Chapter 2

Question 1

DEFINE MAGNIFICATION

Answer 1

How much bigger an image is compared to the original object

Question 2

DEFINE RESOLUTION

Answer 2

Ability to distinguish between two points.

Question 3

DEFINE LIGHT MICROSCOPES

Answer 3

Rely on light and lenses to form an image.
Magnification: x1500
Resolution: 200nm (wavelength of light is large so lower resolution.)

Question 4

STATE 5 ADVANTAGES OF LIGHT MICROSCOPES

Answer 4

Easy to use
Cheap
Portable
Whole living organism studied 
Coloured 3D images

Question 5

STATE TWO DISADVANTAGE OF LIGHT MICROSOCOPES

Answer 5

Low magnification

Low resolution

Question 6

DEFINE LASER SCANNING MICROSCOPES

Answer 6

Use a light to scan an object point by point and assemble. Can focus on structures at different depths. Use a pinhole to get rid of any unfocused light.

Question 7

STATE FOUR ADVANTAGES OF LASER SCANNING MICROSCOPES

Answer 7

High resolution
High contrast.
Coloured images,
3D images

Question 8

STATE TWO DISADVANTAGES OF LASER SCANNING MICROSCOPES

Answer 8

Dead specimen

Expensive

Question 9

TRANSMISSION ELECTRON MICROSCOPES - Define

Answer 9

Uses a beam of electrons which pass through the specimen and are then detected to produce a specimen.
Magnification: x2000000
Resolution:

Question 10

STATE TWO ADVANTAGES OF TRANSMISSION ELECTRON MICROSCOPES

Answer 10

High magnification

High resolution

Question 11

STATE 4 DISADVANTAGES OF TRANSMISSION ELECTRON MICROSCOPES

Answer 11

Produces a 2D black and white image.

Requires cells to be dehydrated, so they are dead. Hard to prepare specimen. Expensive and large.

Question 12

DEFINE SCANNING ELECTRON MICROSCOPES

Answer 12

Electrons bounce of the surface of the specimen and are then detected.

Question 13

STATE ONE ADVANTAGE OF SCANNING ELECTRON MICROSCOPES

Answer 13

3D image produced

Question 14

STATE THREE DISADVANTAGES OF SCANNING ELECTRON MICROSCOPES

Answer 14

Dead specimen required.
Hard to prepare specimen.
Black and white image

Question 15

EXPLAIN THE USE OF STAINING. EXPLAIN WITH EXAMPLE POSITIVE AND NEGATIVE STAINS.

Answer 15

Used to increase contrast and visibility. Allows differentiation between organelles.
Positively charged dyes - crystal violet and methylene blue.
- These are attracted to negatively charged organelles.
Negatively charged dyes - nigrosine and Congo red.
- Repelled by negative charge so stay away, increasing contrast.

Question 16

EXPLAIN DIFFERENTIAL STAINING AND GIVE AN EXAMPLE

Answer 16

Can distinguish between two types of organelles.

• Sudan red stains lipids.
• Iodine stains starch granules blue/black.

Question 17

EXPLAIN HOW A SLIDE IS PREPARED FOR VIEWING.

Answer 17

Before viewing slides must be prepared. They are dehydrated, waxed then very thinly sliced. The thin slices are stained and then mounted.

Question 18

WHAT IS A GRATICULE IS AND HOW IT USED TO CALIBRATE A MICROSCOPE?

Answer 18

Graticules must be used, it is a mini ruler fixed to the eyepiece. As the specimen is viewed the ruler is imposed on to the specimen so measurements can be take. This must be calibrated with a ruler on the stage as the graticule is arbitrary. The eyepiece has to be calibrated for each objective lens.
To calibrate just align the graticules together, if the top one measures 10cm and aligns with the number 4, then for every 4 arbiter units, 10 cm is measured.

Question 19

DEFINE NUCLEUS

Answer 19

Surrounded by nuclear envelope which has pores by which RNA can leave and hormones can enter etc.
Contains DNA in the form of chromatin which is loose and spread out

Question 20

DEFINE NUCLEOLUS

Answer 20

Contains RNA which provides instructions for protein synthesis.
Is within the nucleus but has no membrane

Question 21

DEFINE CYTOPLASM

Answer 21

Jelly like
Where all organelles are suspended
Where chemical reactions occur

Question 22

DEFINE CYTOSKELETON

Answer 22

Network of protein filaments; actin and microtubules.
Allows organelles to move
Allows contraction of muscle cells.

