Topic 2.1

Question 1

In order to investigate onion cells, a stained temporary mount was made. Suggest a food stain to use

Answer 1

Iodine solution or methylene blue

Question 2

Why do onion cells need to be stained

Answer 2

To observe the cells
Nuclei and cell walls absorb the stain more strongly
So they can be distinguished

Question 3

What is the advantage of making a temporary mount of cells

Answer 3

Temporary mounts are quick to prepare: the cells can be observed whilst alive

Question 4

A scientist wishes to study yeast cells using a light microscope. How should the slide be prepared

Answer 4

To create a temporary mount, yeast cells should be placed on a slide with a droplet of iodine solution to stain the organelles. A cover slip should be placed over the cell. Remove air bubbles

Question 5

Stains are used for a number of different purposes when preparing slide. Give 3 examples of how they can be used

Answer 5

-increases contrast, so different parts of a cell can be distinguished
- to observe the location of certain chemicals in the cell
- to differentiate between organisms that can be hard to tell apart

Question 6

Starch granule

Answer 6

Carbohydrates stored in amyloplasts (plastids specialised for storage). Plastids are unique to plants. Non photosynthetic plastids usually store materials.

Question 7

Chloroplast

Answer 7

Specialised plastids containing chlorophyll. They contain dense stacks of membrane (grana) within a colourless Stroma. They are the site of photosynthesis

Question 8

Cell wall

Answer 8

A semi-rigid structure outside the plasma membrane. It is composed of cellulose and supports the cell
Made of peptidoglycan

Question 9

Mitochondria

Answer 9

Ovoid (oval shape) structures bounded by a double membrane called the envelope. They are the cell energy transformers. Converting chemical energy into ATP. The inner membrane is folded to form cristae with matrix on the inside containing all the enzymes needed for respiration

Question 10

Cytoplasm

Answer 10

Contains dissolve structures, enzymes and the cell organelles and structures. The site of translation in the cell

Question 11

Plant cell- endoplastic reticulum

Answer 11

A network of tubes and flattened sacs, may be smooth or have attached ribosomes

Question 12

Nuclear membrane

Answer 12

A double layered structure with pores

Question 13

Ribosomes

Answer 13

Manufactures proteins (site of protein production), made of RNA and proteins. May be free in the cytoplasm or attached to endoplasmic reticulum

Question 14

Golgi apparatus

Answer 14

A series of flattened, disc-shaped sacs, stacked one on top of the other and connected with the ER. The Golgi stores, modifies and packages proteins. It tags proteins so that they go to their destination

Question 15

Nuclear pore

Answer 15

Allows communication between the nucleus and the rest of the cell

Question 16

Rough endoplasmic reticulum

Answer 16

Primary site of protein synthesis, a series of flattened sacs enclosed by a membrane with ribosomes on the surface, it folds and processes proteins made on ribosomes

Question 17

Smooth endoplasmic reticulum

Answer 17

A site for lipid and carbohydrate metabolism, including hormone synthesis, a system of membrane-bound sacs, it processes and produces lipids

Question 18

Lysosome

Answer 18

A vesicle containing digestive enzymes, bounded by a single membrane, contain transport enzymes that break down food and foreign matter

Question 19

Centrioles

Answer 19

Are associated with nuclear (cell) division. They are hollow cylinders composed of a ring of microtubules arranged at right angles to each other

Question 20

Plasmids

Answer 20

Small, circular DNA molecules that can reproduce independently. They can transfer from one cell to another and between species ( conjugation ) this property accounts for the transmission of antibiotic resistance between bacteria, plasmids are also used as vectors in genetic engineering.

Question 21

Fimbriae

Answer 21

Hairlike structures that are shorter, straighter and thinner than flagella, they are used for attachment

Question 22

Glycocalyx

Answer 22

Viscous gelatinous layer outside the cell wall
Composed of polysaccharide and or polypeptide, if it is attached to the wall it is called a capsule. Protects the bacteria from the hosts immune attacks

Question 23

Flagellum

Answer 23

Used for locomotion (movement), tail-like structure which rotates to move the cell

Question 24

Sample preparation- dry mount

Answer 24

Solid specimens are viewed whole or cut into very thin slices ( called sectioning) the specimen is placed on the centre of the slide and a cover slip is placed over the sample. Hair, pollen, dust and insect parts can be used

Question 25

Sampling preparation-wet mount

Answer 25

Specimens are suspended in a liquid such as water or an immersion oil. A cover slip is placed on from an angle. Aquatic samples and other living organisms can be viewed this way

Question 26

Sampling preparation-Squash slides

Answer 26

A wet mount is prepared, then a lens tissue is used to gentle press down the cover slip

Question 27

Sampling preparation-smear slides

Answer 27

The edge of the slide is used to smear the sample, creating a thin, even coating on another slide. A cover slip in placed over the sample-blood.

