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AS level - Biology > M2- Chapter 2 - Basic components of living systems > Flashcards

M2- Chapter 2 - Basic components of living systems Flashcards

1
Q

What is the cell theory

A
  1. Both plants and animal tissue is composed of cells
  2. Cells are the basic unit of all life
  3. Cells only develop from existing life
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2
Q

3 types of microscopes

A
  1. Light microscope
  2. Scanning Electron Microscope (uses a beam of electrons to produce an image.)
  3. Laser scanning confocal microscope (it can use 2D images to create a 3D visual of the structure by using a pinhole to block out-of-focus light.)
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3
Q

2 lenses on a light microscope

A

Eyepiece
Objective
They allow higher magnification and reduced chromatic abberation (when different wavelengths of light move through slightly different angles, creating a blurry image)

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4
Q

2 knobs

A
  1. coarse adjustment - moves stage up and down.

2. fine focus- literally fine tunes the focus.

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5
Q

Sample preparation

A
  1. dry mount
  2. wet mount
  3. squash slides
  4. smear slides
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6
Q

Dry mount

A

The specimen has to be cut to thin slices, a technique called sectioning. No staining, just put a coverslip on top.

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7
Q

Wet mount

A

Use water or immersion oil to introduce pressure
The coverslip must be placed at an angle to reduce the chances of air bubbles.
Ideal for aquatic

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8
Q

Squash slides

A

Wet mount is prepared
a lens tissue is used to gently press the cover slip down.
For specimens that require a delicate touch

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9
Q

Smear slides

A

You use the side of another slide to create a smooth, thin coat of liquid such as blood to view cells

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10
Q

Stain prep

A
  1. Allow to air dry

2. Pass through a flame

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11
Q

Staining techniques

A
  1. Negative staining
  2. Gram stain
  3. Acid fast
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12
Q

Negative staining

A

Dyes that are negatively charges are repelled by the negatively charged cytosol. So the actual cells are left unstained, creating a contrast.

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13
Q

Gram stain

A

used to identify gram+ and gram-
1. apply crystal violet
2. then iodine
3. then wash it out with alcohol
Gram+ will retain the purple stain but gram- won’t because it has thinner cell walls and will lose the dye.
It is then stained with safranin dye causing the bacteria to look red

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14
Q

Examples of negatively charged dyes

A

Congor red or Nigrosin

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15
Q

Acid fast technique

A

Differentiate species of Mycobacterium from all other.
1. A lipid-solvent is used to carry carbolfuchsin dye.
2. All cells are washed with a dilute acid-alcohol solution.
Mycobacterium will retain the C.F dye (red). All other bacteria are exposed to methylene blue stain.

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16
Q

Risk management

A

Many stains are toxic or irritant
Carry out a risk assessment.
CLEAPPS provides framework for students.

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17
Q

What is the size of the ribosomes in a prokaryote

A

70S

Compared to a larger 80S in eukaryote

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18
Q

Cell wall for different organisms

A

Plant - cellulose
Fungi - chitin
Animals - none

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19
Q

cell wall structure

A

A thick layer outside the cell membrane. It gives strength but are freely permeable to solutes. In plants, they are made up of cellulose. They have 3 layers: primary cell wall, the secondary cell wall and the middle lamella. In fungi, they are made up of chitin.

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20
Q

Nucleus structures

A

Surrounded by a nuclear envelope, which is a double membrane with nuclear pores.

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21
Q

Smooth Endoplasmic Reticulum structure

A

Series of flattened membrane channels without ribosomes attached

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22
Q

Ribosomes structure

A

the sites of protein synthesis. They are composed of protein and RNA, and are manufactured in the nucleolus of the nucleus. They are often found in groups called polysomes. All eukaryotic ribosomes are of the larger, “80S”, type.

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23
Q

Flagella and cilia structure

A

Flagella are longer than the cell and cilia are identical in structure. They are much smaller and there are usually very many of them.

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24
Q

Mitochondria structure

A

This is a sausage-shaped organelle which is surrounded by a double membrane

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25
Q

Rough Endoplasmic Reticulum structure

A

Series of flattened membrane channels studded with ribosomes.

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26
Q

Chloroplasts structure

A

Bigger and fatter than mitochondria with a double membrane, they also have a third membrane called the thylakoid membrane. The thylakoid membrane is folded into thylakoid disks, which are then stacked into piles called grana. The space between the inner membrane and the thylakoid is called the stroma.

