B1.1

Question 1

Two type of cells?

Answer 1

Eukaryotic- these are animal and plant cells.

• They contain genetic material in NUCLEUS,
• complex and large.
• Sizes is 10 micr(uM) to 100 micrometers.

Prokaryotic cells are bacterial cells.

• They are simple and small,
• generic material FLOATS IN CYTOPLASM.
• Sizes are 1 to 10 uM.

Question 2

What sub cellular structure do eukaryotic cells in animal contain?

Answer 2

NUCLEUS:
- where genetic informational is held in form of chromosomes, controls CELLS ACTIVITIES

CYTOPLASM:
- where all chemical reactions take place, gel like

MITOCHONDRIA

• where respiration takes place
• contains enzymes that convert glucose and oxygen to carbon dioxide water and ATP

CELL MEMBRANE

• holds cell together
• selective- allows certain substances to come in and out
• contains receptor molecules that are used for COMMUNICATION, like by hormones

Question 3

What sub cellular structure in plant?

Answer 3

Cell wall:
- rigid cell wall made of cellulose, supports the cell

Vacuole:
Substance made of mixtures of salts and sugar, makes cell rigid and upright

Chloroplasts:
where photosynthesis takes place. Contains green pigment chlorophyll which transfers energy by the sun from light.

Question 4

What sub cellular in prokaryotes?

Answer 4

• Cell wall that make it rigid and protects, cell membrane, cytoplasm
• genetic material floats in the cytoplasm

Extra : plasmids, pili, slime capsule, flagella

Flagella:
- tail like structure that propels cell through liquid

Question 5

Plasmid?

Answer 5

Plasmid:
- A circular liked small loop of extra DNA that aren’t part of the chromosomal dna. This contains genes for drug resistance and can be easily passed BETWEEN cells.

Question 6

Pili?

Answer 6

Pili:
- hair like structures that allow cells to attract to surfaces, such as in digestive tract. Also allows for transfer of GENETIC MATERIAL between cells

Question 7

Slime capsule?

Answer 7

Slime capsule
- outside cell wall to protect bacteria from DRYING OUT and from POISONOUS SUBSTANCES. Helps it to stick to smooth surfaces.

Question 8

How does light microscope work?

Answer 8

It passes light through an object placed on a slide on the TSAGE, then through the OBJECTIVE lens and finally eye piece lens, which magnified it.

Question 9

How to prepare a sample for light microscope:

Answer 9

1) thin slice of specimen ( like onion ) or light won’t pass through it.
2) Put it on the SLIP, and use a pipette to add a drop of mounting in the middle to hold it in place.
3) Add a drop of STAIN if needed.
4) Finally add cover slip using mounted needle. Press on it to remove air bubbles. Now ready.

Question 10

How to view microscope:

Answer 10

1) First move the stage to the lowest position it can go to.
2) select the lowest objective lens. (This to make sure it doesn’t crush when you raise it)
3) add the specimen on to the stage- make sure to use the CLIPS
4) Turn the COARSE focus until you see your object, it will be blurred
5) use the FINE focus knob until you see your object clearly
6) repeat with a higher objective lens for greater detail

Question 11

Staining cells

Answer 11

Stain cells because most of them are COLOURLESS and staining them allows us to highlight specific sub cellular structures

Methylene blue: NUCLEUS of animal cell
Iodine solution: NUCLEUS of plant cell
Crystal violet : BACTERIAL CELL WALLS

Question 12

RESOLUTION of a microscope

Answer 12

The smallest distance between two points that can be seen as separate entities.

Question 13

Transmission electron microscope work?

Answer 13

They produce the most magnified image.

They work by passing a beam of electrons through a thin slice of a specimen, and the beam creates an image

Question 14

Scanning electron microscope work?

Answer 14

These create 3D images of a surface.

Send beam of electrons ACROSS the surface of a specimen, and the reflected electrons produce an image.

Question 15

Light vs electron advantage /disadvantage

Answer 15

Light:

• cheap to buy and operate
• portable, small
• easy to operate and PREPARE a sample
• specimens can be dead or alive
• Natural COLOUR of specimen used (unless a stain is used)
• However resolution max is 2 X 10-7 m (0.2Um micrometers)

Electron

• very expensive to buy and operate
• not portable and big
• complex to operate and sample is difficult to PREPARE
• colour is black and white, however false colour can be added
• specimens MUST be dead
• resolution better and 3D with SEM can be produced. Resolution mad is 1 x10-10 (1 nanometer)

Question 16

Equation for total magnification and just magnification

Answer 16

1) eyepiece magnification x objective lens magnification
Eyepiece is typically 10

2) magnification = image size / real size (like a ratio easy)

Question 17

Microscopes summary

Answer 17

Light is max 2x 10-7 resolution, but specimens can be alive, which is good for analysing things like mitosis. Scanning second highest resolution, and produced 3D images. Transmission works same way like light, passing electrons through the specimen, and has highest resolution of 1 x 10-10 m, however specimen must be dead…

Question 18

Cells summary and comparison

All cells
Plant and bacteria 
Animal and plant 
Plant only
Bacteria only

Answer 18

All cells have a: cell membrane, genetic material, cytoplasm
Plant cells and bacteria cells have cell walls
Animal and plant both have mitochondria for respiration
Plant cells only have chloroplasts and vacuoles
Bacterial cells only have genetic material in the cytoplasm, pili, slime capsule and plasmids . (Flagellum can be found in animal too…)