Question 23

DEFINE MITOCHONDRIA

Answer 23

Very small. Have two membranes, inner membrane folded into cristae. It is filled with matrix. Power house of the cell, produces ATP by aerobic respiration

Question 24

DEFINE GOLGI APPARATUS

Answer 24

A stack of membrane bound flattened sacks. Have secretary vesicles which bring materials to and from the golgi apparatus. Folds, modifies and packages proteins

Question 25

DEFINE ROUGH ENDOPLASMIC RETICULUM

Answer 25

This is a system of membranes containing fluid filled cavities (cisternae). They are coated with ribosomes. The cisternae from channels for transporting substances form one area of the cell to another.

Question 26

DEFINE SMOOTH ENDOPLASMIC RETICULUM

Answer 26

A system of membranes, containing fluid filled cavities (cisternae). No ribosomes on its surface. Contain enzymes that catalyse reaction involved with lipid metabolism. Involved with absorption, synthesis and transport of lipids.

Question 27

DEFINE VESICLES

Answer 27

For transport

Question 28

DEFINE CHLOROPLASTS

Answer 28

Surrounded by a double membranes. Inner membrane has stacks called thylakoids. Each stack is called a granum. Fluid filled matrix is called stroma. Contain loops of DNA and starch grains. These are the site of photosynthesis. Light energy s trapped and used to make ATP. Water is also split to supply H+ ions (occurs in grana). Then the H- ions reduce CO2 with ATP making carbohydrates (this occurs in the stroma).

Question 29

DEFINE VACUOLE

Answer 29

Surrounded by a membrane called the tonoplast. Filled with water and solutes to maintain stability by remaining turgidity,

Question 30

DEFINE LYSOSOMES

Answer 30

Small bags formed by golgi apparatus. Contain hydrolytic enzymes. Can ingest and digest invading pathogens. Lysosomes keep the powerful digestive enzyme separate from the cell. They can engulf organelles and foreign matter and return waste to the cell.

Question 31

DEFINE CILIA

Answer 31

Protrusions from the cell. Has microtubules. Formed from centrioles.

Question 32

DEFINE RIBOSOMES

Answer 32

Small. Made of ribosomal RNA. Synthesise proteins to be exported out the cell.

Question 33

DEFINE CENTRIOLES

Answer 33

Consists of two bundles of microtubules at right angles. They are made of tubulin and arranged into cylinders. They pull chromosomes apart during cell division. They are also involved in formation of the cilia.

Question 34

DEFINE CYTOSKELETON

Answer 34

Network of protein structures. Rod like filaments made of actin. Gives support and mechanical strength. They form tracks for movement of substances. Form spindle before cell division. Also make up cilia.

Question 35

WHAT IS A CELLULOSE CELL WALL?

Answer 35

Made of bundles of cellulose fibres. Only in plants. Provides strength and support. Permeable.

Question 36

DESCRIBE THE 8 STEPS OF PHOTOSYNTHESIS

Answer 36

1. The gene that has the coded instruction for a protein is housed on chromatin in the nucleus. 2. It is transcribed into a length of RNA called mRNA. 3. Many copies of mRNA are made and they pass out the nucleu pores to the ribosomes. 4. At the ribosomes, the instruction is translated and the protein assembled for example insulin. 5. Insulin will then pass into cisternae of the RER. 6. Vesicles with insulin inside pinch of and pass via microtubules to the golgi. 7. Vesicle fuses with golgi where insulin molecule may be modified for released. 8. Vesicles pinch of and move to surface membrane. Insulin released.

Question 37

STATE AT LEAST 4 SIMILARITIES AND DIFFERENCES BETWEEN PROKARYOTIC CELLS AND EUAKRYOTIC CELLS

Answer 37

``` SIMILARITIES Have a plasma membrane Cytoplasm Ribosomes DNA and RNA ``` ``` DIFFERENCES Much smaller Less well developed cytoplasm with no centrioles No membrane bound organelles like mitochondria, golgi, ER etc. No nucleus Cell wall made of peptidoglycan Have smaller ribosomes Naked DNA Flagella ```

Question 38

HOW DO PROKARYOTES DIVIDE? EXPLAIN.

Answer 38

Prokaryotic cells divide by binary fission. This is because they do not have linear DNA that can divide by mitosis. The DNA is replicated exactly so that each daughter cell receives the same long strand of DNA and any smaller plasmids. They do not have any membrane bound organelles, simply too small.