chaoter 2 - microscopes

Question 1

how does the stain, crystal violet or methylene blue work

Answer 1

they are positively charged which attracts to negatively charged materials in cytoplasm leading to staining

Question 2

how do nigrosin or congo red stains work

Answer 2

they are negatively charged so are repelled by negatively charged cytosol so dye stays outside of cells , leaving cell unstained against stained background

Question 3

what is differential staining

Answer 3

distingushing 2 types of organisms by staining

Question 4

what is gram stam technique

Answer 4

seperates bacteria in 2 groups by applying crystal violet and iodine. This is washed with alcohol and gram-positive bacteria is retained
gram-negative is restained with counterstain ( safranin) which appears red

Question 5

what is acid fast technique

Answer 5

differentiate species of mycobacterium from other bacteria. Lipid solvent carries carbolfushcin dye into cell and washed with alcohol but only mycbacterium retained dye

Question 6

what is magnification

Answer 6

how many times larger the image is than the actual size of the object being viewed

Question 7

what is resolution

Answer 7

the ability to see individual objects as seperate entities

Question 8

what limits resolution

Answer 8

diffraction of light

Question 9

magnification formula

Answer 9

size of image/ actual size of object

Question 10

what is a transmission electron microscope

Answer 10

a beam of electrons transmitted through specimen and focused to produce image. This has best resolution. 0.5 nm

Question 11

what is scanning electron microscope

Answer 11

beam of electrons sent across surface of specimen and reflected electrons are collected. 3-10nm. 3D images produced

Question 12

what are the difference between light and electron microscope

Answer 12

light:
-inexpensive
-small
-simple sample prep
- vacuum not required
- colour seen
- 2000x magnification
-200nm
-specimen can be alive

electron:
-expensive
-large
-needs vacuum
- black and white image
- 200 000 x magnification
- 0.5nm
-specimens are dead

Question 13

what is artefact

Answer 13

visible structural detail caused by processing the specimen and not feature of specimne

Question 14

what is fluorescene

Answer 14

absorption and re-radiation of light for longer wavelength and lower energy to produce magnified image

Question 15

what is a laser scanning confocal microscope

Answer 15

moves a single spot of focused light across a specimen causing fluorescence.
very high resolution
specimen must be thin

Question 16

what is the function of nucleus

Answer 16

codes genetic information in the form of DNA molecules
DNA is contained within nuclear envelope to prevent damage from cytoplasm
nuclear envelope has nuclear pores

Question 17

what is the function of nucleolus

Answer 17

nucleolus is an area within nucleus responsible for producing ribosome. Composed of proteins and RNA

Question 18

what is the function of mitochondria

Answer 18

produces ATP
has double membrane. inner membrane folds to form crista and fluid interior is matrix
inner membrane has enzymes for aerobic respiration
mitochondria contained mDNA to create own enzymes

Question 19

what are the function of vesicles and lysosomes

Answer 19

vesicles are membranous sacs for storage and transport roles
lysosomes are specialised vesicles that contain hydrolytic enzymes to break down waste material, break down pathogens ingested by phagocytic cells and in apoptosis

Question 20

what is the function of cytoskeleton

Answer 20

controls movement of cell and organelles in cell

Question 21

what are the 3 components of cytoskeleton

Answer 21

microfilament - contractile fibres formed from actin responsible for cell movment
microtubules - globular tubulin proteins form tubes that act as tracks for movement of vesicles. Forms spindles
intermediate fibres - give mechanical strength to cells and help maintain integrity

Question 22

what is the function of centrioles

Answer 22

component of cytoskeleton composed of microtubules
2 centrioles form centrosome

Question 23

wha is thefunction of flagella and cilia

Answer 23

flagella enable cells motility and detects chemical change
cilia beat in a rhythmitic manner creating a current cos fluids or objects such as mucus moves

Question 24

what is ER

Answer 24

network of membranes enclosing flattened sacs called cisternae

Question 25

what is function of SER

Answer 25

responsible for lipid and carbohydrate synthesis and storage

Question 26

what is the function of RER

Answer 26

has ribosomes bound to surface for synthesis and transport of proteins

Question 27

what is function of golgi apparatus

Answer 27

made of cristernae and does not have ribosomes. Modifies and packages vesicles

Question 28

how are proteins formed

Answer 28

proteins synthesises on ribosomes of RER. These pass on to cristernae and are packaged to transport vesicles. Vesicles are moved towards by cytoskeleton to golgi apparatus where it is packaged and modified and secretory vesicles then leave golgi and fuse with cell surface membrane releasing contents by exocystosis

Question 29

what are vacuoles

Answer 29

membrane lined sacs in the cytoplasm containing cell sap. This is called tonoplast. Selectively permeable and permanent

Question 30

what are chloroplasts

Answer 30

responsible for photosythesis. Double membrane structure with fluid enclosed called stroma. Internal network of membranes which form flattened sacs called thylakoids which stack to form granum
Grana are joined by lamellae containing chloropyll pigmenets. Contain own DNA and ribosomes

Question 31

what is the difference between 70s and 80s ribosomes

Answer 31

80s are more bigger and form more complex proteins

Question 32

what is difference between cell wall in prokaryotes and plants

Answer 32

cell wall made from peptidoglycan and plant cell wall made of cellulose

Question 33

what is difference between flagella in prokaryotes and eukaryotes

Answer 33

flagella of prokaryotes is thinner and uses energy from chemiosmosis and not ATP