2.1 Cell Structure

Question 1

Adv and Disadv of light microscopes

Answer 1

About :
- Impossible to resolve between 2 objects closer than half the wavelength of light (500-650nm)

-Adv :
- Small and easy to carry
- Cheap
- Easy sample preparation
- Easy to use
- Specimens can be alive or dead eukaryotic cells
- No vacuum needed
- Colour image

Disadv :
- Max resolution 200nm
- Max magnification 1500
- Cannot observe ribosomes, lysosomes or endoplasmic reticulum

Question 2

Adv and Disadv of Transmission Electron Microscopes. How do they work?

Answer 2

Focus beam of electrons through specimen. denser parts absorb more electrons so appear darker on final image. Produces contrast between different parts of specimen.

Adv :
- High resolution
- Internal structures within cells can be seen
- High magnification

Disadv :
- Only thin specimens
- Cannot observe live specimens
- Vacuum needed
- Water must be removed from specimen
- Artefacts may be introduced due to lengthy preparation of specimens
- Not a colour image

Question 3

Adv and Disadv of scanning electron microscopes. How do they work?

Answer 3

Scan beam of electrons over specimen. Electrons bounce of surface and detected to form an image

Adv :
- 3D external structures of specimen can be observed
- Thick or 3D specimens used

Disadv :
- Lower resolution than TEMs
- Cannot observe live specimens
- No colour

Question 4

What are laser scanning confocal microscopes? Advantages and Disadvantages?

Answer 4

Cells stained with fluorescent dyes
Thick section of tissue scanned with laser beam
Reflected by dye
Multiple depths of tissue scanned to produce image
Adv :
- Thick or 3D (external) specimens
- External and internal structures observed
- High resolution
- Cytoskeleton can be observed
- High magnification

Disadv :
- Slow process
- Laser can cause photodamage
- Vacuum needed
- Length treatment process of sample
- Dead specimen

Question 5

What are Microtubules

Answer 5

• Eukaryotic
• Cytoskeleton
• Made of α and β tubulin combined to form dimers, the dimers are then joined into protofilaments
• 13 protofilaments in a cylinder make a microtubule
• Cytoskeleton provides support and movement of cell

Question 6

Process of protein synthesis

Answer 6

• DNA from nucleus copied to molecule of mRNA via transcription
• mRNA strand leaves nucleus via nuclear pore
• Attaches to ribosome on RER
• Ribosome reads genetic instructions and synthesises a protein via translation
• Protein passes into lumen of RER and is folded and processes
• Processed proteins transported to golgi apparatus via vesicles
• Golgi apparatus modifies protein
• Leaves golgi apparatus via vesicle
• Vesicle fuses with cell surface membrane and releases protein by exocytosis

Question 7

What are microfilaments?

Answer 7

Solid strands
Made from actin
Cause cell movement and movement of organelles

Question 8

What are microtubules?

Answer 8

Tubular hollow strands
Made of tubulin
Organelles move along these fibres using ATP to drive movement

Question 9

Function of cytoskeleton

Answer 9

Strengthening and supporting cell
Intracellular movement
Cellular movement

Question 10

How does the cytoskeleton provide strength and support?

Answer 10

Mechanical strength
Via scaffolding maintaining shape of cell
Supports organelles keeping them in position

Question 11

How does the cytoskeleton provide intracellular movement?

Answer 11

Forms ‘tracks’ along which organelles can move
Movement of vesicles
Chromosomes to opposite ends in cell division

Question 12

How does the cytoskeleton provide cellular movement?

Answer 12

Cilia and Flagella
Hair like extensions containing microtubules responsible for moving them

Question 13

Structures unique to prokaryotic cells

Answer 13

Question 14

Comparison of prokaryotic and eukaryotic cells

Answer 14