Question 28

Nucleus

Answer 28

Surrounded by a double membrane called the envelope containing pores which enable molecules to enter and leave the nucleus. The nucleus also contains chromatin and a nucleolus which is the site of ribosome production

Question 29

Golgi apparatus

Answer 29

A series of fluid filled, flattened and curved sacs with vesicles surrounding the edges, it processes and packages proteins and lipids, also produces lysosomes

Question 30

Cytoskeleton

Answer 30

Provides mechanical strength as well as aiding transport within cells and enabling cell movement

Question 31

Protein transport

Answer 31

1.Proteins are produced on ribosomes 2.proteins which are provided on the surface of RER are folded and processed in the RER 3. The proteins are transported from the RER to the Golgi apparatus in vesicles 4. They are modified in the Golgi apparatus 5. Golgi apparatus packages proteins into vesicles to be transported around cells to where they’re required 6. Some of the proteins such as extra cellular enzymes leave the cell by exocytosis

Question 32

Capsule

Answer 32

Protective slimy layer which helps retain moisture and adhere to surfaces

Question 33

Pili

Answer 33

Hair-like structures which attach to other bacterial cells

Question 34

Eyepiece graticule

Answer 34

Acts like a ruler, allowing structures to be measured under a microscope.

Question 35

stage graticule ( stage micrometer )

Answer 35

A microscope slide with an accurate measuring scale, used to calibrate the value of the eyepiece divisions at different magnifications

Question 36

What are the 5 steps to calibrate an eyepiece graticule

Answer 36

1. Set up microscope to the required magnification to view sample 2. Place a stage graticule on the stage 3. Line up the 2 scales (the stage and eyepiece graticules) 4. Count the number of divisions on the eyepiece graticule equivalent to each division on the stage micrometer 5. As the length equivalent to each division on the stage micrometer are known

Question 37

Why is staining used in microscopy

Answer 37

Provides contrast to distinguish between different structures in the sample

Question 38

What is differential staining

Answer 38

When multiple stains are used, and each stain binds to a specific cell structure, staining each cell differently so the structures can be easily identified

Question 39

Acetic orcein

Answer 39

Binds to DNA and stains chromosomes dark red

Question 40

Eosin

Answer 40

Stains the cytoplasm dark red or pink

Question 41

Iodine

Answer 41

Stains starch blue-black ( appears violet under microscope)

Question 42

Iodine in potassium iodide solution

Answer 42

Stains cellulose yellow

Question 43

Haematoxylin

Answer 43

Stains RNA/DNA a purple/blue colour

Question 44

Methylene blue

Answer 44

Is an all-purpose stain, often used to stain DNA blue

Question 45

What is a wet mount used for

Answer 45

Live specimens such as aquatic animals

Question 46

What is a dry mount used for

Answer 46

Specimens like hairs, parts of insects, pollen, parts of flowers

Question 47

Wet Mount technique

Answer 47

1. Use a pipette to put a drop of water on a slide 2. Use tweezers to place specimen in water 3. Put the cover slip on by standing the it upright on the slide, next to the water droplet 4. Carefully tilt it down onto specimen 5. Avoid air bubbles ( they obstruct view of image) 6. Add stain (making sure its not toxic to specimen)

Question 48

Dry mount technique

Answer 48

1.Slide specimen thinly so light can pass through 2.use tweezers to put on slide 3 place coverslip on top

Question 49

Using a light microscope

Answer 49

1. Clip slide onto stage 2. Select the lowest power objective lens 3. Use the coarse adjustment knob to move the objective lens into focus to just above the slide 4. Look down eyepiece and adjust focus, moving lens away from slide using the fine adjustment knob, until clear image appears 5. If higher magnification is needed, swap to a higher powered objective lens and refocus

Question 50

How do you measure the diameter of an irregularly shaped object

Answer 50

Measure the greatest distance from one side to another

Question 51

How should drawings be done; microscopy

Answer 51

-no shading -labelled -take up at-least half the page -label lines should be horizontal, drawn with a rule, exactly touch object, no arrowheads -drawing lines completely connected -a scale should be given (magnification) -drawn in pencil