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Biology > Ch 2 > Flashcards

Ch 2 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Define magnification

A

How many times larger the image is than the actual object

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2
Q

Define resolution

A

The ability to distinguish individual objects as separate entities

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3
Q

Light Microscope

-how does it work? Explain.

A

light is sent from light source, through a specimen.

Image of the specimen is magnified by the objective lens, and this image is magnified again by the eyepiece lens

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4
Q

Light microscope

-advantages and disadvantages

A 
Inexpensive to buy & operate
Small so portable
Simple(er) sample prep (= less artefacts)
Can view living specimen 
Colour is seen
X 2D image
X Lower magnification (up to 2000X)
X Lower Resolution (resolving power 200nm)
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5
Q

Laser Scanning Confocal Microscope

A

A beam of light is used to create image;
Laser is used to illuminate specimen (point illumination)
Specimen must have been treated with fluorescent dye - fluorescent components emit light. This light is filtered through a pin hole aperture.
Only light radiated from close to the focal plane is detected.

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6
Q

What is diffraction

A

Diffraction is the tendency for light to spread as it passes close to physical structures

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7
Q

Electron Microscopy

A

A beam of electrons with a wavelength less than 1nm is used to illuminate a specimen.
More detail of cell ultra structure can be seen because electrons have a smaller wavelength than light.
+higher magnification & resolution (resolution is no longer a limiting factor)

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8
Q

Transmission Electron Microscope

A 
Electron beam penetrates the cell providing detail of a cell’s internal structures.
\+high resolution (0.5nm)
\+see internal structure of organelles
-2D image
-need v. thin specimen
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9
Q

Scanning Electron Microscope

A 
Beam of electrons moves back n forth across a cell’s surface, creating details of the cell surface characteristics.
\+3D image
\+specimen doesn’t need to be as thin
- Lower resolution than TEM (3-10nm)
-no colour
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10
Q

What is an Artefact

A

An artefact is a visible structural detail caused by processing the specimen and is not a feature of the specimen, e.g., air bubble

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11
Q

Cytoskeleton components

A

Microfilaments
Microtubules
Intermediate fibres

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12
Q

Microfilaments

A

Contractile fibres
Made of actin
Responsible for cell movement and cell contraction in cyokinesis

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13
Q

Microtubules

A

Scaffold-like structure : Globular tubular proteins polymerise to form tubes.
Determines cell shape
Act as tracks for organelle movement
Spindle fibres are composed of microtubules

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14
Q

Intermediate fibres

A

Give mechanical strength to cells

Help to maintain cell integrity

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15
Q

State Methods of Sample Preparation

A

Dry Mount
Wet Mount
- Squash Slides
- Smear Slides

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16
Q

How to prepare a Dry Mount

A 
Solid specimen - whole or thinly sliced (sectioning)
Specimen placed in centre of slide
Place Cover Slip over
whole - hair, pollon, dust 
sectioned - muscle tissue, plants
17
Q

How to prepare a Wet Mount

A

Specimen suspended in liquid such as Water or Immersion Oil
Place Cover Slip on from an Angle
Aquatic sample vied this way

18
Q

How to prepare a Squash Slide

A

Prepare Wet Mount: specimen suspended in liquid
Use Lense Tissue to Gently Press Down Cover Slip
Avoid Damge by Squashing sample between 2 microscope slides
! take care in ensuring cover slip is not broken when pressed !
Root tip squashed are used to look at Cell Division

19
Q

How to prepare a Smear Slide

A

Edge of slide used to Smear sample, creating Thin, Even Coating on another slide.
Cover Slip placed over sample
Blood Sample to view blood cells

20
Q

Why is Staining used?

A

to Increase in Contrast, making Components Visable for identification
- Stains Increase Contrast as Different Components within a cell Take up stains to Different Degrees.

21
Q

How to Prepare Sample for Staining

A

Place Sample on Slide & allow to Air Dry

Pass through a Flame - Heat Fix = Specimen Adheres to microscope Slide and will take up stain

22
Q

What is Differential Staining?

