positive lack outer membrane
    ^surrounded by layers of peptidoglycan, thicker than gram-neg
  • Gram positive are susceptible to penicillin
    (which inhibits the formation of cell walls)
  • Gram negative have thinner cell walls
    ^are not susceptible to penicillin
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8
Q

what is the most common length per unit of a micrometer

A

100 divisions = 1 mm
so 1 division = 10 µm/0.01 mm

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9
Q

what is the formula for finding the unit for 1 eyepiece graticule division

A

1 graticule division = number of µm(found using micrometer)/number of graticule divisions

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10
Q

how does a transmission electron microscopes (TEM) work

A
  • a beam of electrons is transmitted through a specimen and focused to produce an image
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11
Q

How does a scanning electron microscope (SEM) work

A

a beam of electrons is sent across the surface of a specimen and the reflected electrons are collected to produce an image

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12
Q

how to prepare a sample for an electron microscope

A
  • fixation using chemicals or freezing
  • staining using heavy metals and dehydration with solvents.
  • Samples for TEM will be set in resin (for easier slicing) & stained again.
  • samples for SEM, fractured to expose the interior and coated in heavy metals
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13
Q

characteristics of light microscopes

A
  • inexpensive to buy and operate
  • small and portable
  • simple sample preparation
  • sample preparation does not usually lead to distortion
  • natural colour is seen
  • specimens can be living or dead
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14
Q

characteristics of electron microscopes

A
  • expensive to buy and operate
  • large and needs to be installed
  • complex sample preparation
  • sample preparation often leads to distortion
  • vacuum is required
  • black and white images
  • specimens are dead
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15
Q

what is an artefact in microscopy

A
  • a visible structural detail caused by processing a sample and not a feature of the sample.
  • They can appear in both light and electron microscopy
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16
Q

Examples of artefacts, how can they come about

A
  • air bubbles under coverslips
  • changes in the ultrastructure of cells occur during the processing of a sample (electron microscopy samples only).
  • This is seen as disruption of membranes
  • distortion of organelles
  • empty spaces in the cytoplasm of cells.
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17
Q

how does a laser scanning confocal microscopes work

A
  • it moves a single spot of focused light across a specimen,
  • ^this causes fluorescence from the components labelled with a dye
  • the emitted light from the specimen is filtered through a pinhole aperture.
  • Only light radiated from very close to the focal plane is detected
  • an image is then produced
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18
Q

what light is used in laser scanning confocal microscopy

A
  • light having the longest wavelength and the lowest energy (red)
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19
Q

what is laser scanning confocal microscopy used for

A
  • diagnosing diseases of the eye (due to it being non-invasive),
  • used in endoscopic procedures (inserting a tube down your throat)
  • used to see the distribution of molecules within the cell and so can be used in the development of new drugs
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20
Q

how does the beamsplitter in a LSCM work

A

the beamsplitter is a dichroic mirror, it only reflects one wavelength (from the laser),but allows other wavelengths (produced by the sample) to pass through.

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21
Q

max resolutions

A

light microscope = 0.2 μm
TEM = 0.0005 μm
SEM = 0.003 - 0.01μm

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22
Q

max magnififcations

A

light microscope = x1,500
TEM = more than x 1,000,000
SEM = less than x1,000,000 but 3D images are produced

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23
Q

What are the 2 main types of cellular organisms

A

Prokaryotes & Eukaryotes

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24
Q

defintion of organelles

A
  • Membrane bound compartments within cells that provide distinct environments and conditions for different cellular reactions
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25
Q

what would you be able to observe from an animal cell under a light microscope

A
  • Cell membrane
  • cytoplasm
  • nucleus
  • mitochondria
  • centrioles
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26
Q

what would you be able to observe from a plant cell under a light microscope

A
  • cell wall
  • cell membrane
  • cytoplasm
  • Nucleus
  • vacuole
  • tonoplast (a membrane which binds the vacuole of a plant cell)
  • mitochondria
  • starch grains
  • chloroplast
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27
Q

