Lecture 3. Energy, Transport and Scavenging Bacteria Flashcards
What are some things in which bacteria spend energy on ?
- Manufacturing
- Transport
- Surveillance
- Waste Management
- Energy Production
What is the bacteria’s currency ?
Adenosine Triphosphate
What are some things that bacteria do ?
- Self-monitoring
- Monitoring others
- Motility
- Regulation
What do bacteria make decisions in response to ?
Their environment
How does E. coli bacteria produce the energy currency ATP ?
F-ATP synthase
What is the structure of E.coli F-ATP synthase ?
Membrane bound protein with a rotating head
What causes the system (F-ATP synthase) to rotate ?
The large chemiosmotic potential of protons in the periplasm which are unable to pass on their own across the cytoplasmic membrane must pass through the motor complex causing rotation
What does the rotation of the F-ATP synthase cause ?
ADP and pyrophosphate to be physically forced together so they bond and form ATP
What powers the flagellar based systems ?
The proton motive force coming from the rotation of F-ATP synthase
How do E. coli produce ATP ?
Using F-ATP synthase
What complex possesses a rotating head ?
Membrane bound protein
What do protons in the periplasm have ?
Large chemiosmotic potential
What causes the membrane bound protein complex to rotate ?
The passage of protons from the periplasm
What happens as a result of the rotation of the head of the membrane bound protein ?
ADP and pyrophosphate are physically forced together so that they bond to form ATP
Where does the energy to rotate the membrane bound protein complex head come from ?
Central metabolism with the breakdown of carbon sources using ATP in oxidation phosphorylation
What are the carbon atoms released from oxidation phosphorylation used for ?
Creating cellular components
What does the oxidation phosphorylation process also involve ?
Electron transport chain
How are substrates transported across the membrane into the interior of the cell ?
ATP being used to pump hydrogen ions across the inner membrane into the periplasm creating an ion gradient
What does uniport mean ?
Only one molecule is moving
What is the least common method of transmembrane transport ?
Facilitated diffusion
What is an example of facilitated diffusion ?
E. coli glycerol uniporter
What does the E.coli glycerol uniporter system utilise ?
A membrane embedded protein (facilitator) to move the substrate molecule across the membrane
What does the E.coli glycerol uniporter not use ?
Energy which means it cannot move the substrate against a concentration gradient
What type of system is facilitated diffusion ?
Passive
What does the symport ion coupled system require ?
Energy and the substrate to have an ion partner which passes through the symport protein in the same direction in a one for one co-transport fashion
What is a good example of the symport ion couple system ?
The Lac permease
What is the lac permease responsible for ?
Transporting lactose
What do antiport systems require ?
Energy and a counter ion
What direction do the substrate and counter ion move in ?
Opposite directions with antiport systems
How can antiport systems be used ?
They exchange and accumulated compound for an excreted one and can be harnessed to create a chemiomotic circuit
What is bacteria’s favorite carbon source ?
Glucose
Why does bacteria prefer glucose ?
Easiest to metabolise and generate the most amount of energy
What is the function of LacY permease ?
A symport transporter
What operon is LacY permease part of ?
lacZYA
What is the structure of permease of LacY permease ?
A membrane embedded protein with 12 transmembrane regions. It has loops on both the periplasmic and cytoplasmic sides of the membrane
What is LacZ protein?
A beta-galactoside which cleaves disaccharide into glucose and galactose
What does lacA gene code for ?
Beta-galactoside transacetylase
Where is lacl repressor found ?
Upstream of the repressor
What is the function of lacl repressor ?
Regulates the downstream operonic promoter resulting in the expression of the operonic genes
What are the lac operon and the lacl repressor responsible for ?
Transport and metabolism of lactose in the cell at the appropriate time
What happens when there is no lactose in the cell ?
The tetrameric lac repressor binds to operator sites in the operonic promoter and shuts down transcription of the operonic genes
What happens when lactose is present ?
The structure of lacl tretramer changes, causing it to detach from the operator sites in DNA
What does the removal of lacl allow ?
The lacZYA to be transcribed from the de-repressed transcription promoter
What must happen in order to give the promoter full power ?
A transcription factor - dimeric CRP protein must bind
What are the conditions surrounding dimeric CRP binding ?
It only binds to DNA when it has first bound the second messenger cAMP
What only occurs when cAMP is present ?
Binding and de-repression
What does the cAMP-CRP complex bind to ?
A specific consensus DNA sequence contained within the operator site upstream of lacZYA
What controls the production of cAMP ?
Glucose
What is the function of cAMP ?
Controls large numbers of genes and is an important second messenger
When glucose is high, what happens to EIIA ?
It is mainly unphosphorylated and adenine cyclase is inactive
When glucose is low, what happens to EIIA ?
Phosphorylated EIIA accumulates and this activates membrane bound adenylate cyclase
What does adenylate cyclase do ?
Converts ATP into cAMP
What does dephosphorylated EIIA inhibit ?
The lac permease and blocks lactose uptake
What does no cAMP-CRP result in ?
The activation of lac transcription
What does the lactose sugar molecule enter ?
The lacY binding pocket
What blocks the lacY binding pocket ?
Anionic glutamic acid and the cationic lysine
What draws protons into the binding pocket ?
The protein gradient on the periplasmic side of the membrane creates a protein motive force
What breaks the salt bridge ?
The positive charge on the proton balances the negative charge on the glutamic acid
What does cationic lysine do ?
Temporarily forms a new salt bridge with anionic aspartic acid which opens the door for the lactose sugar molecule and the proton to move across the membrane into the cytoplasm
How does the original salt bridge reform ?
The lysine has a higher affinity for salt bridge formation with glutamic acid rather than aspartic acid
What is the PTS system used for ?
Used by bacteria for sugar uptake where the source of energy is PEP
What is PEP ?
Phosphoenolpyruvate
What is PEP catabolised into ?
Pyruvate phosphorylating enzyme I
What does enzyme I phosphorylates ?
The heat stable protein
What does the heat stable protein do ?
Phosphorylates enzyme IIAGc until the incoming sugar is phosphorylated as it passes through the membrane integral permease which has now been converted to glucose-6-phosphate
What prevents the transporter from recognising the substrate again ?
The transfer of phosphate group to substrate once it has been imported through the membrane transporter
What does the PTS system act as ?
A regulator of other sugar uptake systems