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27
Q

Plasma membrane structure

A

This is a thin, flexible layer round the outside of all cells made of phospholipids and proteins

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28
Q

Lysosomes structure

A

These are small membrane-bound vesicles formed from the RER containing a cocktail of digestive enzymes.

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29
Q

Vesicles structure

A

Series of flattened membrane vesicles, formed from the endoplasmic reticulum.

30
Q

Nucleus function

A

Inside it is the nucleoplasm, which has chromatin (DNA/ protein complex in a 1:2 ratio containing the genes). During cell division, the chromatin becomes condensed into discrete observable chromosomes. The nucleolus is responsible for making the ribosomes. The pores are large holes that contain proteins that control the exit of substances (like RNA)

31
Q

mitochondria function

A

where aerobic respiration happens in eukaryotic cells. the outer membrane in highly folded into cristae (gives it a large surface area). The inside part is called the mitochondrial matrix (contains small circular strands of DNA). the inner membrane is studded with stalked particles, which are the site of ATP synthesis.

32
Q

Chloroplasts function

A

The thylakoid membrane contains chlorophyll and other photosynthetic pigments arranged in photosystems, together with stalked particles, and is the site of photosynthesis and ATP synthesis. They also contain starch grains, ribosomes and circular DNA.

33
Q

Vacuoles function

A

Involved in synthesising and transporting materials, mainly lipids and carbohydrates, needed by the cell.

34
Q

Rough ER function

A

The attached ribosomes synthesise proteins, which are processed here (e.g. by enzymatically modifying the polypeptide chain, or adding carbohydrates), before being exported from the cell via the Golgi Body.

35
Q

The Golgi apparatus function

A

It takes proteins from the RER to the cell membrane to take outside the cell. Parts of the RER contain proteins that can fuse with one side of the Golgi body membranes. However, the other side small vesicles bud off and move towards the cell membrane, where they fuse and release their contents by exocytosis (basically throwing out its contents outside the cell)

36
Q

exocytosis

A

simple taking contents out of a cell

37
Q

Lysosomes function

A

They are used to break down unwanted chemicals, toxins, organelles or even whole cells, so that the materials may be recycled. They can also fuse with a feeding vacuole to digest its contents.

38
Q

centrioles function

A

Before each division the centriole replicates itself and the two centrioles move to opposite ends of the cell, where they initiate the spindle that organises and separates the chromosomes. As part of the cytoskeleton, microtubules and their motor proteins are involved in maintaining cell shape, movement of vesicles and movement of chromosomes. the nuclear membrane disintegrates just before cell division takes place, and this is why the centrioles are outside the nucleus.

39
Q

Flagella and cilia function

A

This is a flexible tail present in some cells and used for motility. It is an extension of the cytoplasm, surrounded by the cell membrane, and is full of microtubules and motor proteins so is capable of complex swimming movements. Cilia may be either stationary or motile.

40
Q

Plasma membrane function

A

It separates the contents of the cell from the outside environment, and controls the entry and exit of materials. It also contains receptors for recognition of various chemicals e.g. hormones, antibodies.

41
Q

Cell wall function

A

Used to give a cell strength and rigidity. There are often channels through those belonging to plant cells called plasmodesmata, which link the cytoplasm of adjacent cells.
They prevent the cell from bursting and they allow turgidity.

42
Q

What is cellulose

A

A complicated carbohydrate

43
Q

Vacuoles

A

They contain cell sap. They are very important in the maintenance of turgor, so the cell contents stay pushed against the cell wall and keep it rigid. The membrane of the vacuole is called the tonoplast, which is selectively permeable.

44
Q

Chloroplasts- more information

A

They are responsible for photosynthesis. They have a fluid called stroma inside. They also have a network of membranes, which form flattened sacs called thylakoids. Many thykaloids stacked together is called a granum. The grana are joined together by membranes called lamellac. The grana contain the chlorophyll pigment.

45
Q

what is magnification

A

How many times larger the image is than the object being viewed

46
Q

What is resolution

A

The ability to see the individual structures as separate entities

47
Q

What does the resolution depend on

A

The diffraction of the light as is spreads through the sample. The structures are quite close together and the light reflected can overlap, causing a loss of data as it can’t be seen clearly

48
Q

How can you increase resolution

A

By using a electron beam rather than a light beam. This is because they have a wavelength that is 1000 times shorter. This allows it to focus more into a specific part.

