Topic 2 - A Flashcards

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1
Q

List the sub-cellular organelles in an animal cell?

A
  • nucleus
  • nuclear envelope
  • golgi apparatus
  • ribosomes
  • mitochondria
  • cytoplasm
  • smooth endoplasmic reticulum
  • rough endoplasmic reticulum
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2
Q

List the sub-cellular organelles in a plant cell?

A
  • nucleus
  • nuclear envelope
  • golgi apparatus
  • ribosomes
  • mitochondria
  • cytoplasm
  • chloroplast
  • smooth endoplasmic reticulum
  • rough endoplasmic reticulum
  • vacuole
  • cell wall
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3
Q

Describe the function of the nucleus?

A
  • contains DNA of cell
  • chromatin has genetic material before they form chromosomes
  • site of transcription
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4
Q

Describe the function of the ribosome?

A
  • site of protein synthesis and translation
  • attaches to rough ER as it has ribosomes
  • 80s for large subunits in eukaryotic cells
  • 70s for small subunits in prokaryotic cells
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5
Q

Describe the function of the mitochondria?

A
  • produces ATP for release of energy
  • site of aerobic respiration
  • some cells need large supply of ATP
  • double membrane (cristae, matrix)
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6
Q

Describe the function of the cholorplast?

A
  • thykaloid membrane
  • contains chlorophyll
  • site of photosynthesis
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7
Q

Describe the function of the cytoplasm?

A
  • site of bio-chemical reactions (metabollic)

- protein synthesis and degration

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8
Q

Describe the function of the cell membrane?

A
  • lets nutrients and waste in and out

- selective permeable membrane

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9
Q

Describe the function of the golgi apparatus?

A
  • transports and modifies fats and lipids
  • adds non-protein components to proteins
  • forms lysosomes
  • transfers fats to accurate places and labels them
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10
Q

Describe the function of the lysosome?

A
  • vesicles produce lipase and protease
  • hydrolysis materials ingested by phagocytosis
  • release enzymes
  • digest worn out organelles
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11
Q

Describe the function of the smooth endoplasmic reticulum?

A
  • transports and synthesises lipids and carbohydrates

- lacks ribosomes

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12
Q

Describe the function of the vacoule?

A
  • contains minerals, salts, sugars and amino acids
  • temporary food store
  • helps plants stay turgid and upright
  • fluid sac bound by membrane
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13
Q

Describe the function of the rough endoplasmic reticulum?

A
  • ribosomes on outer surface

- provides pathway for protein synthesis to transport proteins

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14
Q

Describe the function of the cell wall?

A
  • fluid filled sac membrane bound
  • keep cell upright and turgid
  • pass along water movement
  • provides strength to help cells from bursting
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15
Q

Explain the state of DNA in a prokaryotic cell?

A

DNA is short, circular, naked that is freely suspended with no chromosomal structure but a plasmid (coiled nuceiod)

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16
Q

How are prokaryotic cells made and their sizes?

A

They are made by binary fission and are less than 2um in size.

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17
Q

What is murien/peptidoglycagon and where do you find it?

A

It’s the cell wall of a prokaryotic bacteria cell.

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18
Q

What are mesosomes?

A

They are the infolding of the cell membrane and iit unclear what they do but it is likely to be involved in respiration, replication of DNA and secretion.

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19
Q

State the definition of magnification?

A

A measure of how large an image is compared to the real object.

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20
Q

What is the equation for magnification?

A

Magnification = Image/ Actual

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21
Q

What are the conversions for km-m-mm-um-nm

A

x1000 each time

22
Q

State the definition of resolution?

A

The smallest/ closest distance between 2 points where they can still be recognised as 2 points.

23
Q

Why is resolution important?

A

Microscopes with higher resolving power have better detail and clarity.

24
Q

How are object seen on microscopes?

A
  • for an object to be seen it must interfere with at least half of the wavelength of light
  • light wavelength is 400-700nm so anything smaller that 200nm can’t be seen
25
Q

What are the smallest organelle and smallest organism to be seen?