what new features can we observe in an animal cell under a electron microscope

A
  • Rough endoplasmic reticulum (RER)
  • nucleolus
  • smooth endoplasmic reticulum (SER)
  • lysosome
  • ribosome
  • nuclear envelope with pores
  • Golgi apparatus
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28
Q

what new features can we observe from a plant cell under a electron microscope

A
  • rough endoplasmic reticulum (RER)
  • smooth endoplasmic reticulum (SER)
  • plasmodesmata
  • nucleolus
  • ribosome
  • nuclear envelope with pores
  • Golgi apparatus
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29
Q

what are the functions of a cell membrane

A
  • allows the movement of materials in and out of cells
  • has receptor molecules to allow it to respond to chemical messengers
  • compartmentalise
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30
Q

what is the structure of a cell membrane

A
  • fluid mosiac model
  • selectively permeable phospholipid bilayer
  • multiple proteins though-out its structure
  • ^receptors, channels, pumps, etc
  • cholesterol, maintain stabiility and fluidity of cell membrane
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31
Q

what is the function of a plant cell wall

A
  • maintains cell shape (turgor pressure against strong wall)
  • compartmentalise the cells
  • protects cell from pathogens
  • allows cell to cell communication
  • allows gasous exchange
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32
Q

what is the structure of a cell wall

A
  • made of cellulose
  • contains plasmodestama (pores in the cell wall)
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33
Q

what is the function of the nucleus

A
  • houses genetic information in the form of DNA molecules
  • protects DNA from damage
  • allows molecules into and out of the nucleus through nuclear pores (e.g. protein synthesis)
  • houses RNA
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34
Q

what is the structure of a nucleus

A
  • it has a double membrane structure
  • nuclear envelope (membrane) has nuclear pores
  • contains a nucleolus
  • contains nucleoplasm
  • contains nuclear lamina (nucleus cytoskeleton)
35
Q

describe the process of DNA becoming chromosomes

A
  • DNA molecules associate with histone molecules to form complex called chromatin
  • chromatin coils and condenses to form chromosomes.
36
Q

what is the function of DNA in the cell

A
  • DNA directs the synthesis of all proteins required by the cell
    ^u could say DNA controls the metabolic activity of the cell as many proteins synthesised are enzymes needed for metabolism to occur
37
Q

what is the function of the nucleolus

A
  • area in the nucleus responsible for producing ribosomes,
  • its comprised of proteins and RNA
  • RNA is combined with proteins to produce ribosomes.
38
Q

what does a nucleolus look like on a micrograph

A
  • spherical structure that appears as a dark spot in the nucleus of a cell in micrograph
  • membrane within nucleus
39
Q

what is the function of a mitochondria

A
  • site of aerobic respiration
  • produces ATP
  • number of mitochondria differs depending on energy demands of cell (active cells contain more)
40
Q

what is the structure of a mitochondria

A
  • have double membrane
  • inner membrane folds to form cristae
  • fluid interior called matrix
  • inner membrane contains ATP synthase
  • Contains a small amount of (mt) DNA (produce enzymes and duplicate)
  • contains ribosomes
  • have intermembrane space
41
Q

what is the structure of a vesicle

A

they consist of a single membrane with material inside

42
Q

what is the function of a vesicle

A

they transport and store materials

43
Q

what is the function of a lysosome

A
  • break down old/waste materials in the cell such as old organelles
  • breakdown pathogens ingested by phagocytes (immune system)
  • They also play an important role in apoptosis (programmed cell death)
44
Q

what is the structure of a lysosome

A
  • specialised vesicles that contain digestive enzymes
45
Q

which cells is the cytoskeleton found in

A
  • All eukaryotic and some prokaryotic cells
46
Q

what is the overall function of the cytoskeleton

A
  • organelles are held in place by the cytoskeleton
  • controls cell movement and the movement of the organelles
  • necessary for the shape and stability of a cell
47
Q