A

technique that enables 2 types of Organism to be distinguished
It can differentiate between different organelles of a single organism within a tissue sample
E.G. Gram staining and Acid-Fast

23
Q

What is Gram Staining technique of Differential Staining?

A

separates bacteria into Gram-positive (penicillin susceptible) and Gram-negative bacteria
Crystal Violet is first applied to specimen on a slide, then Iodine (fixes the dye)
Wash Slide with Alcohol -
Gram-positive Retain crystal violet stain = Blue/Purple
Gram-negative Lose stain (have thin walls). Then stained with Safrinin dye, a Counterstain = appear Red

24
Q

What is Acid-Fast technique of Differential Staining?

A

Used to Differentiate species of Myobacterium from other bacteria.
Lipid Solvent is used to carry Carbolfuchsin Dye into the cells.
Cells washed with Dilute Acid-Alcohol solution.
Myobacteriam retain Carbolfuchsin stain as not affected by acid-alcohol solution (Red)
Other bacteria Lose the stain and are Exposed to Methylene Blue Stain

25
Q

Rules for Scientific Drawings:

A 
Title
State Magnification
Sharp Pencil 
Use as much paper as possible; at least half space
Smooth, Continuous Lines
Do not Shade
Correct Proportions
Label lines drawn with Ruler, Parallel to Top of Page
26
Q

Using a Graticule to Calibrate a Light Microscope

A

Calibrate Eyepiece Graticule for magnification using Stage Micrometer

27
Q

What is an Eyepiece Graticule?

A

Glass Disc with a scale marked 1 - 100 (No Units)
Scale remains Unchanged by objective lens
Relative Size of Divisions Increase with Increased Magnification
Scale on Graticule is Calibrated using Stage Micrometer
Used to Measure size of Sample under Microscope

28
Q

What is a Stage Micrometer?

A

a Microscope Slide with a very Accurate Scale in Micrometers engraved.
Scale is usually 100 divisions = 1mm (1 division = 10um)
Used to Calibrate Eyepiece Graticule for specific Magnification

29
Q

Golgi Apparatus

A

series of flattened membranous sacs
Transport vesicles fuse with Golgi Apparatus - contents emptied into Golgi. Contents (proteins/lipids) travel through the Golgi; sorted, packaged, tagged, so sent to right place.

30
Q

(Golgi) Vesicles

A

Store and Transport modified proteins/lipids from Golgi Apparatus.
Lysosomes contain Lysozymes

31
Q

Endoplasmic Reticulum

A

a series of interconnected membranous sacs and tubules.
phospholipid bilayer embedded with proteins
RER - process & fold proteins
SER - make & process lipids

32
Q

Centrioles

A

Cylindrical - made of parallel Microtubules that surround a central cavity
Key component of centromeres

33
Q

Flagella

A

eukaryotic - 9 + 2 microtubules (tubulin)
used for locomotion
whipping motion

34
Q

Cilia

A

central core = axoneme
Primary Cilia have 9 + 0
Motile Cilia = 9 + 2
beat rhythmically

35
Q

Emulsion Test

for Lipids

A 
place sample in boiling tube
Add Ethanol
Shake Well. leeave for 5 
Add distilled Water
White, Milky Layers forms if lipid present
36
Q

Biuret Test

for Proteins

A

Add sample to Distilled water + Biuret Solution
Shake Well, leave for 5
Observe Colour change (from blue)
Violet = protein present

37
Q

Benedict’s Test for non-reducing Sugars

A

Boil in Dilute HCl
Add Sodium bicarbonate
Benedicts test - positive if non-reducing sugar present

38
Q

Test for Starch

A

Add few drops of Iodine to sample
Observe colour change:
Orange to blue/black

39
Q

Chromatography

A

separates substances based on their interactions with a Mobile and Stationary phase

Biology (14 decks)

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