microbiology - microorganisms

Question 1

definition of microorganisms

Answer 1

small
usually free living unicells or cluster

fungi, algae, protozoa, bacteria, archaea

Question 2

common features of cells

Answer 2

basic unit of all living organisms

cell envelope
nucleic acids
ribosomes
cytoplasm

prokaryotic and eukaryotic

Question 3

importance of cell membranes

Answer 3

barrier between cell and environment
structural component of cell
site of crucial biochemical reactions

Question 4

lipid bilayer

Answer 4

hydrophobic fatty acids linked by ester bonds
hydrophilic heads
lines up in bilayer

also contains lipid components
sterols and hopanoids

Question 5

cell membrane in archaea

Answer 5

hydrophobic fatty acids ether linked to hydrophilic head (glycerol)

ether linkages more chemically stable than ester
can resist extreme conditions eg temperatures

fatty acids often branched
called isoprenoids

monolayer - cyclic tetra ether lipids can join tail to tail and form a monolayer

Question 6

cell walls

Answer 6

often constructed from polysaccharides

cellulose (glucose) - plants, algae and some fungi
chitin - fungi
mannans and xylans - fungi and plants

Question 7

bacterial cells walls

Answer 7

peptidoglycan
- polysaccharide chains cross linked by peptides

Question 8

cell wall in archaea

Answer 8

pseudopeptidoglycan

different peptide cross links between disaccharides

some cell walls made of glycoprotein, protein and polysaccharides
- forms s-layer
- hexagonal array of proteins or glycoproteins

Question 9

gram stain

Answer 9

cell wall structure basis for differentiation of 2 groupings of bacteria
based on staining procedure

cells stained with dye, binds to cell
stained cells treated with alcohol
extracts dye from negative cells
sample stained again
stains extracted cells - negative

Question 10

results of gram stain

Answer 10

purple = gram positive
pink = gram negative

Question 11

gram positive cells

Answer 11

purple stain

cell membrane
thick peptidoglycan layer
dye binds tightly

Question 12

gram negative cells

Answer 12

pink stain

thin peptidoglycan layer
dye doesn’t bind as well
most have second outer membrane
lipopolysaccharide

Question 13

lipid A

Answer 13

found in outer membrane
anchor for polysaccharides on gram negative cells

overall structure known as lipopolysaccharide

used in immunological testing
different pathogens have different sugar chains on outside

Question 14

nucleic acids

Answer 14

DNA
RNA - r,m,t,si

Question 15

nucleotide structure

Answer 15

phosphate
5 carbon sugar - ribose or deoxyribose

RNA has hydroxyl at 2
DNA has hydrogen at 2

organic bases
- purines or pyrimidines

Question 16

joining of nucleotides

Answer 16

phosphates attach to carbon 5 of sugar

hydroxyl group on carbon 3 forms ester bonds with phosphate group
= sugar phosphate chain

3 hydrogen bonds - CG
2 hydrogen bonds - AT
- those with more CT pairs are stronger and more temperature resistant

Question 17

difference between nucleotide and nucleoside

Answer 17

side = sugar and base
tide = sugar, base and phosphate

Question 18

pyrimidines

Answer 18

single ring structure

cytosine
thymine
uracil

Question 19

purines

Answer 19

twin ring structure

adenine
guanine

Question 20

NAD(P)

Answer 20

nictinamide adenine dinucleotide

oxidant in biochemical reactions
reduced form NADH used in energy metabolism

NADPH used in photosynthesis

Question 21

ribosomes

Answer 21

in all cellular forms of life
large and small subunits

prokaryotes - 70s
eukaryotes - 80s

control protein synthesis and translation
also found on RER

Question 22

prokaryotic cell structures

Answer 22

pili and fimbriae
gas vesicles
heterocysts
capsule
endospores
sheath

Question 23

pili and fimbriae

Answer 23

protein made of pilin
binding and attach cell surfaces
eg proteins on cell surfaces
transferal of genetic material

Question 24

gas vesicles

Answer 24

hold gases in aquatic cells
alter boyency to position for optimum conditions for photosynthesis
different wavelength reach different depths

Question 25

heterocysts

Answer 25

only in some photosynthetic bacteria fixation of nitrogen gas

Question 26

capsule

Answer 26

extracellular polysaccharide capsule pathogens make them to protect from digestion by phagocytes physical barrier to protect cells from environment

Question 27

endospores

Answer 27

produced by bacteria in extreme conditions very heat resistant contain cells DNA used for dispersal in fungi produce endospores in response to extreme conditions germinate and produce new cell when conditions return to favourable

Question 28

sheath

Answer 28

outside cell wall provides physical barrier to protect cell from iron oxides coating cell wall