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Bio1MGC > Bacteria > Flashcards

Bacteria Flashcards

1
Q

what feature surrounds a prokaryotic cell

A

nearly all prokaryotes have a cell wall

most prokaryotes - cell wall surrounded by a sticky layer of polysaccharides called the capsule or slime layer

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2
Q

what are the functions of a cell wall in prokaryotic cells

A

maintains shape
prevents it from bursting in a hypotonic environment
(in a hypotonic environment plasmolyse)

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3
Q

how are the cell walls of bacterial cells different from those of eukaryotes that have cell walls (plants and fungi)

A

prokaryotic cell walls are made of peptidoglycan (sugars and polypeptides)
eukaryotic cells made of cellulose or chitin

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4
Q

what are the cell walls of archaea made from

A

polysaccharides and proteins but lack peptidoglycan

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5
Q

what is a gram stain

A

enables biologists to categorise bacteria by the composition of the cell wall
Gram positive bacteria have simple cell walls composed of a thick layer of peptidoglycan on top of the plasma membrane
Gram negative bacteria have wall that have less peptidoglycan and include lipopolysaccharides
peptidoglycan layer between two plasma membranes

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6
Q

why is gram staining important

A

in medicine enables doctors to match medications to the cell wall structure

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7
Q

capsule

A
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8
Q

capsule

A

sticky layer of polysaccharides or protein surrounds the cell wall of many prokaryotes

enable prokaryotes to adhere to their substrate or to other individuals in a colony

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9
Q

what surrounds the cell wall of many prokaryotes

A

Glycocalyx - outer coating consisting of capsule or slime layer
surrounded by a sticky layer of polysaccharides or protein called the capsule if it is dense and well defined or the slime layer of it is less well organised.
Enables prokaryotes to stick to substrate or each other

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10
Q

what is the function of the capsule or slime layer that surrounds the cell wall of many prokaryotes

A

allows it to stick to substrate or each other
some protect against dehydration
some shield pathogenic prokaryotes from attacks by their host’s immune system

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11
Q

endospore

A

in harsh conditions bacteria develop an endospore - produce a copy of their DNA and surround it with a multilayered structure called an endospore
water is removed and metabolism halts
cell lyses and releases the endospore - remain dormant
e.g. anthrax

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12
Q

fimbriae

A

hairlike appendages that enable some prokaryotes to stick to their substrate or each other

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13
Q

pilli

A

appendages that pull two cells together prior to DNA transfer from one cell to another

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14
Q

taxis in prokaryotes

A

movement in prokaryotes - directed towards or away from stimulus
e.g. chemotaxis - change in movement pattern in response to chemicals

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15
Q

how do more prokaryotes move?

A

flagella - may be scattered all over or at one or both ends

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16
Q

the flagella of prokaryotes and eukaryotes are considered examples of analogous evolution. Why?

A

while they look and behave similarly they are composed of different and unrelated proteins and are structurally different
analogous - perform similar functions but not related by common descent

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17
Q

how is the genome of a prokaryote different to that of a eukaryote

A

prokaryote has less DNA
prokaryotes have circular chromosomes whereas eukaryotes have linear chromosomes
prokaryote chromosomes have many fewer proteins than in the chromosomes of eukaryotes
prokaryotes lack a nucleus - chromosome is located in a nucleoid

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18
Q

nucleoid

A

prokaryotes lack a nucleus

chromosome is located in a nucleoid - a region of the cytoplasm that is not enclosed in a membrane

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19
Q

plasmids

A

in prokaryotic cells - small rings of independently replicating DNA molecules carrying only a few genes

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20
Q

how are prokaryotic ribosomes different to those in eukaryotes

A

prokaryotic ribosomes are slightly smaller than eukaryotic ribosomes
prokaryotic ribosomes differ in their protein and RNA content

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21
Q

how do prokaryotes reproduce

A

binary fission
asexually
offspring are genetically identical

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22
Q

what adaptations enable prokaryotes to survive in harsh conditions

A

capsule
ability to form endospores

biochemical adaptations e.g. enable them to survive in hot or salty environments

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23
Q

while they have no membrane bound organelles some prokaryotes have membranes. Describe

A

some prokaryotes have specialised membranes that perform metabolic functions - usually infoldings of the plasma membrane
cyanbacteria have thylakoid membranes much like those in chloroplasts
some prokaryotes have small compartments

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24
Q

do prokaryotes have a plasma membrane

A

a plasma membrane encloses the cytoplasm

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25
Q

structure of a prokaryotic cell

A 
nucleioid - region for DNA
ribosomes - protein synthesis
plasma membrane
cell wall
glycocalyx - capsule or slime layer
flagella
fimbriae
26
Q

Prokaryotes exhibit extensive genetic variation. How does variation occur in prokaryotic cells

A

rapid reproduction and short generation times and therefore a greater probability of mutation
genetic recombination

27
Q

what is genetic recombination

A

the combining of DNA from two sources
three mechanisms - transformation, transduction, conjugation bring together prokaryotic DNA from different individuals
when those individuals are from different species this is called horizontal gene transfer

28
Q

transformation

A

genotype of a prokaryotic cell altered by the uptake of foreign DNA from its surroundings e.g. harmless bacteria becomes pathogenic when exposed to a pathogenic bacteria
many bacteria have cell surface proteins that recognise DNA from closely related species and transport it into the cell
once inside the cell the foreign DNA can be incorporated into the genome by homologous DNA exchange

