Week 6 Flashcards
(128 cards)
1
Q
What is photosynthesis?
A
A process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms activities
2
Q
Why is photosynthesis important?
A
Nearly every organism on the planet directly or indirectly relies on photosynthesis for energy
3
Q
How much solar energy hits the earth?
A
~3.5 to 7 kWh/m2 per day
Avergae UK houshold usage: 12.7 KWh per day
4
Q
What is the elecromagnetic spectrum?
A
The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies
5
Q
What is the rough energy range across the electromagnetic spectrum?
A
Energy of a single photon is greater in the UV end of the spectrum than infrared
Shorter wavelength = higher frequency = higher energy
6
Q
What spectrums of light can microbes use in photosynthesis?
A
Visible light - 450 nm to 700 nm
Infrared light - 750 nm to 900 nm
7
Q
What are the three different photosynthetic processes in bactertia?
A
Electron independant ATP generation - produces ATP
Cyclic electron transport - produces ATP
Linear electron transport - produces ATP + NADPH
8
Q
What compounds can absorb light energy?
A
Includes carotenoids, chlorophyll ans bilins
9
Q
What do light absorbing molecules contain?
A
A chromophore, a part of the compound where light energy can be absorbed, resulting in production of an excited electron or energy transfer. THis is also responsile for the colour of certain compounds
10
Q
What is an overview of rhodopsin proteins?
A
Light driven proton pump
Involved in ion pumping, sensory transduction and as photosensory pigments
Bacteriorhodopsin - only found in archaea
Proteorhodopsin (bacteria, archaea and eukaryotic algae)
11
Q
What is unique about rhodopsin?
A
They have a retinal (chromophore) which can absorb light
12
Q
What happens when rhodopsin absorbed light?
A
Rhodopsin is in a relaxed trans state and then when light is absrobed it transforms into an energised cis retinal and releases a proton
13
Q
What happens to the proton that is rleased from the excited rhodopsin?
A
It is transported to an aspartate in the proteins and then transported to the other side of the membrane
14
Q
What happens to make sure the rhodopsin is sustainable?
A
At the same time on the other side of the membrane another protein is transported into an aspartate which is transported on to the carotenoid replacing the protein that was lost ie a form of proton pumping releasing on one side and replacing form proton on another
15
Q
What is the end game result of rhodopsin photosynthesis?
A
A build up of protons on one side of membrane eg a build up in proton motive force which can then be used by ATP synthase which can generate ATP
16
Q
What is an overview of generating energy via rhodopsin proteins?
A
Almost free ATP
All spoecies that express proteorhodopsin are photoheterotrophs - utalise both light energy and organic compounds as a source of energy
17
Q
How abundant are rhodopsin expressing organisms?
A
In just in the North Pacific, over 1,500 different proteo/bacterio-rhodopsin genes were identified
Also found in freshwater
18
Q
Why are rhodopsin expressing organisms abundant?
A
Role in enhancing ATP productio, growth under nutrient limitated or stress conditions
Most. absorb blue/green light (500-650 nm)
19
Q
What other photosynthetic molecules are predominately used to absorb light?
A
Chlorophyll seen in a and b (though 5 in nature)
20
Q
What is the structure of cholorophyll?
A
Porphyrin ring attatches to hydrocarbon tail
21
Q
What is the absorbtion maxima of the different types of chlrophyll a and b?
A
C.a = two peaks at 420 nm and 680 nm
C.b = two peaks at 470nm and 620 nm
22
Q
Why do chlorophyll a and b have different absorbtion ranges?
A
Different porphyrin ring structure - on a carbon ring carboxyl group in C.a is methyl group in C.b
23
Q
What is an overview of purple non-sulphur bacteria?
A
Belong to the Rhodospirillaceae group (Alphaproteobacteria)
Include Rhodobacter sphaeroides and Rhodopseudomonas palustris (genetically manipulatable)
Can grow aerobically in the dark by respiring on organic carbons sources
24
Q
What is an overview of purple sulphur bacteria?
