Bio2-lec14&15 Flashcards
(84 cards)
1
Q
What defines a prokaryote?
A
A unicellular organism lacking a nucleus and membrane-bound organelles. Includes bacteria and archaea.
2
Q
Why do prokaryotic cells have size limits?
A
Their function is limited by surface area to volume ratio, which affects diffusion efficiency.
3
Q
Prokaryotes are an example of what kind of organism?
A
Ancient
4
Q
Prokaryotes are Ubiquitous, meaning:
A
occur / thrive almost everywhere
- including extreme habitats too hostile for most
organisms
5
Q
Why are prokaryotes successful?
A
due to structural, functional, genetic
adaptations
6
Q
What kind of internal organization do prokaryotes have?
A
Have simple internal organization (no nucleus, no membrane-bound organelles)
7
Q
Prokaryotes are classified into 2 domains based on
A
structure, physiology and biochemistry
8
Q
Prokaryotes are morphologically simple but metabolically diverse playing a key role in
A
The cycling of matter on Earth
9
Q
Describe the internal bacterial cell structure
A
− cytoplasm
− internal membranes (specialized)
− genome organization
- nucleoid region: one circular
chromosome
- plasmids
− ribosomes
10
Q
Describe the external bacterial structure
A
− plasma membrane
− cell wall (peptidoglycan)
− flagella
− capsule
− pili
11
Q
What are characteristics of bacteria in terms of structure?
A
- unicellular
- simple shapes
- very small
- Most have diameters that range
from 0.002 m (or 2 nm) to 2
m
12
Q
What are the bacterial shapes?
A
- sphere (coccus)
- rod (bacillus)
- helix (spirillus)
13
Q
Bacterial genomes are smaller than
A
those of eukaryotes
14
Q
Bacterial genomes lack
A
non-coding stretches of DNA compared to
eukaryotes
15
Q
What causes the diversity in Prokaryotes
A
Diversity in prokaryotes (like eukaryotes) due to mutations and recombination through vertical gene transfer from parent cells to daughter cells (mitosis)
16
Q
bacteria have some additional unique processes that add to
genetic diversity, called
A
horizontal gene transfer
17
Q
What are the 3 types of horizontal gene transfer?
A
- conjugation, 2. transformation, 3. transduction (viruses)
18
Q
Describe conjugation
A
- Transfer of plasmids via direct cell-to-cell contact through a pilus.
- Some bacteria synthesize thin strands of cytoplasm that connect them to other bacteria = pilus (pili)
- Spreads novel genes in bacterial populations e.g. antibiotic resistance
- Plasmids used in genetic
engineering techniques (for GMOs)
19
Q
Describe transformation
A
- Uptake of DNA fragments from the environment by bacterial cells.
- Genes can be transferred from cell-to-cell without direct contact
- Demonstrated when experiments
showed that harmless strains of
bacteria could become virulent
when exposed to media containing
dead cells of the virulent strains
20
Q
Describe transduction
A
- Transfer of genetic material via viruses (bacteriophages).