49
Q

Eyepiece graticule

A

It is fitted into the eyepiece lens. It is just a line with 100 divisions on it. There are no units, you have to work out how much each division is in units by calibrating it, using a stage micrometer

50
Q

Disadvantages of electron microscope

A

Expensive
Big + bulky
Electron beam can lead to artefacts

51
Q

TEM

A

Transmission Electron Microscope

A beam of electrons is passed through the specimen

52
Q

SEM

A

Scanning Electron Microscope
A beam of electrons is sent across the surface of the specimen.
It can create 3D images.

53
Q

Sample prep for electron mic.

A

There needs to be a vacuum inside the microscope to focus the beam. The specimen must be fixed using chemicals or freezing, staining with heavy metals and dehydration with solvents.
TEM: set in resin and stained again
SEM: may be fractured and then coated with heavy metals on the inside

54
Q

Identifying artefacts

A

ex:
They found inside foldings and they thought it was part of the structure. However, it disappeared in specific conditions, making it an artefact

55
Q

LSCM

A

Laser Scanning Confocal Microscope
They use fluorescent lights, which has a higher light intensity.
There is a single spot of focused light which is sent from a laser. It reflected off of a dichroic mirror (a beamsplitter) Then it goes to the specimen. The emitted light from the specimen is filtered through a pinhole aperture. Light is reflected/ radiated on the focal plane.

56
Q

What is fluorescence

A

The absorption and re-radiation of light

57
Q

3D and 2D on LSCM

A

2D images are made when only 1 focal point is used, but when more than 1 is used, 3D images can be made.

58
Q

Dichroic mirror

A

This is used in LSCM. It reflected 1 wavelength (from the laser) and all others are allowed to just go through. The position of the 2 pinholes means the light from the laser follows the same path as the light radiated from the sample. This gives them the same focal point.

59
Q

advantages of light micrososcopes

A 
Quick
Easy to use
Small and portable 
Cells are alive 
Vacuum not required
60
Q

What is the resolution of light microscopes

A

200nm

61
Q

Resolution of TEM

A

0.5nm

62
Q

Magnification of TEM

A

500,000

63
Q

Resolution of SEM

A

3-10nm

64
Q

Steps in making a protein

A
  1. The nucleus is the site of where ribosomes are made (nucleolus).
  2. Some ribosomes will stay inside the nucleolus to make other proteins. Others will leave to go to the Rough ER, and will attach to the other membrane of the ER.
  3. The proteins are transported to the Golgi Body from the Rough ER by vesicles.
  4. At the Golgi Body, the proteins are processed, modified and packaged into other vesicles. Some proteins even have sugars added on to make glycoproteins.
  5. The vesicles will travel from the Golgi Body as they are ‘pinched’ off towards the plasma membrane.
  6. At the plasma membrane, the vesicles will fuse with the plasma membrane, and as they do so, undergo exocytosis, where the contents of the vesicles are thrown outside of the cell.
65
Q

What is the cytoskeleton

A

The cytoplasm has a network of protein threads running through it. This is called the cytoskeleton

66
Q

What does the cytoskeleton do

A

Supports the cell’s organelles (because everything stays in place because of it)
Allows organelles to move in the cell (such as the movement of chromosomes during mitosis)
Maintains the shape of the cell
Allows the cell to move around (the flagella)
Allows the cell to change shape (ex: cytokinesis)

67
Q

What are the 3 things the cytoskeleton is made up of

A

Microtubules
Microfilaments
Intermediate fibres

68
Q

Microtubules

A

Found in all eukaryotic cells, and are involved with mitosis, cell motility and maintenance of the cell. They are made up of strands of globular proteins, called Actin. They act as a track for transport for vesicles and organelles. They also make up spindle fibres and polymerise.

69
Q

Microfilaments

A

They are made up of 2 intertwined strands of globular proteins, called Actin. They act as a track for transport for vesicles and organelles. They also make up spindle fibres and polymerise. Fibres that can contract, made of actin and are responsible for cytokinesis.

70
Q

Intermediate fibres

A

Gives strength

They are made up of long fibres or polymers and subunits.

71
Q

how can you calibrate an eyepiece graticule

A

For each magnification:
find 2 lines that line up on the stage micrometer and the eyepiece graticule.
Then, the
distance on stage micrometer/ units on the eyepiece graticule
gives you what distance each eyepiece unit is worth.

72
Q

What is a stage micrometer

A

It is just a slide that you put in to measure the sample size. Usually, it is 1mm long. This means it is 1000 micrometers, and therefore as there are 100 divisions on it,each division is worth 10 micrometers.

AS level - Biology (12 decks)

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