29
Q

transduction

A

phages (viruses that infect bacteria) carry genes from one host cell to another

30
Q

conjugation

A

DNA is transferred between two prokaryotic cells (usually the same species) that are temporarily joined.
in bacteria DNA transfer is always one way - one cell donates and the other receives e.g. e coli
pilli pull together - formation of a mating bridge
reliant on F factor (fertility) in genome
F factor can exist as a plasmid or segment of DNA

31
Q

R plasmids

A

plasmids (small pieces of DNA in the cytoplasm) carry antibiotic resistant genes
problem is compounded by the fact that many R plasmids have genes that encode for pili and enable DNA transfer by conjugation
some R plasmids carry genes for resistance to as manu as 10 antibiotics

32
Q

phototrophs

A

organisms that obtain energy from light

33
Q

chemotrophs

A

obtain energy from chemicals

34
Q

autotrophs

A

need only carbon dioxide or related compounds as a carbon source

35
Q

heterotrophs

A

require at lease one organic unit such a glucose to make organic compounds

36
Q

photoautotroph

A

use light as an energy source
use carbon dioxide as a carbon source
photosynthetic organisms - photosynthetic prokaryotes e.g. cyanobacteria / plants / some protists

37
Q

chemoautotroph

A

energy source - inorganic chemicals
carbon source - carbons dioxide or related
e.g. certain prokaryotes

38
Q

photoheterotroph

A

energy source - light
carbon source - organic compounds
example - certain aquatic and salt loving prokaryotes

39
Q

chemoheterotroph

A

energy source - organic compounds
carbon source - organic compounds
e.g. many prokaryotes, protists, animals, fungi, some plants

40
Q

obligate aerobes

A

must use oxygen for cellular respiration and cannot grow without it

41
Q

obligate anaerobes

A

poisoned by oxygen
use anaerobic respiration - substances other than oxygen drive electron transport chains in cellular respiration (nitrate ions or sulphate ions)
may use fermentation

42
Q

facultative anaerobes

A

in cellular respiration - use oxygen if available but can also carry out fermentation in an anaerobic environment

43
Q

how many prokaryotic species are there

A

10,600 have been named

44
Q

how many prokaryotes in a handful of soil

A

book says - 10,000 prokaryotic species

lecture - 100 million and a billion in a teaspoon of soil

45
Q

major groups of bacteria

A 
proteobacteria
chlamydias
spirochetes
cyanobacteria
gram positive bacteria
46
Q

proteobacteria

A

five groups - alpha, beta, gamma, delta, epsilon

47
Q

there are differences between gene expression in bacteria and archaea/ eukaryotes (who are similar)

A

bacteria - only one RNA polymerase
initiator amino acid for protein synthesis is formyl methionine (A and Es have methionine)
no introns in genes
no histones associated with genes

48
Q

extremophiles

A

archaea - lovers of extreme conditions

49
Q

extreme halophiles

A

archaea that live in highly saline environments

50
Q

extreme thermophiles

A

archaea that thrive in very hot environments

e.g. sulfolobus

51
Q

methanogens

A

archaea
anaerobes - poisoned by oxygen
use carbon dioxide to oxidise hydrogen - produces energy and methane (marsh gas)
decomposers / live in gut of cattle, termites, herbivores

52
Q

CRISPR-Cas system

A

helps bacteria and archaea defend against attack by viruses
has been developed into a tool for altering genes in any organisms
Cas proteins can cut DNA

53
Q

how is the cell wall of archaea different from bacterial

A

bacteria - unbranched hydrocarbons

archaea - some branched hydrocarbons / no peptidoglycan present

54
Q

thermoacidophiles

A

archaea that survive in extreme acidity and temperature

55
Q

endosymbiosis

A

eukaryotic cells originated by endosymbiosis when a prokaryotic cell engulfed a small cell that would evolve into the mitochondrion

56
Q

serial endosymbiosis hypothesis

A

ancestral prokaryote - bacteria - developed infoldings of plasma membranes that developed into a nucleus and ER
Engulfed an aerobic bacterium - the bacterium became the mitochondria
Secondary symbiosis - engulfed a photosynthetic bacterium to form plastids

57
Q

evidence for endosymbiosis

A

inner membranes of mitochondrion and plastids is homologous to inner membranes of bacteria
mitochondria and plastids replicate by a process like binary fission
mitochondria and plastids have circular DNA / no histones
mitochondria and plastids have ribosomes / these ribosomes are more similar to bacterial ribosomes than to the cytoplasmic ribosomes of eukaryotic cells

58
Q

protists

A

very small eukaryotes just 0.5 - 2 um in diameter
eukaryotes that are not plants, animals or fungi
most protists are unicellular
most common of eukaryotes

59
Q

why was the kingdom of protista abandoned

A

genetic studies revealed that some protists are most closely related to plants, fungi or animals than to other protists
most biologists

60
Q

what are the three domains of life

A

eukaryotes, bacteria and archaea

61
Q

what types of eukaryotes are there

A

animals plants fungi protists

62
Q

how are eukaryotes different from prokaryotes

A

nucleus and other membrane bound organelles

cytoskeleton - prokaryotic cells lack a well developed cytoskeleton

Bio1MGC (11 decks)

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