A
Belong to the Chromatiaceae and Ectothiorhodospiraceae groups (Gammaproteobacteria)
Can tolerate high sulphur environments
Strictly anaerobic (no oxygen for respiration)
Must fix carbon dioxide to survive - tricarboxylic acid cycle
25
How do Purple bacteria absorb infrared light via bacteriochlorophylls?
They absorb light via Light harvesting complex 2
Energy transfer between bacteriochlorophylls ie from LHC2 to LHC1
THe LHC1 encompass a reaction centre. The reaction centre is a large protein complex
This energy excites electron in RC, which goes to a ubiquinone which moves through membrane to Cytochrome bc1 complex which provides energy for proton pumping to create a proton motive force
Electron is transported from cytochrome c then back to RC
26
What are the absorbtion peaks for purple bacteria that absorb infrared light?
Small peak around 470 nm but larger peak around 850 nm, infrared light reduce competiton
27
How do purple bacteria maximise photosynthesis?
They use intracytoplasmic vesicles to pack, LHC1 and 2 and RC together increasing amount that can be stored. The cell is turned into a factory to produce ATP
Stored hexagonally
28
How do purple bacteria use ATP?
Purple bacteria use ATP to fix carbon (and some fix nitrogen too)
Some are photoautotrophs (Utilise chemical energy to fix carbon dioxide into sugars)
Some species also fix nitrogen (anaerobic conditions)
29
What is the process that purple bacteria fix carbon?
Imported through HCO3-
Taken into carboxysome
Carbonic anhydrase converts HCO3- into CO2
CO2 binds with riboluse 1-5 phosphate and through rubisco makes 2x 3-phosphoglycerate which it used in the cell for things like biomass formation
30
What is required for nitrogen fixation in purple bacteria?
Electrons are consumed by the nitrogenase and NADPH (required for carbon fixation
Reduced sulphur compounds, i.e. hydrogen sulphide, can act as electron donors but are not widespread in most environments
31
What are the opening steps for nitrogen fixation?
H2S is oxidised and electron enters electron transport chain
The electron is the transported to the reaction centre
When in the reaction centre it gets excited and is transported to the protein Ferredoxin
32
What are the 2 outcome when an electron is at the Ferredoxin?
2e- goes to Ferredoxin NAD(P)+ reductase and reduces NAD(P)+ + H+ to NAD(P)H
8e- goes to nitrogenase and converts N2 + 8H+ + 16ATP --> 2NH2 + H2 + 16 ADP
33
What is an overview of Green sulphur bacteria?
Strict anaerobic bacteria mostly found in low light environments
For example Chlorobiaceae
34
What structure absorbs light in Green sulphur bacteria?
A chlorosome
Protein/monolipid membrane which contain upto 250,000 bacteriochlorophyll c,d or e
35
What structure absorbs light in Green sulphur bacteria?
A chlorosome
Protein/monolipid membrane which contain up to 250,000 bacteriochlorophyll c,d or e
Embedded next to plasma membrane
To maximise any energy in photons
36
How do Green sulphur bacteria produce ATP?
Energy is absorbed by the bacteriocholoropyll which is then passed to base plate (FMO + B.C a)
Then energy is passed to a reaction centre where it undergoes a processs similar to purple bacteria
37
How can green sulphur bacteria produce NAD(P)H?
Through a similar pattern to purple sulphur pattern but no pathway leading to nitrogenase
38
Why are oxygenic photosynthesis most abudnant?
Seen in plants, algae and cyanobacteria
Use water as an electron donor
39
Where are cyanobacteria and algae found?
Desert surface
Antarctica
Freshwater ecosystem
Oceans
Massively impactful
40
What is the model cyanobacteria?
Synchocystis PCC 6803
41
What are the key features of cyanobacteria physiology for photosynthesis?
Thylokoid lumen containing stacked thylakoid membranes to maximise light absorbtion
Carboxysomes to concentrate CO2
42
What is the origin of the choloplasts?
