2 Cells- Methods of studying cells Flashcards

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1
Q

What is magnification?

A

How many times bigger the image of a specimen observed is in compared to the actual (real-life) size of the specimen.

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2
Q

How is magnification calculated?

A

Size of image/ size of real object

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3
Q

What is resolution?

A

The ability of a microscope to distinguish two adjacent structures as separate. Higher resolution = better clarity and detail of image

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4
Q

What does cell fractionation do?

A

Separates organelles according to size, so they can be studied in an electron microscope

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5
Q

What are the steps of cell fractionation?

A

1.)Homogenisation
The tissue sample is homogenised in a blender to break the cells in ice cold, isotonic and buffered solution
2.)Filtration
The tissue sample is filtered into tubes through a gauze, separating larger components from smaller ones
3.) Ultracentrifugation
Samples are spun at a low speed in centrifuge , this separates the sample into fractions, heavier at the bottom, lighter on top.
4.)Cell debris forms a pellet at bottom, leaving a supernatant above with organelles. This is poured off and centrifuged at a higher speed to separate the next highest organelle. This is repeated at increasingly higher speeds

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6
Q

Why is the homogenised tissue sample kept in specific conditions?

A

Ice cold= reducing enzyme activity that could damage organelles
Isotonic solution= Prevents osmosis, could shrink or bust organelles
Buffered solution= Keeps pH constant, avoids damage to protein structure

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7
Q

What is the order of fractionation?

A

Heaviest to lightest:
-Nucleus
-Chloroplast
-Mitochondria
-Lysosomes
-Endoplasmic Reticulum
-Ribosomes

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8
Q

How do optical (light) microscopes work?

A

-Visible light passes, is bent through the lens so the user can see the specimen
-The specimen can be alive
-Individual cells are generally transparent and components aren’t distinguishable unless stained, which usually kills cells

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9
Q

What are the uses of light microscopes?

A

-Most student microscopes
- Max resolution is 0.2 micrometres
-Nucleus and mitochondria can be seen
-Max magnification is x1,500.

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10
Q

How do electron microscopes work?

A

-Beam of electrons passes through the lens, not beam of light
-Higher magnification and resolution (more detail seen)

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11
Q

What are the uses of electron microscopes?

A

-Max resolution 0.0002 micrometers (1000 times more than light)
-Max magnification is x1,500,000

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12
Q

What is a transmission electron microscope (TEM) ?

A

A type of electron microscope, where the electron beam penetrates the cell and provides details of a cell’s internal structures
-Use electromagnets to focus the electron beam
-High resolution
-Internal structures like chloroplasts can be seen in thin specimens

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13
Q

What is a scanning electron microscope (SEM)?

A

A type of electron microscope, where a beam of electrons moves back and forth across a cell’s surface , creating details of its characteristics
-Knock electrons off specimen which come together to form an image
-Can be 3D images
-Don’t have to be thin specimens like in TEM
-Lower resolution than in TEM

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14
Q

What is an artefact and how are they created?

A

Occur in various forms during specimen or slide preparation, from:
-Trapped air bubbles
-Folds in thin specimen slices
-Contamination from other cells/tissues

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