A

organelle - ribosomes

organism - virus

26
Q

Why do electron microscopes work if you need to interfere with wavelengths?

A

Electrons are particles but behave like waves and their wavelength is much small at 0.01nm which is why much smaller objects can be seen.

27
Q

What is the max. resolution and magnification on a light microscope?

A

resolution - 200nm

magnification - x1500

28
Q

Why must the specimen be one cell thick in a light microscope?

A

Specimen must be one cell thick so light can pass through.

29
Q

Why do add a dye to a specimen?

A

Dyes make certain structures stand out e.g. toluyene makes nuclei red

30
Q

How do you prepare a slide?

A
  • add a small drop of water on a slide
  • place a thin section of specimen
  • add stain
  • add cover slip to protect stain
  • blot to remove an excess liquid
31
Q

What is the max. resolution and magnification on a electron microscope?

A

resolution - 0.005nm

magnification - x1500000

32
Q

Why must specimen be in a vaccum in an electron microscope?

A

Specimen is placed in a vaccum so no air particles deflect the electrons.

33
Q

Why do images from a electron microscope have a colour concentration gradient despite only producing black and white images?

A

Denser parts will appear darker as more elctrons have been absorbed.

34
Q

What are artefacts?

A

Artefacts are things that can be seen in the image but are not part of the specimen.

35
Q

Describe how artefacts are produced?

A
  • usually made during preparation of specimen
  • common in electron microscopes
  • preparing SEM + TEM requires heavy metal which could be a reason however the experiments are usually repeated
36
Q

State the advantages of TEM microscopes?

A
  • high resolution

- image show extremely small structures

37
Q

State the disadvantages of TEM microscopes?

A
  • only used in thin specimens
  • only on non-living
  • production of artefact
38
Q

State the advantages of SEM microscopes?

A
  • used in thick specimen
39
Q

State the disadvantages of SEM microscopes?

A
  • lower resolution compared to TEM
  • only non-living
  • production of artefacts
40
Q

How does a TEM microscope work

transmission electron microscope

A

Electron beams pass through a thin sample.

41
Q

How does a SEM microscope work?

scanning electron microscope

A

Electron beams scan over surface of sample.

42
Q

What is a capsule?

A

A slime layer around prokaryote which protects it from immune system.

43
Q

What is cell fractionation?

A

A process in which cells are broken up to separate organelles due to size and density.

44
Q

State the order of separation?

A
  1. nucleus (largest organelle)
  2. chloroplast (only in plants)
  3. mitochondria
  4. lysosomes
  5. endoplasmic reticulum
  6. ribosomes
45
Q

Describe the homeganisation stage?

A
  • grind/blend to break cells open
  • breaks cell wall and plasma membrane to see content
  • releases organelles into solution
46
Q

Describe the filtration stage?

A
  • filter homogenate to remove debris (unbroken cells, large connective tissue)
  • remaining organelle into solution
47
Q

What happens after homogenisation and filtration?

A

The filtrate is then put through a differential centrifugation which spins the solution at a fast speed to extract organelles.

48
Q

Why should the solution be ice-cold?

A

Ice-cold solution reduces enzyme activity to stop them from digesting other organelles.

49
Q

Why should the solution be isotonic?

A

Isotonic solution ensures the water potential is same inside and outside organelles so reduction of water movements by osmosis will stop organelles from bursting.

50
Q

Why should the solution be buffered?

A

Buffered solution will maintains the pH throughout the ultracentrifugation process and you don’t want to damage cells and protein structure.

51
Q

Explain the steps that are carried out in ultracentrifugation in detail?

A
  1. Prepare an ice-cold, buffered, isotonic solution (water potential same inside tissue as outside)
  2. Mix the solution and tissue then place it in a blender to homogenise
  3. Mixture should be filtered and homogenate should be spun at low speed using centrifuge
  4. Collect pellet formed and return supernatant to centrifuge to be spun at a higher speed
  5. Continue process until all organelles are isolated