- Common in nature and as a technique in
research labs (genetic engineering) - viruses can integrate their
DNA into host bacterial cells and persist as bacteria divide and grow - Then viruses undergo process to remove themselves from the host cell’s DNA but this excision process is not always precise
– sometimes viruses take some additional bacterial DNA with them - Viruses are then released into the environment and go on to infect other bacteria transferring new genes in a process called transduction
21
Q
Prokaryotes play key roles in major
biogeochemical nutrient cycles:
A
carbon, oxygen, nitrogen, sulfur
22
Q
Prokaryotes are almost everywhere and display remarkable:
A
Metabolic diversity
23
Q
Describe carbon cycling in Eukaryotes and many prokaryotes
A
- Acquire energy through cellular
respiration and photosynthesis - Photosynthesis is oxygenic
- Cellular respiration is aerobic
24
Q
Carbon cycling is linked to
A
oxygen cycling
25
Changes in oxygen levels linked to
evolutionary changes/biological diversity
26
The evolution of oxygenic photosynthesis by cyanobacteria is key to
O2 accumulation in the Earth’s
atmosphere
27
Why is carbon cycling more diverse in Prokaryotes
Involves more than oxygenic photosynthesis and aerobic cellular
respiration found in eukaryotes = more expanded carbon cycle
28
What are autotrophs
- “self” feeders = producers
29
What are photoautotrophs
- Energy source = light
- carbon souce = co2
- type of organism= photosynthetic prokaryotes (e.g cyanobacteria), plants; certain protists (algae)
30
What are chemoautotrophs
- energy source= inorganic chemicals
- carbon source = co2
- types of organisms= certain types of prokaryotes (sulfolobus)
31
What are heterotrophs
“other” feeders = consumers / decomposers
32
What are photoheterotrophs
- energy source = light
- carbon source = organic compounds
- types of organisms = certain prokaryotes (e.g chloroflexus)
33
What are chemoheterotrophs?
- energy source = organic compounds
- carbon cource = organic compounds
- types of organisms = many prokaryotes and protists; fungi; animals; and some plants
34
What is anoxygenic photosynthesis?
Photosynthesis that does not produce O2, uses bacteriochlorophyll and donors like H2S or Fe2+
- CO2 reduced to organic carbon
- Sunlight absorbed using a different pigment – bacteriochlorophyll
* Uses a single photosystem and electron transport chain (ETC) to produce ATP only
* Electron donors are H2S, H2, ferrous iron (Fe2+) and arsenite (AsO33-)
35
Describe the metabolic process of microbial mats
- Surface layers have access to O2, CO2 and light – use oxygenic photosynthesis and aerobic cellular respiration
- Deeper layers use anoxygenic photosynthesis and anaerobic respiration
and fermentation
36
Without oxygen, prokaryotes can still perform cellular respiration by using
lternative electron acceptors to oxidize organic molecules into CO₂ (anaerobic respiration)
37
What are the alternative oxidants involved in anaerobic respiration
- ferric iron (Fe3+)
- sulfate (SO42-)
- nitrous oxide (NO3-)
- manganese (Mn4+)
- arsenate (AsO43-)
38
What are the parts of the nitrogen fixation
1) Root nodule bacteria
2) Cyanobacteria
3) Archaea spp
Anammox (in Archaea)
NH4+ + NO2
- N2 + 2 H2O
39
What are the key processes involving prokaryotes in the nitrogen cycle
1) Nitrogen Fixation
- Converts atmospheric N₂ → NH₄⁺ (ammonium)
- Done by: Root nodule bacteria (e.g., Rhizobium)
- Cyanobacteria (with heterocysts)
- Some archaea
2) Ammonification (Decomposition)
- Organic nitrogen → NH₄⁺
- Performed by bacteria and fungi
3) Nitrification
- NH₄⁺ → NO₂⁻ → NO₃⁻ (oxidation)
- Done by nitrifying bacteria (e.g., Nitrosomonas, Nitrobacter)
4) Denitrification
- NO₃⁻ → N₂ gas (reduction)
- Done by anaerobic bacteria in low-O₂ soils
5) Anammox (Anaerobic Ammonium Oxidation)
- NH₄⁺ + NO₂⁻ → N₂ + 2H₂O
- Carried out by archaea, especially in sediments and wastewater
40
What is the significance of prokaryotes in the nitrogen cycle
Prokaryotes drive every major transformation in the nitrogen cycle, maintaining soil fertility, plant growth, and atmospheric balance. Without them, nitrogen would remain locked in unusable forms.