Chloroplasts descend from an internalized (eaten) cyanobacterium, different organisation eg chloroplasts dont have carboxysomes
A cyanobacterium (UCYN-A) ‘captured’ by alga (haptophyte)
43
What is the relationship between alga and the cyanobacterium (UCYN-A)?
Alga does photosynthesis in return cyanobacteria does nitrogen fixing
44
How is Alga body adapted to maximise photosynthesis?
Most of the body is made up of chloroplast to maximise carbon fixation
45
How diverse as alga?
Algae can be as evolutionary diverse from each other as humans are from yeast but similar types of photosynthetic processes
46
How can photosynthetic photosynthesis be maintained?
Electron is excited and passed through proteins
4 magnesium complex breaks down 2 waters into O2 + 4H+ and electrons
Oxygen released into envrionment
Protons into lumen
Electrons used to replace high energy electrons released
47
What happens during oxygenic photosynthesis?
Light excites an electron in photosystem 2 which then reduces plastoquinone to plastoquinol
Plastoquinol moves through the membrane to Cytochrome b6f and then binds to plastocyanin
The plastocyanin then moves through the lumen and the electron then goes to photosystem 1 (trimer molecule)
48
What happens to the electron in photosystem I?
Light energy excites the electron again then the electron moves to ferredoxin then ferredoxin NADP reductase, redcuing NADP+ + H+ --> NADPH
49
How is ATP made during oxygenic photosynthesis?
Cytochrome b6f is pumping protons across the membrane from the Thylakoid membrane to the cytoplasm generating ATP from ATP synthase
50
What is the function of the NADPH made during oyxgenic photosynthesis?
Primarily used in carbon fixation
Alga have pyrenoid complex structure in the centre of chloroplast to concentrate CO2 take make C fixation more efficient
Bacteria have carboxysomes
51
What is an overview of photorespiration?
Converts Ribulose-1,5 phosphate + oxygen to glycerate-2P, expensive process to convert back to r-1,5 p
Wants to maximise carbon fixation rather than photorespiration
52
Whats an overview of the calvin cycle?
Carbon fixation - 3 x CO2 + 3 RUBP (rubisco) --> 6 x 3-PGA
Reduction - Using 6ATP and 6NADPH --> 6xPGA turned into 6xG3P
Regeneration of starting molecule - 1 molecule of G3P leaves to central metabolism. Other 5 G3P, have 2 Pi leave and 3ATP are converted to ADP
Energetically expensive
53
What is the outcome of cyclic electron transport?
No electron input is required (Therefore no oxygen is produced)
Only ATP is produced
Protons pumped by Cyt b6f from cytoplasm to thylakoid membrane so they can diffuse across ATP synthase
54
What is an overview of cyclic electron transport method?
Light excites electron in PS1
Electron goes to ferrodixin
Then transported to NAD(P)H dehydrogenase
Transported to Cytb6f via plastiquinol
Then plastocyanin transports low energy electron back to photosystem 1
55
What is the overview of light abosorbtion for oxygenic respiration?
Photoharvesting complex
Absorbs light and funnels it to PSII reaction centre and cyanobacteria increase light spectrum absorbed
Found in plants, cyanobacteria and bacteria
Use chromophore phycocrythrobilia/phycocyanobilin
56
What are the advantages of phycocrythrobilia / phycocyanobilin?
Increase surface area of light absorbed
Increase spectrum of light absorbed
In some bacteria if also produce phycoerythin can abosrb whole spectrum
Energetically expensive
57
What colours are cyanobacteria?
Range of colours, from green to brown, maximise range of light absorbed
58
What is a main difference in plant photosystems?
Have light harvesting systems next to PS1 and PS2
Contain chlorophyll (broaden the area of light harvested, not the spectra (why plants are green and cyanobacteria are blue-green)
59
How important are photosynthetic organisms?
Plants: ~50%
Algae: ~25%
Cyanobacteria: ~25%
60
How did photosynthesis change earth atmosphere?
Changed from weakly reducing atmosphore to oxidising atmosphere
All oxygen produced by photosynthesis
61
What is the downside of oxygen production?