how many components are there of the cytoskeleton

A

3
microfilaments
microtubules
intermediate fibres

48
Q

what does metabolism involve

A

the building up and breaking down of molecules

49
Q

what is the structure of microfilaments

A
  • contractile fibres
  • ^formed from the protein actin
50
Q

what is the function of microfilaments

A
  • responsible for cell movement and cell contraction during cytokinesis
    ^formation of cleavage furrows
51
Q

what is the structure of microtubules

A
  • Tube like structures
  • ^ formed from the polymerisation of globular tubular proteins
52
Q

what is the function of microtubules

A
  • they determine the shape of the cell
  • they also act as tracks for the movement of organelles, including vesicles, around the cell
  • form spinal fibres in cell division
53
Q

what is the function of intermediate fibres

A

give mechanical strength to cells and help to maintain their intergrity

54
Q

how do cells moves without flagella/cillia and diffusion

A
  • polymerisation of microfilaments at the ‘leading edge’ of the cell cause the cell to be pushed along
  • while microtubules at the opposite end help to direct the cell
55
Q

what is the structure of centrioles
in which cells are they found

what are they made of

A
  • they are composed of microtubules
  • found in most eukaryotic cells apart from all flowering plants and most fungi
  • nine circularly arranged triplet microtubules (9 + 3 arrangement)
56
Q

what is the function of centiroles

brief function of centrosome

A
  • 2 assocaited centrioles form the centrosome
    ^(centrosomes are involved in the assembly and organisation of spindle fibres)
  • in cells with a flagella and cilla centrioles are though to play a role in there positioning
57
Q

what is the structure of the flagella and cilla

A
  • contains 2 central microtubules surrounded by 9 pairs of microtubules (arranged like a wheel)
  • ^9+ 2 arrangment
58
Q

what is the function of flagella

A
  • used to grant motility
  • can be used as sensory organelles
59
Q

what is the funtion of cillia

A
  • stationary - used as sensory organelles e.g. in nose
  • mobile - beat in rhythmic manner creating a current that causes fluids/objects adjacent to cell to move, present in the traechea to move mucus away from the lungs
60
Q

what is the structure of the endoplasmic reticulum as a whole

A
  • it is a network of membranes enclosing flatterened sacs called cristernae
  • it is connected to the membrane of the nucleus
  • ribosomes are bound to one side of it (the side that is the RER)
61
Q

what is the function of the smooth endoplasmic reticulum (SER)

A
  • lipid and carbohydrate synthesis and storage
62
Q

what is the function of rough endoplasmic reticulum (RER)

A
  • responsible for the synthesis and transport of proteins
  • sectretory cells which release hormones or enzymes have more RER that cells than do not release proteins
63
Q

what is the structure of ribosomes

A
  • free floating in the cytoplasm or bound to the RER
  • not surrounded by a membrane
  • constructed of RNA and protein (made in the nucleolus)
  • contain rRNA

  • mitochondira, chloroplast and prokaryotic cells also contain ribosomes
64
Q

what is the function of ribosomes

A

they are the site for protein synthesis

65
Q

what is the structure of the golgi apparatus

A
  • single membrane structure
  • a compact structure formed of cristernae (highly folded membrane)
  • it has a cis face (facing nucleus) and a trans face (facing away from nucleus)
66
Q

what is the function of the golgi apparatus

A
  • modifies & packages proteins into vesicles
  • ^these can be secretory vesicles (leave cell) or lysosomes (stay in the cell)
67
Q

what are the stages of vesicle production

A

1)Proteins synthesised on ribosomes on RER
2)then pass into its cisternae and are packaged into transport vesicles
3)Vesicles containing the synthesised proteins move to Golgi apparatus via the cytoskeleton
4)vesicles fuse with the cis face (faces nucleus) of the Golgi apparatus and the proteins enter the Golgi,
proteins are structurally modified then leave the Golgi apparatus in vesicles from its trans face (face away from nucleus).

