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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
structure of a prokaryotic cell
``` nucleioid - region for DNA ribosomes - protein synthesis plasma membrane cell wall glycocalyx - capsule or slime layer flagella fimbriae ```
26
Prokaryotes exhibit extensive genetic variation. How does variation occur in prokaryotic cells
rapid reproduction and short generation times and therefore a greater probability of mutation genetic recombination
27
what is genetic recombination
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
transformation
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
transduction
phages (viruses that infect bacteria) carry genes from one host cell to another
30
conjugation
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
R plasmids
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
phototrophs
organisms that obtain energy from light
33
chemotrophs
obtain energy from chemicals
34
autotrophs
need only carbon dioxide or related compounds as a carbon source
35
heterotrophs
require at lease one organic unit such a glucose to make organic compounds
36
photoautotroph
use light as an energy source use carbon dioxide as a carbon source photosynthetic organisms - photosynthetic prokaryotes e.g. cyanobacteria / plants / some protists
37
chemoautotroph
energy source - inorganic chemicals carbon source - carbons dioxide or related e.g. certain prokaryotes
38
photoheterotroph
energy source - light carbon source - organic compounds example - certain aquatic and salt loving prokaryotes
39
chemoheterotroph
energy source - organic compounds carbon source - organic compounds e.g. many prokaryotes, protists, animals, fungi, some plants
40
obligate aerobes
must use oxygen for cellular respiration and cannot grow without it
41
obligate anaerobes
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
facultative anaerobes
in cellular respiration - use oxygen if available but can also carry out fermentation in an anaerobic environment
43
how many prokaryotic species are there
10,600 have been named
44
how many prokaryotes in a handful of soil
book says - 10,000 prokaryotic species | lecture - 100 million and a billion in a teaspoon of soil
45
major groups of bacteria
``` proteobacteria chlamydias spirochetes cyanobacteria gram positive bacteria ```
46
proteobacteria
five groups - alpha, beta, gamma, delta, epsilon
47
there are differences between gene expression in bacteria and archaea/ eukaryotes (who are similar)
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
extremophiles
archaea - lovers of extreme conditions
49
extreme halophiles
archaea that live in highly saline environments
50
extreme thermophiles
archaea that thrive in very hot environments | e.g. sulfolobus
51
methanogens
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
CRISPR-Cas system
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
how is the cell wall of archaea different from bacterial
bacteria - unbranched hydrocarbons | archaea - some branched hydrocarbons / no peptidoglycan present
54
thermoacidophiles
archaea that survive in extreme acidity and temperature
55
endosymbiosis
eukaryotic cells originated by endosymbiosis when a prokaryotic cell engulfed a small cell that would evolve into the mitochondrion
56
serial endosymbiosis hypothesis
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
evidence for endosymbiosis
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
protists
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
why was the kingdom of protista abandoned
genetic studies revealed that some protists are most closely related to plants, fungi or animals than to other protists most biologists
60
what are the three domains of life
eukaryotes, bacteria and archaea
61
what types of eukaryotes are there
animals plants fungi protists
62
how are eukaryotes different from prokaryotes
nucleus and other membrane bound organelles | cytoskeleton - prokaryotic cells lack a well developed cytoskeleton

Bio1MGC (11 decks)

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