41
Explain how bacteria and archaea manage sulfur transformations
Plants absorb SO₄²⁻ (sulfate) from the soil
- It is reduced to sulfhydryl groups (-SH) for building amino acids like cysteine
Animals/fungi obtain sulfur from food
Bacteria and archaea:
- Perform anaerobic respiration using sulfate as a terminal electron acceptor (e.g., sulfate-reducing bacteria → produce H₂S)
- Perform chemoautotrophic or phototrophic sulfur oxidation (e.g., oxidizing H₂S → SO₄²⁻)
42
Notes on H₂S:
- Rapidly oxidized in presence of O₂
- Toxic to eukaryotes – explains niche dominance by prokaryotes in sulfide-rich environments (like hydrothermal vents)
43
What is the significance of prokaryotes in the sulfur cycle?
Like the nitrogen cycle, the sulfur cycle would not function without prokaryotes. They make sulfur bioavailable and detoxify environments rich in sulfide.
44
Prokaryotes are a
Domain
45
Bacteria is a
classification
46
Prokaryotes consist of two domains:
Bacteria and Archaea.
47
The key distinguishing feature used for classification within prokaryotes—especially bacteria is
the composition of the cell wall.
48
Most diverse, medically important
or ecologically interesting groups
of Bacteria are
1. Proteobacteria
2. Green bacteria
3. Cyanobacteria
4. Gram-positive bacteria
(Firmicutes)
5. Spirochetes
6. Chlamydias
49
Why is it difficult to define species when talking about bacteria
- cannot interbreed
- lack sexual
reproduction
- have horizontal gene
transfer
50
What are proteobacteria
1. Proteobacteria:
* Most diverse group of bacteria
* Gram-negative bacteria
− purple sulfur bacteria
− colour due to unique type of chlorophyll
− photoautotrophic or photoheterotrophic
* Free-living gram-negative proteobacteria
− chemoheterotrophs
− intestinal bacteria – Escherchia coli (E. coli)
− some cause human diseases (e.g. bubonic plague, gonorrhea, gastroenteritis, dysentery)
51
What are green bacteria
* Gram-negative photosynthetic bacteria
− found in hot springs (photoautotrophic)
− marine and high-salt environments (photoheterotrophic)
− distinctive chlorophyll compared to plants
− do not release oxygen as by-product of photosynthesis
52
What are cyanobacteria
- bluegreen algae
- gram-negative aerobic photosynthetic
prokaryotes
− responsible for oxygen-based life on earth (e.g. algae, plants)
− most morphologically diverse group of bacteria
− some species may form colonies
− some species have specialized cell types (e.g. heterocysts for nitrogen fixation)
53
What is gram positive bacteria
4. GRAM-POSITIVE BACTERIA (OR FIRMICUTES)
− primarily chemoheterotrophs
− many pathogenic species including
- Bacillus anthracis - causes anthrax
- Staphylococcus - causes food poisoning, toxic shock syndrome, pneumonia, bacterial meningitis
- Streptococcus - causes strep throat, pneumonia, necrotizing fasciitis
some beneficial species
- Lactobacillus spp. - uses lactic acid fermentation to produce pickles, sauerkraut, yogurt
54
What are spirochetes
- gram negative bacteria
- propelled by rotation of helical (or spiraled) flagella
- enables movement in thick mud or sewage
- both beneficial and harmful species
- found in human mouth
- in termite intestines that digest cellulose
- some pathogenic species (e.g sphyllis)
55
What are Chlamydias
- gram negative bacteria
- obligate intracellular pathogens of humans and animals
- cause sexually-transmitted infections and respiratory infections
- cell walls differ from other bacteria by lacking peptidoglycans
- significantly reduced genome size compared to other bacteria
56
What is the bacteria Deinococcus radiodurans
− tolerant to radiation
− can break down radioactive waste
57
What is the bacteria Thermus aquaticus
− tolerant to high temperature
− enzyme DNA polymerase is very heat-stable
- used in PCR (polymerase chain reaction)
techniques to create copies of DNA sequences for genetic engineering techniques
58
Archea have some unique characteristics, including:
− some features like Bacteria (prokaryote,
chromosomes, ribosomes)
− some features like eukaryotes (histones, enzymes)
− some unique features (membranes, protein synthesis)
59
How many evolutionary branches of archea
5
60
What is used to identify clues to
evolutionary relationships in archea
Use tolerance/ adaptations
to extreme environmental
conditions
61
Cell contains a nucleus and other membrane-bound organelles
- Archea: no
- bacteria: no
- Eukarya: yes
62
DNA occurs in a circular form*
- archea: yes
- bacteria: yes
- eukarya: no
63
Membrane lipids are ester-linked (vs. ether-linked)
- archea: no
- bacteria: yes
- eukarya: yes
64
Photosynthesis with chlorophyll
- archea: no
- bacteria: yes
- eukarya: yes
65
Capable of growth at temperatures greater than 80°C
- archea: yes
- bacteria; yes
- eukarya: no
66
Histone proteins present in cell
- archea: yes
- bacteria: no
- eukarya: yes
67
Operons present in DNA
- archea: yes
- bacteria: yes
- eukarya: no
68
Introns present in most genes
- archea:no
- bacteria: no
- eukarya: yes
69
Capable of methanogenesis
- archea: yes
- bacteria: no
- eukarya: no
70
Sensitive to the antibiotics chloramphenicol, kanamycin, and streptomycin
- archea: no
- bacteria: yes
- eukarya: no
71
Capable of nitrogen fixation
- archea: yes
- bacteria: yes
- eukarya: no
72
Capable of chemoautotrophy
- archea: yes
- bacteria: yes
- eukarya: no
73
What are the three classifications of archea
1. Euryarchaeota
2. Crenarchaeota
3. Korarchaeota
74
Describe the types of Euryarchaeota
(a) Methanogens
- methane generators
- Live in low-oxygen environments
Obligate anaerobes in
- anoxic sediments of swamps, lakes, marshes, sewage works
- large intestine of dogs and humans
- hindguts of insects
- in rumen of cattle, sheep, etc.
(b) Halophiles - salt loving
- * Live in highly saline environments
* Aerobic chemoheterotrophs
- obtain energy from sugars, alcohols, amino acids
- some use light as a secondary energy source
(c) Extreme Thermophiles - heat loving
Live in extremely hot environments
- hydrothermal vents, hot springs
- tolerate temperatures between 70°C
and 95°C
75
Describe the types of Crenarchaeota
a) Extreme thermophiles
* Higher optimal temperature range than
Euryarchaeota organisms
(b) Psychrophiles (“cold loving” )
* Thrive at temperatures between –10°C to –20°C
* Found in Antarctic and Arctic oceans
(c) Mesophiles
* Many plankton in cool marine waters
76
describe Korarchaeota
* Recognized only by sequences in DNA
samples
* Found in hydrothermal environments but have never been isolated and cultivated in lab
* Nothing known about their physiology
77
Describe Thaumarchaeota
* May be the most abundant cells in the oceans
* Chemoautotrophs that use ammonia (involved in Anammox reaction in
nitrogen cycle)
78
What does TACK stand for
Thaumarchaeota
Aigarcheota
Crenarchaeota
Korarchaeota
79
describe phylogeny of bacteria and archea
- a work in progress
- Evolution viewed as a network or web
instead of as a tree
- Evolution of Bacteria and Archaea seen
as integral part of evolution of Eukarya
(e.g. organelles, mutualistic relationships like human microbiome)
80
Describe the human microbiome
Community of prokaryotes on/in the body critical for digestion, immunity, and overall health.
81
GI (gastrointestinal) bacteria often considered
harmful causing health problems (e.g. irritable bowel syndrome)
82
Most intestinal bacteria are
beneficial
- help to break down food
- secrete vitamins/other biomolecules into colon for
absorption of nutrients
- produce molecules that signal other systems (e.g.
immune system, nervous system)
83
How does diet affect the human microbiome?
Plant-based diets favor Bacteroidetes (fiber digestion); Western diets favor Firmicutes (animal fat/sugar digestion).
84
Why is it important to study prokaryotes?
They help us understand health, ecosystem roles, biotechnology, sustainability, and co-evolution with humans.