Oxygen + excited electrons = reactive oxygen molecules
Reactive oxygen molecules kill cells
62
What reduces impact of reaction electrons?
Carotenoids dissipate excess energy as heat and fluorescence, and scavenge reactive oxygen species (and also transfer energy back to chlorophylls)
Certain proteins also act as electron sinks (transfer oxygen to protons to generate water) Integrated at each point of the electron transport chain
63
What is the Winogradsky column?
Shows many cyanobacteria living together
Bacteria live in there own area - cyanobacteria/alga at top then nonsulphur phototrophic bacteria, pruple sulphur bacteria, green sulphur bacteria then non photosynthetic organism at the bottom
Decident by level of sulphur
64
What is innate immunity?
Mostly present before infection; not specific to pathogen
65
What are anatomic barriers in the innate immunity?
skin - Multiple layers of tightly packed cells, continually replaced
mucous membranes - Goblet cells produce mucous – traps pathogens; expelled
66
What are physiological barriers in the innate immunity?
temperature
pH - skin pH ~4 (maintained by sebum)
chemical mediators
sweat – salt and lysozyme
67
Whats an overview for phagocytic/endocytic barriers?
Innate
monocytes differentiate into macrophages
neutrophils (and eosinophils)
Phases of phagocytosis - chemotaxis, adherence, ingestion, digestion, elimination
68
What are compliments?
act as opsonins (promote phagocytosis), chemotactic factors, trigger
inflammation/fever
Create membrane attack complex => lysis
Recognise the antibodies that have bound to antigens
Generates cascade through multiple complete proteins creating attack complex
69
tWhats an overview of interferons?
a, b and gIFN inhibit viral infections
1957: discovery that cells exposed to inactivated viruses produce soluble factors (termed ‘interferons’) that can “interfere” with viral replication.
70
Whats an overview of Type 1 interferons?
Type I interferons are made by almost all cells in the body and have high antiviral potency. Type I interferons include IFN-alpha (IFN-α), IFN-beta (IFN-β).
71
Whats an overview of Type 2 interferons?
Type II interferon, IFN-gamma (IFN-γ), has an immunomodulatory function by activating macrophages, natural killer cells, and T cells to, among other things, increase MHC-presented antigens.
72
Whats an overview of Type 3 interferons?
Type III interferons (IFN-λ) also induce antiviral responses, but primarily in epithelial cells.
73
How do Type 1 interferons directly fight viruses?
Type I interferons bind receptors on uninfected host cells and 1) render those cells resistant to viral infection or 2) cause them to sacrifice themselves if they become infected
74
How do Type 1 interferons indirectly fight viruses?
Type I interferons induce dozens of interferon-stimulated genes (ISGs) that inhibit viral entry, destroy RNA (eg by up-regulating RNAseL (ds endoribonuclease)), or prevent translation of RNA (elF2 is activated to prevent ribosomes translating mRNA).
75
What is an overview of inflammatory barriers?
Dilation and increased permeability of blood vessels
histamine, prostaglandin and leukotrienes released
Migration of phagocytes
Tissue repair
76
What is an overview of fever?
Interleukin-1 mediates increase in temperature
enhances effects of IFNs, inhibits microbes, enhances phagocytic activity
77
How does the innate immune system detect pathogen recognition?
PRR detects PAMPS
Pattern recognition recptors detct pathogen associated molecular patterns
78
What are types of PRRs?
Membrane bound PRRs - lectin receptors and TLRs
Soluble PRRs - Complements, CRP (C reactive protein levels)
79
What are examples of TLRs?
TLR5 - flagellin, bacteria, on cell surface of macriphages and dendritic cells
TLR3 - double-stranded RNA, viruses, cell compartment of dendritic cell and b cells
80
Which immune cells differentiate from the lymphoid progenitor?
Dendritic cell
T-cells (including T-helper and T-cytotoxic)
B-cell
NK (innate lymphocyte cell)
81
What are the different immune cells that differentiate from the myeloid progenitor?