68
Q

what is the structure and function of the vacuole

A
  • membrane lined sacs in the cytoplasm
  • contain cell sap
  • membrane surrounding vacoule is the tonoplast, is it selectivly permeable (small molecules can pass)
  • many plant cells contain a large permanent vacuole
  • if vaculoes appear in animals they are small and transient (only last a small amount of time)
69
Q

what is the function of chloroplast

A

organelles responsible for photosynthesis in plant cells.

70
Q

what is the structure of chloroplasts

A
  • double membrane structure (like mitochondria)
  • Fluid interior is called stroma
  • interior membranes form thylakoids
  • thylakoids stack to form grana
  • grana connected by stromal lamella
  • contain own DNA and ribosomes, can make own proteins (similar to mitochondria)
71
Q

what is the structure and function of granum

A
  • The grana (plural) are joined by membranes called lamellae
  • thylakoid and therefore grana contain chlorophyll pigments
  • thylakoids stacked to form grana
  • site of light dependent reaction

image of chloroplast

72
Q

what cells make up animals, plants and fungi

A

Eukaryotic cells

73
Q

what appeared earlier eukarytoic and prokayotic cells

A
  • Prokaryotic cells (appeared 3.5 billion years ago)
74
Q

what are extremophiles and where can they be found

A
  • a microorganism, especially archaeans, that live in conditions of extreme temperature, acidity, alkalinity, or chemical concentration.
  • they can be found near hydrothermal vents and salt lakes
75
Q

what are the features of DNA in prokaryotes

A
  • structure of DNA is basically same but packaged differently
    ^DNA is circular
  • have 1 chromosome (molecule of DNA)
    ^supercoiled to make compact.
  • genes on chromosome grouped into operons
  • ^genes are under control of single promoter and so will be switched on/off together
76
Q

what are the features of ribosomes in prokaryotes

A
  • They are smaller than those in eukaryotic cells
    (eukaryotic ribosomes are 80s, prokaryotic ribosomes are 70s)
  • Eukaryotic ribosomes make more complex proteins
77
Q

what are feautues of cell walls in prokaryotes

A
  • made of peptidoglycan (also known as murein)
  • ^it is a complex polymer formed from amino acids and sugars
78
Q

what are the features of flagella in prokaryotes

A
  • thinner than flagella on eukaryotes
  • do not have the 9+2 arrangement
  • energy to rotate filament supplied by chemiosmosis,
    ^not from ATP
79
Q

How does the flagella connected to a prokayotic cell actually move

A
  • molecular motor causes the flagella to move in whip like way
  • ^this movement propels the cell
  • energy to do so provided by chemiosmosis
80
Q

when did the first eukaryotic cells appear

A

The first eukaryotic cells appeared about 1.5 billion years ago.

81
Q

what is the theory of endosymbiosis

A
  • mitochondria and chloroplasts (possibly other eukaryotic organelles), were formerly free-living bacteria (prokaryotes).
  • ^these prokaryotes were taken inside another cell as an endosymbiont (organism that lives within the body or cells of another organism).
  • This eventually led to the evolution of eukaryotic cells
82
Q

what are the main differences between eukaryotes and prokaryotes

A
  • Eukaryotic:
    reproduce via asexual/sexual
    nucleus
    ribosome is 80s
    organelles membrane bound (some exceptions)
    chitin and cellulose cell walls
    linear DNA
  • Prokaryotic:
    reproduce via binary fission
    no nucleus
    ribosome is 70s
    organelles not membrane bound
    peptidoglycan cell wall
    circular DNA

dont have to remember all of these just a few

83
Q

what is a mnemonic to remeber the difference between independent and dependent variables

A

dairy milk, ice cream
- dependent measured, independent changed

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