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Biology > Cells and Microscopes > Flashcards

Cells and Microscopes Flashcards

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1
Q

Light microscopes use, advantages and disadvantages

A

Allows scientists to see biological structures in more detail.

Adv
- Cheap
- Small and portable
- Sample dead or alive
- Natural colour of sample seen
- Vacuum not required
- Simple preperation

Disadv
- Low resolution- o.25um
- Low magnification- x1500
- Stain needed to see important features
- Sample has to be thin
- 2D image

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2
Q

SEM use, advantages disadvantages

A

Allows scientists to see 3-dimensional structure of cells.

Adv
- 3D image
- High resolution 5-50nm
- High magnification x200,000

Disadv
- Expensive
- Large and static
- Black and white or false colour
- Samples must be in dead
- Vacuum required

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3
Q

TEM use

A

Allows scientists to see subcellular structures in more detail.

Adv
- High resolution 0.05-2nm
- High magnification x500,000
- Detailed image

Disadv
- Expensive
-Large and static
- Images black and white or false colour
- 2D images
- Samples must be dead
- Vacuum required

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4
Q

Laser Scanning confocal microscopy
- How it works
- Image formed
- Specimen features

A

Uses laser beams to scan a specimen that has been tagged with fluorescent dye. Laser causes dye to fluoresce, which is then focused into a pinhole into a detector, which generates an image onto a computer.
Pinhole aperture is so light from outside focal plane is blocked, reducing blurriness.

Form 3D by scanning multiple layers of a specimen and stacking together to form 3D image.
- In colour
- 2D/3D
- Lower resolution than electron microscopes

  • Live specimen
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5
Q

Definition of:
Resolution
Magnification

A

Resolution- Smallest distance at which 2 separate structures can be distinguished from one another

Magnification- How many times larger an image is compared to its real size.

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6
Q

Stain uses
Differential staining

A
  • Contrast
  • Higher resolution
  • X organelles more visible

Differential staining- when multiple stains are used and each binds to different structures.

M–>mm–>um–>nm

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7
Q

Microscope slides
Artefact meaning

A

Wet mount- Specimens are suspended in a liquid such as water or immersion oil, and cover slip placed at an angle (aquatic samples)

Dry mount- Dry sample viewed whole in sections and cover slip placed on top (muscle tissue, plants)

Smear slide- Edge of slide used to spread sample across another slide, creating even coating (blood)

Artefact- structural detail caused by *processing the specimen** and not a feature of the specimen (bubbles)

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8
Q

Preparing light microscope

A
  • Clip slide containing specime onto stage.
  • Select lowest powered lens and use coarse adjustment to bring stage up to below objective lens.
  • Using course adjustment, move stage downwards to focus image
    Use fine adjustment knob to get clear image of the specimen
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9
Q

How to calibrate eyepiece graticule

A
  • Eye eyepiece graticule
  • Calibrate using stage micrometre/find length of 1epu
  • Measure diamtere of nucleus in epu
  • Take repeat measurements and calculate mean (in epu)
  • Use calibrated epu to find diametre (in um)

Eyepiece- scale inside eyepiece lens. Units are arbitrary (unknown)

Stage micrometre- scale in coverslip.
- Whole is 1mm long
- 100 divisions
- eac division is 0.01mm long

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10
Q

Eukaryote and Prokaryote difference

A

Eukaryote
- multicellular
- membrane bound organelles
- 80S ribosomes
- linear DNA (with histones)
- Nucleus
- Flagella made of microtubules in 9+2 arrangement
- Cellulose cell wall

Prokaryote
- unicellular
- no membrane bound organelles
- 70 S ribosomes
- Circular DNA (plasmids and nucleoid)
- no nucleus
- Flagella made of flagellin and helix structure
- Cell wall made of peptidoglycan

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11
Q

Nucleus structure and function

A

Nuclear envelope- double membrane
Nuclear pore- allows substances to exit or enter nucleus (ribosomes and mRNA)
Chromatin- DNA wrapped around histone proteins
Nucleolus- packed with DNA and protein, makes ribosomes

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12
Q

Ribosomes structure and function

A
  • 2 subunits 60S and 40S
  • made of ribosomal RNA and protein
  • site of translation
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13
Q

SER structure and function

A
  • network of cisternae
  • no ribosomes
  • storage and synthesising lipids and carbohydrates
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14
Q

RER structure and function

A
  • Network of cisternae
  • Ribosomes
  • continuous with the nuclear membrane
  • Folds and processes proteins
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15
Q

Golgi Apparatus structure and function

A
  • Network of cisternae and vesicles
  • no ribosomes
  • Processes and packages proteins and new lipids
  • also makes lysosomes
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16
Q

Vesicles structure and function

A
  • single membrane
  • transport substances in and out of cells and between organelles
17
Q

Lysosomes structure and function

A
  • type of single membrane vesicle
  • break down waste materials in cell
  • Break down pathogens in phagocytosis
18
Q

Chloroplasts structure and function

A
  • Double membrane
  • thylakoids in stacks called granum (many granum are grana)
  • Connected by membrane called lamellae
  • fluid called stroma
  • site of photosynthesis
19
Q

Mitochondria structure and function

A
  • Double membrane
  • Cristae in fluid called matrix
  • Site of cellular respiration
20
Q

Plasma membrane structure and function

A
  • Double membrane
  • Controls what enters and exits cell
21
Q

Centrioles structure and function

A
  • Made of microtubules
  • 2 form centrosomes
  • involved in spindle fibre arrangement
22
Q

Cell wall structure and function

A
  • Made of cellulose
  • supports cell
23
Q

Flagella structure and function

A
  • Made of microtubules in a 9+2 arrangement
  • helps propel through liquids
24
Q

Cilia structure and function

A
  • Made of microtubules in a 9+2 arrangement
  • allows substances to move across cell surface
25
Q

Plasmodesmata structure and function

A

Narrow thread of cytoplasm that passes between cell walls of adjacent plant cells

  • allows communication and exchange of substances
26
Q

Protein synthesis

A

1) Proteins synthesised on ribosomes on RER
2) They then pass through cisternae and packaged into transport vesicles
3) Vesicles move proteins to cis face of golgi via transport function of cytoskeleton
4) Proteins are structurally modified before leaving golgi apparatus via trans face
5) Secretory vesicles carry proteins to cell membrane and fuses, releasing proteins by exocytosis.

Biology (7 decks)

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