Megakaryocyte - further produce platelets
Monocyte - can differentiate into macrophage and dendritic cells
Neutrophil
Basophil
Eosinophil
Mast cell
Erythroblast - develops into erythrocyte
82
What is NET?
Neutrophil extracellular trap - neutrophil has bust open trapping bacteria in sticky substance
83
What is an overview of apative immunity?
Comes into play when there is an antigenic challenge
High degree of specificity
Acquired
Diversity
Memory
Self/non-self recognition
Humoral and cell-mediated responses
84
How dooes the adaptive immune system recognise microbial pathogens?
Secreted by b cells and plasma cells or can be membrane bound acting as a b cell receptor
85
Whats an overview of B cells?
B lymphocytes
Originate and mature in bone marrow
Unique antigen-binding receptor (B cell receptor)
Membrane bound antibody molecule
86
What happens when B cell encounter antigen matching antibody?
Rapid division
Differentiation:
Memory B cells
Plasma cells that secrete Ab
87
What is an overview T cells?
T lymphocytes
mature in thymus (originate in bone marrow)
Unique antigen binding molecule
T cell receptor (TCR) recognises Ag bound to MHC molecules (major histocompatibility complex)
TH (T helper) and TC (T cytotoxic) subpopulations
88
What happens when T cell encounters antigen with MHC?
Rapid division
Differentiation
Memory T cells
Various effector T cells
89
What are an overview of primary microenvironment?
Primary - microenvironment for development and maturation of lymphocytes eg bone marrow and thymus where T cells mature
90
What are an overview of secondary microenvironment?
Secondary - trap antigen, mature lymphocytes and antigen interact eg tonsil and spleen
91
What are peyers patches?
Concentrated areas of B cells and T cells, called germinal centres that protects gi tracts (around small intestine)
92
What is an overview of Lymph nodes?
Lymph nodes - clustered at junctions of lymphatic vessels
Sites where immune responses are mounted to antigens in lymph
93
Whats an overview of immunoglobulins (antibodies)?
IgM, IgG, IgA, IgD, IgE
Antibody molecules have a common structure of four peptide chains:
Two identical light chains
Two identical heavy chains (determins isotype ie heavy chain alpha = IgA)
94
What are the functions of anitbodies?
Trigger:
Opsonisation
Antibody dependant cell mediated cytotoxicity (ADCC)
Activation of complement
Precipitation (agglutination)
Neutralisation
95
Whats an overview of opsonaisation?
Promotion of phago- cytosis by macrophages and neutrophils
96
Whats an overview of Antibody dependant cell mediated cytotoxicity (ADCC)?
Ab bound to target cells (virus infected) with Fc receptors of NK cells directs cytotoxic activity. Apoptosis not phagocytosis
97
Whats an overview of of activation of compliment?
IgM and IgG activate series of serum glycoproteins lysis of bacterial cell by perforation of membranes
98
Whats an overview of precipitation (Agglutination)?
Hinders activity of pathogens, increases chance of phagocytosis
99
Whats an overview of neutralisation?
Blocks toxin binding, bacteria attachment
100
What makes the symptoms of infection worse?
Tissue injury and disease following infections may be caused by the immune response itself rather than by the microbe
101
What is disease X?
Disease X represents the knowledge that a serious international epidemic could be caused by a pathogen currently unknown to cause human disease
102
How has infections disease impacted human history?
Infectious disease has had a huge effect on the human race
History has been shaped by a plethora of epidemics and pandemics
Until we started to understand the causes of disease, we were unable to fight it
103
How do we come into contact with numerous microorganisms daily?
Breathe in, ingest with food and drink, pick up on skin
Most do not harm us
Some may colonize body surfaces; others shed with dead epithelial cells
Most swallowed microorganisms die in stomach or are eliminated in faeces
Relatively few are pathogens that cause damage
104
What was an idea about disease pre germ theory?
Miasmatic theory
Disease was transmitted by miasma
A poisonous vapour or mist
Pre-1850
105
Whats an overview of Germ Theory?
Proposed microorganisms are the cause of many diseases
Highly controversial when first proposed
Cornerstone of modern medicine & clinical microbiology
Led to antibiotics and hygienic practices…
Louis Pasteur 1822 – 1895 Developed Pasteurisation in 1864 Saved Millions of lives…
106
What was the work of Robert Koch?
Founder of public health…
Developed “Koch’s Postulates”
In late 1800’s discovered causal agents of:
Tuberculosis - Mycobacterium tuberculosis
Cholera - Vibrio cholerae
Anthrax - Bacillus anthracis
107
What is an overview of vaccination?
Immunity to disease can be generated by vaccination
Important role in protecting individuals against illness
Vaccination works by safely exposing individuals to a specific pathogenic microbe
Artificially increases immunity
108
Whats an overview in the eradication of Dipthera in England?
Early 1880s organism caused identified
Mid 1880s antitoxin first used - deaths per million decline
Late 1930s national vaccination campaign - death plummeted to 0
109
When did the eradication start and end?
Began in 1950
Declared successful in 1980 - Variola major few minor after
110
How did we control infectious diseases?
Vaccination
Antibiotics
Public health measures - public sanitation and chlorination of water supply
Social measures - improved housing. reduced poverty and over crowding
111
How did antibiotics impact deaths by pneumonia?
Introduction of Sulfa and Penicillin caused huge drops in the number of deaths cuased by pneumonia
112
How did chlorination of water supply impact incidence of Typhoid in USA?
Early 1930s, chlorination of water cases number of incidences to dramatically reduce
113
What does personal hygine impact diseases?
Handwashing reduces incidence of diarrhoeal disease, flu and colds
114
What was the quote by William H. Stewart 1967?
“It is time to close the book on infectious diseases and shift all national attention and dollars to the ‘New Dimensions’ of health: chronic diseases”
Bit optimistic with hinds sight
115
What was the WHO leading causes of disease state about infectious diseases?
In top 10 killers include Lower respiratory infections. neonatal conditions, diarrhoeal diseases
116
Whats an overview of diarrhoeal disease?
Biggest cause of infant mortality worldwide
200 million people worldwide suffer - fluid loss equal to volume of wateer flowing Victoria Falls every minutes
117
Why is infectious disease relate diseases no longer decreasing?
Increased antibiotics resistance - some treatments no longer work
New diseases - emerging infections
118
What are the advantages of first line antibiotics?
Few side effects
Cheap
119
What are the downsides of second and third line antibiotics?
Greater toxicity to people
More expensive
120
Why has antibiotics resistance occured?
Pressure on doctors, by patients, to prescribe antibiotics even when they are not needed.
Patients being prescribed antibiotics without the doctor knowing the cause of the infection
Use of antibiotics in animals for growth promotion & prophylaxis - Antibiotics enter the human food chain.
121
Whats an overview of Salmonella Typhimurium DT104 R-type ACDDuT?
Major outbreaks in 2000
ACSSuTCp antibiotic resistant to 5 different antibiotics
Developed anitbiotic resistance to enrofloxacin soon after enrofloxacin use in veterinary. Increased in cases and species infected over time
122
Whats an overview of infectious disease cases?
Infectious disease is the second major cause of death in the US, and third worldwide
Infectious disease mortality
1900 - 1980: declined 20-fold
1980 - 1995: increased two-fold
123
What are examples of virus emerging infectious diseases?
Ebola
H5N1 flu
H1N1 flu
SARS virus
West Nile Virus
124
What are examples of bacterial re-emerging infectious diseases?
Plague
MDR Salmonella
Clostridium difficile
TB
125
How has air travel impacted spread of diseases?
No city on earth is more than 24 hours away from any other
At any one moment ~ half a million people are flying in commercial aircraft worldwide
126
Whats an overview of SARS outbreak?
8098 patients and 774 deaths
2003
Infections followed flight paths people followed
127
What is a major factor behind emerging infectious diseases?
Zoonotic
128
What is an overview of avian flu?
Avian H5N1
Outbreak began in 2003
261 deaths by June 2009
